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A Cloud Detection Algorithm Over Land Based on the Polarized Characteristics Difference Between Cloudless and Cloud Targets

, , Wei Fang, Dekui Yin
Published: 14 September 2019
Earth and Space Science ; doi:10.1029/2019ea000677

Abstract: The accurate identification of cloud over land is one of the key issues of the satellite data processing and the product retrievals. This paper describes a new cloud detection algorithm based on Level 1 data of Polarization and Directionality of Earth's Reflectance (POLDER). The simulation of multi‐angular normalized polarized reflectance is done for cloudless targets over land before the cloud identification processing. Firstly, the Normalized Difference Vegetation Index (NDVI) over land and reflectance of 670nm are used as two initial criterions for the cloud mask. Then, the difference between the simulation and POLDER observation of polarized reflectance is used as the third criterion to distinguish cloudless pixels from cloud ones. And this algorithm is proved to be more convenient and effective. This algorithm is also applied to cloud mask processing of the Multi‐Angular Polarization Imager (MAPI, onboard the Tiangong‐2) observation. The results show that this algorithm can effectively detect cloud targets over land, and its consistency with POLDER official cloud mask products is about 90%. This algorithm can provide reliable cloud mask products for the retrieval of optical and physical properties of land aerosol using MAPI data.
Keywords: algorithm / NDVI / polarization / cloud detection / criterion / mask / Mapi / Cloud Targets / Multiâ

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