Construction Of Microwave Land Surface Emissivity Database In East Asia And Its Application In Vegetation Remote Sensing

The spaceborne passive microwave remote sensing has long being utilized as an important approach of learning and monitoring land surface and atmosphere properties.The microwave land surface emissivity(MLSE)and its ramification microwave emissivity difference vegetation index(EDVI)are two effective parameters indicating plenty of surface information thus worthy of thorough study.There are two main subjects in this thesis:1)Retrieval of microwave land surface emissivity database using multi-source satellite observations and its application in China.2)Analysis of the characteristics of satellite-derived multiple channel microwave emissivity difference vegetation index(EDVI)over different vegetation types.In the first part,a MLSE database is established in China,derived from the observations of Advanced Microwave Radiometer-Earth Observing System(AMSR-E),Moderate Resolution Imaging Spectroradiometer(MODIS),and ancillary atmospheric profiles and land surface temperature(LST)from the European Centre for Medium-Range Weather Forecasts(ECMWF)reanalysis dataset.Developed with a improved method,the database is featured with a higher quality due to the utilization of dynamic high resolution reanalysis data to represent the real atmospheric conditions,along with a full spectra of AMSR-E radiometer to detect the surface sufficiently,especially for low band 6.9 and 10.65 GHz with better penetration into vegetation canopy comparing to high frequencies.The atmospheric correction on cloud presence extends the ability of illustrating the surface emissivity under all-weather conditions.The applicability of this database in China is investigated along with the interactions between geographical and seasonal patterns of the emissivity and topography,vegetation,snow cover and cloud effect.The application value is promised in better understanding the interactions between MLSE and various factors.The potential application of this database is serving as a precondition in estimations of various atmospheric properties(e.g.,precipitation,cloud water content)over land,as well as the widespread use in monitoring the changes of numerous surface properties related to weather changes,climate changes and vegetation growth status.In the second part,the satellite-derived Microwave Land Surface Emissivity Difference Vegetation Index(EDVI)is a good indicator of vegetation water content(VWC).And it can be used under cloudy sky and over dense vegetation area where satellite optical vegetation index can be easily saturated.Previous studies on EDVI used the two frequencies of 19 and 37 GHz only.The associated EDVI can only represent VWC in one single layer of the canopy.Measurements from AMSR-E onboard Aqua satellite provide multiple choices of satellite remote sensing VWC with ED VI.In this study,we synergize multiple source measurements,including microwave brightness temperature from AMSR-E,cloud parameters from MODIS,reanalysis of atmosphere states from ECMWF,to retrieve the Microwave Land Surface Emissivity at 6.925?10.65?18.7?36.5 GHz in eastern and southeastern Asia during 2003 to 2010.We then use the retrievals to define multiple channel ED VIs of EDVI(6v,37v),EDVI(10v,37v),EDVI(18v,37v),EDVI(6v,10v)and EDVI(10v,18v)and study the characteristics of those ED VIs over forest and cropland areas.The results show that,EDVI(6v,37v)and EDVI(10v,37v)are greater than EDVI(18v,37v)in forest dominated areas.This is most likely due to the fact that the penetration depth of EDVI(6v,37v)and EDVI(10v,37v)are deeper than that of EDVI(18v,37v)thus represent relatively more VWC in thinker canopy layer of the forest.ED VI(6v,10v),ED VI(10v,18v)and ED VI(18v,37v)can be used to represent the vertical distribution of VWC in upper,middle and lower layers of high and dense vegetation.However,for those shallow and sparse vegetation without significant vertical variation of VWC,the three ED VIs are too small to be used.Based on the above two problems,this study attempts to get a more comprehensive understanding of the spatial distribution characteristics of microwave land surface emissivity in China and reveal abundant information of the surface vegetation.This research will expand the topics of satellite microwave remote sensing,enrich the methods of remote sensing,especially for vegetation remote sensing,and serve as data base for retrievals of various atmospheric parameters.