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Recent regulatory policies in East Asia reduce ozone precursors, but these changes are spatially and temporally nonuniform. This study investigates variations in the long-term trends of tropospheric NO2, HCHO, and HCHO/NO2 ratios to diagnose ozone sensitivity to changes in NOx and volatile organic compound using the Ozone Monitoring Instrument (OMI). Using an adaptive-degree polynomial filter, we identify extremums of time series of NO2 to determine when and how NO2 change. Due to the regulations in China, trends which were predominantly upward turned downward. The years undergoing these changes primarily happened in 2011 and 2012. OMI column densities, however, suggest that NOx sources in South Korea, the Pearl River Delta (PRD), Taiwan, and Japan have not consistently decreased. Specifically, as Chinese exports of NO2 started subsiding, increasing trends in NO2 columns over several Korean cities, including Seoul, become evident. To quantify the changes in NOx emissions from summertime 2010 to 2014, we conduct a 3D-Var inverse modeling using a regional model with MIX-Asia inventory and estimate NOx emissions (in 2010 and 2014) for the PRD (1.6 and 1.5 Gg/d), the Yangtze River Delta (3.9 and 3.0 Gg/d), north China (15.6 and 14.3 Gg/d), South Korea (1.6 and 1.5 Gg/d), and Japan (2.7 and 2.6 Gg/d). OMI HCHO shows upward trends in East Asia resulting from anthropogenic effects; however, the magnitudes are negative in the PRD, Japan, North Korea, and Taiwan. OMI HCHO/NO2 ratios reveal that while South Korea, Japan, and the south of China have undergone toward more NOx-sensitive regime, areas around the Bohai Sea have become more NOx saturated.

[1] Potential impacts of global climate change and emissions on the total nitrogen and sulfur deposition over the US are investigated. Three future years' annual average deposition rates (i.e., 2049–2051) are compared with historic ones (i.e., 2000–2002) accounting for existing US and individual State's emission regulations and strategies. Impacts of global climate change alone on regional nitrogen and sulfur deposition are small compared to impacts from emission control-related reductions for the projections used in this study. The combined effect of climate change and emission reductions is a decrease in the annual average nitrogen and sulfur deposition over the US. Reduced nitrogen species dominate oxidized nitrogen deposition in the future. Spatial distribution plots for both components show lower deposition rates in the future mainly in the middle and eastern States where reductions in NOx and SO2 emissions are more pronounced.

[1] High resolution in situ measurements of atmospheric CO2 were made from the NASA DC-8 aircraft during the Intercontinental Chemical Transport Experiment–North America (INTEX-NA) campaign, part of the wider International Consortium for Atmospheric Research on Transport and Transformation (ICARTT). During the summer of 2004, eighteen flights comprising 160 h of measurements were conducted within a region bounded by 27 to 53°N and 36 to 139°W over an altitude range of 0.15 to 12 km. These large-scale surveys provided the opportunity to examine the characteristics of the atmospheric CO2 signal over sparsely sampled areas of North America and adjacent ocean basins. The observations showed a high degree of variability (≤18%) due to the myriad source and sink processes influencing the air masses intercepted over the INTEX-NA sampling domain. Surface fluxes had strong effects on continental scale concentration gradients. Clear signatures of CO2 uptake were seen east of the Mississippi River, notably a persistent CO2 deficit in the lowest 2–3 km. When combining the airborne CO2 measurements with LANDSAT and MODIS data products, the lowest CO2 mixing ratios observed during the campaign (337 ppm) were tied to mid-continental agricultural fields planted in corn and soybeans. We used simultaneous measurements of CO, O3, C2Cl4, C2H6, C2H2 and other unique chemical tracers to differentiate air mass types. Coupling these distinct air mass chemical signatures with transport history permitted identification of convection, stratosphere-troposphere exchange, long-range transport from Eastern Asia, boreal wildfires, and continental outflow as competing processes at multiple scales influencing the observed concentrations. Our results suggest these are important factors contributing to the large-scale distribution in CO2 mixing ratios thus these observations offer new constraints in the computation of the North American carbon budget.

