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 first and the effects were removed before emissivity calculation.Also we studied the characteristics and influencing 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 fluctuated 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.