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The atmospheric input of anthropogenic total reactive oxygenated nitrogen (NOy) to ocean regions in East Asia during 2002–2004 was revisited with an updated regional chemical transport model and the latest emissions inventory. The updated model treats both fine- and coarse-mode nitrate (NO3−). Coarse-mode NO3− is produced by the reaction of nitric acid (HNO3) and sea salt particles. The modeling system reproduced the atmospheric concentration and wet deposition amount of NO3− quantitatively compared with observations. The fraction of coarse-mode NO3− was also well captured. NOy deposition amounts over marginal seas and open oceans were 733 and 730 Gg N/yr, which are increases of 1.6- and 2.2-fold, respectively, by including coarse-mode NO3−. Anthropogenic NOx emissions from China were 5377 Gg N/yr, and 3060 Gg N/yr was exported from China; therefore, the NOy deposition amount over ocean regions in East Asia (1463 Gg N/yr) corresponded to almost half (48%) of the export amounts.

We observed a long-lasting dust event from 25 May to 2 June 2014, using a polarization optical particle counter (POPC). The transport of dust plumes over East Asia was verified on the basis of observations of Moderate Resolution Imaging Spectroradiometer, a lidar network, and surface synoptic observation stations. Mixing of dust and anthropogenic pollutants was investigated according to the variation in the depolarization ratio as a function of particle size. The nonsphericity of dust particles varied due to the impact of anthropogenic pollutants on their pathway. In the coarse mode, dust particles always had a clear nonspherical configuration, although large amounts of nitrate were also present. Supermicron particles are occasionally present in a spherical configuration, possibly due to the complex mixing of natural dust and anthropogenic particles. Statistically, ~64% of the total nitrate mass was deemed to be transported from outside of Japan due to a trapping effect in the dust plume.

Emission source contributions of tropospheric ozone (O3) were comprehensively investigated by using the higher-order decoupled direct method (HDDM) for sensitivity analysis and the ozone source apportionment technology (OSAT) for mass balance analysis in the comprehensive air-quality model with extensions (CAMx). The response of O3 to emissions reductions at various levels in mainland China, Korea, and Japan were estimated and compared with results calculated by the brute force method (BFM) where one model parameter is varied at a time. Emissions were assessed at three receptor sites in Japan that experienced severe pollution events in May 2009. For emissions from China, HDDM assessed O3 response with a bias of only up to 3 ppbv (a relative error of 4.5%) even for a 50% reduction but failed to assess a more extreme reduction. OSAT was reasonably accurate at 100% reduction, with a −4 ppbv (−7%) bias, but was less accurate at moderate ranges of reduction (∼50–70%). For emissions from Korea and Japan, HDDM captured the nonlinear response at all receptor sites and at all reduction levels to within 1% in all but one case; however, the bias of OSAT increased with the increasing reduction of emissions. One possible reason for this is that OSAT does not account for NO titration. To address this, a term for potential ozone (PO; O3 and NO2 together) was introduced. Using of PO instead of O3 improved the performance of OSAT, especially for emissions reductions from Korea and Japan. The proposed approach with PO refined the OSAT results and did not degrade HDDM performance.

A yellow sand transport episode from the Asian continent to Japan and North America which occurred in April 1998 is simulated. A new on-line dust tracer model coupled with a regional-scale meteorological model is developed and applied to this dust storm episode. The results for two large dust events that started during April 14–15 and 19–20, 1998, have been analyzed and discussed. The first dust storm was trapped in a cutoff vortex developed over the China plain. A modeled 3-D structure of dust associated with this cutoff vortex agreed with an observed time-height cross section of dust concentration. Results show that the strong subsidence at the backside of the vortex restricted the dust layer below 3 km level. Model analysis revealed that the second dust event that started during April 19–20 over inland China was the origin of a dust episode reported over North America. The trans-Pacific dust transport simulation successfully showed the dust onset near the West Coast of North America. Elevation of the dust layer during the long-range transport was below 3 km. The model is extended to include the transport of an Asian origin anthropogenic tracer over the North Pacific Rim. Both the natural-origin mineral dust and the Asian-origin anthropogenic tracer are simultaneously transported even if their emission regions are different.

To determine the variability of chemical properties in marine aerosols, a stationary shipboard measurement study was carried out at a station over the Northwest Pacific for 29 hours in the summer of 1999. Under a North Pacific high pressure system, carbonaceous substances, major inorganic ions, and particle numbers of typical marine aerosols were measured with little influence from continental and anthropogenic sources. The mass median diameter of organic aerosol was larger than 0.5 μm and its behavior over time was similar to sea-salt aerosol. Although the source of marine organic aerosol was believed to be mainly from continents, this result suggested that organic substances in micro layer of the sea surface is one of the sources to supply fine organic aerosol to the marine atmosphere. The further investigation would be necessary over various oceanic regions to find out the effects of marine biological activities.

