Carbon monoxide (CO) is a key species for tracking pollution plumes. The Measurement Of Pollution in The Troposphere (MOPITT) mission onboard the Terra satellite has already provided 7.5 years of CO atmospheric concentration measurements around the globe. Limited sensitivity to the boundary layer is well known to be a weakness of nadir looking thermal infrared sounders. This paper investigates the possibility of using the MOPITT surface measurements to detect CO emitted by cities and urban centers. By selecting the data and averaging them over long time periods, we demonstrate that the CO pollution arising from the large cities and urban areas can be distinguished from the background transported pollution. The more favorable observations are obtained during daytime and at locations where the thermal contrast ( temperature gradient) between the surface and lower atmosphere is significant.

We present a global chemical data assimilation system using a global atmosphere model, the Community Atmosphere Model (CAM3) with simplified chemistry and the Data Assimilation Research Testbed (DART) assimilation package. DART is a community software facility for assimilation studies using the ensemble Kalman filter approach. Here, we apply the assimilation system to constrain global tropospheric carbon monoxide (CO) by assimilating meteorological observations of temperature and horizontal wind velocity and satellite CO retrievals from the Measurement of Pollution in the Troposphere (MOPITT) satellite instrument. We verify the system performance using independent CO observations taken on board the NSF/NCAR C-130 and NASA DC-8 aircrafts during the April 2006 part of the Intercontinental Chemical Transport Experiment (INTEX-B). Our evaluations show that MOPITT data assimilation provides significant improvements in terms of capturing the observed CO variability relative to no MOPITT assimilation (i.e. the correlation improves from 0.62 to 0.71, significant at 99 provides evidence of median CO loading of about 150 ppbv at 700 hPa over the NE Pacific during April 2006. This is marginally higher than the modeled CO with no MOPITT assimilation (similar to 140 ppbv). Our ensemble-based estimates of model uncertainty also show model overprediction over the source region (i.e. China) and underprediction over the NE Pacific, suggesting model errors that cannot be readily explained by emissions alone. These results have important implications for improving regional chemical forecasts and for inverse modeling of CO sources and further demonstrate the utility of the assimilation system in comparing non-coincident measurements, e.g. comparing satellite retrievals of CO with in-situ aircraft measurements.

One of the largest uncertainties for the modeling of tropospheric carbon monoxide ( CO) concentration is the timing, location, and magnitude of biomass burning emissions. We investigate the sensitivity of simulated CO in the Unified Chemistry Transport Model ( UCTM) to several biomass burning emissions, including four bottom-up and two top-down inventories. We compare the sensitivity experiments with observations from MOPITT, surface and airborne NOAA Global Monitoring Division network data, and the TRACE-P field campaign. The variation of the global annual emissions of these six biomass burning inventories is within 30 much higher ( factor of 2 - 5). These uncertainties translate to about 6 but more than a 100 mean CO variation is greater in the Southern Hemisphere (> 12 because biomass burning is a higher percentage of the total source in the Southern Hemisphere. Comparisons with CO observations indicate that each model inventory has its strengths and shortcomings, and these regional variations are examined. Overall the model CO concentrations are within the observed range of variability at most stations including Ascension Island, which is strongly influenced by fire emissions. In addition, we discuss the systematic biases that exist in the inventories developed by the similar methodologies and original satellite data.

[1] Intercontinental Transport of Ozone and Precursors (ITOP), part of International Consortium for Atmospheric Research on Transport and Transformation (ICARTT), was a large experimental campaign designed to improve our understanding of the chemical transformations within plumes during long-range transport (LRT) of pollution from North America to Europe. This campaign took place in July and August 2004, when a strong fire season occurred in North America. Burning by-products were transported over large distances, sometimes reaching Europe. A chemical transport model, Modelisation de la Chimie Atmospherique Grande Echelle (MOCAGE), with a high grid resolution (0.5 degrees x 0.5 degrees) over the North Atlantic area and a daily inventory of biomass burning emissions over the United States, has been used to simulate the period. By comparing our results with available aircraft in situ measurements and satellite data (MOPITT CO and SCIAMACHY NO2), we show that MOCAGE is capable of representing the main characteristics of the tropospheric ozone-NOx-hydrocarbon chemistry during the ITOP experiment. In particular, high resolution allows the accurate representation of the pathway of exported pollution over the Atlantic, where plumes were transported preferentially at 6 km altitude. The model overestimates OH mixing ratios up to a factor of 2 in the lower troposphere, which results in a global overestimation of hydrocarbons oxidation by-products ( PAN and ketones) and an excess of O-3 ( 30 - 50 ppbv) in the planetary boundary layer (PBL) over the continental United States. Sensitivity study revealed that lightning NO emissions contributed significantly to the NOx budget in the upper troposphere of northeast America during the summer 2004.

[1] Optimal estimation methods, such as the “maximum a posteriori” solution, are commonly employed for retrieving profiles of atmospheric trace gases from satellite observations. To complement the information actually contained in the measured radiances, such methods exploit a priori information describing the gases' variability characteristics. We show that in situ surface-based data sets for carbon monoxide ( CO) volume mixing ratio (VMR) indicate that the variability of CO is more accurately modeled in terms of a “lognormal” probability distribution function (PDF) than a “VMR-normal” PDF. The VMR-normal PDF is particularly poor at describing CO variability in unpolluted conditions. We also compare retrievals of carbon monoxide ( CO) vertical profiles based on Measurements of Pollution in the Troposphere (MOPITT) observations for 1 day using both VMR-normal and lognormal statistical models. Use of the lognormal model improves retrieval convergence and yields fewer profiles with unphysically small VMR values. Generally, these results highlight the importance of properly representing the variability of trace gas concentrations in optimal estimation-based retrieval algorithms.

The sensitivity of Measurements of Pollution in the Troposphere (MOPITT) observations to carbon monoxide (CO) concentrations in the lower troposphere (LT) varies widely as the result of variability in thermal contrast conditions. This effect is evident in both the MOPITT weighting functions and averaging kernels, particularly after these quantities are properly normalized to remove grid effects. Comparisons of simulated weighting functions and averaging kernels with operational data confirm the significance of thermal contrast effects. Retrieval sensitivity to LT CO is greatest in daytime observations over land, particularly in tropical and midlatitude regions exhibiting large diurnal variations in surface temperature. Nighttime observations over land typically exhibit poor sensitivity to LT CO. On the global scale, analysis of MOPITT averaging kernels for 1 month indicates that daytime MOPITT observations offer useful sensitivity to LT CO over large areas of most continents. Exceptions include tropical rainforests in Africa and South America, where thermal contrast conditions are relatively weak.

It has been suggested that simultaneous satellite measurements of mid-visible fine mode aerosol optical depth tau(f) and CO concentrations can aid in improving the characterization of biomass burning in chemical transport models. However different approaches for retrieving tau(f) have recently been proposed. Using MODIS and MOPITT data, we examine the impact these have on the regression slope between enhancements of tau(f) and CO (Delta tau(f)/Delta CO) for representative biomass burning cases, including savanna and extratropical forests. Both MODIS Collection 4 and recent Collection 5 aerosol products are used in our study. We find that tau(f) varies systematically with retrieval method causing systematic differences in the slope of regression. Regardless of method used, noticeable differences in regression slope are observed for different types of biomass burning. Our results point out the need for consistency in defining tau(f) between satellite measurements and models if the Delta tau(f)/Delta CO ratio is to be used as a constraint.

[1] We analyze aircraft observations obtained during INTEX-A ( 1 July to 14 August 2004) to examine the summertime influence of Asian pollution in the free troposphere over North America. By applying correlation analysis and principal component analysis (PCA) to the observations between 6 and 12 km, we find dominant influences from recent convection and lightning (13 observations), Asia (7 boreal forest fires (2 to background. Asian air masses are marked by high levels of CO, O-3, HCN, PAN, C2H2, C6H6, methanol, and SO42-. The partitioning of NOy species in the Asian plumes is dominated by PAN ( similar to 600 pptv), with varying NOx/HNO3 ratios in individual plumes, consistent with individual transit times of 3 - 9 days. Export of Asian pollution occurred in warm conveyor belts of midlatitude cyclones, deep convection, and in typhoons. Compared to Asian outflow measurements during spring, INTEX-A observations display lower levels of anthropogenic pollutants (CO, C3H8, C2H6, C6H6) due to shorter summer lifetimes; higher levels of biogenic tracers ( methanol and acetone) because of a more active biosphere; and higher levels of PAN, NOx, HNO3, and O-3 reflecting active photochemistry, possibly enhanced by efficient NOy export and lightning. The high Delta O-3/Delta CO ratio (0.76 mol/mol) in Asian plumes during INTEX-A is due to strong photochemical production and, in some cases, mixing with stratospheric air along isentropic surfaces. The GEOS-Chem global model captures the timing and location of the Asian plumes. However, it significantly underestimates the magnitude of observed enhancements in CO, O-3, PAN and NOx.

