1. Aerosol Outflows and Their Interactions with Gaseous Species in East Asia during Springtime, 2001: Three- Dimensional Model Study Combining Observations Youhua Tang 1, Gregory R. Carmichael 1, John H. Seinfeld 2, Donald Dabdub 3, Rodney J. Weber 4, Barry Huebert 5, Antony D. Clarke 5, Gakuji Kurata 6, Itsushi Uno 7, Jung-Hun Woo 1, David G. Streets 8, Chul-Han Song 4, Adrian Sandu 9, Theodore L. Anderson 10, Robert W. Talbot 11 and Jack E. Dibb 11 1.Center for Global and Regional Environmental Research, University of Iowa 2.Dept. of Chemical Engineering and Environmental Science Engineering, California Institute of Technology 3. Dept. of Mechanical and Aerospace Engineering, U. of California at Irvine 4. School of Earth and Atmospheric Sciences, Georgia Institute of Technology 5. School of Ocean and Earth Science and Technology, University of Hawaii 6.Dept. of Ecological Engineering, Toyohashi University of Technology, Japan 7. Research Institute for Applied Mechanics, Kyushu University, Japan 8. Decision and Information Sciences Division, Argonne National Laboratory 9. Dept. of Computer Science, Virginia Technical University 10. Dept. of Atmospheric Science, University of Washington at Seattle 11. Dept. of Earth Sciences, University of New Hampshire Framework of Chemical Mechanism To represent the involvement of dust in heterogeneous chemistry, we define the dust surface fresh ratio as where Ca active is the amount of dust active calcium that is available for heterogeneous reactions: Cloud field Dobson O 3 On-line TUV Aerosol Optical Properties Gas-phase absorption Tropospheric O 3 Photolysis Rates Aerosol Equilibrium Module SCAPE Gaseous Reactions SAPRC-99 Heterogeneous Reactions (Dust) Gas-Aerosol Equilibrium interaction Gaseous Loss Dust surface saturation Aerosol Production Four aerosol size bins are used: 0.1µm- 0.3µm, 0.3µm-1.0µm, 1.0µm-2.5µm, and 2.5µm-10µm (referred to as bins 1 to 4, respectively). TAS Total Ca (µg/std m 3 ) Ca Increase Simulated Total Ca (µg/std m 3 ) Ca Increase Irregular Points Re-Colored in Coarse Dust Fresh Ratio During dust events of all C-130 flights, sulfate and nitrate coarse ratios show different correlations under different dust loading, represented by the Ca concentrations. When dust loading increased, the correlation became less varied and converge to a certain point related to dust coarse ratio. Both model and measurements show the similar trend. The simulation also show some points do not follow this trend. For these points, nitrate and sulfate coarse ratios are linearly related. Re-colored in coarse dust fresh ratio, these points were identifies as fresh dust loading. When dust was very fresh, nitrate and sulfate did not repel each other, since follow the similar uptake mechanism. Three Simulations: NODUST: without dust NORMAL: consider dust radiative impact FULL: consider both heterogeneous and radiative impacts Dust influences on Gaseous Species along C-130 Flight 6 C-130 Flight 8 encountered aged dust Dust did not influence the sub-micron sulfate, but significantly increased the super-micron sulfate concentration. Sub-micron dust ages faster than the super-micron dust. Extracted model results along trajectory B (shown left) illustrating the dust aging process and composition variation. Measurements Compared to the Simulations with and without Dust along C-130 Flight 6 Simulations with and without dust clearly show the dust influence on secondary aerosols. Dust appearance increased total sulfate and nitrate concentrations, especially increased their coarse portions, but the high Ca loading repelled ammonia uptake. Dust storm also significantly increased aerosol extinction coefficient. Averaged Dust Concentration (µg/m 