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城市是陆表重要的覆盖类型之一,精确提取城市微波发射率、研究其辐射特征和影响因素有利于提高城市密集区被动微波遥感反演土壤水分的精度。利用2008年AMSR-E(Advanced Microwave Scanning Radiometer for Earth Observing System)6.925GHz和10.65GHz双极化的时间序列亮温数据和其他多种辅助数据,在分析并去除无线电干扰的前提下,提取中国区域相对纯净城市像元的发射率,并分析其辐射特征的季节变化和影响因素。结果表明,根据本文方法提取得到的中国区域纯净城市像元有两个,分别位于北京和上海。城市亮温受到无线电干扰影响,一年内不同城市、波段、过境时间的卫星观测亮温受到的干扰强度不同。去除无线电干扰后,各通道的城市发射率在一年中变化不大,且卫星降轨观测时刻的发射率比升轨时刻更加稳定。降雨是影响城市发射率的重要因子,当降雨量达到一定程度后,城市发射率与降雨量呈现明显的负线性相关。
Cities are one of the important land cover types. Accurately extracting the urban microwave emissivity and studying its radiation characteristics and influencing factors are conducive to improving the accuracy of passive microwave remote sensing data retrieval of soil moisture in dense urban areas. Using the time-series brightness temperature data of 6.925GHz and 10.65GHz dual-polarization of the AMSR-E (Advanced Microwave Scanning Radiometer for Earth Observing System) 2008 and other kinds of auxiliary data, the Chinese region was extracted and analyzed under the premise of analyzing and removing the radio interference Relatively pure urban pixel emissivity, and analysis of the seasonal variation of radiation characteristics and influencing factors. The results show that there are two pure pixels in China, which are extracted according to the method of this paper, located in Beijing and Shanghai respectively. The brightness temperature of the city is affected by radio interference, and the intensity of interference caused by the brightness temperature of satellite observations in different cities, bands and transit time within one year is different. After radio interference was removed, the emissivity of each channel changed little in one year, and the emissivity of satellite at orbit observation was more stable than that at orbital time. Rainfall is an important factor affecting the emissivity of the city. When the rainfall reaches a certain level, the urban emissivity and rainfall show a significant negative linear correlation.