REOF-Based Spatiotemporal Variation of Dryness/Wetness Conditions over Guangdong Province
The monthly dryness/wetness conditions were calculated by applying the Standardized Precipi-tation index (SPI)at the 6 month scale based on the daily precipitation records of 25 meteorological sta-tions in Guangdong Province from 1960 to 2011.The methods including Mann-Kendall trend test,Rota-ted Empirical Orthogonal Function (REOF)and wavelet analysis were employed to detect the spatial and temporal patterns of dryness/wetness conditions over Guangdong Province.The results indicate:decrea-sing trends of SPI are identified mainly in January,February and March,while increasing trends are dominantly concentrated in July,August and September.In the middle part of the study area,the num-ber of months with increasing trends is more than in eastern and western parts.In addition,the eastern and coastal regions of Guangdong are characterized by increasing trends (wet tendency)of SPI in the rainy season (April to September),and the majority portion of Guangdong shows decreasing trends (dry tendency)of SPI in winter.According to the results of REOF,there are four main anomaly sub modes in Guangdong,i.e.,the Nanling,Leizhou Peninsula,the East and West Guangdong.All corresponding ro-tated principal components (RPC)of REOF indicate a wet-dry tendency in the rainy season,and all of them show a dry tendency in winter except the West Guangdong sub mode.1.5-year and 2 to 3-year peri-ods (significant atα=0.05 confidence level)can be investigated in all sub modes with the help of wave-let analysis.
SPIMann-Kendall trend testREOFwavelet analysisGuangdong Province
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