Abstract: Along with global warming,the global and regional water balance and climate dryness/wetness status and its variation will be changed.Therefore,the regional water cycle and dryness/wetness status has become study focus.Based on the climate data of 86 meteorological stations in Guangdong Province,the daily potential evapotranspiration(ET0) from 1954 to 2005 in the area was calculated using the Penman-Monteith formulation,and the spatial-temporal variation of the precipitation and ET0 was analyzed.The climate dryness/wetness status was evaluated by Moisture Index(MI) which was recommended by the national criterion(BG/T20481-2006).The results showed that: 1) It was humid in Guangdong Province as a whole,however,the dryness/wetness status was spatially uneven.The spatial distribution pattern of MI was consistent with that of precipitation,i.e.there were three wet centers including Enping,Longmen and Haifeng.2) The seasonal variation of MI was mainly influenced by the precipitation,it showed distinct characteristics of wet and dry season.3) Both in Spring and in Autumn,MI spatially varied with latitude,but changing direction was opposite.The spring drought was more serious in the South than in the North of the Province,while the autumn drought was more serious in the North than in the South of the Province.As a whole,the autumn drought was more serious than spring drought in the Province.4) The annual average MI decreased slowly in last 50 years,implied that climate dryness/wetness status was tending to be hotter and drier in Guangdong Province.This study provided references for response measures to climate change,the exploitation and utilization of climate resources and planting zoning adjustment.

Key words: Potential evapotranspiration, Potential evapotranspiration, Relative moisture index, Dryness/wetness status, Penman-Monteith equation