Simulated future summers (i.e., 2049-2051) and annual (i.e., 2050) average regional O 3 and PM2.5 concentrations over North America are compared with historic (i.e., 2000-2002 summers and all of 2001) levels to investigate the potential impacts of global climate change on regional air quality. Meteorological inputs to the CMAQ chemical transport model are developed by downscaling the GISS Global Climate Model simulations using an MM5-based regional climate model. Future-year emissions for North America are developed by growing the US EPA CAIR inventory, Mexican and Canadian emissions and by using the IMAGE model with the IPCC A1B emissions scenario that is also used in projecting future climate. Reductions of more than 50% in NOX and SO2 emissions are forecast. The impacts of global climate change alone on regional air quality are small compared to impacts from emission control-related reductions in the US and Canada. The combined effect of climate change and emission reductions lead to a 20% decrease (regionally varying from -11% to -28% regionally) in the mean summer maximum daily 8-hr ozone levels (M8hO3) over the US, -8% over Canada and -10% over Northern Mexico. The mean annual PM2.5 concentrations are estimated to be 23% lower (varies from -9% tomore » -32%) over the US, -7% and -15% over Western and Eastern Canada, respectively and -25% over Northern Mexico. Major reductions are expected in sulfate, nitrate and ammonium fractions of annually-averaged PM2.5 for all sub-regions. The limited reduction in organic carbon over the US and Northern Mexico and the higher concentrations over Canada suggests that organic carbon will be the dominant component of PM2.5 mass over most of the continent in the future. Regionally, the Eastern US benefits more than the rest of the regions from reductions in both M8hO3 and PM2.5, due to both spatial variations in the meteorological and emissions changes. Reduction in the higher M8hO3 concentrations is also estimated for all sub-regions and less days with M8hO3 above the air quality standards in urban sites with Atlanta in the Southeast benefiting most.« less

[1] The regional radiative impact of biomass-burning aerosols in Asia is estimated using the new and detailed emission data during the experimental period of Transport and Chemical Evolution over the Pacific (TRACE-P) in March 2001. Integration of the USA National Oceanic and Atmospheric Administration (NOAA) Hybrid Single-Particle Lagrangian Integrated Transport model (HYSPLIT) and a solar radiative transfer model (CLIRAD-SW) allow us to simulate the spatial and temporal distributions of black carbon (BC) and organic carbon (OC) aerosols from biomass burning in the South Asian region. It also allows us to estimate further their aerosol optical properties and radiative forcing. We find that an anticyclone over Bay of Bengal dominates the transport of pollutants of the South Asian region. The monthly mean surface concentration of OC and BC is 1.1 μg m−3 in this region. Western Myanmar has the maximum value, with the concentration reaching 12.5 μg m−3. The monthly mean clear-sky direct shortwave radiative forcing ranges from −1.9 to 0.4 W m−2 at the top of the atmosphere and from −0.5 to −12.0 W m−2 at surface, resulting in an increase of the atmospheric heating rate from 0.01 to 0.3°C day−1. Owing to the spatial distributions of the aerosol optical depth ratio (OC/BC) and the surface albedo, there is a strong gradient of heating rate near the source regions, which may modify local circulations.

[1] Mercury tracer model simulations are performed to support the analysis of the total gas phase mercury (TGM) observations on 15 flights of the NSF/NCAR C-130 aircraft during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) campaign conducted during April 2001. Ninety-seven percent of the observed mercury concentrations are greater than 1.2 ng/m3. The mean value of the observations is 1.9 ng/m3. No simple relationships between Hg-CO and Hg-total sulfur are found; however, strong correlations are observed in individual flight segments. Backward trajectory analysis is used to help characterize regional of Hg/CO ratios, and these are compared with emission-based ratios from the various sectors. Model predictions using new Hg emission estimates are presented and compared to the observations. Under the condition of a mercury background level of 1.2 ng/m3 the tracer model underestimates the observations when the flights were over the Yellow Sea but is consistent with the observations when the flights were over the Japan Sea. Further analysis suggests that Hg emissions are underestimated in north central China and the eastern coastal areas of China. Model sensitivity studies indicate that the emissions of China may be underestimated by 80–200%.

[1] Measurements from the Transport and Chemical Evolution over the Pacific (TRACE-P) and Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) field experiments obtained during the period of March–April 2001 are used to evaluate the impact of megacity emissions on regional air quality in east Asia. A classification method built upon back trajectory analysis and sensitivity runs using the Sulfur Transport and Emissions Model 2001 (STEM-2K1) regional chemical transport model are used to identify the aircraft observations that were influenced by megacity emissions. More than 30% of measurement points are classified as urban points, with a significant number of plumes found to have originated from Shanghai, Qingdao, Beijing, Taiyuan, Tianjin and Guiyang, Seoul, and Pusan. These data are then analyzed, and chemical characteristics of these megacities are compared. Emission estimates for the megacities are also presented and discussed in the context of expected similarities and differences in the chemical signals in the ambient air impacted by these cities. Comparisons of the observation-based ratios with emission-based estimates are presented and provide a means to test for the consistency of the emission estimates. The observation-based ratios are shown to be generally consistent with the emissions ratios. The megacity emissions are used in the STEM-2K1 model to study the effects of these emissions on criteria and photochemical species in the region. Over large portions of the Japan Sea, Yellow Sea, western Pacific Ocean, and the Bay of Bengal, megacity emissions contribute in excess of 10% of the near-surface ambient levels of O3, CO, SO2, H2SO4, HCHO, and NOz. The megacity emissions are also used to study ozone levels in Asia under a scenario where all cities evolve their emissions in a manner such that they end up with the same VOC/NOx emission ratio as that for Tokyo. Monthly mean ozone levels are found to increase by at least 5%.