A global chemical transport model (MOZART-2; model of ozone and related tracers, version 2) was used to assess physical and chemical processes that control the budget of tropospheric carbon monoxide (CO) in North China. Satellite observations of CO from the measurements of pollution in the troposphere (MOPITT) instrument are combined with model results for the analysis. The comparison between the model simulations and the satellite observations of total column CO (TCO) shows that the model can reproduce the spatial and temporal distributions. However, the model results underestimate TCO by 23 underestimation of TCO may be caused by the uncertainties of emissions. The tropospheric CO budget analysis suggests that in North China, surface emission is the largest source of tropospheric CO. The main sinks of tropospheric CO in this region are chemical reaction and stratosphere(-)and(-)troposphere exchange. The analysis also shows that most of inflow CO to Pacific regions comes from the upwind regions of North China. This transport of CO is significant during Winter and Spring time. (c) 2006 Elsevier Ltd. All rights reserved.

The summer of 2004 was one of the largest fire seasons on record for Alaska and western Canada. We construct a daily bottom-up fire emission inventory for that season, including consideration of peat burning and high-altitude (buoyant) injection, and evaluate it in a global chemical transport model (the GEOS-Chem CTM) simulation of CO through comparison with MOPITT satellite and ICARTT aircraft observations. The inventory is constructed by combining daily area burned reports and MODIS fire hot spots with estimates of fuel consumption and emission factors based on ecosystem type. We estimate the contribution from peat burning using drainage and peat distribution maps for Alaska and Canada; 17 reported 5.1 x 10(6) ha burned were located in peatlands in 2004. Our total estimate of North American fire emissions during the summer of 2004 is 30 Tg CO, including 11 Tg from peat. Including peat burning in the GEOS-Chem simulation improves agreement with MOPITT observations. The long-range transport of fire plumes observed by MOPITT suggests that the largest fires injected a significant fraction of their emissions in the upper troposphere.

Recent developments in satellite remote sensing technologies resulted in the ability to observe major pollution events such as dust and smoke around the world on a daily basis. Satellite imagery can sometimes detect long-range transport episodes. In this paper, a high CO episode at remote GAW station, Mt. Waliguan, detected by MOPITT CO dataset during the end of April 2002, is described. CO concentrations above 600 hPa almost doubled on 27 April and CMDL surface sample measurements also observed this significant CO enhancement. Using NCEP data, satellite fire products data and backward trajectory model we suggest that this high CO episode of 27 April is not a local pollution event, but that it is due to long-range transport from active biomass burning and biofuel burning areas located in the border areas of Pakistan and India. The trajectory cluster analysis shows that the origins of 5-day backward trajectories, for air masses reaching Mt. Waliguan station, at all altitudes, mainly overlap with the fire spot locations detected by TRMM data and biofuel burning in India.

Estimates of CO sources derived from inversions using satellite observations still exhibit discrepancies. Here, we conduct controlled inverse analyses to elucidate the influence of model transport on the robustness of regional CO source estimates. We utilized Model of Ozone and Related chemical Tracers global chemical transport models (GCTM) driven by National Centers for Environmental Prediction and European Centre for Medium-Range Weather Forecast reanalyses, and GEOS-Chem GCTM driven by Global Modeling and Assimilation Office assimilated meteorology to generate response functions for prescribed regional CO sources. We find that inter-model differences in CO due to differences in transport are within 10 - 30 concentration. However, these differences can translate to regionally significant spread in source estimates. While we find that CO source estimates for East Asia and North Africa are reasonably robust, we find inconsistencies and inter-model spread of greater than 40 estimates for Indonesia, South America, Europe and Russia. This indicates the need for rigorous assessment on uncertainties in top-down source estimates through model inter-comparisons and ensemble approaches.

[ 1] We present an inverse-modeling analysis of CO emissions using column CO retrievals from the Measurement of Pollution in the Troposphere (MOPITT) instrument and a global chemical transport model (GEOS-CHEM). We first focus on the information content of MOPITT CO column retrievals in terms of constraining CO emissions associated with biomass burning and fossil fuel/biofuel use. Our analysis shows that seasonal variation of biomass-burning CO emissions in Africa, South America, and Southeast Asia can be characterized using monthly mean MOPITT CO columns. For the fossil fuel/biofuel source category the derived monthly mean emission estimates are noisy even when the error statistics are accurately known, precluding a characterization of seasonal variations of regional CO emissions for this source category. The derived estimate of CO emissions from biomass burning in southern Africa during the June - July 2000 period is significantly higher than the prior estimate ( prior, 34 Tg; posterior, 13 Tg). We also estimate that emissions are higher relative to the prior estimate in northern Africa during December 2000 to January 2001 and lower relative to the prior estimate in Central America and Oceania/Indonesia during April - May and September - October 2000, respectively. While these adjustments provide better agreement of the model with MOPITT CO column fields and with independent measurements of surface CO from National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostics Laboratory at background sites in the Northern Hemisphere, some systematic differences between modeled and measured CO fields persist, including model overestimation of background surface CO in the Southern Hemisphere. Characterizing and accounting for underlying biases in the measurement model system are needed to improve the robustness of the top-down estimates.

[1] Biomass burning is a major source of pollution in the tropical Southern Hemisphere, and fine mode carbonaceous particles are produced by the same combustion processes that emit carbon monoxide ( CO). In this paper we examine these emissions with data from the Terra satellite, CO profiles from the Measurement of Pollution in the Troposphere (MOPITT) instrument, and fine-mode aerosol optical depth (AOD) from the Moderate-Resolution Imaging Spectroradiometer ( MODIS). The satellite measurements are used in conjunction with calculations from the MOZART chemical transport model to examine the 2003 Southern Hemisphere burning season with particular emphasis on the months of peak fire activity in September and October. Pollutant emissions follow the occurrence of dry season fires, and the temporal variation and spatial distributions of MOPITT CO and MODIS AOD are similar. We examine the outflow from Africa and South America with emphasis on the impact of these emissions on clean remote regions. We present comparisons of MOPITT observations and ground-based interferometer data from Lauder, New Zealand, which indicate that intercontinental transport of biomass burning pollution from Africa often determines the local air quality. The correlation between enhancements of AOD and CO column for distinct biomass burning plumes is very good with correlation coefficients greater than 0.8. We present a method using MOPITT and MODIS data for estimating the emission ratio of aerosol number density to CO concentration which could prove useful as input to modeling studies. We also investigate decay of plumes from African fires following export into the Indian Ocean and compare the MOPITT and MODIS measurements as a way of estimating the regional aerosol lifetime. Vertical transport of biomass burning emissions is also examined using CO profile information. Low-altitude concentrations are very high close to source regions, but further downwind of the continents, vertical mixing takes place and results in more even CO vertical distributions. In regions of significant convection, particularly in the equatorial Indian Ocean, the CO mixing ratio is greater at higher altitudes, indicating vertical transport of biomass burning emissions to the upper troposphere.

[ 1] Biomass burning is an annual occurrence in the tropical Southern Hemisphere (SH) and represents a major source of regional pollution. Vegetation fires emit carbon monoxide ( CO), which because of its medium lifetime is an excellent tracer of tropospheric transport. CO is also one of the few tropospheric trace gases currently observed from satellite, and this provides long-term global measurements. In this paper, we use the 5-year CO data record from the Measurement of Pollution in the Troposphere (MOPITT) instrument to examine the interannual variability of the SH CO loading and show how this relates to climate conditions which determine the intensity of fire sources. The MOPITT observations show an annual austral springtime peak in the SH zonal CO loading each year with dry season biomass burning emissions in South America, southern Africa, the maritime continent, and northwestern Australia. Although fires in southern Africa and South America typically produce the greatest amount of CO, the most significant interannual variation is due to varying fire activity and emissions from the maritime continent and northern Australia. We find that this variation in turn correlates well with the El Nino - Southern Oscillation precipitation index. Between 2000 and 2005, emissions were greatest in late 2002, and an inverse modeling of the MOPITT data using the Model of Ozone Research in the Troposphere (MOZART) chemical transport model estimates the Southeast Asia regional fire source for the year August 2002 to September 2003 to be 52 Tg CO. Comparison of the MOPITT retrievals and NOAA surface network measurements indicate that the latter do not fully capture the interannual variability or the seasonal range of the CO zonal average concentration because of biases associated with atmospheric and geographic sampling.

