Surface temperature correction in TVDI to evaluate soil moisture over a large area

Abstract

The Temperature-Vegetation Dryness Index (TVDI), based on an empirical relationship between land surface temperature (LST) and vegetation index (VI), has been widely used in large area drought monitoring. Temporal and spatial variations of LST and VI (NDVI) over a large area in southern Hebei Plain of China that covers five degrees North latitude are analyzed in this paper. We show that there were significant changes in crop phenological stages and VI in different latitudes giving rise to a parabolic relationship between LST and latitude. The lower LST in the northern area caused by lower air temperature leads to some errors in the use of TVDI. After removal of the influence of lower air temperature on LST, the accuracy of soil moisture monitoring by TVDI is improved compared with observations of soil moisture.