Effects of Elevation and Longitude on Precipitation and Drought on the Yunnan-Guizhou Plateau, China

In this study, the effects of elevation and longitude on precipitation and drought on the Yunnan-Guizhou Plateau (YGP) are investigated, and the performance of four precipitation datasets (China Meteorological Forcing Dataset [CMFD], Global Precipitation Climatology Centre [GPCC], Climatic Research Unit [CRU] and Integrated Multi-satellite Retrievals for Global Precipitation Measurement [IMERG]) is evaluated for the YPG. On an intra-annual scale, the precipitation is bimodal and unimodal at 12 and 35 observation stations, respectively. The stations with bimodal precipitation are primarily located on the southeastern YGP. The first peak of the bimodal precipitation regime occurs in May or June and is higher than the second peak that occurs in October. The peak of the unimodal precipitation regime appears in either June or July. On an interannual scale, annual and seasonal precipitation have been decreasing at most stations, significantly so at some stations. The average precipitation on an annual scale and the spring, winter, and drought season gradually decreases from northeast to southwest and is significantly negatively correlated with the elevation and significantly positively correlated with the longitude. The average precipitation for the summer, spring, and rainy season has a relatively complex spatial distribution and is relatively weakly correlated with the elevation and longitude. The standard deviation (SD) of the precipitation is significantly negatively correlated with the elevation and significantly positively correlated with the longitude. The coefficients of variation (Cv) for the annual, seasonal and monthly precipitation are significantly correlated with the elevation and longitude at various time scales. For the spring and drought season, the standardized precipitation index (SPI) has significant negative and positive correlations with elevation and longitude, respectively, whereas the opposite is true for the summer, autumn, and rainy season. The SD of SPI for summer, autumn, rainy, and drought seasons shows a significant negative (positive) correlation with elevation (longitude). The evaluation results show that CMFD performs best, followed by GPCC, with the worst for CRU and IMERG. Different sources of water vapor influence YGP precipitation and thus YGP drought. Overall, the average precipitation and drought and their SD and Cv are more strongly correlated with the longitude than with the elevation.