MODIS遥感中国东部海域气溶胶光学厚度与现场测量数据的对比分析

Comparison of Remote Sensing Aerosol Optical Depth from MODIS Data with In-Situ Sky Radiometer Observations Over East China Sea

利用2006年4月至2007年11月间中国东部海域五个航次的天空辐射计海上观测资料,以10 km×10 km和±1 h作为时空匹配窗口,对中分辨率成像光谱仪(MODIS)标准海色产品中的869 nm气溶胶光学厚度数据进行了对比检验。结果显示,在全部匹配数据中,72%非常接近或在NASA公布的期望误差Δτ=±0.03±0.05τ范围以内。MODIS的反演精度具有一定的地域性和季节性差异,东海匹配数据的一致性明显好于黄海,2006年冬季匹配数据的一致性较好,2007年秋季MODIS反演值存在系统性偏高的情况,其主要原因可能与气溶胶模型的不适用有关。通过对全部匹配数据的进一步分析印证了这一点。

The in-situ data of sky radiometer observed on ship at East China Sea during five cruises from April 2006 to November 2007 are used to validate the corresponding 869 nm aerosol optical depth data included in MODIS standard ocean color products.The spatial box of 10 km×10 km and temporal interval of ±1 h are used as the matching criterion.The results show that： 72% of the match-up data fall close to,or within the expected error range of Δτ=±0.03±0.05τ.As there are some differences in the precision of MODIS-derived aerosol optical depth according to regions and seasons,data consistency over the East China Sea is better than the Yellow Sea,while the consistency in the winter of 2006 is better than the fall of 2007.In the fall of 2007,MODIS retrieval values are systematically overestimated.The reason for this phenomenon was analyzed.It seems that twelve pre-calculated aerosol models used by MODIS retrieval algorithms can′t match the optical properties of the actual aerosol very well,and further analysis with all of match-up data confirmed the conclusion.