Outflow patterns of air pollutants, and mechanisms associated with a monsoon condition that is peculiar to the East Asian region in winter, have been studied. To capture the continental outflow, airborne and shipboard measurements of aerosols and trace gases were conducted over the northern part of the East China Sea and the western part of the Sea of Japan on January 17-26, 1991 (airborne), January 28-29, 1992 (airborne), January 22-31, 1993 (shipboard), and January 29-30, 1993 (airborne). At least two types of highly polluted air masses were found at different times of the monsoon. Type 1 polluted air mass, which contained more than 10 μg m -3 of non-sea-salt SO 4 2- and more than 5 μgC m -3 of black carbon aerosols, typically appeared over the East China Sea at the beginning of the monsoon period. Chemical and microphysical characteristics suggest that the type 1 polluted air mass is chemically aged. Type 2 air mass appeared in the later half of the monsoon period and had characteristics of freshly emitted pollutants. It consisted of several high concentrations of SO 2 (>10 ppbv) confined in narrow horizontal width (10 to 30 km wide). Analyses using an Eulerian chemical transport model and detailed backward trajectories indicate that the type 1 polluted air mass was subcontinental in extent and its formation and the transport were dominated by a synoptic-scale weather cycle; it was formed over the Asian continent under anticyclonic conditions that persisted for 3-4 days, and transported intermittently to the east over the Pacific Ocean by the passage and the development of traveling cyclones. This study suggests that aerosols that flow out from East Asia are enriched with carbonaceous materials and consequently have low single-scattering albedo, which may affect the direct radiative forcing by aerosols over the North Pacific.

Using observations from the Cheeka Peak Observatory in northwestern Washington State during March-April, 1997, we show that Asian anthropogenic emissions significantly impact the concentrations of a large number of atmospheric species in the air arriving to North America during spring. Isentropic back-trajectories can be used to identify possible times when this impact will be felt, however trajectories alone are not sufficient to indicate the presence of Asian pollutants. Detailed chemical and meteorological data from one of these periods (March 29th, 1997) indicates that the surface emissions were lifted into the free troposphere over Asia and then transported to North America in ∼6 days.

Ozone transport and chemistry in the springtime in east Asia are studied by use of the STEM-II (Sulfur Transport Eulerian Model) regional-scale transport/chemistry model. Three-dimensional simulations are performed for the period May 1–15, 1987. This was a period of strong downward transport of ozone in east Asia, associated with traveling low-pressure systems. Elevated ozone levels were observed at high-altitude surface sites in Japan during this period. Model simulations both with and without photochemical processes are performed in order to assess the relative importance of the transport and chemical sources of tropospheric ozone. The model results are compared with measured values at a network of stations in Japan and are found to accurately capture most of the important observed features. Near-surface ozone levels are found to be strongly influenced both by continental outflow of precursors occurring behind the cold fronts as they move out over the Pacific Ocean and by the strong downward transport of ozone-rich air from the upper troposphere which occurs in association with these weather systems.

[1] We expanded the variational assimilation system of a regional dust model by using size-resolved inversion. Dust emissions and particle-size distributions of a severe dust and sandstorm (DSS) in April 2005 were inversely optimized with optical measurements by the National Institute for Environmental Studies lidar network. The inversion results successfully compensated underestimates by the original model and increased the Angstrom exponent around the DSS core by 13–17%, shifting the particle-size distribution to finer. The a posteriori size distribution was distinctly different between eastern and western source regions. In the western regions, dust emissions in the 3.19 and 5.06μm size bins increased considerably, and the peak size shifted from 5.06 to 3.19 μm, whereas in the eastern regions, emissions of finer particles (bins 0.82–2.01 μm) increased. Differences in vegetation and soil type and moisture between eastern and western regions might explain the characteristics of the inverted size distribution.

[1] To evaluate temporal variations in nitrogen wet deposition across Japan during 1989–2008, we analyzed results of a chemical transport model (the Models-3 Community Multiscale Air Quality) and observational data. The model successfully reproduced the general patterns of spatial and temporal variations of observed NO3− wet deposition rates. Wet deposition rates of NO3− across Japan increased during 1989–2008, with rates of increase of 2–5%/yr. Sensitivity simulations indicated that the increase of NO3− wet deposition rates was mostly (61%–94%) explained by the increased emissions of atmospheric pollutants in China. Contributions of China's emissions increased from 29%–35% during 1989–1993 to 43%–61% during 2004–2008, suggesting that transboundary pollution had a large impact on NO3− wet deposition in Japan. The contribution of observed NO3− to total nitrogen wet deposition (i.e., NO3− + NH4+) increased in southwestern Japan, and currently, NO3− and NH4+ make similar contributions to nitrogen wet deposition across Japan. Interannual variation of NO3− wet deposition was further evaluated using a meteorological index, area-weighted surface pressure anomaly (ASPA). When ASPA was negative, air masses from the Asian continent were more directly transported to Japan, and NO3− concentrations across Japan became high. Thus, anomalies of NO3− concentrations were negatively correlated with ASPA. Anomalies of NO3− wet deposition rates, however, showed a weak positive correlation with ASPA, reflecting a positive correlation between anomalies in precipitation rates and ASPA. This result strongly suggests that precipitation patterns have a large impact on the interannual variation of NO3− wet deposition across Japan.

[1] Springtime outflow of Asian dust and air pollutants was investigated by a synergetic analysis of ground-based/space-borne Lidar observations and numerical models. We identified two prominent outflow patterns, and its occurrence frequency. Pattern I was induced within a typical warm-sector which lifted up dust particles into the free troposphere, and the existence of two sequential low-pressure systems played an important role. Pattern II was a ‘behind cold front’ outbreak. Atmospheric stratification was significantly different; Pattern I had weak stratification within the troposphere (potential temperature gradient of ∼2–3.4 K/km), and most of elevated dust layer (typically horizontally 1500–2000 km, vertically 2.5–4 km AGL) remained unmixed with pollutants. Pattern II was characterized by a strong stratification of ∼5 K/km; dust and pollutants were trapped and well mixed within the PBL, forming ‘polluted’ dust. Among the six cases of large-scale dust/pollutants outbreaks, only two cases are belonged to Pattern I.