We report an intriguing feature observed in daytime measurements of CO over the Middle East, in spring and summer, by the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument. Enhanced CO is observed over the Zagros mountains of Iran, following the local topography over this region ( 25 - 40N, 40 - 60E). The MOPITT averaging kernels do not seem to indicate any data artifacts in this area. We argue that this feature likely forms by the process of mountain venting by thermal winds caused by strong daytime differential heating. This is consistent with an analysis of vertical velocity in the NCEP reanalysis data in this region. The phenomenon was observed in all the years of available MOPITT measurements and may have implications for the pollution episodes in the region and the Middle East ozone maximum that has been observed earlier.

[1] We have examined the influence of synoptic processes on the distribution of atmospheric CO as observed by the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument. In the MOPITT data, large horizontal gradients in CO, coherent at the synoptic scale, have been observed. The concentration of CO varies rapidly by as much as 50 - 100 distinct boundaries in the CO distribution. These can last one to several days and span horizontal distances of 600 - 1000 km. On average, such events were observed in the MOPITT CO daily images once every 3 - 4 days over North America in spring and summer 2000. We focused on three case studies over North America in August 2000 to understand the mechanisms responsible for the large gradients in CO. Through an analysis of meteorological data from the National Centers for Environmental Prediction/ National Center for Atmospheric Research Reanalysis, parcel trajectory modeling, and global three-dimensional chemical transport modeling, we found that the large horizontal gradients typically reflect the differential vertical and horizontal transport of air with different chemical signatures. In the first case, the large gradients in CO over North Dakota resulted from the lifting ahead of a cold front that transported boundary layer air enriched with CO from forest fires in Montana, combined with the descent of clean air from the Canadian Prairies behind the front. In the second case, the large gradients over northeastern Texas were produced by the convective lifting over Arkansas of air with high concentrations of CO from the oxidation of volatile organic compounds and the onshore transport of clean air from the Gulf of Mexico. In the third case, we examined an example of outflow of surface pollution from North America by a cyclone. The largest gradients in this case were observed along the boundary between the boundary layer air transported by the warm conveyor belt ahead of the cold front and the clean air transported from the Atlantic by the semipermanent high-pressure system in the central Atlantic. Our results demonstrate that MOPITT can capture the influence of synoptic processes on the horizontal and vertical distribution of CO. The large gradients in COobserved on synoptic scales represent valuable information that can be exploited to improve our understanding of atmospheric CO. In particular, these results suggest that the MOPITT observations provide a useful data set with which to address a range of issues from air quality on local/ regional scales to long-range transport of pollution on continental/global scales.

The development of remote sensing satellite technology potentially will lead to the technical means to monitor air pollution emitted from large cities on a global basis. This paper presents observations by the moderate resolution imaging spectroradiometer (MODIS) and measurements of pollution in the troposphere (MOPITT) experiments of aerosol optical depths and CO mixing ratios, respectively, in the vicinity of Mexico City to illustrate current satellite capabilities. MOPITT CO mixing ratios over Mexico City, averaged between January-March 2002-2005, are 19 above regional values and the CO plume extends over 10 degrees(2) in the free troposphere at 500 hPa. Time series of Red Automatica de Monitoreo Ambiental (RAMA) PM10, and (Aerosol Robotic Network) AERONET and MODIS aerosol optical depths, and RAMA and MOPITT CO time series are inter-compared to illustrate the different perspectives of ground based and satellite instrumentation. Finally, we demonstrate, by examining MODIS and MOPITT data in April 2003, that satellite data can be used to identify episodes in which pollution form fires influences the time series of ground based and satellite observations of urban pollution. (c) 2006 Elsevier Ltd. All rights reserved.

The global chemistry and transport model MOCAGE (Modele de Chimie Atmospherique a Grande Echelle) is used to investigate the contribution of transport to the carbon monoxide (CO) distribution over West Africa during spring 2001. It is constrained with the CO profiles provided by the Measurements Of Pollution In The Troposphere (MOPITT) instrument through a sequential assimilation technique based on a suboptimal Kalman filter. The improvement of tropospheric CO distribution from MOCAGE is evaluated by comparing the model results (with and without assimilation) with the MOPITT CO concentrations observed during the analysed period (between 2001 March 15 to 2001 April 30), and also with independent in situ CMDL and TRACE-P observations. The initial overestimation in high CO emissions areas (Africa, SE Asia and NW coast of South America) is considerably reduced by using the MOPITT CO assimilation. We analysed the assimilated CO for a period of three successive 15 d periods in terms of average fields over West Africa and contributions to the CO budget of transport and chemical sources. It is found that the horizontal and vertical CO distributions are strongly dependent on the characteristics of the large-scale flows during spring, marked by the onset of the low-level southerly monsoon flow and the gradual increase of the well-known African and tropical easterly jets at middle and upper levels, respectively. Total transport by the mean flow (horizontal plus vertical advection) is important in the CO budget since it mostly compensates the local sink or source generated by chemical reactions and small-scale processes. The major source of CO is concentrated in the lower troposphere (1000-800 hPa) mainly due to convergent low-level flow advecting CO from surrounding regions and surface emissions (biomass burning). Vertical transport removes 70 the middle troposphere (800-400 hPa) where chemical reactions and horizontal exports contribute to the loss of CO. A lesser proportion is transported upwards into upper troposphere, and then horizontally, out of the considered domain.

We analyze present-day and future carbon monoxide (CO) simulations in 26 state-of-the-art atmospheric chemistry models run to study future air quality and climate change. In comparison with near-global satellite observations from the MOPITT instrument and local surface measurements, the models show large underestimates of Northern Hemisphere (NH) extratropical CO, while typically performing reasonably well elsewhere. The results suggest that year-round emissions, probably from fossil fuel burning in east Asia and seasonal biomass burning emissions in south-central Africa, are greatly underestimated in current inventories such as IIASA and EDGAR3.2. Variability among models is large, likely resulting primarily from intermodel differences in representations and emissions of nonmethane volatile organic compounds (NMVOCs) and in hydrologic cycles, which affect OH and soluble hydrocarbon intermediates. Global mean projections of the 2030 CO response to emissions changes are quite robust. Global mean midtropospheric (500 hPa) CO increases by 12.6 +/- 3.5 ppbv (16 ppbv (2 8.1 +/- 2.3 ppbv (11 scenario. Projected 2030 climate changes decrease global 500 hPa CO by 1.4 +/- 1.4 ppbv. Local changes can be much larger. In response to climate change, substantial effects are seen in the tropics, but intermodel variability is quite large. The regional CO responses to emissions changes are robust across models, however. These range from decreases of 10-20 ppbv over much of the industrialized NH for the CLE scenario to CO increases worldwide and year-round under A2, with the largest changes over central Africa (20-30 ppbv), southern Brazil (20-35 ppbv) and south and east Asia (30-70 ppbv). The trajectory of future emissions thus has the potential to profoundly affect air quality over most of the world's populated areas.

Satellite data (MODIS, GOME, and MOPITT) together with a chemical transport global model of the atmosphere (MOZART-2) are used to characterize air pollution in Eastern China and the Eastern US to assess the differences between the photochemical conditions in these two regions. Observations show that aerosol concentrations (both fine (radius < 0.5 mu m) and coarse modes (radius > 0.5 mu m)) are higher in Eastern China than in the Eastern US. The NOx concentrations in both regions are substantially higher than in remote regions such as over the oceans (150 compared to 5 (10(14)##cm(-2)) over the Pacific Ocean). The CO concentrations are high in both urbanized areas (30 compared to 10 (10(17)#cm(-2)) over the Pacific Ocean). However, the concentrations of non-methane hydrocarbons from both anthropogenic and biogenic sources are considerably lower in Eastern China than in the Eastern US. As a result, the rate of photochemical ozone production and ozone concentrations during summer is significantly lower in Eastern China (daily averaged concentrations of 40-50 ppbv in summer) than in the Eastern US (daily averaged values of 60-70 ppbv). The analysis also shows that in Eastern China, the O-3 production is mainly due to the oxidation of carbon monoxide (54 while, in the Eastern US, the O-3 production is attributed primarily to the oxidation of reactive hydrocarbons (68 total O-3 production). The results also indicate that biogenic emissions of hydrocarbons contribute substantially to the production of O-3 in the Eastern US. The O-3 production due to the oxidation of biogenic hydrocarbons represents approximately one third of total O-3 photochemical production in this region. Measurements of surface ozone in the Eastern US and Eastern China seem to support that the summer ozone production is lower in Eastern China than in the Eastern US. However, additional surface measurements, especially of reactive hydrocarbons and ozone are needed in Eastern China in order to improve the present analysis and to confirm our current conclusions. A sensitivity study shows that with increase in anthropogenic emissions of HCs, the surface ozone concentrations significantly increase in Eastern China, indicating that the increase in the emissions of HCs plays an important role for the enhancement in surface ozone in this region. (c) 2006 Elsevier Ltd. All rights reserved.

