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Title
Japanese:Radiative Characteristics at 89 and 36 GHz for Satellite-Based Cloud Water Estimation Over Land 
English:Radiative Characteristics at 89 and 36 GHz for Satellite-Based Cloud Water Estimation Over Land 
Author
Japanese: 瀬戸 里枝, Kentaro Aida, 小池 俊雄, 鼎 信次郎.  
English: Rie Seto, Kentaro Aida, Toshio Koike, Shinjiro Kanae.  
Language English 
Journal/Book name
Japanese:IEEE Transactions on Geoscience and Remote Sensing 
English:IEEE Transactions on Geoscience and Remote Sensing 
Volume, Number, Page Volume 59    Issue 2    Page 1355-1368
Published date Feb. 2021 
Publisher
Japanese: 
English:IEEE 
Conference name
Japanese: 
English: 
Conference site
Japanese: 
English: 
Official URL https://ieeexplore.ieee.org/abstract/document/9113659
 
DOI https://doi.org/10.1109/TGRS.2020.2996239
Abstract Satellite-based passive microwave (PMW) remote sensing is an essential technique to clarify long-term and large-scale distribution patterns of cloud water content (CWC). However, most CWC estimation methods are not implemented over land because of high heterogeneity of land radiation, and the detailed characteristics of microwave (MW) radiative transfer between land and atmosphere including clouds have not been elucidated. This study aims to elucidate these characteristics and reveal the accuracy of land emissivity representation necessary for adequate CWC estimation over land using satellite-based PMW under various CWC conditions. First, important parameters related to MW radiative transfer between land and atmosphere at CWC-relevant frequencies in the presence of clouds are determined theoretically. Next, the relationship between errors in these parameters and the brightness temperatures used for CWC estimation is clarified through considerations based on radiative transfer equations. Then, ground-based PMW observations and numerical simulation are used to reveal the actual values of these important parameters and the size of errors. Finally, the results show that for any cloud liquid water path (LWP) value greater than 1.6 kg/m 2 at 89 GHz and 5 kg/m 2 at 36 GHz, we can reasonably neglect the heterogeneity of emissivity and radiation from the land surface for CWC estimation. However, when LWP values are below the threshold, the error in the representation of land emissivity should be kept below 0.015 for both 89- and 36-GHz data, and volumetric soil moisture content should have an error lower than 5%-6% for both frequencies.

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