Dynamic changes of the dryness/wetness characteristics in the largest river basin of South China and their possible climate driving factors

Abstract

Abstract Although numerous studies have investigated the evolution of regional dryness/wetness, few studies have discussed the association with climatic extremes and large-scale ocean-atmosphere teleconnections from the perspectives of the duration and severity of dryness/wetness. This study took the largest river basin in South China, namely, Pearl River basin (PRB), as a study example. We use the Standardized Precipitation Evapotranspiration Index (SPEI) and the run theory to extract the dryness/wetness characteristics (i.e., duration and severity). Then, the one-dimensional (i.e., Spearman rank correlation) and multi-dimensional (i.e., cross wavelet transform (XWT) and partial wavelet coherence analysis (PWC)) correlation methods were applied to explore the dryness/wetness characteristics with association of climate extreme indices and teleconnection patterns during the past few years (1960–2015). The results show that two dominant sub-regions (i.e., northwestern and southeastern) are showing distinct spatial differences in the temporal evolution of the duration and severity of dryness/wetness, including the change trends, periodical oscillations, and association with climatic extremes and teleconnection patterns in the PRB. The most regional differences in the trends of the dryness/wetness could be explained by the temperature variability and precipitation extremes. The multi-dimensional analysis method especially the PWC is superior to the one-dimensional signal method in the analysis of the time-frequency correlations between dryness/wetness evolution and large-scale ocean-atmosphere teleconnections. For PRB, the teleconnections of Pacific Decadal Oscillation (PDO) and especially with El Nino–Southern Oscillation (ENSO) were highly associated with the evolution of the dryness/wetness and occurred principally at the inter-annual (32–64 months) and inter-decadal (128–256 months) scales.