【摘要】 地表微波比辐射率植被指数(emissivity difference vegetation index, EDVI)可以很好地指示地表植被含水量,并且可以应用于有云情况和浓密植被区域.以往的研究仅限于使用19GHz和37GHz微波信号,仅能反映植被某单层的含水情况,而Aqua卫星的Advanced Microwave Radiometer-Earth Observing System (AMSR-E)微波辐射计观测可为植被含水量遥感提供更多的通道选择.本研究利用多源卫星遥感产品,包括AMSR-E亮温、Moderate Resolution Imaging Spectroradiometer (MODIS)云参数和欧洲中期天气预报中心(ECMWF)的再分析资料等,反演了东亚及东南亚地区6.925、10.65、18.7、36.5GHz垂直极化微波通道的陆地表微波比辐射率,并以此建立了三组多通道微波比辐射率植被指数EDVI(6v, 37v)、EDVI(10v, 37v)和EDVI(18v, 37v),研究了该三组EDVI指数在森林和农田两类植被类型区的特点.结果表明,在森林区域,EDVI(6v, 37v)和EDVI(10v, 37v)普遍大于EDVI(18v, 37v),这很可能是由于前两者对于浓密植被的穿透更深,能反映更多的植被含水量,而EDVI(18v, 37v)的穿透性相对较弱,主要反映冠层顶部、相对浅薄植被层的植被含水量.综合利用这三组EDVI指数之间的差异,在高大浓密植被区域,可以实现对植被含水量在上、中、下三层的垂直分布的估计.对于低矮植被,其垂直结构不丰富,此三者的差异不明显.更多还原

【Abstract】 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 a cloudy sky and over dense vegetation areas 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 Advanced Microwave Scanning Radiometer-Earth Observing System(AMSR-E) onboard NASA’s Aqua satellite provided multiple choices of satellite remote sensing VWC with EDVI. In this study, multiple source measurements, including microwave brightness temperature from AMSR-E, cloud parameters from Moderate-resolution Imaging Spectroradiometer(MODIS), and reanalysis of atmosphere states from ECMWF were synergized, to retrieve the microwave land surface emissivity at 6.925, 10.65, 18.7 and 36.5 GHz in eastern and southeastern Asia from 2003 to 2010. The retrievals were then used to define multiple channel EDVIs of EDVI(6 v, 37 v),EDVI(10 v, 37 v) and EDVI(18 v, 37 v) and the characteristics of those EDVIs over forest and cropland areas were studied. The results showed that, EDVI(6 v, 37 v) and EDVI(10 v, 37 v) are greater than EDVI(18 v, 37 v) in forest dominated areas. This is most likely due to the fact that the penetration depth of EDVI(6 v, 37 v) and EDVI(10 v, 37 v) are deeper than that of EDVI(18 v, 37 v), thus indicating relatively more VWC in thicker canopy layer of the forest. The differences among the three EDVIs can be used to represent the vertical distribution of VWC in upper, middle and lower layers of high and dense vegetation. However, for the shallow and sparse vegetation without significant vertical variation of VWC, the differences among the three EDVIs are too small to be used.更多还原