[1] In mid-August 2009, ground-based lidar networks on both sides of the Pacific Basin detected an elevated dust layer. A combined analysis by ground-based lidars, space-borne lidar CALIOP, and numerical models revealed that dust particles emitted in the Taklimakan Desert were transported across the Pacific Ocean in 12 to 13 days. This was the first evidence of summertime trans-Pacific transport of Asian dust from the Taklimakan Desert. A large-scale dust storm occurred in the Taklimakan Desert during 12–16 August due to a strong surface wind accompanied by a cold front. Many dust particles were lifted up into the free atmosphere by the upslope wind formed by the steep slope of the surrounding mountains. This dust injection process was analogous to that for springtime cases. The Taklimakan dust was then transported eastward at 6–8 km altitude. This high transport altitude allowed the Taklimakan Dust to be transported beyond the Pacific Ocean without the effect of the southeasterly outflow of the summertime Pacific high. The wind field anomaly at 500 hPa in mid-August 2009 shows increases of northwesterly winds driven by SE–NW pressure gradients around 110–140°E and 180–140°W, indicating that the pressure pattern during the dust event favored the trans-Pacific transport.

[1] The current debate about the role of anthropogenic pollutants in a unique broad summer maximum pattern at a remote site (Waliguan, 3810 asl) on the northern edge of the Tibetan Plateau is continuing. This study quantifies the impacts of anthropogenic emissions and stratosphere-to-troposphere exchange (STE) on surface ozone on the Tibetan Plateau using a regional chemical transport model with an on-line tracer tagging module. The model is shown to be well suited for simulating the unique seasonal variation at Waliguan. Model results clearly show that the regional transport of photochemically produced ozone in China is responsible for the summer maximum on the northern Tibetan Plateau with a contribution of ∼10–25 parts per billion by volume (ppbv) in summer, which is more than ∼5 ppbv of the contribution to STE. The weak local ozone photochemical production (−0.5–0.1 ppbv/day) suggests that this transport to the Tibetan Plateau mostly concentrates on photochemical products. The unique strong near-surface convergence and upper layer divergence driven by elevated surface heating and low air density over the Tibetan Plateau in summer is its dynamic cause. These transported anthropogenic pollutants are likely to rise to the upper troposphere and circulate globally. This study also demonstrates that the effect of convection on surface ozone over the northern Tibetan Plateau is compensated by the advective updrafts in summer.

[1] We examine springtime ozone trends at nine remote locations in Japan during the last decade. The observed decadal ozone trends are relatively small at surface sites but are substantially larger at a mountainous site. We use a regional chemistry-transport model to explore the observed changes and how changes in Asian anthropogenic emissions have contributed to the observed increasing trends. The model with yearly-dependent regional emissions successfully reproduces the levels, variability, and interannual variations of ozone at all the surface sites. It predicts increasing trends at the mountainous site, suggesting that increasing Asian anthropogenic emissions account for about half the observed increase. However, the discrepancy between the observation and model results after 2003 (the time of largest emission increase) suggests significant underestimation of the actual growth of the Asian anthropogenic emissions and/or incompleteness in the modeling of pollution export from continental Asia.

[1] Vertical dust structures and meteorological conditions over the Taklimakan Desert during the summertime periods (July–September) in 2006 and 2007 were investigated using satellite data including the CALIPSO lidar (CALIOP) measurements and the Weather Research and Forecasting (WRF) model simulation. Summertime convective velocity simulated by WRF was greater than 3 m/s, and the convective time scale was about 1000 s (ca. 15 min). We examined 42 CALIPSO paths (24 daytime and 18 nighttime paths) of data acquired under convective dusty conditions. The dust layer thickness derived from the CALIOP measurements reaches 3000–4000 m, which is approximately equal to the Tarim Basin depth. This thickness shows a good correlation with the WRF simulated depth of the convective boundary layer (BL). The dust remains suspended during both daytime and nighttime; the CALIOP average dust extinction coefficients in the BL are respectively 0.151 ± 0.102 km−1 and 0.128 ± 0.079 km−1 for daytime and nighttime. Finally, we estimated the dust amount transported from the BL to the free atmosphere. Typically, 10–20 Gg/day of dust (assuming area of 600 km × 300 km as a main part of the Taklimakan Desert) is transported from the Taklimakan Desert by vertical mixing. The daily horizontal dust flux above the BL was estimated to be 40–50 Gg/day over the Taklimakan Desert.

