Abstract: Based on the observational data in 63 weather stations from 1971 to 2010 in Heilongjiang province, the spatial and temporal characters of pan evaporation and actual evaporation were analyzed using methods of a climate trend coefficient and a climatic tendency. The results show that pan evaporation is in a decreasing trend in Heilongjiang province and its climatic trend is -62.7 mm per decade in the recent 40 years, especially in spring and summer. For the spatial distribution, pan evaporation is also in a decreasing trend in the whole province, while its trend in the local region is not synchronized with the whole one. Among the meteorological factors, wind speed and diurnal temperature range (DTR) are the key elements effecting pan evaporation. The annual actual evaporation accounts for 30% of pan evaporation and is in a slightly increasing trend, while its trend is not significant. The actual evaporation is significantly correlated with precipitation, sunshine duration and DTR, especially with diurnal temperature range.

Key words: Heilongjiang province, Pan evaporation, Actual evaporation