利用中国地区AERONET (AErosol RObotic NETwork)地基观测资料对Terra/Aqua MODIS (Moderate Resolution Imaging Spectroradiometer)气溶胶产品精度进行验证,提供资料可靠性分析,并分析了各地区MODIS反演气溶胶光学厚度(Aerosol Optical Depth,AOD)的误差来源,为进一步改进算法提供依据.结果表明:(1)香河、兴隆、榆林、寿县、合肥、香港和台湾等站点MODIS AOD的质量较好.对大多数站点,Terra和Aqua MODIS AOD质量差别不大,除个别站点Terra略优于Aqua.(2)选取香河、太湖、SACOL、北京、兴隆和台湾成功大学站进行详细分析.香河站Terra和Aqua MODIS AOD质量均较好,相关系数分别为0.96和0.97,且落在期望误差内的百分数分别为72％和65％.太湖和北京站MODIS AOD存在统一高估现象,可以通过拟合直线的截距对其进行订正,得到较接近真实值的AOD.SACOL,Terra和Aqua MODIS AOD与AERONET AOD的相关系数分别为0.66和0.77,且存在一定的高估.同时验证SACOL MODIS Deep Blue AOD,总体上其精度低于MODIS C005 AOD.兴隆和成功大学站反演误差均小于期望误差,数据质量较好.(3)误差分析表明香河和SACOL站的MODIS反演误差主要来自地表反射率关系的不合适;太湖和北京站的反演误差可能是由于地表和气溶胶模型两方面的共同作用导致的.个别站点随着云量增大,MODIS反演结果对AOD的高估也越大.
Evaluation of the MODIS Aerosol Products and Analysis of the Retrieval Errors in China
By using sunphotometer (AERONET) data as ground truth,the MODIS AOD from both Terra and Aqua in China were evaluated.The error sources of retrieval algorithm were investigated and analyzed.The resuits show that:(1)Xianghe,Yulin,Shouxian,Hefei,Hong Kong and Taiwan sites MODIS AOD accuraciesare better than other sites.We compared Terra and Aqua AOD data separately to AERONET data,and found no significant differences.(2)MODIS AOD at Xianghe,Taihu,SACOL,Beijing,Xinglong and ChenKung_Univ sites was selected for detailed analysis.As compared to other sites,MODIS AOD at Xianghe site shows much closer to the 1:1 line,and higher correlations (0.96 and 0.97 for Terra and Aqua,respectively).In addition,72％ and 65％ of the MODIS retrievals of the comprehensive data set lie within the expected error for Terra and Aqua,respectively.MODIS AOD was overestimated,and can be revised using the intercept of the fitted line at Taihu and Beijing site.At SACOL,the relationship between Terra and Aqua MODIS AOD and AERONET AOD is poor;with the correlation coefficient is 0.66 and 0.77,respectively.MODIS C005 AOD products precision is higher than Deep Blue AOD product precision at SACOL.(3) Error analysis shows error mainly from surface reflectance relationship inaccurate,at Xianghe and SACOL.At Taihu and Beijing sites,retrieval errors may be due to effect of both surface and aerosol model.The majority of cases have low cloud fraction and there is no significant bias,however,MODIS overestimates AOD when cloud fraction is higher.
NETL
NSTL
万方数据
维普