[1] Present and future tropospheric ozone (O3) concentrations over east Asia have been simulated by the Models-3 Community Multiscale Air Quality Modeling System (CMAQ) coupled with the Regional Emission Inventory in Asia (REAS) to predict surface O3 variations caused by future anthropogenic emissions changes. For future prediction, REAS provides three emission scenarios for China (the reference (REF), the policy succeed case (PSC), and the policy failure case (PFC) scenarios) and one emission scenario (the REF scenario) for the other countries. Simulated O3 concentration in summer was relatively high (70–80 ppbv in June and 65–75 ppbv in August) over the North China Plain in 2000. The projected REF emissions for 2020 (2020REF) enhance the monthly averaged O3 to 75–90 ppbv in June and 75–85 ppbv in August. The projected PSC emissions for 2020 (2020PFC), including a slight NOx reduction of –0.2 Tg (–2%) and a large NMVOC increase of 14.3 Tg (97%) for total Chinese emissions during 2000–2020, cause the monthly and annually averaged O3 concentrations to decrease by less than 2 ppbv in northeastern and central China. Over the North China Plain, the projected PFC emissions for 2020 (2020PFC) cause significant increases, more than 20 ppbv in the monthly averaged O3, and the O3 will be 85–105 ppbv in June and 80–95 ppbv in August for 2020. The 2020PFC also affect O3 increases in early summer in South Korea (14–18 ppbv increase for monthly average) and Japan (2–14 ppbv increase for monthly average) during 2000–2020 despite the slight NOx increase of 0.4 Tg (25%) in South Korea and the slight NOx reduction of –0.2 Tg (–10%) in Japan during 2000–2020. The pollutant in these regions seems to be transport from upwind source regions. These experiments show that over central eastern China at midday in June, the O3 concentration is largely affected by NOx emission increases but is insensitive to NMVOC emission increases.

[1] We present detailed 3D structure of Asian dust outflow from a dust source region to the northwestern Pacific ocean retrieved by NASA/CALIOP onboard CALIPSO and results simulated by a four-dimensional variational (4DVAR) data assimilation version of a dust transport model (RC4) based on the NIES Lidar network. The modeled and CALIOP dust extinction showed good agreement, both for horizontal scale (600–1200 km) and vertical depth (1600–3600 m) near the dust source regions. Cross-section analyses of CALIOP and RC4 assisted by forward trajectory revealed that dust from the Gobi Desert on 5 May traveled approximately 1000–1500 km/day to the east and passed over Japan on 8 May. The elevated dust subsequently passed to the Pacific Ocean while maintaining the major dust layer height of 2500–4000 m MSL trapped within the potential temperature of 302–306 K. Results of our analyses demonstrate the importance of integration of CALIOP measurement and the dust model for clarifying the overall structure of an Asian dust event.>

[1] A rapid increase of NO2 columns over China has been observed by satellite instruments in recent years. We present a 10-a regional trend of NOx emissions in China from 1995 to 2004 using a bottom-up methodology and compare the emission trends with the NO2 column trends observed from GOME and SCIAMACHY, the two spaceborne instruments. We use a dynamic methodology to reflect the dramatic change in China's NOx emissions caused by energy growth and technology renewal. We use a scenario analysis approach to identify the possible sources of uncertainties in the current bottom-up inventory, in comparison with the satellite observation data. Our best estimates for China's NOx emissions are 10.9 Tg in 1995 and 18.6 Tg in 2004, increasing by 70% during the period considered. NOx emissions and satellite-based NO2 columns show broad agreement in temporal evolution and spatial distribution. Both the emission inventory data and the satellite observations indicate a continuous and accelerating growth rate between 1996 and 2004 over east central China. However, the growth rate from the emission inventory is lower than that from the satellite observations. From 1996 to 2004, NOx emissions over the region increased by 61% according to the inventory, while a 95% increase in the NO2 columns measured by satellite was observed during the same period. We found good agreement during summertime but a large discrepancy during wintertime. The consistency between the summertime trends suggests that the bias cannot be due to systematic error of activity data or emission factors. The reasons for the discrepancy cannot yet be fully identified, but possible explanations include an underestimation in seasonal emission variations, variability of meteorology, NOx injection height, and the increasing trend of sulfate aerosols.

[1] Atmospheric input of anthropogenic total nitrate to marginal seas in the western North Pacific region was simulated using a regional chemical transport model over East Asia based on year-to-year emission estimates during 1980-2003. Seasonal cycles and concentration levels of gas and aerosol were examined using observation data from various studies. The model simulated total nitrate deposition over the East China Sea (ECS) as 140 GgN/yr, which is the same order of the annual river discharge from the Yangtze River. The ratio of dry and wet deposition over ECS was obtained as approximately 6: 4. Total nitrate deposition over ECS corresponds to 3.2% (N base) of total NO x emission in China. The total deposition at present is three times larger than that of 1980, corresponding with increased NO x emissions.

[1] A four-dimensional variational (4DVAR) data assimilation system was developed for a regional dust model. This report presents results of the first adjoint inversion of Asian dust emissions over East Asia using NIES LIDAR observations, targeting the extreme dust phenomenon on 30 April 2005. Optimized dust emissions mitigated underestimation of dust concentrations and brought the structure of the elevated dust layer (both onset timing and extinction coefficient intensity) into better agreement with LIDAR observations. We obtained a 31% (3.2 Tg) increase of calculated dust emissions through data assimilation, especially over the Mongolian region. The assimilated results agree with the TOMS AI distribution and indicate that the 4DVAR method is very powerful for unification of observation and numerical modeling. The method provides better estimation capability.

[1] Vertically integrated anthropogenic aerosol mass concentration Ma and low-level water cloud properties (optical depth τ, effective particle radius re, and columnar droplet number Nc) were correlated over east Asia to elucidate human-induced effects on low-cloud properties. Aerosol and cloud properties were obtained from numerical simulations and satellite observations, respectively. Monthly averages of geographical matches between collocated Ma and cloud properties for three seasons showed that as Ma increased, τ and Nc increased and re decreased, which is consistent with the Twomey effect. Their changing rates became less steep when Ma was large. However, the importance of a dynamical effect was also suggested. A comparison of different cloud top heights revealed that values of τ and re of middle and lower clouds followed those of the total water cloud cases and reflected vertical characteristics.