[1] We evaluate the TRACE-P emission inventories for gaseous and particulate pollutants from East Asia using chemical measurements made at a rural site in China during the China-MAP Field Intensive in conjunction with a coupled regional climate/chemical transport modeling system. Time-dependent, three-dimensional fields for trace gas and particulate matter concentrations over East Asia are simulated by an updated version of the Regional Acid Deposition Model (RADM) driven by the TRACE-P emission inventories along with meteorology fields calculated by the NCAR Regional Climate Model (RegCM) for the month of November 1999. Model-calculated SO2 is in good agreement with measurements, while CO and particulate carbon (PC) are significantly smaller, and particulate sulfate (SO4� ) is somewhat smaller. Our calculations suggest that increases in the TRACE-P emission inventory of CO by � 50% and PC by 60–90% would bring the model-calculated CO, PC, and particulate sulfate concentration into agreement with the China-MAP observations. If these increases were spread uniformly throughout China and the year, it would require that there be additional emissions in China of CO and PC of 60 Tg yr � 1 and 2.5–4 Tg yr � 1 , respectively. Further analysis of high resolution gas species measurements suggests that the missing CO emissions are likely to be associated with SO2 emissions from coal burning. This in turn suggests that coal-burning facilities in China are operating at significantly lower efficiencies than currently assumed. INDEX TERMS: 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry; KEYWORDS: anthropogenic emissions, East Asia, regional modeling

[ 1] Regional modeling analysis for the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) experiment over the eastern Pacific and U. S. West Coast is performed using a multiscale modeling system, including the regional tracer model Chemical Weather Forecasting System (CFORS), the Sulfur Transport and Emissions Model 2003 (STEM-2K3) regional chemical transport model, and an off-line coupling with the Model of Ozone and Related Chemical Tracers ( MOZART) global chemical transport model. CO regional tracers calculated online in the CFORS model are used to identify aircraft measurement periods with Asian influences. Asian-influenced air masses measured by the National Oceanic and Atmospheric Administration (NOAA) WP-3 aircraft in this experiment are found to have lower DeltaAcetone/DeltaCO, DeltaMethanol/DeltaCO, and DeltaPropane/DeltaEthyne ratios than air masses influenced by U. S. emissions, reflecting differences in regional emission signals. The Asian air masses in the eastern Pacific are found to usually be well aged (> 5 days), to be highly diffused, and to have low NOy levels. Chemical budget analysis is performed for two flights, and the O-3 net chemical budgets are found to be negative ( net destructive) in the places dominated by Asian influences or clear sites and positive in polluted American air masses. During the trans-Pacific transport, part of gaseous HNO3 was converted to nitrate particle, and this conversion was attributed to NOy decline. Without the aerosol consideration, the model tends to overestimate HNO3 background concentration along the coast region. At the measurement site of Trinidad Head, northern California, high-concentration pollutants are usually associated with calm wind scenarios, implying that the accumulation of local pollutants leads to the high concentration. Seasonal variations are also discussed from April to May for this site. A high-resolution nesting simulation with 12-km horizontal resolution is used to study the WP-3 flight over Los Angeles and surrounding areas. This nested simulation significantly improved the predictions for emitted and secondary generated species. The difference of photochemical behavior between the coarse (60-km) and nesting simulations is discussed and compared with the observation.

In this paper, aerosol composition and size distributions in east Asia are simulated using a comprehensive chemical transport model. Three-dimensional aerosol simulations for the TRACE-P and ACE-Asia periods are performed and used to help interpret actual observations. The regional chemical transport model, STEM-2K3, which includes the on-line gas-aerosol thermodynamic module SCAPE II, and explicitly considers chemical aging of dust, is used in the analysis. The model is found to represent many of the important observed features. The Asian outflow during March and April of 2001 is heavily polluted with high aerosol loadings. Under conditions of low dust loading, SO_2 condensation and gas phase ammonia distribution determine the nitrate size and gas-aerosol distributions along air mass trajectories, a situation that is analyzed in detail for two TRACE-P flights. Dust is predicted to alter the partitioning of the semivolatile components between the gas and aerosol phases as well as the size distributions of the secondary aerosol constituents. Calcium in the dust affects the gas-aerosol equilibrium by shifting the equilibrium balance to an anion-limited status, which benefits the uptake of sulfate and nitrate, but reduces the amount of aerosol ammonium. Surface reactions on dust provide an additional mechanism to produce aerosol nitrate and sulfate. The size distribution of dust is shown to be a critical factor in determining the size distribution of secondary aerosols. As much of the dust mass is found in the supermicron mode (70–90%), appreciable amounts of sulfate and nitrate are found in the supermicron particles. For sulfate the observations and the analysis indicate that 10–30% of sulfate is in the supermicron fraction during dust events; in the case of nitrate, more than 80% is found in the supermicron fraction.

