基于Ts-EVI特征空间的春旱遥感监测——以河北省为例

Application of Ts-EVI character space to monitor spring drought——a case study in Hebei China

春季干旱是影响我国农业生产的重要自然灾害。以河北省为研究区,采用Ts-EVI构建的特征空间,以温度植被干旱指数TVDI作为土壤水分估算因子对2005年4～5月的春旱发生与发展进行遥感监测,主要得出以下结论:(1)表层土壤相对湿度RSM_(10)与TVDI的相关性均通过了α=0.001水平的置信度的t检验而表现出显著相关性,基于Ts-EVI特征空间构建的TVDI可以较好地估算土壤表层水分状况。(2)TVDI与不同土壤深度RSM的相关性在不同时期存在一定的差异,4月上旬～4月中旬以10 cm深度处的相关性最高,20 cm处次之;4月下旬～5月下旬以20 cm土壤深度处的相关性最好,10 cm处次之。(3)在不统计云覆盖地区旱情的情况下,2005年4月上旬河北省春旱面积为15 014.4 km^2;4月中旬～5月下旬的春旱面积分别为43 350.4 km^2、13 889.3km^2、71 664.3 km^2、12 864.8 km^2和44381.5 km^2。

Spring drought is one of the most serious disasters to agriculture in China. In this paper, MYDO9A1 and MYD11A2, the 8 -day reflectivity and land surface temperature composite productions provided by NASA, which derived from MODIS （Moderate Resolution Imaging Spectroradiometer） images from April to May in 2005 were used to study drought conditions in Hebei China. Enhanced vegetation index （EVI） was acquired from refleetivity productions and triangle character space with land surface temperature （Ts） and EVI was contributed. Equations of the dry and the wet edges in the spaces were got and temperature vegetation drought indices （TVDI） for each ten days were calculated. Relations between TVDI and relative soil moisture （RSM） in different depth were analyzed. Besides, soil moisture estimation models for TVDI images were also given and error tested. According to criterion of soil moisture drought levels of China, areas and developments of spring drought from April to May in 2005 in Hebei were monitored and analyzed. Results showed that： （1） Correlation between surface relative soil moisture （RSM） and TVDI passed t - test with the level of c~ = 0. 001, and TVDI got from Ts - EVI character space could estimate surface RSM successfully. （2） At different time, there were great changes existed in the correlations between TVDI and RSM with different depth. In the first twenty days in April, RSMl0（With the depth of 10 era） showed the high- est correlation with TVDI and the correlation between TVDI and RSM20 （with the depth of 20 cm） was higher. How- ever, from last ten days in April to last ten days in May, RSM20 showed the highest correlation with TVDI and cor- relation between TVDI and RSMx0 was higher. （3） On the condition that areas covered with cloud were not he con- sidered in Hebei China, spring drought area in the first ten days in April was 15014.4 km2, and from the second ten days in April to the last ten days in May, drought areas for each ten days were 43350.4 km2, 13889.3 km2, 71664.3 km2, 12864.8 km2 and 44381.5 km2, respectively.