Abstract. Emission inventories for major reactive tropospheric CI species (particulate CI, HC1, C1NO2, CH3CI, CHCI3, CH3CCI3, C2C14, C2HC13, CH2C12, and CHCIF2) were integrated across source types (terrestrial biogenic and oceanic emissions, sea-salt production and dechlorination, biomass burning, industrial emissions, fossil-fuel combustion, and incineration). Composite emissions were compared with known sinks to assess budget closure; relative contributions of natural and anthropogenic sources were differentiated. Model calculations suggest that conventional acid-displacement reactions involving Sov)+O3, S(Iv)+ H202, and H2SO4 and HNO3 scavenging account for minor fractions of sea-salt dechlorination globally. Other important chemical pathways involving sea-salt aerosol apparently produce most volatile chlorine in the troposphere. The combined emissions of CH3CI from known sources account for about half of the modeled sink, suggesting fluxes from known sources were unde:estimated, the OH sink was overestimated, or significant unidentified sources exist. Anthropogenic activities (primarily biomass burning) contribute about half the net CH3CI emitted from known sources. Anthropogenic emissions account for only about 10% of the modeled CHCl3 sink. Although poorly constrained, significant fractions of tropospheric CH2C12 (25%), C2HC13 (10%), and C2C14 (5%) are emitted from the surface ocean; the combined contributions of C2C14 and C2HC13 from all natural sources may be substantially higher than the estimated oceanic flux.

A size‐segregated soil dust emission and transport model, Northern Aerosol Regional Climate Model (NARCM), was used to simulate the production and transport of Asian soil dust during the Aerosol Characterization Experiment‐Asia (ACE‐Asia) period from March to May 2001. The model is driven by the NCEP reanalyzed meteorology and has all the atmospheric aerosol physical processes of soil dust: production, transport, growth, coagulation, and dry and wet deposition. A Chinese soil texture map that infers the soil grain‐size distribution with 12 categories was generated to drive the size‐distributed soil dust emission scheme [Alfaro et al., 1997; Marticorena and Bergametti, 1995]. The size distribution of vertical dust flux was derived from the observed surface dust‐size distribution in the desert regions. Parameters applicable to the Asian deserts for the dust emission scheme are assessed. Model simulations were compared with ground‐based measurements in East Asia and North America and with satellite measurements for the same period of time. The model captured most of the dust mobilization episodes during this period in China and reasonably simulated the concentrations in source regions and downwind areas from East China to western North America. About 252.8 Mt of soil dust below d < 40 μm was estimated to be emitted in the East Asian deserts between 1 March and 31 May 2001 with ∼60% attributed to four major dust storms. The vertical dust loadings above 700 hPa correlate reasonably well with Total Ozone Mapping Spectrometer aerosol index (TOMS AI) observations. The sensitivity analysis of model performance to soil size distribution, water moisture, and meteorology was carried out with the observational data to establish the most appropriate parameters and conditions for the Chinese soil dust production and transport.

[1] Simulations of Asian dust emissions over the past 43 years are presented based on a size-dependent soil dust emission and transport model (NARCM) along with supporting data from a network of surface stations. The deserts in Mongolia and in western and northern China (mainly the Taklimakan and Badain Juran, respectively) contribute $70% of the total dust emissions; non-Chinese sources account for $40% of this. Several areas, especially the Onqin Daga sandy land, Horqin sandy land, and Mu Us Desert, have increased in dust emissions over the past 20 years, but efforts to reduce desertification in these areas may have little effect on Asian dust emission amount because these are not key sources. The model simulations indicate that meteorology and climate have had a greater influence on the Asian dust emissions and associated Asian dust storm occurrences than desertification.