[1] An extensive set of carbonyl sulfide (OCS) and carbon disulfide (CS2) observations were made as part of the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) project, which took place in the early spring 2001. TRACE-P sampling focused on the western Pacific region but in total included the geographic region 110°E to 290°E longitude, 5°N to 50°N latitude, and 0–12 km altitude. Substantial OCS and CS2 enhancements were observed for a great many air masses of Chinese and Japanese origin during TRACE-P. Over the western Pacific, mean mixing ratios of long-lived OCS and shorter-lived CS2 showed a gradual decrease by about 10% and a factor of 5–10, respectively, from the surface to 8–10 km altitude, presumably because land-based sources dominated their distribution during February through April 2001. The highest mean OCS and CS2 levels (580 and 20 pptv, respectively, based on 2.5° × 2.5° latitude bins) were observed below 2 km near the coast of Asia, at latitudes between 25°N and 35°N, where urban Asian outflow was strongest. Ratios of OCS versus CO for continental SE Asia were much lower compared to Chinese and Japanese signatures and were strongly associated with biomass burning/biofuel emissions. We present a new inventory of anthropogenic Asian emissions (including biomass burning) for OCS and CS2 and compare it to emission estimates based on regional relationships of OCS and CS2 to CO and CO2. The OCS and CS2 results for the two methods compare well for continental SE Asia and Japan plus Korea and also for Chinese CS2 emissions. However, it appears that the inventory underestimates Chinese emissions of OCS by about 30–100%. This difference may be related to the fact that we did not include natural sources such as wetland emissions in our inventory, although the contributions from such sources are believed to be at a seasonal low during the study period. Uncertainties in OCS emissions from Chinese coal burning, which are poorly characterized, likely contribute to the discrepancy.

[1] A comprehensive regional-scale chemical transport model, Sulfur Transport and Emissions Model 2001 (STEM-2K1), is employed to study dust outflows and their influence on regional chemistry in the high-dust Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) period, from 4–14 April 2001. In this period, dust storms are initialized in the Taklamagan and Gobi deserts because of cold air outbreaks, are transported eastward, and are often intensified by dust emitted from exposed soils as the front moves off the continent. Simulated dust agrees well with surface weather observations, satellite images, and the measurements of the C-130 aircraft. The C-130 aircraft observations of chemical constituents of the aerosol are analyzed for dust-rich and low-dust periods. In the submicron aerosol, dust-rich air masses have elevated ratios of ΔCa/ΔMg, ΔNH4+/ΔSO42−, and ΔNO3−/ΔCO (Δ represents the difference between observed and background concentrations). The impacts of heterogeneous reactions on dust involving O3, NO2, SO2, and HNO3 are studied by incorporating these reactions into the analysis. These reactions have significant influence on regional chemistry. For example, the low O3 concentrations in C-130 flight 6 can be explained only by the influence of heterogeneous reactions. In the near-surface layer, the modeled heterogeneous reactions indicated that O3, SO2, NO2, and HNO3 are decreased by up to 20%, 55%, 20%, and 95%, respectively, when averaged over this period. In addition, NO, HONO, and daytime OH can increase by 20%, 30%, and 4%, respectively, over polluted regions. When dust encounters fresh pollutants, these heterogeneous reactions can lead to a series of complex responses of the photochemical system. In addition, these reactions can alter the chemical-size distribution of the aerosol. Under heavy dust loadings, these reactions can lead to >20% of the sulfate and >70% of the nitrate being associated with the coarse fraction. The radiative influence of dust can also affect the photochemical system. For example, OH levels can decrease by 20% near surface. The dust radiative influence is shown to be weaker than the heterogeneous influence for most species.

[1] We present a global tabulation of black carbon (BC) and primary organic carbon (OC) particles emitted from combustion. We include emissions from fossil fuels, biofuels, open biomass burning, and burning of urban waste. Previous ‘‘bottom-up’’ inventories of black and organic carbon have assigned emission factors on the basis of fuel type and economic sector alone. Because emission rates are highly dependent on combustion practice, we consider combinations of fuel, combustion type, and emission controls and their prevalence on a regional basis. Central estimates of global annual emissions are 8.0 Tg for black carbon and 33.9 Tg for organic carbon. These estimates are lower than previously published estimates by 25–35%. The present inventory is based on 1996 fuel-use data, updating previous estimates that have relied on consumption data from 1984. An offset between decreased emission factors and increased energy use since the base year of the previous inventory prevents the difference between this work and previous inventories from being greater. The contributions of fossil fuel, biofuel, and open burning are estimated as 38%, 20%, and 42%, respectively, for BC, and 7%, 19%, and 74%, respectively, for OC. We present a bottom-up estimate of uncertainties in source strength by combining uncertainties in particulate matter emission factors, emission characterization, and fuel use. The total uncertainties are about a factor of 2, with uncertainty ranges of 4.3–22 Tg/yr for BC and 17–77 Tg/yr for OC. Low-technology combustion contributes greatly to both the emissions and the uncertainties. Advances in emission characterization for small residential, industrial, and mobile sources and topdown analysis combining field measurements and transport modeling with iterative inventory development will be required to reduce the uncertainties further. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 0360 Atmospheric Composition and Structure: Transmission and scattering of radiation; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry; KEYWORDS: emission, black carbon, organic carbon, fossil fuel, biofuel, biomass burning

