利用TRMM/TMI资料反演青藏高原中部土壤湿度

The Retrieval of Soil Moisture from TRMM/TMI Data in Central of Tibetan Plateau

用辐射传输理论提出的地表微波辐射极化指数PI的定义,分别指出了PI对土壤湿度、地面粗糙度、植被层和大气层的影响。用热带降水测量(TRMM—Tropical Rainfall Measuring Mission)卫星上携带的微波辐射仪(TMI—TRMM Microwave Imager)的1B11的6年亮温数据,统计得到青藏高原中部地区PI值月平均分布。并用归一化距平,反演得到了该区域年、季以及干湿季土壤湿度变化的空间图像。结果表明,PI距平分布图可以很好地表征土壤湿度的变化,从而为大尺度评估高原土壤湿度变化提供了理论依据。另外,在同一时间段内,在已知区域平均PI值与平均土壤湿度的条件下,用归一化距平的方法可以定量反演该区域的土壤湿度。

Denoting the polarization difference,a polarization index（PI） of microwave radiance from the terrain surface is derived from the radiative transfer model.The PI shows the radiance effects of the soil surface moisture,surface roughness,vegetation canopy and atmosphere,and can be focused on mapping the land surface moisture.Statistics of the monthly average from multitemporal 6-year data of the TMI observations at the lowest 10.7 GHz channels obtained to individually demonstrate variation of the land surface moisture.Through this result,the interannual /seasonal variation as well as dry/wet season variation images of the volumetric moisture are retrieved in this area.It can help us evaluate the Mv variation in Tibetan Plateau well from the large scale.When the monthly average and the ground truth of average volumetric moisture of the region are available,it is tractable to retrieve the land surface moisture by using the PI data at the same month and the same region without much knowledge of surface roughness,vegetation canopy and others.