[1] An intercomparison study involving eight dust emission/transport models over Asia (DMIP) has been completed. Participating dust models utilize a variety of dust emission schemes, horizontal and vertical resolutions, numerical methods, and different meteorological models. Two huge dust episodes occurred in spring 2002 and were used for the DMIP study. Meteorological parameters, dust emission flux and dust concentration (diameter < 20 μm) are compared within the same domain on the basis of PM and NIES lidar measurements. We found that modeled dust concentrations between the 25% and 75% percentiles generally agreed with the PM observations. The model results correctly captured the major dust onset and cessation timing at each observation site. However, the maximum concentration of each model was 2–4 times different. Dust emission fluxes from the Taklimakan Desert and Mongolia differ immensely among the models, indicating that the dust source allocation scheme over these regions differs greatly among the various modeling groups. This suggests the measurements of dust flux and accurate updated land use information are important to improve the models over these regions. The dust vertical concentration profile at Beijing, China, and Nagasaki, Japan, has a large scatter (more than two times different) among the models. For Beijing, the scaled dust profile has a quite similar vertical profile and shows relatively good agreement with the lidar extinction profile. However, for Nagasaki, the scaled dust profiles do not agree. These results indicate that modeling of dust transport and removal processes between China and Japan is another important issue in improving dust modeling.

[1] The climatology of surface ozone over East Asia was investigated at a wide range of latitudes by integrating continuous measurements from Japanese monitoring networks. Although a spring maximum and a summer minimum were observed at all seven remote stations, significant latitudinal differences in the seasonal cycles were found, particularly in spring. At low latitudes (20–30°N) the spring maximum appears in March, while it appears in April at high latitudes (40–50°N), and in May at middle latitudes (30–40°N). A regional-scale chemical transport model was applied to examine factors contributing to the latitudinal dependence observed. The model reproduces the latitudinal gradient and the overall seasonal variations well, and suggests that transport patterns of Asian continental outflow coupled with photochemistry result in latitudinal inhomogeneity over East Asia. These results highlight the key role of dynamical processes in modulating the amplitude and phase of the spring maximum in surface ozone.

[1] The seasonal variation of boundary layer ozone over East Asia is investigated using a regional scale chemical transport model, with the initial and boundary conditions of chemical species obtained from a global chemistry model. Comparisons with observations indicate that the model reproduces the main daily and seasonal features of ozone over eastern Asia. The seasonal variation of ozone has a summer maximum and winter minimum at Waliguan station (on the northeastern edge of the Tibetan Plateau), rather than the spring maximum and summer minimum seen at many other observational sites in the East Asian Pacific rim region. Model results suggest that there is band of a high ozone between 35°N∼45°N from the western boundary (70°E) to 130°E in the summertime. It is concluded that the seasonal transitions associated with the Asian monsoon system and transport from eastern/central China, Central/South Asia and even Europe are significantly responsible for the distinct ozone seasonal cycle at Waliguan.

[ 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] Aerosol chemical composition and number size distributions were measured aboard the R/V Ronald H. Brown during the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) from 14 March to 20 April 2001. This manuscript focuses on the prefrontal and postfrontal air masses sampled aboard the ship in the Sea of Japan between 6 and 15 April 2001 to illustrate the different chemical sources/mixtures off the coast of Asia resulting from the contrasting meteorological transport patterns. The prefrontal air masses had a dominant accumulation mode composed of pollution and volcanic aerosols. The aerosol was predominately ammonium sulfate and organic carbon. Minor amounts of dust were present in the marine boundary layer (MBL) as a result of subsidence from a pronounced Taklimakan dust aerosol layer aloft. The sea salt in both the submicron and supermicron modes was highly depleted in chloride from reaction with sulfuric and nitric acid vapors. The passage of a large low-pressure center, surrounded by a widespread distribution of airborne dust, on 10 April brought elevated concentrations of submicron and supermicron Gobi desert dust to the ship. The supermicron dust particles contained high concentrations of sulfate, nitrate, organic, and elemental carbon. The MBL aerosol properties and controlling processes described here provide data to evaluate and refine chemical transport models.

[1] The regional-scale aerosol transport model Chemical Weather Forecasting System (CFORS) is used for analysis of large-scale dust phenomena during the Asian Pacific Regional Characterization Experiment (ACE-Asia) intensive observation. Dust modeling results are examined with the surface weather reports, satellite-derived dust index (Total Ozone Mapping Spectrometer (TOMS) Aerosol Index (AI)), Mie-scattering lidar observation, and surface aerosol observations. The CFORS dust results are shown to accurately reproduce many of the important observed features. Model analysis shows that the simulated dust vertical loading correlates well with TOMS AI and that the dust loading is transported with the meandering of the synoptic-scale temperature field at the 500-hPa level. Quantitative examination of aerosol optical depth shows that model predictions are within 20% difference of the lidar observations for the major dust episodes. The structure of the ACE-Asia Perfect Dust Storm, which occurred in early April, is clarified with the help of the CFORS model analysis. This storm consisted of two boundary layer components and one elevated dust (>6-km height) feature (resulting from the movement of two large low-pressure systems). Time variation of the CFORS dust fields shows the correct onset timing of the elevated dust for each observation site, but the model results tend to overpredict dust concentrations at lower latitude sites. The horizontal transport flux at 130°E longitude is examined, and the overall dust transport flux at 130°E during March–April is evaluated to be 55 Tg.