[1] We report on mercury in the atmosphere of east Asia (Japan, Korea, and China) as measured from sea level to ∼7000 m during 16 research flights in the National Science Foundation (NSF)/National Center for Atmospheric Research (NCAR) C-130 aircraft during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) campaign (http://saga.pmel.noaa.gov/aceasia/). The air at all altitudes contained concentrations of atmospheric mercury above the global background. The atmosphere was highly stratified with plumes originating from massive dust storms carried out of China, from local industrial pollution, from volcanoes, and, less well defined, from biomass burning. Most often the air masses were mixtures, e.g., dust layers contained anthropogenic emissions or volcanic plumes were embedded in anthropogenic pollution; thus the total data set showed no significant correlations of gaseous mercury with the most common anthropogenic pollutants in the area (CO and SO2), but good correlations were observed for identifiable plumes. Highest mixing ratios for gaseous elemental mercury (GEM) were found in industrial plumes exiting China (∼6.3 ng/m3), Korea (∼3 ng/m3), and Japan (∼3 ng/m3). The core of the plume from Miyake Jima volcano contained ∼3.7 ng/m3 of GEM. Crustal mercury was also present, emitted and subsequently deposited during the outbreak of the spring dust storms. Some of the nondust aerosols contained soluble mercury in highly variable ratios with the gas-phase mercury contained in the same plume. Preliminary estimates for the export from China are 5–15 t of crustal mercury during the dust storms, ∼150 t/yr of gas-phase mercury from biomass/biofuel combustion, and ∼600 t/yr from industrial sources, mostly from coal combustion. Gaseous mercury is a useful tracer for industrial, volcanic, and biomass-burning sources, but in most cases, robust plume identification required one or more cotracers. Because of the inertness of GEM and the ease of its measurement it is well suited for the tracking of long-range transport.

[1] A comprehensive emission inventory with enhanced spatial and temporal resolution is used to help quantify the contribution from three source categories (fossil, biofuel, and biomass burning) during the NASA TRACE-P experiment. Daily biomass burning emissions are developed to support this analysis. Emissions of 27 species and their ratios, by sector, region, and source category are presented. The emission distributions and chemical composition are further analyzed using various statistical techniques. Using cluster analysis, the 27 chemical species are combined into 8 groups that have similar regional distribution, and 52 regions are assembled into 11 regional groups that have similar chemical composition. These groups are used in Chemical Mass Balance analysis to characterize air masses and to quantify the contribution of the three source categories to the observed species distributions. Five DC8 flights with 16 flight segments associated with outflow events are analyzed. In general, Asian outflow is a complex mixture of biofuel, biomass, and fossil sources. Flights in the post frontal regions at high latitudes and low altitudes have a high contribution of fossil fuel emissions. Flights in the warm sector of cold fronts are dominated by biomass burning contributions (about 70%). Biofuel contributions are high (about 70%) when air masses come from central China. The receptor model results are shown to be consistent with other 3-D chemical model sensitivity studies and analysis using ratios of indicator species (e.g., dK+/dSO42−, CH3CN/SOy, SOy/CO, and C2Cl4/CO).

[1] Measurements obtained during the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) experiment are used in conjunction with regional modeling analysis to evaluate emission estimates for Asia. A comparison between the modeled values and the observations is one method to evaluate emissions. Based on such analysis it is concluded that the inventory performs well for the light alkanes, CO, ethyne, SO2, and NOx. Furthermore, based on model skill in predicting important photochemical species such as O3, HCHO, OH, HO2, and HNO3, it is found that the emissions inventories are of sufficient quality to support preliminary studies of ozone production. These are important finding in light of the fact that emission estimates for many species (such as speciated NMHCs and BC) for this region have only recently been estimated and are highly uncertain. Using a classification of the measurements built upon trajectory analysis, we compare observed species distributions and ratios of species to those modeled and to ratios estimated from the emissions inventory. It is shown that this technique can reconstruct a spatial distribution of propane/benzene that looks remarkably similar to that calculated from the emissions inventory. A major discrepancy between modeled and observed behavior is found in the Yellow Sea, where modeled values are systematically underpredicted. The integrated analysis suggests that this may be related to an underestimation of emissions from the domestic sector. The emission is further tested by comparing observed and measured species ratios in identified megacity plumes. Many of the model derived ratios (e.g., BC/CO, SOx/C2H2) fall within ∼25% of those observed and all fall outside of a factor of 2.5.

