青藏高原土壤水热分布特征及冻融过程在季节转换中的作用

利用GAME-Tibet期间所取得的高分辩率土壤温度和含水量资料，对青藏高原（主要是藏北高原）土壤水热分布特征及冻融过程在季节转换中的作用进行了分析。指出藏北高原4cm学深处土壤在10月份开始冻结，次年4-5月份开始消融，冻结持续时间长达5-7个月。冻结过程有利于土壤维持其水分，因此，在刚刚开始消融时土壤含水量仍然很高。从而为夏季风爆发前土壤通过蒸发向大气提供水分打下了基础。指出土壤冻融过程可能在高原季节转换中起着重要作用。

The Role of Soil Moisture-Energy Distribution and Melting-Freezing Processes on Seasonal Shift in Tibetan Plateau

Based on the in situ high resolution observation soil moisture and temperature data obtained during GAME Tibet, the effects of the soil energy moisture distribution and the melting freezing progresses on seasonal shift were preliminarily discussed. The shallow layers start to freeze in October and to melt from April at all sites, with about 6 months frozen period. But the beginning time of freezing melting and frozen period varied at different sites. The temporal and spatial variation of the soil heat content and soil moisture is the very important component in energy and water cycle in land atmosphere system, because the heat capacity and moisture content of soil is larger that that in the atmosphere. The freezing processes could prevent the soil moisture from evaporating. Thus, there is little precipitation in winter (frozen period), but higher soil moisture when the soil begins to melt. The temporal consistent of the abrupt increase and decrease of atmospheric net heat with the melt and freeze of soil showed that the soil melting and freezing processes may play an important role in the seasonal shift in Tibetan Plateau.