Process-based Accumulated Drought Index (PADI) For Impact Assessment

Droughts severely affect the plant growth, crop yields and global food production. The enhanced risk of droughts is even more relevant in the context of the globally changing climate. This study aims to analyze the typical droughts occurring globally and quantify the drought severity, which is directly correlated with the loss in crop yield. For this purpose, long term multi-sensor datasets of precipitation, root zone soil moisture and vegetative states are used to calculate the Process-based Accumulated Drought Index (PADI). This newly proposed drought assessment method integrates drought evolution with crop phenology.

In this study, the four main phases of evolution of an agricultural drought - Incubation, Onset, Intensification, and Elimination phases are identified. The crop growth stages and soil moisture deficit coefficients, are then integrated with the prior drought evolution process, using the PADI model. Thus, the spatial-temporal evolution, duration, intensity, and severity are obtained and the accumulated drought impact on crops is quantified.

PADI is tested over China, India and Midwest U.S. and the detailed drought development patterns and an assessment of drought impact on crop production, are presented. Findings from this study will help in the understanding of global drought occurrences and provide further guidance for improved agricultural practices.