[1] Data obtained during the TRACE-P experiment is used to evaluate how well the CFORS/STEM-2K1 regional-scale chemical transport model is able to represent the aircraft observations. Thirty-one calculated trace gas and aerosol parameters are presented and compared to the in situ data. The regional model is shown to accurately predict many of the important features observed. The mean values of all the model parameters in the lowest 1 km are predicted within ±30% of the observed values. The correlation coefficients (R) for the meteorological parameters are found to be higher than those for the trace species. For example, for temperature, R > 0.98. Among the trace species, ethane, propane, and ozone show the highest values (0.8 < R < 0.9), followed by CO, SO2, and NOy. NO and NO2 had the lowest values (R < 0.4). Analyses of pollutant transport into the Yellow Sea by frontal events are presented and illustrate the complex nature of outflow. Biomass burning from SE Asia is transported in the warm conveyor belt at altitudes above ∼2 km and at latitudes below 30N. Outflow of pollution emitted along the east coast of China in the postfrontal regions is typically confined to the lower ∼2 km and results in high concentrations with plume-like features in the Yellow Sea. During these situations the model underpredicts CO and black carbon (among other species). An analysis of ozone production in this region is also presented. In and around the highly industrialized regions of East Asia, where fossil fuel usage dominates, ozone is NMHC-limited. South of ∼30–35N, ozone production is NOx-limited, reflecting the high NMHC/NOx ratios due to the large contributions to the emissions from biomass burning, biogenics sources, and biofuel usage in central China and SE Asia.

[1] A three-dimensional regional chemical transport model, STEM 2K1, coupled with a detailed radiation model is used to study the influences of aerosols and clouds on photolysis rates and photochemical processes over East Asia-Western Pacific during the TRACE-P period. Measured J-values are compared with those calculated using three-dimensional modeled fields of clouds and aerosols. The model is shown to accurately represent observed J-values over a broad range of conditions. Model studies with and without aerosols and clouds are performed and compared with clear-sky conditions to isolate the various influences. Clouds are shown to have a large impact on photolysis rates during the observation periods of TRACE-P, with J[NO2] decreased by 20% below clouds and enhanced by ∼30% from 1 km to 8 km. Clouds also exert a dominant influence on short-lived radicals, like OH and HO2. For March, clouds reduce OH by 23% at altitudes below 1 km and increase OH by ∼25% above 1 km. Asian aerosols contain large amounts of carbonaceous material, inorganic components such as sulfates, and mineral oxides. These aerosols significantly influence J-values and photochemical processes. When averaged over all TRACE-P DC-8 and P-3 flights, the aerosol influence via affecting J-values reduces OH by ∼40% below 1 km, and by ∼24% above 1 km. Aerosols have a stronger impact on longer-lived chemical species than clouds do because aerosols tend to be coemitted with precursors and have a longer contact time with the polluted air masses. The accumulated aerosol impact generally is to reduce O3 concentrations by about 6 ppbv in the biomass burning plumes emitted from Southeast Asia. In megacity plumes, aerosols can increase NOx concentration by 40% via reducing its photolytic loss and reduce NOz concentration by a similar amount. A detailed case study of the DC-8 and P-3 flights on 27 March is used to make comparisons for cloud and aerosol influences. During these flights, the cloud impact on J-values is stronger than the aerosol impact, but aerosols are shown to exert a much stronger accumulated influence on O3 production.

[1] An inventory of air pollutant emissions in Asia in the year 2000 is developed to support atmospheric modeling and analysis of observations taken during the TRACE-P experiment funded by the National Aeronautics and Space Administration (NASA) and the ACE-Asia experiment funded by the National Science Foundation (NSF) and the National Oceanic and Atmospheric Administration (NOAA). Emissions are estimated for all major anthropogenic sources, including biomass burning, in 64 regions of Asia. We estimate total Asian emissions as follows: 34.3 Tg SO2, 26.8 Tg NOx, 9870 Tg CO2, 279 Tg CO, 107 Tg CH4, 52.2 Tg NMVOC, 2.54 Tg black carbon (BC), 10.4 Tg organic carbon (OC), and 27.5 Tg NH3. In addition, NMVOC are speciated into 19 subcategories according to functional groups and reactivity. Thus we are able to identify the major source regions and types for many of the significant gaseous and particle emissions that influence pollutant concentrations in the vicinity of the TRACE-P and ACE-Asia field measurements. Emissions in China dominate the signature of pollutant concentrations in this region, so special emphasis has been placed on the development of emission estimates for China. China's emissions are determined to be as follows: 20.4 Tg SO2, 11.4 Tg NOx, 3820 Tg CO2, 116 Tg CO, 38.4 Tg CH4, 17.4 Tg NMVOC, 1.05 Tg BC, 3.4 Tg OC, and 13.6 Tg NH3. Emissions are gridded at a variety of spatial resolutions from 1° × 1° to 30 s × 30 s, using the exact locations of large point sources and surrogate GIS distributions of urban and rural population, road networks, landcover, ship lanes, etc. The gridded emission estimates have been used as inputs to atmospheric simulation models and have proven to be generally robust in comparison with field observations, though there is reason to think that emissions of CO and possibly BC may be underestimated. Monthly emission estimates for China are developed for each species to aid TRACE-P and ACE-Asia data interpretation. During the observation period of March/April, emissions are roughly at their average values (one twelfth of annual). Uncertainties in the emission estimates, measured as 95% confidence intervals, range from a low of ±16% for SO2 to a high of ±450% for OC.