In this study, we used satellite data (GOME and MOPITT) together with a global chemical-transport-model of atmosphere (MOZART-2) to characterize the chemical/aerosol composition over eastern China. We then estimated the effects of local emissions in China on the chemical budgets in other regions of the world. Likewise, we also investigated the effects of air pollution from other regions on the chemical budget over eastern China. The study shows that the column CO and NOx concentrations are also high in eastern China. The high CO and NOx concentrations produce modest levels of O-3 concentrations during summer (about 40 to 50 ppbv) and very low O-3 during winter (about 10 to 20 ppbv) in eastern China. The calculated NO2 column is fairly consistent from the GOME measurement. The calculated CO column is underestimated from the MOPITT measurement. One of the reasons of the underestimation of the predicted CO is due to a fact that the CO emissions were taken without considering the rapid increase of emissions from 1990 to 2000. The calculated surface O-3 is consistent with the measured values, with strong seasonal variations. However, the measurement is very limited, and more measurements in eastern China will be needed. The column NO2 has a very strong seasonal variation in eastern China, with the highest concentrations during winter and the lowest concentrations during summer. The cause of this seasonal variability is mainly due to the seasonal changes in the chemical loss of NOx, which is very high in summer and very low during winter. The effects of the local emissions in China and long-range transport from other regions on the chemical distributions in eastern China are studied. The results show that NOx concentrations in eastern China are mostly caused by the local emissions in China, especially during the winter. The CO concentration over eastern China is from both the local emissions (30 regions. Likewise, the CO emissions in China have an important effect on the other regions of the world, but the effect is limited in the northern hemisphere. The local emissions in China also have an important effect on surface O-3 concentrations. During winter, the local emissions reduce the surface O-3 concentrations by 30 to 50 summer, the local emissions produce about 50 to 70 O-3 concentration in eastern China.

[1] Carbon monoxide ( CO) is an important tropospheric trace species. The Measurements of Pollution in the Troposphere (MOPITT) instrument uses the 4.7 mu m CO band to measure the global CO profile and total column amount in the troposphere from space. In the operational MOPITT CO retrieval algorithm, surface skin temperature (T-s) and emissivity ( E) are retrieved simultaneously with the CO profile. However, because both Ts and E are retrieved from the same piece of information from the MOPITT measurements, the accuracy of both variables may be limited, which leads to an increase of uncertainty in the CO retrievals. An accurate specification of the surface skin temperature is required to determine surface emissivity and vice versa. In this study, a method is developed which uses Ts from the Moderate Resolution Imaging Spectroradiometer ( MODIS) and MOPITT radiances to derive an improved 4.7 mu m surface emissivity estimate ( E) for use in retrievals by the MOPITT instrument. Monthly mean 4.7 mu m surface emissivity maps for 1 year are generated and used as the a priori E in the MOPITT Ts and CO retrieval algorithm. We show that the geographical distribution of the 4.7 mu m emissivity is very consistent with MODIS normalized difference vegetation index distribution, which is strongly tied to the surface emissivity. This a priori E has a much smaller standard deviation than values currently used in the MOPITT retrieval. As a result, more radiance information tends to be used in the MOPITT T-s and CO retrievals. By using the improved a priori E over the land, the information content of MOPITT radiances increases 15 the day relative to the current version MOPITT data products. The difference between day and night information content ( or diurnal difference) decreases from 0.3 ( current version) to 0.21, showing that nighttime retrievals are improved. Over the global ocean the diurnal difference of the MOPITT information content decreases from 0.15 ( current version) to 0.06. The differences between the new profile retrievals and those of current profile retrievals are very consistent with their corresponding diurnal and geographical information content distributions. Over the global ocean the new MOPITT CO profile is lower by 3 - 11 during the night in the lower troposphere. Over the global land the new CO profile is higher by 3.2 troposphere during the night. The differences between the new profile retrieval and those of current retrieval are small during the day.

We present a study on MOPITT (Measurements Of Pollution In The Troposphere) detection of CO emission from large forest fires in the year 2000 in the northwest United States. Fire data used are from the space-borne Advanced Very High Resolution Radiometer (AVHRR) at 1 -km resolution. The study shows that MOPITT can reliably detect CO plumes from forest fires whenever there are > 30 AVHRR hotspots in a 0.25 degrees x 0.25 degrees grid, which is comparable to the pixel area of MOPITT in the region. The spatial CO pattern during the fire events is found to be consistent with the location and density of AVHRR hotspots and wind direction. While the increase of CO abundance inside the study area is closely correlated to the AVHRR-derived hotspot number in general (R > 0.75), the non-linearity of fire emission with fuel consumption is also observed. MOPITT can also capture the temporal variation in CO emission from forest fires through 3 -day composites so it may offer an opportunity to enhance our knowledge of temporal fire emission over large areas. The CO emission is quantitatively estimated with a one-box model. The result is compared with a bottom-up approach using surface data including burnt area, biomass density, and fire emission factors. If mean emission factors for the region are used, the bottom-up approach results in total emission estimates which are 10 MOPITT-based estimate. In spite of the limitations and uncertainties addressed in this study, MOPITT data may provide a useful constraint on uncertain ground-based fire emission estimates. (c) 2005 Elsevier Inc. All rights reserved.

The amount of solar radiation emerging from the top of the atmosphere is strongly influenced by the reflectance of the underlying surface. For this reason, some information about the magnitude and the spectral variability of the surface reflectance typically has to be included in the retrieval of atmospheric parameters from reflected solar radiation measurements. Sufficient information about the surface reflectance properties is rarely available, and the integration of this effect in the retrieval might turn out to be a challenge, especially for broadband instruments. In this paper the focus is on the Measurements of Pollution in the Troposphere (MOPITT) remote sensing instrument. Theoretical studies are performed to investigate how a spectrally varying surface reflectance might impact the retrieval of the total column amount of methane from MOPITT radiance measurements, and the current findings are compared to observed biases. However, the findings present herein might be valuable and applicable for other remote sensing instruments that are sensitive to the amount of solar radiation reflected from the earth's surface.

We present an inverse model analysis to quantify the emissions of wildfires in Alaska and Canada in the summer of 2004 using carbon monoxide (CO) data from the Measurements of Pollution in the Troposphere (MOPITT) remote sensing instrument together with the chemistry transport model MOZART ( Model for Ozone and Related Chemical Tracers). We use data assimilation outside the region of the fires to optimally constrain the CO background level and the transport into that region. Inverse modeling is applied locally to quantify the fire emissions. Our a posteriori estimate of the wildfire emissions gives a total of 30 +/- 5 Tg CO emitted during June - August 2004 which is of comparable order to the anthropogenic emissions for the continental US. The simulated CO fields have been evaluated by comparison with MOPITT and independent aircraft data.

