Space-time variability of drought over Vietnam

Drought may have severe societal, economic, and environmental consequences. However, the space-time characteristics of drought over Vietnam remain poorly understood. In this study, we investigate the spatio-temporal variability of drought using the Palmer Drought Severity Index (PDSI) over mainland Vietnam for the 1980-2014 period. Through data analysis at 131 stations, we identified the main characteristics, historical trends, and dominant variability of drought across seven climatic sub-regions in Vietnam. The results show regional patterns of drought duration, inter-arrival time, frequency, and severity, but no consistent trend of drought variation during the study period. Based on the supply and demand concepts of water balance, PDSI captures well the large frequency and severity of drought in some sub-regions that are related to soil moisture deficit associated with high temperature and low rainfall during summer. Moreover, drought over Vietnam was predominantly controlled by climate seasonality. The linkages between drought in Vietnam and large-scale drivers are quite different among areas, suggesting a possibility of early prediction for drought at some sub-regions using ENSO.