(� HCN/� CO � 0.0015) and potassium (� K + /� CO � 0.0038) but very low NOy (� NOy/ � CO � 0.005) mixingratios,whichmaybeassociated withthespecialburning condition in this region. The biomass burning air masses have high ozone production efficiency. The observedO3/� NOz values were � 17 in biomass events and 1.7 in other events. The BB influence on the trace gas distributions can be divided into two categories: the influence through direct reactions and the influence caused by BB aerosols changing J values. These two influences are discussed for the BB-affected TRACE-P flights and for east Asia. The BBinfluencesonchemicalspeciesarenotonlydeterminedbytheBBplumeintensitybutalso bytheambientenvironmentcausedbyotheremissions.InSoutheastAsia,wherethebiogenic emissions are very strong, the OH background concentration is low, and the BB gas-phase compounds mainly contribute to OH production. Arranged in the sensitivity to the J value change caused by BB aerosols, we have OH > HO2 > HCHO > O3 when evaluated on a regional average.AveragedoverMarch,thebiomassburningnetinfluenceisashighas50% forOH,40%forHO2,60%forHCHO,and10ppbvforO3forthelayersbelow1km. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 0345 Atmospheric Composition and Structure: Pollution—urbanandregional(0305);3337MeteorologyandAtmospheric Dynamics:Numericalmodelingand data assimilation; 3359 Meteorology and Atmospheric Dynamics: Radiative processes; KEYWORDS: biomass burning, chemical transport model, TRACE-P, photochemical process, aerosols, radiative influence Citation: Tang, Y., et al., Influences of biomass burning during the Transport and Chemical Evolution Over the Pacific (TRACE-P) experiment identified by the regional chemical transport model, J. Geophys. Res., 108(D21), 8824, doi:10.1029/2002JD003110, 2003.

We investigate the sources, prevalence, and fine-particle inorganic composition of biosmoke over the western Pacific Ocean between 24 February and 10 April 2001. The analysis is based on highly time-resolved airborne measurements of gaseous and fine- particle inorganic chemical composition made during the NASA Transport and Chemical Evolution over the Pacific (TRACE-P) experiment. At latitudes below approximately 25 deg. N, relatively pure biomass burning plumes of enhanced fine-particle potassium, nitrate, ammonium, light-absorbing aerosols, and CO concentrations were observed in plumes that back trajectories and satellite fire map data suggest originated from biomass burning in southeast Asia. Fine-particle water-soluble potassium (K+) is confirmed to be a unique biosmoke tracer, and its prevalence throughout the experiment indicates that approximately 20% of the TRACE-P Asian outflow plumes were influenced, to some extent, by biomass or biofuel burning emissions. At latitudes above 25 deg. N, highly mixed urban/industrial and biosmoke plumes, indicated by SO(sup 2, sub 4) and K+, were observed in 5 out of 53 plumes. Most plumes were found in the Yellow Sea and generally were associated with much higher fine-particle loadings than plumes lacking a biosmoke influence. The air mass back trajectories of these mixed plumes generally pass through the latitude range of between 34 deg. and 40 deg. N on the eastern China coast, a region that includes the large urban centers of Beijing and Tianjin. A lack of biomass burning emissions based on fire maps and high correlations between K+ and pollution tracers (e.g., S(sup 2, sub 4) suggest biofuel sources. Ratios of fine-particle potassium to sulfate are used to provide an estimate of relative contributions of biosmoke emissions to the mixed Asian plumes. The ratio is highly correlated with fine-particle volume (r(sup 2) = 0.85) and predicts that for the most polluted plume encounter in TRACE-P, approximately 60% of the plume is associated with biosmoke emissions. On average, biosmoke contributes approximately 35-40% to the measured fine inorganic aerosol mass in the mixed TRACE-P plumes intercepted north of 25% latitude.

[1] The Models-3 Community Multiscale Air Quality modeling system (CMAQ) coupled with the Regional Atmospheric Modeling System (RAMS) is used to analyze the Asian continental outflow of carbon monoxide (CO), ozone (O3), and aerosol sulfate (SO42−) to the western Pacific Ocean during the period 17–24 March 2001. In this time period eight airborne observations (DC-8 flights 11–14 and P-3B flights 13–16) of the NASA Transport and Chemical Evolution Over the Pacific (TRACE-P) mission were being conducted over a broad area covering Hong Kong, Okinawa, the East China Sea, and southern Japan. Comparison of model results with observations shows that the model reproduces the main observed features of CO, O3, and SO42−, including horizontal and vertical gradients, of the Asian pollution outflow over the western Pacific. Model results show that the fast boundary outflow from Asia to the western Pacific is largely restricted to the middle latitudes, and the maximum outflow fluxes are in the lower free atmosphere (3–6 km) north of 25°N. Simulations with and without biomass burning emissions are conducted to quantify the impacts of biomass burning on tropospheric concentrations of CO and O3. Biomass burning is found to contribute more than 50% of the CO concentrations and up to 40% of the O3 concentrations in the boundary layer over the major source regions. The largest percentage contributions to CO and O3 levels (up to 40% and 30%, respectively) over the western Pacific are in the lower free troposphere (2–6 km).