[1] Continuous observations of aerosols in China and Japan were made by polarization lidars during March to May 2001, corresponding with the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) field campaign period. Lidars in Beijing, Nagasaki, and Tsukuba were continuously operated regardless of weather conditions. Scatterers in the atmosphere were categorized for all vertical profiles, and occurrence frequencies of dust, spherical aerosols, and clouds up to 6 km were calculated. The frequency of dust was highest in Beijing for the whole height range. There was a peak of dust occurrence near the ground in Nagasaki. Dust was frequently detected in the free troposphere in Tsukuba. The contributions of dust and spherical aerosols to the total backscattering coefficient were estimated from the depolarization ratio with the assumption of the external mixture of both kinds of aerosols. Vertical profiles of backscattering by dust and by spherical aerosols represented the different characteristics of these aerosols. The monthly averaged backscattering coefficients by dust near the surface were 0.003/km/sr in Beijing, 0.001–0.002/km/sr in Nagasaki, and 0.0006/km/sr in Tsukuba. The backscattering coefficients by spherical aerosols near the surface were 0.002–0.004/km/sr at all three observatories. We compared the derived backscattering coefficients with aerosol mass concentrations calculated by a numerical model, Chemical Weather Forecasting System (CFORS). CFORS reproduced well the vertical structures of the tall dust events and the enhancements of spherical aerosols throughout the observation period. A specific dust event on 16–19 May 2001 was analyzed by using five lidars in Japan, and its fine structure is described.

[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] The transport and optical thickness of tropospheric aerosols (dust, sulfate, carbonaceous aerosols, and sea salt) during the ACE-Asia intensive observation period (spring 2001) were simulated using a CFORS chemical transport model coupled with a regional meteorological model. Simulated aerosol fields were examined intensively with surface monitoring stations (PM10, sulfate, and total carbonaceous aerosol), Mie Lidar, and satellite observation data. It was shown that CFORS aerosol fields agree with observations and reproduced many observed characteristics including the several high concentration levels associated with the continental outflow, aerosol vertical profiles and strong correlation between dust and sulfate transports. We found the presence of the latitudinal gradient of aerosol concentrations from these comparisons. The two-month (March and April) averaged aerosol concentration and AOT fields show this latitudinal gradient more clearly, and indicated that the main dust field is located between 30°N and 45°N, while sulfate and carbonaceous field are mainly dominant from their main sources in central China and Southeast Asia to northern Japan (between 25°N and 45°N). Analyses of aerosol horizontal fluxes were also performed. We found that these distributions are closely related to characteristics of wind field of springtime and that each aerosol has the following transport route; the main dust flow is eastward along the 45°N parallel and is located in the free atmosphere; sulfate and carbonaceous aerosols within the boundary layer has a clockwise and divergent flow pattern over central China, which produce the strong outflow associated with anthropogenic emissions at northern latitudes and constrain the continental outflow at the southern latitude; and carbonaceous aerosols at the upper level (2–6 km) have another transport pathway that is along about 30°N from Thailand and Laos. Regional budgets of tropospheric aerosols showed that total emissions were 105 Tg for dust, 8.3 Tg-SO2 for sulfur (73% from human activities and 27% from volcanic activities), and 3.07 Tg for carbonaceous aerosols. Dry deposition, gravitational settling, and northward outflow of dust accounted for 33%, 27%, and 14% of total emissions, respectively. Wet deposition, eastward outflow, and dry deposition of sulfur accounted for 33%, 27%, and 21%, respectively. Regarding carbonaceous aerosols, the outflow to the east has the highest fraction (49%), followed by dry deposition (16%) and the outflow to the north (14%).

[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.

(� 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.

[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).

[1] A record heavy Yellow Sand event was observed on 20 March in Beijing. This event was unusual because the wind speed was low and the dust concentration was extremely high at the dust front. Observations with a polarization lidar, an optical particle counter, and a high-volume sampler were performed throughout the event in Beijing. The visibility derived from the lidar data was 650 m, and the total suspended particle concentration was 11 mg/m3 at the peak. Chemical transport model analysis revealed that the main part of the dust originated in the Mongolian border area near Ejinaqi. This dust event severely affected Korea and northern Japan. Continuous lidar observations in Beijing, Nagasaki and Tsukuba revealed that the frequency of dust events in 2001 and 2002 was similar in Beijing but much higher in 2002 in Nagasaki and Tsukuba. The model showed dust was transported to the east more frequently in 2002 and the difference is probably related to the smaller perturbation of the westerly jet. This indicates that a slight change in climate can cause a large difference in dust phenomena in the northwestern Pacific region.

[1] The spatial and temporal variation of the mineral aerosol concentration and its total deposition flux over the western North Pacific region were analyzed with a regional chemical transport model (AQPMS) for the period March 1994 through May 1995. Dry deposition accounted for more than 60% of the total deposition of Asian mineral dust throughout the period. The annual deposition flux was found to decrease rapidly from the coastal area (21 g m−2 yr−1) to the open ocean (0.8 g m−2 yr−1) over the study region. Sporadic dust deposition events over the HNLC region may increase the dissolved iron concentration in seawater and hence stimulate marine biological activity. The main eastward flow of mineral dust is located in the free troposphere between 30 and 40°N, above the layer of maximum concentration. These results support the intercontinental transport of Asian mineral dust across the North Pacific as background aerosol.

