City microwave emissivity extraction and characteristic analysis in China
中国城市微波发射率提取与特征分析

City is a very important land cover type on the earth, making understanding city microwave emissivity essential in improving soil moisture retrieval accuracy using passive microwave remote sensing data, especially in urbanized regions. In this paper, time series Advanced Microwave Scanning Radiometer for Earth Observing System (AMSR-E) data in 2008 and other auxiliary data were used to extract and analyze the characteristics of city emissivity in China. During the process, radio frequency interference (RFI) in each pixel was evaluated f irst and the effects were removed before emissivity calculation. Also we studied the characteristics and infl uencing factors of city emissivity during the year. The results show that with the extraction method, only two pure city pixels in China are found, which are Beijing and Shanghai, respectively. Satellite observed city brightness temperature can be affected by RFI, but its effects varied between cities, bands and sensor crossing time. After eliminating RFI, the city emissivity fl uctuated slightly in a year and was more stable in descending time than in ascending time. Rainfall played an important role in city emissivity variation. There was an obvious negative correlation relationship between city emissivity and rainfall when rainfall reached a certain value.