Consistency and comparison among remote sensing drought indices and SMAP soil moisture in Kazakhstan

SUN Bo;QIAN Jing;CHEN Xi;XING Xiu-wei;ZHOU Qi-ming;Shenzhen Institutes of Advanced Technology,Chinese Academy of Sciences;Research Center for Ecology and Environment of Central Asia,Chinese Academy of Sciences;Department of Geography,Hong Kong Baptist University;

remote sensing drought index;;SMAP;;soil moisture;;validity test;;Kazakhstan

In order to evaluate the applicability of remote sensing drought indices for agricultural drought monitoring in the arid zone of Central Asia,several typical indices (i. e.,AVI,VHI,and VSWI) from current global drought monitoring systems were assessed using active and passive microwave soil moisture data (SMAP). Data from late June,the middle and late period in the plant growing season,were utilized for this experiment. According to datasets for existing land use and land cover,more than 2 650 samples fully covered by vegetation were chosen. Correlations between remote sensing drought indices and soil moisture were examined using the Pearson correlation coefficient (r) and Kendall rank correlation coefficient (τ) . Resultes show that AVI and soil moisture are not significantly correlated. However,VHI and VSWI are significantly positively correlated with soil moisture at two layers,including the surface layer (0-10 cm) and the root zone layer (0-100 cm). By comparison,VSWI exhibits a strong correlation with soil moisture at root zone level (r > 0. 6),which also shows a good response to drought conditions in the middle and late stages of the growing season in Kazakhstan. For determining drought grade,VHI shows a weak positive correlation with soil moisture.