[1] Investigations of chemical properties and transport mechanisms of continental aerosols are necessary for estimating their influences on global radiative budget and on the global material cycle. Intensive measurements of atmospheric aerosols and the associated species on Rishiri Island, near the northern tip of Japan, were conducted from March to May 2001, in order to understand the chemical properties, source regions, transport pathways, and transport patterns of anthropogenic and mineral aerosols over the east Asian Pacific Rim region during the spring. Mean concentrations of nss-SO42−, NO3−, NH4+, nss-Ca2+ in aerosols were 2.48, 0.64, 0.72, and 0.17 μg m−3, respectively. Elemental carbon and organic carbon in fine particles (d < 2.5 μm) yielded mean concentrations of 0.25 and 0.80 μg m−3, respectively. The concentrations of these species frequently increased to higher values because of outbreaks of continental polluted air masses, whereas under background conditions, they decreased to lower values similar to those observed over the remote ocean. Our results demonstrate that nss-SO42− and NH4+ coexist in fine particles, that NO3− and nss-Ca2+ coexist in coarse particles, and that each set is transported in an alternate manner. Continentally derived NO3− is transported as coarse particle to the east Asian Pacific Rim region. Anthropogenic pollutants and dust particles are not necessarily transported together. It was often found that anthropogenic fine particles containing abundant nss-SO42− appeared first and were then followed by large mineral particles that had absorbed NO3−. Short-term intrusion of the air masses containing abundant particulate carbonaceous compounds, probably due to the influence of biomass burning, also often occurred during the outflow events of continental air masses. Atmospheric behaviors of sulfate, nitrate, and carbonaceous species are different from one another, although they are all derived mainly from combustion processes.

[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] Vertical profiles of aerosol size, composition, and hygroscopic behavior from Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter and National Oceanic and Atmospheric Administration R/V Ronald H. Brown observations are used to construct a generic optical model of the Asian Pacific Regional Aerosol Characterization Experiment (ACE-Asia) aerosol. The model accounts for sulfate, black carbon, organic carbon, sea salt, and mineral dust. The effects of relative humidity and mixing assumptions (internal versus external, coating of dust by pollutants) are explicitly accounted for. The aerosol model is integrated with a Monte Carlo radiative transfer model to compute direct radiative forcing in the solar spectrum. The predicted regional average surface aerosol forcing efficiency (change in clear-sky radiative flux per unit aerosol optical depth at 500 nm) during the ACE-Asia intensive period is −65 Wm−2 for pure dust and −60 Wm−2 for pure pollution aerosol (clear skies). A three-dimensional atmospheric chemical transport model (Chemical Weather Forecast System (CFORS)) is used with the radiative transfer model to derive regional radiative forcing during ACE-Asia in clear and cloudy skies. Net regional solar direct radiative forcing during the 5–15 April 2001 dust storm period is −3 Wm−2 at the top of the atmosphere and −17 W m−2 at the surface for the region from 20°N to 50°N and 100°E to 150°E when the effects of clouds on the direct forcing are included. The model fluxes and forcing efficiencies are found to be in good agreement with surface radiometric observations made aboard the R.H. Brown. Mean cloud conditions are found to moderate the top of atmosphere (TOA) radiative forcing by a factor of ∼3 compared to clear-sky calculations, but atmospheric absorption by aerosol is not strongly affected by clouds in this study. The regional aerosol effect at the TOA (“climate forcing”) of −3 Wm−2 is comparable in magnitude, but of opposite sign, to present-day anthropogenic greenhouse gas forcing. The forcing observed during ACE-Asia is similar in character to that seen during other major field experiments downwind of industrial and biomass black carbon sources (e.g., the Indian Ocean Experiment (INDOEX)), insofar as the primary effect of aerosol is to redistribute solar heating from the surface to the atmosphere.

[1] Sea-viewing Wide Field-of-view Sensor observation of the east Asian seas during the March–April 2001 Aerosol Characterization Experiment-Asia shows large areas of underestimated or even negative water-leaving radiance in the blue. To investigate the cause of the problem, three cloud-free matchup stations around Japan were analyzed, where in situ measurements were made onboard R/V Ronald H. Brown at the time of satellite overpass. Using an optimization method, information on the possible composition of aerosols was obtained from sky radiance data collected onboard the ship. An iterative radiative transfer simulation was carried out in an attempt to reproduce the satellite-measured top-of-atmosphere reflectance. The resulting water reflectance and aerosol optical thickness (AOT) agreed well with in situ measurements when the effect of submicron absorbing particles was considered in the radiative transfer simulation. The error in the retrieved water reflectance was much decreased, with average values of about 6% at 412 and 443 nm for the three stations. The effect of the Asian dust was also simulated in comparison with that of small absorptive aerosols. The underestimation could not be solely attributed to Asian dust. It was also found that at one of the stations, where the presence of dust aerosols was anticipated, an aerosol model mixed with both dust and soot improved the accuracy of the estimated AOT compared with the case of soot as the only absorptive aerosol (error of 13% at 865 nm instead of 44%). Submicron absorbing particles, in addition of the Asian dust, should be considered in the optical remote sensing of east Asian waters.

[1] The transport and chemical transformation of boundary layer ozone in east Asia in January 1997 was investigated using the Models-3 Community Multiscale Air Quality (CMAQ) modeling system with meteorological fields calculated by the Regional Atmospheric Modeling System (RAMS). The predicted ozone concentrations were compared with ground-level observations at four remote sites in Japan and it was found that the model reproduces many of the important features in the observations. Examination of several high ozone episodes indicates that elevated ozone levels are found in association with continental outflow. Net ozone production is found to occur during the daytime over the lower marine atmosphere, and this is also evident from the observations, demonstrating the critical role of the rapid transport of ozone precursors from the Asian continent. An analysis of the ozone budget indicates that the supply and loss of boundary layer ozone in east Asia in winter are dominated by photochemistry.

