Comparison of Temperature Vegetation Dryness Indexes through Two Approaches in Drought Monitoring: a case of Henan Province

摘要

Temperature vegetation dryness index (TVDI) is widely used for its physical significance. In this study, using the historical MODIS data, we consider Henan Province, a large grain province in Central China, an example for constructing feature space and calculating TVDI. Multi- and single-group image approaches are then compared, and the applicability of the TVDI in Henan Province is analyzed through the space-time analysis of the relative soil moisture (RSM) with different depths. Results show that: 1) These two approaches have the same spatial correlation between the TVDI and RSM, although the time correlation between TVDI and RSM is improved by the multi-group approach. 2) The single-group approach of TVDI exaggerates the wet (dry) conditions during dry conditions (normal or wet). The TVDI spatial distribution provided by the multi-group approach (especially in the wet condition) is consistent with the actual condition. 3) The spatial correlation between the TVDI and 20 cm RSM is higher than other depth, denoting a certain indication function to the soil moisture from April to July and in October in Henan Province. However, this correlation lacks stability. In general, the multi-group approach improves the comparability among the TVDIs of the different times and simplifies the calculation. However, the TVDI also has several uncertainties in terms of drought monitoring.