A New Comprehensive Drought Index Based on Response Adjustment for Vegetation Types

Drought, leading to water supply deficits and vegetation growth anomalies, is one of the most serious but least understood natural phenomenon. Different vegetation types vary in sensitivity to drought and exhibit diverse kinds of responses. However, few studies have focused on the sensitivity and the response of various types of vegetation. Thus, in this paper, a new Drought Index based on land cover Types Response Adjustment (TRADI) is proposed based on response adjustment for vegetation, to gauge the response factors among various vegetation types and provide a comprehensive assessment of drought conditions. Multisource data from the Moderate Resolution Imaging Spectroradiometer (MODIS), the Tropical Rainfall Measuring Mission (TRMM) and the Global Land Data Assimilation System (GLDAS) was used to derive drought condition indices (CIs) and construct the TRADI. A correlation analysis between TRADI and Palmer Drought Severity Index (PDSI) monitoring results for typical drought events in the CONtinental United States (CONUS) was carried out to evaluate the reliability and efficiency of the proposed method. These results showed that drought was underestimated or overestimated by varying degrees when using traditional condition-based indices (CIs), but the TRADI can correct these misestimates and improve the drought monitoring accuracy.