Classification-Based Spatiotemporal Variations of Pan Evaporation Across the Guangdong Province, South China

Change in pan evaporation (E-pan) has evoked general scientific interest because it involves both climatic and hydrological effects. The enhanced greenhouse effect may be the casual factor, although the mechanism still needs to be further confirmed. Based on meteorological data (Pan evaporation, rainfall, air temperature, sunshine duration, relative humidity, wind speed, cloud cover, and water vapor pressure) of 85 sites from 1957 to 2006, classification-based spatiotemporal variations of pan evaporation and possible causes were studied in the Guangdong province, South China (with a coastline of 8,500 km), which is one of China's most prosperous provinces with the largest population. The Guangdong province was spatially divided into 4 parts, i.e., Southwest part, East part, Central part, and Northwest part, according to E-pan and seven other climatic factors based on cluster analysis. Results showed that pan evaporation in this study area declined -3.35 mm year(-1) on average in time, and mainly decreased from the seashore area to the inland area in space. Results also showed that all the climatic factors can contribute to change in E-pan, but their contributions were different over the space. Sunshine duration (SD) and wind speed (WS) had a positive correlation with E-pan, while rainfall (R) and air temperature (T-a) were negatively correlated to E-pan. Among all the 7 climatic factors, SD was identified as the dominant driving force of E-pan change in the Guangdong province.