We compare space-based measurements of carbon monoxide ( CO) during April 1994 and October 1984 and 1994 from the early MAPS instrument with those during 2000-2004 from the MOPITT instrument. We show that a three-dimensional global composition model can be used to account for differences in retrieval sensitivity between the two instruments and between the different years of MOPITT data. This allows direct comparison of CO amounts over most of the globe at different times. These types of changes in short-lived constituents cannot be assessed with local measurements. Though the existing space-based data are too sparse both temporally and geographically to allow trend estimates, we find substantial variations in midtropospheric CO between the different years in many continental-scale regions. During April, average CO is similar to 12-18 ppbv (similar to 10-20 North America, southeast Asia and North Africa though the global mean value is nearly the same. During October 1994, observations show CO enhancements of 15-20 ppbv relative to 1984 or 2000-2004 over South America and a similar, though slightly smaller (9-19 ppbv), enhancement globally. Southeast Asia, Europe and North America all show similar October CO levels in 1994 and 2000-2004, with both times showing substantially more pollution (13-29 ppbv) than 1984. Variations over Europe and Africa are consistent in both seasons, while changes elsewhere are not. Changes over southeast Asia and North Africa are substantially in excess of interannual variability, while those over North and South America and southern Africa are only marginally so. Model sensitivity studies examining the response to changes in emissions indicate probable causes of the CO changes over different regions. Over southeast Asia and North America, CO is most sensitive to industrial and biomass burning emissions, implying that changes in these sources likely account for the 13-29 ppbv increases seen there between 2000-2004 and earlier years. Over North Africa, CO is strongly influenced by numerous sources as well as meteorology, precluding attribution of increases to particular factors. Over South America and southern Africa, variations in both biomass burning and isoprene emissions likely contributed to the similar to 10-20 ppbv changes.

Carbon monoxide total column amounts in the atmosphere have been measured in the High Northern Hemisphere (30degrees - 90degrees N, HNH) between January 2002 and December 2003 using infrared spectrometers of high and moderate resolution and the Sun as a light source. They were compared to ground-level CO mixing ratios and to total column amounts measured from space by the Terra/MOPITT instrument. All these data reveal increased CO abundances in 2002 - 2003 in comparison to the unperturbed 2000 - 2001 period. Maximum anomalies were observed in September 2002 and August 2003. Using a simple two-box model, the corresponding annual CO emission anomalies (referenced to 2000 - 2001 period) have been found equal to 95 Tg in 2002 and 130 Tg in 2003, thus close to those for 1996 and 1998. A good correlation with hot spots detected by a satellite radiometer allows one to assume strong boreal forest fires, occurred mainly in Russia, as a source of the increased CO burdens.

Carbon monoxide (CO) measurements from the Measurements of Pollution in the Troposphere (MOPITT) experiment are used to explore the correlation between biomass burning and ozone profiles at six tropical stations namely Reunion, Irene, Natal, Ascension, San Cristobal, and Paramaribo. Distinct seasonal patterns of CO at each station indicate the strong influence of African and South American biomass burning. All stations show enhanced CO columns during September-November ( SON) corresponding to austral burning. Furthermore, the effects of Sahelian burning can be seen at Natal and Ascension. Similarly, the signature of northern Amazonian fires can be observed at San Cristobal. The CO variations are generally similar to the variations of aerosol optical depth (AOD) retrieved contemporaneously from Moderate Resolution Imaging Spectroradiometer (MODIS) at most stations, with notable differences at Irene, San Cristobal, and Paramaribo. Tropospheric ozone from Southern Hemisphere Additional Ozonesonde (SHADOZ) ozonesonde measurements at all stations show elevated levels, corresponding to the CO enhancements in SON months. However, there are several instances of ozone enhancements unaccompanied by any CO increase. This might indicate that sources other than biomass burning such as stratospheric tropospheric exchange (STE) or lightning related NOx may be operative. At San Cristobal, strong CO enhancements during March April are not accompanied by any significant change in ozone.

During Transport and Chemical Evolution over the Pacific (TRACE-P), there were several opportunities to perform in situ sampling coincident with overpasses of the Measurements of Pollution in the Troposphere (MOPITT) instrument on board the EOS Terra satellite. This sampling consisted of in situ vertical profiles of CO by NASA's DC-8 aircraft intended to provide data useful for validating MOPITT observations of CO column. One particular profile conducted over the central North Pacific revealed a layer of pollution characterized by CO mixing ratios more than double background values. Sampling of the surrounding region by both the NASA DC-8 and P-3B aircraft showed this layer to have a considerable geographic extent, at least 25degrees longitude (similar to2500 km) and 4degrees latitude (similar to400 km). Using back trajectory analysis, this polluted layer is followed back in time and compared with four consecutive MOPITT overpasses. MOPITT observations during these four overpasses agree well with the location of the layer as inferred by the trajectories; however, the detected CO column amount increases backward in time by just over 20 majority of this change in detected column abundance is consistent with two factors: ( 1) changes in the thickness of the polluted layer over time (9 +/- 3 in retrieved column abundance due to the altitude of the layer (7 +/- 3 real and artificial sources of variability that must be understood before MOPITT observations can be quantitatively useful. An unexpected finding was the difference in the variance of MOPITT observations depending on whether observations were taken under daylight or nighttime conditions. The variance in daytime observations of the polluted layer was approximately double that for nighttime data. The results of this analysis indicate that targeted in situ sampling of large-scale pollution events can provide insight leading to more realistic interpretation of MOPITT observations. Strategies for sampling such events repeatedly during their evolution could also provide more interesting opportunities for validation.

The ability of operational radiative transfer models to accurately predict remote sensing instrument observations (e.g., calibrated radiances) over a wide variety of geophysical situations is critical to the performance of trace gas retrieval algorithms. As part of the validation of the Measurements of Pollution in the Troposphere (MOPITT) satellite instrument, we present a technique for comparing operational calibrated thermal band (4.7 mum) Earth-view MOPITT radiances with corresponding values calculated using the MOPITT operational radiative transfer model. In situ carbon monoxide (CO) profiles sampled from aircraft in coordination with MOPITT overpasses serve as the foundation for MOPITT validation. Characteristics of radiance errors due to in situ sampling characteristics, CO temporal and spatial variability, and surface emissivity are discussed. Results indicate that radiance biases for most of the MOPITT thermal channel radiances are typically on the order of 1 and most variable for the pressure modulation cell difference-signal radiances, probably because of the lack of in situ data in the upper troposphere and lower stratosphere.

The MOPITT ( Measurements of Pollution in the Troposphere) remote sensing instrument monitors the global distribution of carbon monoxide from a polar-orbiting platform. Calculated averaging kernels for operational MOPITT CO profiles indicate the capability of independently retrieving mid- and upper-tropospheric CO. The information content in MOPITT retrievals is objectively quantified through calculation of the Degrees of Freedom for Signal (DFS), which indicates the number of independent pieces of information in the retrieved profile. DFS values larger than 1 ( indicating some amount of profile shape information) are common in tropical and midlatitude scenes. The existence of shape information in actual MOPITT retrieved profiles is also verified through ( 1) a quantitative comparison with in-situ data acquired as part of MOPITT validation and ( 2) a qualitative comparison with monthly mean rain rate ( as an index for convection) in the Tropical Eastern Pacific Ocean.

Measurements from the Terra satellite launched in December of 1999 provide a global record of the recent interannual variability of tropospheric air quality: carbon monoxide (CO) from the Measurement of Pollution in the Troposphere (MOPITT) instrument and aerosol optical depth (AOD) from the Moderate-Resolution Imaging Spectroradiometer (MODIS). This paper compares and contrasts these data sets with a view to understanding the general features of the overall pollutant loading of the Northern Hemisphere (NH). We present a detailed examination of the seasonal and recent interannual variability of the fine mode AOD and CO column, first considering the variation of the global zonal average for both quantities, and then concentrating on several geographical regions with the aim of isolating different emissions. In a zonal sense, the principal NH sources are related to anthropogenic urban and industrial activity. We show that both the CO and the AOD zonal seasonal variations reflect the atmospheric oxidant concentration, which determines the primary sink of CO and the production of sulfate aerosol. As a consequence, the seasonal cycles are several months out of phase, with perturbations resulting from sporadic wildfire or biomass-burning emissions. In these cases, carbonaceous particles dominate the AOD, and this results in the best correlation with the CO column. Of the 4 years of data available from the Terra satellite, the winter and spring of 2002-2003 showed anomalously high NH pollution compared to the previous years. This was a result of fires in western Russia in the late summer and fall of 2002 and intense fires in the southeast of Russia in the spring and summer of 2003. We examine these events using fire counts from MODIS to indicate the burning regions and investigate how the timing of the fires in relation to atmospheric oxidant concentrations affects the resultant seasonal pollutant loadings. Finally, we trace the emissions from these fires to indicate how intense local pollution sources can impact continental- and global-scale air quality.

