Retrieval of vertical columns of sulfur dioxide from SCIAMACHY and OMI: Air mass factor algorithm development, validation, and error analysis
Retrieval of vertical columns of sulfur dioxide from SCIAMACHY and OMI: Air mass factor algorithm development, validation, and error analysis
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DOI：
10.1029/2009jd012123
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发表时间：
2009-11
影响因子：
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通讯作者：
C. Lee;R. Martin;A. van Donkelaar;G. O'Byrne;N. Krotkov;A. Richter;L. G. Huey;J. Holloway
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文献类型：
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作者：
C. Lee;R. Martin;A. van Donkelaar;G. O'Byrne;N. Krotkov;A. Richter;L. G. Huey;J. Holloway
[1]我们开发了一种改进的从两个卫星仪器(SCIAMACHY和OMI)上反演二氧化硫(SO2)垂直柱的方法，这些仪器测量紫外线太阳后向散射。对于每个SCIAMACHY和OMI观测，局部空气质量系数(AMF)算法使用由辐射传输模式(LIDORT)计算的高度相关的散射权重，通过由全球大气化学模式(GEOS-Chem)本地确定的相对垂直SO2廓线(形状因子)加权，将视线“倾斜”柱转换为垂直柱。散射权重考虑了观测几何形状、表面反照率、云散射、臭氧吸收以及气溶胶的散射和吸收。矿物粉尘对辐射的吸收可使仪器的季节平均灵敏度降低50%。用GEOS-Chem模拟的用于AMF计算的SO2平均形状因子与航空现场测量(INTEX-A和INTEX-B)高度一致；差异将对反演的SO2柱产生10%的影响。恢复的垂直柱得到了符合的航空现场测量(INTEX-A、INTEX-B和中国东部的一次活动)的验证。在污染地区(如东亚和美国东部)，AMF的年平均误差估计为35%-70%，而在晴朗的海洋地区，AMF的年平均误差不到10%。对于污染区域的年平均值，SO2的总体误差评估为45%-80%。从SCIAMACHY和OMI中提取的2006年季节平均SO2柱与GEOS-Chem，特别是美国的季节平均SO2柱在空间上显著相关(SCIAMACHY和OMI的相关系数分别为0.85和0.82)。一项敏感性研究证实了SCIAMACHY和OMI对人为SO2排放的敏感性。
[1] We develop an improved retrieval of sulfur dioxide (SO2) vertical columns from two satellite instruments (SCIAMACHY and OMI) that measure ultraviolet solar backscatter. For each SCIAMACHY and OMI observation, a local air mass factor (AMF) algorithm converts line-of-sight “slant” columns to vertical columns using altitude-dependent scattering weights computed with a radiative transfer model (LIDORT), weighted by relative vertical SO2 profile (shape factor) determined locally with a global atmospheric chemistry model (GEOS-Chem). The scattering weights account for viewing geometry, surface albedo, cloud scattering, absorption by ozone, and scattering and absorption by aerosols. Absorption of radiation by mineral dust can reduce seasonal mean instrument sensitivity by 50%. Mean SO2 shape factors simulated with GEOS-Chem and used in the AMF calculation are highly consistent with airborne in situ measurements (INTEX-A and INTEX-B); differences would affect the retrieved SO2 columns by 10%. The retrieved vertical columns are validated with coincident airborne in situ measurements (INTEX-A, INTEX-B, and a campaign over east China). The annual mean AMF errors are estimated to be 35–70% in polluted regions (e.g., East Asia and the eastern United States) and less than 10% over clear ocean regions. The overall SO2 error assessment is 45–80% for yearly averages over polluted regions. Seasonal mean SO2 columns retrieved from SCIAMACHY and OMI for 2006 are significantly spatially correlated with those from GEOS-Chem, in particular over the United States (r = 0.85 for SCIAMACHY and 0.82 for OMI). A sensitivity study confirms the sensitivity of SCIAMACHY and OMI to anthropogenic SO2 emissions.