Analyzing the spatial-temporal variation of wet and dry spells during 1962-2007 in Guangdong province

The multi-scale standardized precipitation and evapotranspiration index (SPEI) is calculated using the monthly precipitation and temperature data observed at 74 meteorological stations during 1962-2007 in Guangdong.The spatial-temporal variation of wet and dry spells is analyzed using the methods of the rotated empirical orthogonal function (REOF), the Mann-Kendall trend test and the wavelet analysis.Results show that both the frequency and spatial extent of drought have increased over time since the 1970s.The whole Guangdong can be divided into six wet and dry regions based on the first six modes of REOF.These regions are located in the Pearl River Delta, the upper Hanjiang River and Dongjiang River basins, the Xijiang River basin and the middle and lower Beijiang River basin, the eastern coastal district, the upper Beijiang River basin, and the western coastal district.The trend of wet and dry spells in Guangdong varies significantly across the province from east to east.Significant upward trends in drought have been detected in the Leizhou Peninsula, the Xijiang River basin and the middle and lower Beijiang River basin, the western coastal district.In addition, the temporal variation of wet and dry spells exhibits a periodic oscillation of period of 2 to 8 years in the six regions.