A New Physically Based Self-Calibrating Palmer Drought Severity Index and its Performance Evaluation

In this study, a new Palmer Drought Severity Index (PDSI) variant is developed by coupling Variable Infiltration Capacity (VIC) model with the self-calibrating PDSI (SCP). Evaluation of the new drought index (denoted as SCPV) is conducted during 1961-2012 over whole Yellow River basin (YRB) through a series of comparisons with SCP, including intermediate variables (moisture departure d, climatic characteristic K and moisture anomaly index Z), long-term series of PDSI values, and their each relationship with other meteorological and agricultural indices. Results show that SCPV generally inherits the advantages of SCP, and improves the deficiencies of SCP in the hydrologic accounting section to some extent. Comparing to SCP, SCPV ameliorates the negative departure of accumulated moisture anomaly index Z of SCP in the semiarid zone. The introduction of physically based VIC model in SCPV reinforces its connection with hydrological variables and hence shows better correlation with other meteorological and agricultural drought indices. Spatial drought trends reflected by SCPV are more reasonable, especially for the source region and northern parts of the YRB. With more preferable behavior in moisture departure simulations, SCPV shows its strength and is promising to be a competent reference in future drought researches.