3 ) Averaged in the layers below 3km GMS-5 Dust-Enhanced Image Simulated Total Dust below 3 km with Weather Stations where Dust Were Reported Simulated Dust Fresh Ratio in the 400m levelSimulated Sulfate Coarse Ratio in the 400m level C-130 Flight 6 & 7 Trajectory B Simulated Dust Fresh Ratio D fresh Simulated Sulfate (contour, µg/m 3 ) and its Coarse Ratio (color-coded) Apr 7 Apr 9 Apr 11 Apr 13 The dust storms occurred from April 4-14, 2001 in East Asia were named “perfect storm”by some ACE-Asia investigators. These dust storms accompanied with cold-air outbreak and were transported eastward. Dusts became aged (shown by dust fresh ratio) when passing over polluted areas, and sulfate increased its coarse ratio. The interaction of dust, secondary aerosols and gaseous species through equilibria and heterogeneous processes significantly affected related species and aerosol size distributions, which was verified by aircrafts (C-130 and Twin Otter), NOAA ship (Ronald H. Brown), and ground measurements. C-130 flight 6 encountered the strongest dust events. Trajectory A C-130 Flight 8 Reaction #Reaction Equations 1 NO 2 + hv  NO + O 3 P 2 O 3 P + O 2  O 3 7 O 3 + NO  NO 2 + O 2 8 O 3 + NO 2  NO 3 + O 2 9 NO + NO 3  2NO 2 17 O 3 + hv  O 2 + O 3 P 18 O 3 + hv  O 2 + O 1 D 19 O 1 D + H 2 O  2OH 21 OH + NO  HONO 22 HONO + hv  OH + NO 25 OH + NO 2  HNO 3 29 OH + CO + O 2  HO 2 + CO 2 30 OH + O 3  HO 2 + O 2 31 HO 2 + NO  NO 2 + OH 32 HO 2 + NO 2  HNO 4 41 H 2 O 2 + hv  2OH 44 OH + SO 2 + H 2 O + O 2  H 2 SO 4 + HO 2 125 OH + HCHO  HO 2 + CO 236 NO 2 + Dust  0.5Nitrate + 0.5 Nitrite 237 O 3 + Dust  1.5O 2 Chemical budget when trajectory A passed over the polluted region, Beijing The model simulations (FULL, NORMAL and NODUST) extracted along trajectory A (see map in left corner) show the impacts of dust heterogeneous and radiative processes on gaseous species and photochemistry. The main influence of dust heterogeneous reactions is reducing O 3 concentration, which decreased NO 2 /NO ratio, but increased HONO concentration. During this journey, O 3 difference was nearly linearly correlated with O 3 -Dust heterogeneous reactions, except over heavily polluted areas. Trajectory A passed over the polluted area Averaged Dust Radiative Impact on OH (%) below 1 km Averaged Dust Radiative Impact on O 3 (%) below 1 km Averaged Dust Heterogeneous Impact (%) on O 3 (left) and NO 2 (right) below 1 km Simulated dust influences below km averaged for April 4-14, 2001 show OH is mainly affected (up to 20% reduction) by dust reducing photolysis rates, which also results in O 3 decrease in polluted areas and their downwind sites. In clean area, dut radiative influence tends to increase O 3 by decreasing its photolytic loss. In average during this period, dust heterogeneous reactions have stronger impacts on O 3 than its radiative influence. Regional O 3 decrease due to heterogeneous reactions also affect other species, like NO 2, through photochemical reactions. Thank you for your attention For further information, please check our papers: Tang, Y., et al. The impacts of dust on regional tropospheric chemistry during the ACE-Asia experiment: a model study with observations, J. Geophys. Res., doi: 10.1029/2003JD003806, in press, 2003. Tang, Y., et al. Three-dimensional studies of aerosol ions and their Size Distribution in East Asia during spring 2001, submitted to J. Geophys. Res.. Or contact us : Youhua Tang (ytang@cgrer.uiowa.edu) Greg Carmichael (gcarmich@engineering.uiowa.edu) C-130 flight 6 encountered the strongest dust storm during ACE-Asia campaign, which strongly affected both aerosol (left) and gaseous (up) species via equalibria, heterogeneous and radiative processes. J. Geophys. Res.,