[1] A quantitative appraisal of the formation processes and distribution of mineral aerosols internally mixed with anthropogenic substances is necessary for estimating the aerosol radiative forcing, especially over the North Pacific region. A large-scale Kosa (“Yellow Dust”) phenomenon associated with the movement of a low-pressure system was observed at Nagasaki, about 1000 km east of the Asian continent in the spring of 1996. During the Kosa period (April 16–17), fine sulfur particles appeared first, and after 12 hours, a major plume of large mineral particles reached Nagasaki, which was detected and measured by the single-particle analysis with sampling intervals of 2 hours. The results demonstrate that Asian dust storms are occasionally capable of transporting mineral and anthropogenic particles in separate air masses from the source regions via the marginal seas to the western North Pacific. We note that it takes a certain time to admix the different air masses containing various types of aerosols along their transport paths from the Asian continent to remote marine atmosphere. The interactions of mineral particles with anthropogenic substances predominantly take place within the marine boundary layer toward the east over the North Pacific.

� 8W /m 2 at the top of atmosphere (TOA) and � 10 to � 23 W/m 2 at Earth’s surface of Gosan (33.28N, 127.17E) and Amami-Oshima (28.15N, 129.30E) sites, though there is a large regional difference caused by changes in the aerosol optical thickness and single scattering albedo. The cloud forcing is estimated as � 20 to � 40 W/m 2 , so that the aerosol direct forcing can be comparable to the cloud radiative forcing at surface. However, the estimate of the aerosol direct forcing thus obtained strongly depends on the estimation method of the aerosol properties, especially on the single scattering albedo, generating a method difference about 40%. The radiative forcing of the aerosol indirect effect is roughly estimated from satellite method and SPRINTARS model as � 1t o� 3W /m 2 at both TOA and surface. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0345 Atmospheric Composition and Structure: Pollution—urban and regional (0305); 1610 Global Change: Atmosphere (0315, 0325); 9320 Information Related to Geographic Region: Asia

[1] A three-dimensional aerosol transport-radiation model, SPRINTARS, successfully simulates the long-range transport of the large-scale Asian dust storms from East Asia to North America which crossed the North Pacific Ocean during the springtime of 2001 and 2002. It is found from the calculated dust optical thickness that 10 to 20% of the Asian dust around Japan reached North America. The simulation also reveals the importance of the contribution of anthropogenic aerosols, which are carbonaceous and sulfate aerosols emitted from the industrialized areas in East Asia, to air turbidity during the dust storms. The contribution of the anthropogenic aerosol to the total optical thickness is simulated to be of a comparable order to that of the Asian dust, which is consistent with the observed values of the particle size index from the satellite and ground-based sun/ sky photometry. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0365 Atmospheric Composition and Structure: Troposphere— composition and chemistry; 0368 Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry; 3359 Meteorology and Atmospheric Dynamics: Radiative processes. Citation: Takemura, T., I. Uno, T. Nakajima, A. Higurashi, and I. Sano, Modeling study of long-range transport of Asian dust and anthropogenic aerosols from East Asia, Geophys. Res. Lett., 29 (24), 2158, doi:10.1029/2002GL016251, 2002.

[1] Dust and anthropogenic aerosol plumes from the Asian continent were observed in the Northwest Pacific (32.0° to 38.0°N, 146.5°E) with a two-wavelength polarization lidar on board the research vessel Mirai during the MR01-K02 cruise (May 14 to 28, 2001). Dust aerosols were identified from the aerosol depolarization ratio at 532 nm and the ratio of the backscattering coefficient at 1064 nm and 532 nm. High aerosol density air masses with a low depolarization ratio and a small wavelength ratio (indicating small particle size) were also detected in the plume. The distribution patterns of the dust and the spherical aerosols were conceptionally explained by the model prediction for dust and sulfate with the Chemical Weather Forecast System (CFORS). Aerosols with large particle size but with low depolarization ratio were also observed in between the layers of dust and sulfate. This indicates that the aerosols were possibly an internal mixture of dust and sulfate.

We coordinated a ground-based network that has been in use since 1997 to observe Asian dust during springtime. Huge Asian dust events that occurred in the middle of April 1998 were captured by this network. In this paper we present the organization of the network; a description of the instruments, including the lidar, sky radiometer, and optical particle counter; and the results of the observation, and offer discussions regarding the transport mechanism of Asian dust in east Asia using an on-line tracer model. We discussed the time series of the surface concentration and the height distribution of the dust. A cutoff cyclone generated during the dust episode was responsible for trapping and sedimentation during the transportation of the Asian dust, particularly in the southern parts of China and Japan. Horizontal dust images derived from NOAA/AVHRR clearly revealed the structure of the vortex. The lidar network observation confirmed the general pattern of dust height distribution in this event; the height of the major dust layer was about 3 km over Japan but was higher (4 to 5 km) in Seoul and Hefei. A thin dust layer in the upper troposphere was also commonly observed in Hefei and Japan. Evidence of the coexistence of dust and cirrus was shown by the polarization lidar. The lidar network observation of Asian dust and satellite remote sensing provide key information for the study of the transport mechanism of Asian dust. Further extension of the lidar network toward the interior of the continent and the Pacific Rim would reveal the greater global mechanism of the transportation.