Spatiotemporal variation and multivariate controls of short-cycle drought-flood abrupt alteration in China’s north-south transitional zone

Abstract

A full knowledge of the alteration patterns of drought and flood in adjacent months is crucial to facilitate climate adaptation and mitigation strategies. However, the exploring of short-cycle drought-flood abrupt alteration (s-DFAA) and its multi-scale responses to multiple environmental factors remains poorly understood due to insufficient formula construction (e.g., drought standards cannot be introduced) of the existing short-cycle drought-flood abrupt alternation index (SDFAI). In this study, we proposed a new short-cycle drought-wetness abrupt alternation index (SDWAI) allowing to customize drought standards and applied which to China’s north-south transition zone. The multi-scale relationships (i.e. small scales (<4 years), medium scales (4-8 years), large scales (>8years) and all scales) between the s-DFAA(SDWAI) and its pertinent factors (i.e., precipitation, relative humidity, sunshine duration, temperature, evaporation; Arctic Oscillation, AO; NINO 3.4 SSTA Index, NINO3.4; Total Sunspot Number Index, TSNI; Pacific Decadal Oscillation Index, PDO) were further investigated using the wavelet transform coherence and multiple wavelet coherence. Results showed that the SDWAI outperformed the traditional one. Different-level s-DFAA events(i.e., mild, moderate, severe, extreme and total) identified by SDWAI exhibited insignificant downward trends. Spatially, there were more s-DFAA events in the east than the west. Among the single and multiple meteorological elements, precipitaion was the dominant factor influencing the SDWAI, with the highest percent area of significant coherence (PASC) at different scales. Each teleconnection and their combinations, which were irreplaceable, had the most siginificant influence on SDWAI at large scales where TSNI and NINO3.4 that contributed higher PASC were substantiated the predominant roles.