Spatiotemporal variations of drought in the Yunnan-Guizhou Plateau, southwest China, during 1960–2013 and their association with large-scale circulations and historical records

Abstract

Abstract It is imperative that more powerful drought indicators are used to objectively quantify the characteristics of droughts. A revised reconnaissance drought index (RDI) was used to detect drought in the Yunnan-Guizhou Plateau (YGP), and the impacts of potential evapotranspiration, precipitation, and climate index anomalies were also considered. This will help to further elucidate the causes of meteorological droughts from a climate change perspective, and is of great importance in guiding future drought prediction and control. The non-parametric Mann-Kendall test was applied to identify points of change for meteorological droughts in the YGP during 1960–2013, and a cross wavelet analysis was used to reveal correlations between monthly climate indices and the RDI. The results are as follows: (1) The decreasing RDI trends (annual (−0.066/10a), summer (−0.18/10a), autumn (−0.196/10a), and winter (−0.056/10a)) indicate increasing drought severity, while the increasing trend in spring (0.084/10a) indicates a decreasing drought severity. However, these trends were insignificant, and no mutations occurred in the YGP during 1960–2013. (2) The drought duration was longest in the central, southern, northwestern, and northeastern edge of Yunnan Province (YP) and in the western parts of Guizhou Province (GP), while the drought severity was higher in the southwestern, eastern, and western edge of YP, and throughout GP. For the entire YGP, the duration and severity of droughts in the 1960s, 1980s, and 2000s was generally stronger than in 1970s and 1990s (3) Drought events that were identified by the RDI are consistent with those in historical records, but there are also inconsistencies during individual years. It was found that the RDI accounts for both the influence of precipitation and evaporation on drought: a decreased annual precipitation (84.6%) and an increased evaporation (40.7%) both contributed to decreased RDI (59.3%) for all stations. Therefore, the decrease in precipitation may lead to drought in the YGP. (4) The El Nino Southern Oscillation and the Arctic Oscillation play major roles in meteorological droughts in the YGP and affect the RDI over a relatively short timescale (1–8 years); severe droughts in spring occurred mainly during El Nino events, whereas both El Nino and La Nina events were associated with droughts in summer, autumn, and winter. Overall, severe droughts occurred more frequently during the El Nino event than during the La Nina event.