Validation of the Measurements of Pollution in the Troposphere (MOPITT) retrievals of carbon monoxide (CO) has been performed with a varied set of correlative data. These include in situ observations from a regular program of aircraft observations at five sites ranging from the Arctic to the tropical South Pacific Ocean. Additional in situ profiles are available from several short-term research campaigns situated over North and South America, Africa, and the North and South Pacific Oceans. These correlative measurements are a crucial component of the validation of the retrieved CO profiles and columns from MOPITT. The current validation results indicate good quantitative agreement between MOPITT and in situ profiles, with an average bias less than 20 ppbv at all levels. Comparisons with measurements that were timed to sample profiles coincident with MOPITT overpasses show much less variability in the biases than those made by various groups as part of research field experiments. The validation results vary somewhat with location, as well as a change in the bias between the Phase 1 and Phase 2 retrievals ( before and after a change in the instrument configuration due to a cooler failure). During Phase 1, a positive bias is found in the lower troposphere at cleaner locations, such as over the Pacific Ocean, with smaller biases at continental sites. However, the Phase 2 CO retrievals show a negative bias at the Pacific Ocean sites. These validation comparisons provide critical assessments of the retrievals and will be used, in conjunction with ongoing improvements to the retrieval algorithms, to further reduce the retrieval biases in future data versions.

[ 1] During a west to east crossing of the tropical Atlantic Ocean in October - November 2002 on R/V Meteor (M55), carbon monoxide ( CO) and ozone were continuously monitored, and pressurized air samples were collected and later analyzed in the laboratory for various volatile organic compounds. A sequence of alternating CO and propane rich events were observed over the east Atlantic, the events of enhanced carbon monoxide being out of phase with those observed for propane. A combined study of air mass origin ( back trajectories and backward emission sensitivity calculations) and source region distribution comparison ( CO satellite data from MOPITT and propane emission data from the EDGAR database) showed that the CO events were due to African biomass burning emissions, whereas the propane events were due to industrial emissions from areas of northern Africa. Both events were associated with elevated ozone. A comparison of the measured concentrations of CO and propane with those simulated by the global Model of Atmospheric Transport and Chemistry-Max Planck Institute for Chemistry (MATCH-MPIC) shows that the model reproduces the general longitudinal gradient observed for both compounds and simulates elevated CO concentrations during the pollution events. However, it systematically overestimates the CO mixing ratios. It is suggested that the northern African biomass burning emissions used in the model are not distributed correctly ( incorrect timing) and, in particular, that too high emissions from the region “northern Sudan-Sahel” are used for this period. The model does not capture the influence from industrial emissions from northern Africa, which may be caused by too strong diffusion of the plume.

We use an inverse model analysis to compare the top-down constraints on Asian sources of carbon monoxide (CO) in spring 2001 from (1) daily MOPITT satellite observations of CO columns over Asia and the neighboring oceans and (2) aircraft observations of CO concentrations in Asian outflow from the TRACE-P aircraft mission over the northwest Pacific. The inversion uses the maximum a posteriori method (MAP) and the GEOS-CHEM chemical transport model (CTM) as the forward model. Detailed error characterization is presented, including spatial correlation of the model transport error. Nighttime MOPITT observations appear to be biased and are excluded from the inverse analysis. We find that MOPITT and TRACE-P observations are independently consistent in the constraints that they provide on Asian CO sources, with the exception of southeast Asia for which the MOPITT observations support a more modest decrease in emissions than suggested by the aircraft observations. Our analysis indicates that the observations do not allow us to differentiate source types (i.e., anthropogenic versus biomass burning) within a region. MOPITT provides ten pieces of information to constrain the geographical distribution of CO sources, while TRACE-P provides only four. The greater information from MOPITT reflects its ability to observe all outflow and source regions. We conducted a number of sensitivity studies for the inverse model analysis using the MOPITT data. Temporal averaging of the MOPITT data (weekly and beyond) degrades the ability to constrain regional sources. Merging source regions beyond what is appropriate after careful selection of the state vector leads to significant aggregation errors. Calculations for an ensemble of realistic assumptions lead to a range of inverse model solutions that has greater uncertainty than the a posteriori errors for the MAP solution. Our best estimate of total Asian CO sources is 361 Tg yr(-1), over half of which is attributed to east Asia.

[ 1] Vertical profiles of carbon monoxide ( CO) mixing ratio retrieved from MOPITT measurements have been analyzed. We find that variations in the vertical structure of CO can be detected in the MOPITT data. The Asian summer monsoon plume in CO is observed for the first time as a strong enhancement of CO in the upper troposphere ( UT) over India and southern China indicating the effect of deep convective transport. Similarly, zonal mean height latitude cross-sections for the months of September-December, 2002 indicate deep convective transport of CO from biomass burning in the southern tropics. These findings show that MOPITT CO can provide valuable information on vertical transport phenomena in the troposphere.

[1] This study discusses an improved technique for the assimilation of carbon monoxide retrievals from the Measurements of Pollution in the Troposphere (MOPITT) instrument in a chemistry-transport model using a suboptimal Kalman filter. An online bias estimator algorithm is employed to identify systematic biases in the model and account for them during the assimilation. Results suggest a large decline ( both locally and globally) in the observation minus forecast diagnostics and provide insights about possible model deficiencies by enabling explicit examination of model biases.

The Measurements of Pollution in the Troposphere (MOPITT) Airborne Test Radiometer (MATR) uses gas correlation filter radiometry from high-altitude aircraft to measure tropospheric carbon monoxide. This radiometer is used in support of the ongoing validation campaign for the MOPITT instrument aboard the Earth Observation System Terra satellite. A recent study of MATR CO retrievals that used data from the autumn of 2001 in the western United States is presented. Retrievals of the CO total column were performed and compared to in situ sampling with less than 10 as instrument sensitivity, retrieval sensitivity, and the bias between observations and the radiative transfer model, are discussed. Comparisons of MATR and MOPITT retrievals show promising consistency. A preliminary interpretation of MATR results is also presented. (C) 2004 Optical Society of America.

This paper presents results of the inverse modeling of carbon monoxide surface sources on a monthly and regional basis using the MOPITT (Measurement Of the Pollution In The Troposphere) CO retrievals. The targeted time period is from April 2000 to March 2001. A sequential and time-dependent inversion scheme is implemented to correct an a priori set of monthly mean CO sources. The a posteriori estimates for the total anthropogenic (fossil fuel + biofuel + biomass burning) surface sources of CO in TgCO/yr are 509 in Asia, 267 in Africa, 140 in North America, 90 in Europe and 84 in Central and South America. Inverting on a monthly scale allows one to assess a corrected seasonality specific to each source type and each region. Forward CTM simulations with the a posteriori emissions show a substantial improvement of the agreement between modeled CO and independent in situ observations.

CO is a well-suited indicator for the transport of pollutants in the troposphere on a regional and global scale. For the study presented here, simulations of CO concentrations from a global chemistry transport model (MOZART-2), with the CO being tagged according to the emission type and the source region, have been used to diagnose the contributions of different processes and regions to the CO burden over Europe. Model simulations have been performed with both a priori emissions and an optimized set of CO surface emissions derived from the inversion of CO retrievals of the Measurements of Pollution in the Troposphere (MOPITT) remote sensing instrument. The annual mean difference between the modeled and the observed CO at 850 hPa over Europe is -38 +/- 13 ppb with the a priori set of emissions and -7 +/- 7 ppb when the optimized emissions are employed in the model. The general difficulties arising from an intercomparison of remote sensing data with model simulations are discussed. Besides data from MOPITT, ground-based CO measurements have been employed in the evaluation of the model and its emissions. The comparisons show that the model represents the background conditions as well as large-scale transport relatively well. The budget analysis reveals the predominant impact of the European emissions on CO concentrations near the surface, and a strong impact of sources from Asia and North America on the CO burden in the free troposphere over Europe. On average, the largest contribution (67 sources, biomass burning) CO at the surface originates from regional anthropogenic sources, but further significant impact is evident from North America (14 With increasing altitude, anthropogenic CO from Asia and North America gains in importance, reaching maximum contributions of 32 50 emissions weakens with increasing altitude (8 hPa).

The multi-year retrievals of carbon monoxide ( CO) by the MOPITT ( Measurements Of Pollution In The Troposphere) instrument onboard the NASA Terra satellite provide an opportunity for the first time to study quantitatively the transport and sources of pollution in the mid-troposphere. This paper presents the assimilation of the Phase I ( March 3, 2000 - May 6, 2001) MOPITT retrievals with optimized CO emissions constrained by monthly MOPITT CO data. The observed-minus-forecast (OmF) CO distributions illustrate improvement of this data analysis compared with the assimilation that employs climatological surface fluxes.

