Assessing spatiotemporal variation in dry-wet abrupt alternation using an improved process-based approach

Abstract

Study region: The Pearl River Basin (PRB), located in the south of China, has a tropical to subtropical climate. Study focus: In this study, we present an improved process-based approach to assess the intensity of the Dry-Wet Abrupt Alternation (DWAA) events, considering both the transition gap (alternation) and the transition rate (urgency) between dry and wet states. Using daily precipitation data from 1961 to 2020 across 75 meteorological stations in the PRB, we analyze the temporal and spatial evolution patterns of DWAA events. New hydrological insights for the region: The findings reveal that: (1) DWAA events in the western region generally occur less frequently but with higher intensity. (2) Dry-to-wet (D-W) events have an urgency intensity of 1.35, almost twice that of wet-to-dry (W-D) events at 0.69. However, the alternation intensity of W-D is only slightly higher by 0.17 compared to D-W. (3) The alternation and urgency changes in D-W events are asynchronous, with alternation intensity initially decreasing from 9.7 to 9.27, then increasing to 9.58, while urgency decreases continuously from 1.66 to 1.07. (4) The alternation and urgency changes in W-D events are synchronous. The alternation intensity initially decreases from 9.7 to 9.06, then rises to 10.1, while the urgency intensity decreases from 0.68 to 0.58 before subsequently climbing to 0.8.

Keywords

• Dry-wet abrupt alternation
• Evolution characteristics
• Transition time
• Transition gap