Atmospheric Chemistry and Physics Contribution of Ammonium Nitrate to Aerosol Optical Depth and Direct Radiative Forcing by Aerosols over East Asia
Atmospheric Chemistry and Physics Contribution of Ammonium Nitrate to Aerosol Optical Depth and Direct Radiative Forcing by Aerosols over East Asia
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R. Park;S. Lee;S.-K Shin;C. H. Song
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作者：
R. Park;S. Lee;S.-K Shin;C. H. Song
研究了硝酸铵（NH4NO3）对东亚地区气溶胶光学厚度（AOD）和气溶胶直接辐射强迫（DRF）的贡献。为了评估的贡献，化学传输模式（CTM）估计的气溶胶光学厚度与卫星反演的气溶胶光学厚度相结合，利用数据同化技术，在东亚地区的2006年全年。利用同化的气溶胶光学厚度和CTM估算的气溶胶光学特性，通过辐射传输模式（RTM）估算了东亚地区气溶胶的DRF。同化的气溶胶光学厚度和估算的DRF值与AERONET气溶胶光学厚度和DRF值都有较好的一致性。在此基础上，估算了2006年东亚地区四季NH4NO3对气溶胶AOD和DRF的贡献。在晴空条件下，东亚地区气溶胶光学厚度和DRF的季节变化范围分别为4.7%（夏季）和31.3%（冬季），以及4.7%（夏季）和30.7%（冬季），年平均贡献率分别为15.6%和15.3%。在全天条件下，DRF在3.6%（夏季）和24.5%（冬季）之间变化，表明东亚地区的年平均贡献率为12.1%。NH4NO3对气溶胶光学厚度和DRF的贡献与NH4NO3在PM 2.5和PM 10中的年均质量分数（分别为17.0%和14.0%）相当。在NH3和NOx排放强度大的地区，如中东部和四川盆地，气溶胶光学厚度和DRF值更大。例如，在晴朗的天空条件下，CEC区域的AOD和DRF分别在6.9%（夏季）和47.9%（冬季）之间以及6.7%（夏季）和47.5%（冬季）之间。在此基础上，得出的结论是，在东亚空气质量和辐射强迫的研究，特别是在冬季，气溶胶光学厚度和DRF不能忽略。
This study focused on the contribution of ammo-nium nitrate (NH 4 NO 3) to aerosol optical depth (AOD) and direct radiative forcing (DRF) by aerosols over an East Asian domain. In order to evaluate the contribution, chemistry-transport model (CTM)-estimated AOD was combined with satellite-retrieved AOD, utilizing a data assimilation technique , over East Asia for the entire year of 2006. Using the assimilated AOD and CTM-estimated aerosol optical properties , the DRF by aerosols was estimated over East Asia via a radiative transfer model (RTM). Both assimilated AOD and estimated DRF values showed relatively good agreements with AOD and DRF by aerosols from AERONET. Based on these results, the contributions of NH 4 NO 3 to AOD and DRF by aerosols (AOD and DRF) were estimated for the four seasons of 2006 over East Asia. Both AOD and DRF showed seasonal variations over East Asia within the ranges between 4.7 % (summer) and 31.3 % (winter) and between 4.7 % (summer) and 30.7 % (winter), respectively, under clear-sky conditions, showing annual average contributions of 15.6 % and 15.3 %. Under all-sky conditions, DRF varied between 3.6 % (summer) and 24.5 % (winter), showing annual average contribution of 12.1 % over East Asia. These annual average contributions of NH 4 NO 3 to AOD and DRF are almost comparable to the annual average mass fractions of NH 4 NO 3 in PM 2.5 and PM 10 (17.0 % and 14.0 %, respectively). AOD and DRF were even larger in the locations where NH 3 and NO x emission rates are strong, such as the central East China (CEC) region and Sichuan Basin. For example, under clear-sky conditions, both AOD and DRF over the CEC region range between 6.9 % (summer) and 47.9 % (winter) and between 6.7 % (summer) and 47.5 % (winter), respectively. Based on this analysis, it was concluded that both AOD and DRF cannot be ignored in East Asian air quality and radiative forcing studies, particularly during winter.