Potential Evaptranspiration and Dry-Wet Conditions in Seasonal Frozen Soil Region of Northern Tibetan Plateau

Based on the observed data at Automatic Weather Site(AWS) of MS3478 in the seasonal frozen soil region of northern Tibetan Plateaufrom March 2007 to February 2008. Using Penman-PEMonteith method recommended by FAO ,researchers from Nagqu Observatory for High-Cold Climate and Environment, Cold and Arid Regions Environmentaland Engineering Research Institute(CAEERI), Chinese Academy of Sciences analyzed the variation characteristics of potential evapotranspiration (PE) ,and discussed the contributions of dynamic, thermal and water factors to PE.

They further studied the wet-dry conditions of that region. The results indicated that the daily PE was between 0.52 mm and 6.46 mm in the whole year. In summer, the evaporation was the most intensive, and month PE from May to September was over 100 mm. In November, there wasa clear mutant. Annual potential evapotranspiration was 1037.83 mm. In summer, thermal evapotranspiration was much more significantly than dynamic evapotranspiration; in winter it was on the contrary.

In addition, the drought and semi-drought climate lasted for a long time while semi-humid climate short. The effect of water and dynamic factors on PE varied considerably with the season. Soil moisture was not the main factor affected PE.