[1] Measurements of Pollution in the Troposphere (MOPITT) is a new remote sensing instrument aboard the Earth Observing System (EOS) “Terra” satellite which exploits gas correlation radiometry principles to quantify tropospheric concentrations of carbon monoxide (CO) and methane (CH4). The MOPITT CO retrieval algorithm employs a nonlinear optimal estimation method to iteratively solve for the CO profile which is statistically most consistent with both the satellite-measured radiances and a priori information. The algorithm's theoretical basis is described in terms of the observed radiances and their weighting functions, the a priori information, and the retrieval averaging kernels. Examples of actual CO retrievals over scenes with contrasting pollution conditions are demonstrated, and interpreted in the context of the retrieval averaging kernels and a priori.

[1] We use satellite sensor measurements to obtain a broad picture of the processes affecting tropical tropospheric O-3 production over Africa and the Atlantic in the early part of the year. Terra/MOPITT CO retrievals correlate well with biomass burning fire counts observed by the TRMM/VIRS instrument in Northern Hemisphere savanna regions and allow investigation of the subsequent convection of the biomass burning plume at the intertropical convergence zone and interhemispheric transport. Measurements of NO2 from the ERS-2/GOME instrument enable identification of two important tropical sources of this O-3 precursor, biomass burning and lightning. Good correlation is seen between NO2 retrievals and TRMM/LIS lightning flash observations in southern African regions free of biomass burning, thus indicating a probable lightning source of NOx. The combination of MOPITT CO, GOME NO2, and TRMM fire and lightning flash counts provides a powerful tool for investigating the tropospheric production of O-3 precursors. These data are used in conjunction with the MOZART-2 chemical transport model to investigate the early year tropical Atlantic tropospheric O-3 distribution using January 2001 as a case study. Inconsistencies between the various tropical tropospheric O-3 column products obtained from EP/TOMS data, and between these products, in situ measurements, and modeling, have led to questions about how the Northern Hemisphere biomass burning is connected to the TOMS derived O-3 maximum in the tropical southern Atlantic. We show that the early year tropical O-3 distribution is actually characterized by two maxima. The first arises due to biomass burning emissions, is located near the Northern Hemisphere fires, and is most evident in the lower troposphere. The second is located in the southern tropical Atlantic midtroposphere, and results from NOx produced by lightning over southern Africa and South America.

Satellite observations of carbon monoxide (CO) from the Measurements of Pollution in the Troposphere (MOPITT) instrument are combined with measurements from the Transport and Chemical Evolution Over the Pacific (TRACE-P) aircraft mission over the northwest Pacific and with a global three-dimensional chemical transport model (GEOS-CHEM) to quantify Asian pollution outflow and its trans-Pacific transport during spring 2001. Global CO column distributions in MOPITT and GEOS-CHEM are highly correlated (R-2 = 0.87), with no significant model bias. The largest regional bias is over Southeast Asia, where the model is 18 burning emissions in the model (to 39 Tg yr(-1)) would correct the discrepancy; this result is consistent with TRACE-P observations. MOPITT and TRACE-P also give consistent constraints on the Chinese source of CO from fuel combustion (181 Tg CO yr(-1)). Four major events of trans- Pacific transport of Asian pollution in spring 2001 were seen by MOPITT, in situ platforms, and GEOS-CHEM. One of them was sampled by TRACE-P (26-27 February) as a succession of pollution layers over the northeast Pacific. These layers all originated from one single event of Asian outflow that split into northern and southern plumes over the central Pacific. The northern plume (sampled at 6-8 km off California) had no ozone enhancement. The southern subsiding plume (sampled at 2-4 km west of Hawaii) contained a 8-17 ppbv ozone enhancement, driven by decomposition of peroxyacetylnitrate (PAN) to nitrogen oxides (NOx). This result suggests that PAN decomposition in trans- Pacific pollution plumes subsiding over the United States could lead to significant enhancements of surface ozone.

The NASA Transport and Chemical Evolution over the Pacific (TRACE-P) aircraft mission was conducted in February-April 2001 over the NW Pacific (1) to characterize the Asian chemical outflow and relate it quantitatively to its sources and (2) to determine its chemical evolution. It used two aircraft, a DC-8 and a P-3B, operating out of Hong Kong and Yokota Air Force Base (near Tokyo), with secondary sites in Hawaii, Wake Island, Guam, Okinawa, and Midway. The aircraft carried instrumentation for measurements of long-lived greenhouse gases, ozone and its precursors, aerosols and their precursors, related species, and chemical tracers. Five chemical transport models (CTMs) were used for chemical forecasting. Customized bottom-up emission inventories for East Asia were generated prior to the mission to support chemical forecasting and to serve as a priori for evaluation with the aircraft data. Validation flights were conducted for the Measurements Of Pollution In The Troposphere (MOPITT) satellite instrument and revealed little bias (6 +/- 2 columns. A major event of transpacific Asian pollution was characterized through combined analysis of TRACE-P and MOPITT data. The TRACE-P observations showed that cold fronts sweeping across East Asia and the associated warm conveyor belts (WCBs) are the dominant pathway for Asian outflow to the Pacific in spring. The WCBs lift both anthropogenic and biomass burning ( SE Asia) effluents to the free troposphere, resulting in complex chemical signatures. The TRACE-P data are in general consistent with a priori emission inventories, lending confidence in our ability to quantify Asian emissions from socioeconomic data and emission factors. However, the residential combustion source in rural China was found to be much larger than the a priori, and there were also unexplained chemical enhancements (HCN, CH3Cl, OCS, alkylnitrates) in Chinese urban plumes. The Asian source of CCl4 was found to be much higher than government estimates. Measurements of HCN and CH3CN indicated a dominant biomass burning source and ocean sink for both gases. Large fractions of sulfate and nitrate were found to be present in dust aerosols. Photochemical activity in the Asian outflow was strongly reduced by aerosol attenuation of UV radiation, with major implications for the concentrations of HOx radicals. New particle formation, apparently from ternary nucleation involving NH3, was observed in Chinese urban plumes.

[1] This study focuses on the identification of carbon monoxide ( CO) released during the forest fires that took place primarily in Montana and Idaho during the summer of 2000. We focus our analysis on the most intense period of the fires during the second half of August. During that period, the MOPITT instrument onboard the EOS-Terra platform collected extensive measurements of CO. A simulation of the dispersal of the CO from the fires, constrained by the AVHRR observations of fire location and extent, clearly identifies the affected regions. The model results are compared with the CO observations from the COBRA experiment flight on August 19. Using these various data, we are able to identify the transport of the CO plume originating from the fires. In particular, it is shown that the CO travels eastward from the fires, reaching as far as the East coast and the Gulf of Mexico in a few days. Although the distribution of CO over the U. S. is clearly a combination of a variety of sources it is found that wildfires are a strong component of the summer tropospheric CO.

[1] This study focuses on improvement to the modeling of the evolution of the model error variance in the problem of assimilating satellite observations of chemical species. The model error variance evolution equation for the assimilation of CO is described here with localized sources in addition to transport and error growth. The assimilation of carbon monoxide (CO) observations from MOPITT is performed using a sub-optimal Kalman filter in the MOZART-2 chemistry-transport model. It is shown that this new approach can dramatically improve the ability of the assimilation to diverge from erroneous model-generated features.

Four inversion schemes based on various retrieval approaches (digital gas correlation, nonlinear least squares, global fit adjustment, and neural networks) developed to retrieve CO from nadir radiances measured by such downward-looking satelliteborne instruments as the Measurement of Pollution in the Troposphere (MOPITT), the Tropospheric Emission Spectrometer (TES), and the Infrared Atmospheric Sounding Interferometer (IASI) instruments were compared both for simulated cases and for atmospheric spectra recorded by the Interferometric Monitor for Greenhouse Gases (IMG). The sensitivity of the retrieved CO total column amount to properties that may affect the inversion accuracy (noise, ancillary temperature profile, and water-vapor content) was investigated. The CO column amounts for the simulated radiance spectra agreed within 4 atmospheric spectra recorded by the IMG instrument were analyzed. The assumed vertical temperature profile is shown to be a critical parameter for accurate CO retrieval. The instrument's line shape was also identified as a possible cause of disagreement among the results provided by the groups of scientists who are participating in this study. (C) 2002 Optical Society of America.

