Meteorological Drought Migration Characterisitics Based on an Improved Spatiotemporal Structure Approach

Abstract

Spatiotemporal synchronism of drought event is basic for accurately examining drought migration processes, showing significance to drought risk management and mitigation. However, migration characteristics remain poorly understand in a changing environment as numerous previous studies discarded 3-dimentional information (latitude, longitude and time) for drought characteristics. Moreover, the existing approaches based on a fixed overlapping area for identifying 3-dimentional drought events are not perfect. To this end, an improved and simple approach based on spatiotemporal relations was proposed to derive the optimal threshold for identifying drought event on temporal continuity in this study. Based on the one monthly Nonparametric Standardized Precipitation Index (NSPI), this improved approach was applied for investigating the migrations characteristic of meteorological drought events in Loess Plateau, China. Results showed that: (1) improved approach has a better performance on identifying prolonged droughts than fixed overlapping area threshold through comparing identified droughts with history recorded droughts; (2) spatially, meteorological drought events with high severity (DS), long duration (DD), large effected area (DA) and fast migration velocity (DV) mainly occur in the central part; temporally, DS and DA increase significantly; (3) meteorological drought event centroids move toward the northwest and southeast; and (4) meteorological droughts have a preferred westward migration direction and three dominant movement paths, which is critically important for local drought prevention and control. The findings of this study shed new insight into drought migration characteristics, which is a fundamental for drought driving mechanisms exploration, risk assessment as well as future forecasts.

Keywords: spatiotemporal synchronism, meteorological drought, migration characteristics, dynamics