Abstract:

The research is to assess the uncertainty of aerosol optical depth (AOD) and Ångström exponent products retrieved from the Multi-angle Imaging SpectroRadiometer (MISR) data by means of comparing them with ground measured data in Hong Kong in the period of 2005 to 2013. Further analysis of how these uncertainties are spread into the calculation of UV Index (UVI) is conducted based on a radiative transfer model. The results indicate that the maximum values of UVI uncertainty caused by MISR/AOD uncertainty are 0.55 and 0.36 in summer and winter, respectively. The maximum of UVI uncertainty caused by Ångström exponent uncertainty are 0.13 and 0.11 in summer and winter, respectively. Compared with the UVI exposure grades put forward by the World Health Organization, the uncertainty of both AOD and Ångström exponent can cause at most one grade deviation in the worst situation. In this sense, MISR/AOD and Ångström exponent products are reliable as input in the calculation of UVI.

Key words: MISR, AOD, Ångström exponent, UVI, uncertainty

摘要：

以地面站观测为参照, 分析香港地区2005—2013年间MISR气溶胶光学厚度产品和Ångström指数的不确定性, 通过辐射传输方程模拟该不确定性对香港地区夏季和冬季地方时06:00—18:00之间紫外线指数造成的影响。结果表明, 气溶胶光学厚度的不确定性在夏季和冬季对紫外线指数造成的偏差最大分别为0.55和0.36, Ångström指数不确定性在夏季和冬季对紫外线指数造成的偏差最大分别为0.13和0.11。对比世界卫生组织划分的紫外线危害等级, 不论是气溶胶光学厚度还是Ångström指数的不确定性, 所引起的紫外线风险等级的最大偏差为一级, 夏、冬季基本上都不会影响对民众发布的紫外线风险分级。因此, 可认为使用MISR气溶胶光学厚度产品以及Ångström指数计算紫外线指数是可靠的。

关键词: MISR, 气溶胶光学厚度, Å, ngströ, m 指数, 紫外线指数, 不确定性