半干旱地区地表水平衡的特征和模拟

作者分析了我国半干旱区草原典型地区的水量平衡的特点。由于地处东亚季风区和西风带的过渡带，降水主要集中在夏季，且多短时间对流性降水，其中绝大部分消耗于蒸发，地表径流很少，土壤比较干燥。冬季积雪, 春季融雪集中，能产生较强的径流，这与夏季降水形成的径流构成双峰型特征，在我国半干旱区较为典型。由于这些特点，在地表水量平衡的计算和模拟中，蒸发的估算十分重要，为此在植被-大气相互作用模式 (AVIM) 中对水文过程作了改进，模式中包含了大气-植被-土壤间的能量和水分传输过程，特别是半干旱区地表蒸发和植被的蒸腾过程作了比较细致的处理，考虑了蓄满和超渗两种产流机制，同时采用了一个简化的雪盖模型。以此模型模拟了内蒙古半干旱草原上锡林河流域的地表水文过程。计算结果显示，半干旱区地表水平衡，蒸发大而径流小及产流的春夏双峰型特征都能很好地模拟。这些过程的参数化方案也适用于非干旱区。

Features and Simulation of Surface Water Balance in Semi-arid Areas

In this paper, the features of surface water balance in semi-arid regions of northern China were analyzed. These regions are located along the northern margin of East Asian monsoon region, where precipitation concentrates in summer and is mostly produced by convection system. Dry climate causes high potential evapotranspiration, most precipitation is exhausted by evaporation, and surface runoff accounts for only a small part. In winter, snow accumulates and melts fast in spring. Snowmelt flood and a summer flood display a double peak pattern of discharge route. In order to simulate the precipitation-runoff features in semi-arid regions, an Atmosphere-Vegetation Interaction model (AVIM) with detailed energy and water transfer processes between atmosphere, vegetation and soil was used. In this version of AVIM, runoff production caused by both excess infiltration and over saturation were taken into consideration and a snowcover model is involved. New schemes were validated for Xilin River basin and surface water budgets, and runoff generation and snowmelting processes were simulated well. The simulation results show the efficiency of new schemes.