Optical bandpass filters in the Measurements of Pollution in the Troposphere (MOPITT) satellite remote sensing instrument selectivity limit the throughput radiance to absorptive spectral bands associated with the satellite- observed trace gases CO and CH4. Precise specification of the spectral characteristics of these filters is required to optimize retrieval accuracy. The effects and potential causes of spectral shifts in the optical bandpass filter profiles are described. Specifically, a shift in the assumed bandpass profile produces a relative bias between the calibrated satellite radiances and the corresponding values calculated by an instrument- specific forward radiative transfer model. Conversely, it is shown that the observed bias (as identified and quantified using operational MOPITT satellite radiance data) can be used to determine the relative spectral shift between the nominal (prelaunch) filter profiles and the true operational (in orbit) profiles. Revising both the radiance calibration algorithm and the forward radiative transfer model to account for the revised filter profiles effectively eliminates the radiance biases.

The Measurements of Pollution in the Troposphere (MOPITT) instrument, which was launched aboard the Earth Observing System (EOS) Terra spacecraft on 18 December 1999, is designed to; measure tropospheric CO and CH4 by use of a nadir-viewing geometry. The measurements are taken at 4.7 mum in the thermal emission and absorption for the CO mixing ratio profile retrieval and at 2.3 and 2.2 mum in the reflected solar region for the total CO column amount and CH4 column amount retrieval, respectively. To achieve the required measurement accuracy, it is critical to identify and remove cloud contamination in the radiometric signals. We describe an algorithm to detect cloudy pixels, to reconstruct clear column radiance for pixels with partial cloud covers, and to estimate equivalent cloud top height for overcast conditions to allow CO profile retrievals above clouds. The MOPITT channel radiances, as well as the first-guess calculations, are simulated with a fast forward model with input atmospheric profiles from ancillary data sets. The precision of the retrieved CO profiles and total column amounts in cloudy atmospheres is within the expected +/-10 cloud-detecting thresholds with the moderate-resolution imaging spectroradiometer airborne simulator data and MOPITT airborne test radiometer measurements were performed. The validation results showed that the MOPITT cloud detection thresholds work well for scenes covered with more than 5-10 the model input profiles are less than 2 K for temperature, 10 Optical Society of America.

This paper presents a new radiative transfer model based on the correlated-k technique that is particularly suitable for applications associated with broadband infrared satellite remote sounding of the atmosphere. We describe new developments to the approach which improve the accuracy of correlated-k distribution radiative transfer calculations. These include methods to model an instrument response function, spectral line overlap for multiple: gases, and the spectral variation of solar and thermal source functions. We also describe all approach to improving vertical spectral correlation along ray paths through a nonhomogeneous atmosphere. For a radiative transfer model to be efficient as the forward model of a retrieval scheme, the calculation of analytical jacobians is particularly important. This is implemented in the model using a variation on the correlated-k approach. The application of the new model, RADCKD, is demonstrated with example calculations for the EOS Terra satellite Measurements of Pollution in the Troposphere (MOPITT) instrument.

The Measurement of Pollution in the Troposphere (MOPITT) instrument is an eight-channel gas correlation radiometer selected for the Earth Observing System (EOS) Terra spacecraft launched in December 1999. Algorithms for the retrieval of tropospheric carbon monoxide (CO) profiles from MOPITT measurements have been developed, in this paper, validation studies of the MOPITT CO retrieval algorithm using observations by the Interferometric Monitor for greenhouse Gases (IMG) during the Winter Clouds Experiment (WINCE) conducted from 23 January to 13 February 1997 are described. Synthetic radiance spectra calculated by a line-byline radiative transfer model, FASCOD3, using the retrieved CO profile agrees well with IMG-measured radiance spectra. Observations by the Moderate Resolution Imaging Spectrometer (MODIS) Airborne Simulator (MAS) from the NASA ER-2 platform during WINCE were successfully used to assist in the identification of clear and cloudy IMG observations.

This paper describes the radiative transfer modeling effort in support of the EOS Measurements of Pollution in the Troposphere (MOPITT) instrument. MOPITT is due to be launched on the AM-1 Terra platform in the summer of 1999 and is a nadir-viewing gas correlation radiometer designed to measure CO and CH4 in the troposphere using a CO thermal channel at 4.7 mu m and reflected solar channels for CO at 2.3 mu m and CH4 at 2.2 mu m. We describe the spectroscopic considerations and radiative transfer studies that have been performed for this instrument and the implications for operational algorithm design. We outline the construction of MOPITT project forward models, both the research codes and the fast transmittance module that forms part of the operational retrieval algorithm. Several different approaches have been considered for these models: full line-by-line calculations using the general purpose line-by-line transmittance and radiance model GENLN2, absorption coefficient look-up tables, and regression techniques using a recurrence parameterization of transmittance. These models are capable of reproducing MOPITT channel signals and their dependence on temperature, viewing geometry, and the mixing ratios of target and contaminating gases.

Measurement of Pollution in the Troposphere (MOPITT) is an eight-channel gas correlation radiometer selected for the Earth Observing System AM-1 platform to be launched in 1999. Its primary objectives are the measurement of tropospheric carbon monoxide (CO) and methane (CH4). In this paper, the sensitivities of instrument signals and CO retrieval errors to various instrument parameters, especially the gas cell pressure and temperature variations, instrument radiometric noise, and ancillary data errors (such as atmospheric temperature and water vapor profile errors), are presented and discussed. In the MOPITT pressure modulator sell pressure sensitivity study, the instrument calibration process is considered, which leads to the relaxation of previous stringent requirements on the accuracy of in-orbit cell pressure monitoring. The approach of MOPITT CO retrieval error analysis is described, and the error analysis results are compared with retrieval simulation statistics. The error analysis results indicate that tropospheric CO distributions can be retrieved with a precision of 10 troposphere.

Global tropospheric carbon monoxide (CO) distributions can be retrieved from observations by spaceborne gas correlation radiometers and high-resolution interferometers. The Measurement of Pollution in the Troposphere (MOPITT) is a gas correlation radiometer designed for tropospheric CO and CH4 remote sensing. It is being developed at the University of Toronto and the National Center for Atmospheric Research for launch on the EOS/AM-1 platform in 1999. Spaceborne high-resolution interferometers with troposphere CO remote sensing capability include the Interferometric Monitor for Greenhouse gases (IMG) instrument and the Troposphere Emission Spectrometer (TES). IMG was developed by the Ministry of International Trade and Industry (MITI) of Japan. It was on the ADEOS-1 spacecraft launched in October 1996. TES is being developed by the Jet Propulsion Laboratory for launch on the EOS/CHEM-1 platform in 2002. For the purpose of testing the MOPITT data processing algorithms before launch, a new digital gas correlation (DGC) method was developed. This method makes it possible to use existing IMG observations to validate the MOPITT retrieval algorithms. The DGC method also allows the retrieval of global troposphere CO from MOPITT, IMG, and TES observations with a consistent algorithm. The retrieved CO profiles can be intercompared, and a consistent long time series of tropospheric CO measurements can be created. In this paper, the DGC method is described. The procedures for using the DGC method to retrieve atmospheric trace species profiles are discussed. As an example, CO profiles from IMG observations have been retrieved with the DGC method as a demonstration of its feasibility and application in MOPITT retrieval algorithm validation.

This paper discusses the retrieval scheme associated with the gas correlated radiometer-MOPITT which will be on board of EDS-AM 1 to measure the global vertical profiles of carbon monoxide. The vertical resolution and retrieval errors caused by errors in the temperature profiles and in the surface temperature have been assessed. The main results are: a. Assuming the noise equivalent radiance (NER) of 1.8 x 10(5) W m(-2) sr(-1), the surface tem perature can be deduced from the wide band signals with uncertainty less than 1 K, and the atmospheric term of the modulated signal can be deduced with errors almost equal to the NER which does not significantly increase errors in the retrieved CO profiles. b. With typical uncertainty in temperature profiles, errors in the retrieved profiles at latitudes lower than 70 degrees are generally less than 20 with the first guess of 100 ppbv. (If a better first guess was used, the errors may decrease). c. By incorporating the total column CO amount derived from the reflected solar radiation in 2.3 mu m spectral region into the retrieval, the accuracy of the retrieved CO profile below 6 km may be greatly improved. d. In the retrieval experiment with 10 CO profiles representing the typical CO profiles, the r.m.s. relative / absolute errors of the retrieved CO profiles are