The research on climate change features and affecting factors of Linyi pan evaporation in recent 48 years

Based on 1961-2008 day-by-day meteorological data observed by Linyi stations, using correlation analysis and wavelet analysis method, the correlation and tendency of the pan evaporation and the main influence factors (sunshine, temperature, daily temperature range, relative humidity and wind speed, etc.) of the recent 48 years are researched. The results show that, in recent 48 years, the average annual pan evaporation of Linyi city is significantly decreased by 35mm/10a, by 95% confidence inspection. Annual pan evaporation is mainly reduced in spring, summer and autumn, and especially in summer the confidence level reached 99 percent. In 1983, annual pan evaporation reduced suddenly. The main reason of the decrease of pan evaporation is the significant reduction of sunshine duration and daily temperature range and the significant increase of low cloud cover and vapor pressure.