Estimates of biomass burning in Asia are developed to facilitate the modeling of Asian and global air quality. A survey of national, regional, and international publications on biomass burning is conducted to yield consensus estimates of 'typical' (i.e., non-year-specific) estimates of open burning (excluding biofuels). We conclude that 730 Tg of biomass are burned in a typical year from both anthropogenic and natural causes. Forest burning comprises 45% of the total, the burning of crop residues in the field comprises 34%, and 20% comes from the burning of grassland and savanna. China contributes 25% of the total, India 18%, Indonesia 13%, and Myanmar 8%. Regionally, forest burning in Southeast Asia dominates. National, annual totals are converted to daily and monthly estimates at 1{sup o} x 1{sup o} spatial resolution using distributions based on AVHRR fire counts for 1999--2000. Several adjustment schemes are applied to correct for the deficiencies of AVHRR data, including the use of moving averages, normalization, TOMS Aerosol Index, and masks for dust, clouds, landcover, and other fire sources. Good agreement between the national estimates of biomass burning and adjusted fire counts is obtained (R{sup 2} = 0.71--0.78). Biomass burning amounts are converted to atmospheric emissions, yielding themore » following estimates: 0.37 Tg of SO{sub 2}, 2.8 Tg of NO{sub x}, 1100 Tg of CO{sub 2}, 67 Tg of CO, 3.1 Tg of CH{sub 4}, 12 Tg of NMVOC, 0.45 Tg of BC, 3.3 Tg of OC, and 0.92 Tg of NH{sub 3}. Uncertainties in the emission estimates, measured as 95% confidence intervals, range from a low of {+-}65% for CO{sub 2} emissions in Japan to a high of {+-}700% for BC emissions in India.« less

[1] The regional-scale aerosol transport model (CFORS) is used in the analysis of black carbon (BC) observed at five remote Japanese islands during the ACE-Asia experiment. BC is modeled online in the regional-scale meteorological model, using emissions estimates for 2000. Two model experiments are conducted (1) a control run that includes all the BC emission, and (2) a sensitivity run without open biomass burning emissions to clarify the impact of biomass burning on the BC levels in the western Pacific. The regional aerosol model (CFORS) is shown to accurately reproduce many of the important features observed. Model analysis shows that the spatial and temporal distributions of black carbon between the northern sites (Rishiri and Sado; located in the Japan Sea) and the southern stations (Hachijo, Chichijima, and Amami-Oshima; in the western Pacific Ocean) are under different flow regimes. It is shown that the major synoptic features controlling BC levels are associated with outflow in the warm conveyor belt of traveling cold fronts and the subsequent postfrontal transport. At the northern stations (Rishiri and Sado), elevated BC concentrations are calculated to be mainly below the heights of 2000 m, and the biomass burning fraction is estimated to be below 20%. At the southern sites (e.g., Chichijima) the contribution due to biomass burning reaches 32% at the surface and 52% in the free atmosphere. CFORS results indicate that the major black carbon source and transport height are different between the northern and southern sites.

[1] We report here airborne measurements of atmospheric CO2 over the western North Pacific during the March–April 2001 Transport and Chemical Evolution over the Pacific (TRACE-P) mission. The CO2 spatial distributions were notably influenced by cyclogenesis-triggered transport of regionally polluted continental air masses. Examination of the CO2 to C2H2/CO ratio indicated rapid outflow of combustion-related emissions in the free troposphere below 8 km. Although the highest CO2 mixing ratios were measured within the Pacific Rim region, enhancements were also observed further east over the open ocean at locations far removed from surface sources. Near the Asian continent, discrete plumes encountered within the planetary boundary layer contained up to 393 ppmv of CO2. Coincident enhancements in the mixing ratios of C2Cl4, C2H2, and C2H4 measured concurrently revealed combustion and industrial sources. To elucidate the source distributions of CO2, an emissions database for Asia was examined in conjunction with the chemistry and 5-day backward trajectories that revealed the WNW/W sector of northeast Asia was a major contributor to these pollution events. Comparisons of NOAA/CMDL and JMA surface data with measurements obtained aloft showed a strong latitudinal gradient that peaked between 35° and 40°N. We estimated a net CO2 flux from the Asian continent of approximately 13.93 Tg C day−1 for late winter/early spring with the majority of the export (79%) occurring in the lower free troposphere (2–8 km). The apportionment of the flux between anthropogenic and biospheric sources was estimated at 6.37 Tg C day−1 and 7.56 Tg C day−1, respectively.