Statistical analyses of spatial and temporal variabilities in total, daytime, and nighttime precipitation indices and of extreme dry/wet association with large-scale circulations of Southwest China, 1961-2016

The spatial and temporal variabilities of total precipitation (TP), daytime precipitation (DP), nighttime precipitation (NP), and their corresponding extremes in Southwest China (SWC) were investigated based on daily precipitation records from 112 meteorological stations obtained during 1961-2016. The standardized precipitation index was used to analyze extreme dry/wet events, and correlations with climate indices were detected using cross-wavelet analysis. The results indicated that on annual and seasonal scales, the majority of meteorological station records displayed downward trends for TP, DP, and NP (except in spring), which were particularly evident in autumn. Spatially, on both annual and seasonal timescales, higher values of TP and NP were found in southwestern parts of the Hengduan Mountains (HDM), southern and eastern parts of the Yunnan-Guizhou Plateau (YGP), and in southwestern and southeastern areas of the Sichuan Basin (SCB). The occurrences of dry/wet events in SWC were found correlated particularly well with ENSO. Furthermore, extreme dry/wet events were found to occur during El Nino and La Nina years, whereas the frequency of extreme dry events was found higher than extreme wet events during both El Nino and La Nina years since 2001. The findings of this study suggest that TP (TPd), DP (DPd), and NP (NPd) all showed decreasing trends, while extreme precipitation showed an increasing trend, indicating that both the intensity and the concentration of precipitation are increasing. Therefore, the risks of heavy precipitation and flooding are likely to increase in SWC, particularly in the SCB and that extreme events might be strengthened in certain seasons.