三峡下垫面变化对重庆气象要素影响的数值模拟

Numerical Simulation of Chongqing Meteorological Elements Influenced by the Underlying Surface Changes in the Three Gorges Reservoir Area

利用中尺度数值模式WRF,通过改变三峡库区两次具有代表性的强降水过程中长江下垫面水体和三峡地区地形高度状况,检验三峡库区下垫面变化对重庆主要气象要素的影响.结果表明:三峡下垫面水体的变化并没有引起三峡地区的气温出现明显的变化,水体面积的变化仅在白天对水体附近的气温略有影响;去掉三峡下垫面水体时,地面风速略减小,当加大水体面积时,仅在水体附近风速略有增大;三峡下垫面水体对当地的水汽来源相当重要,当去掉水体时,库区腹地近地层的比湿有较为明显的降低;但是当水体面积扩大一倍后,库区近地层的比湿没有产生明显的变化,仅在水体区域有弱的增大;长江三峡水体的变化对库区附近降水的影响较为明显,特别是三峡库区腹地(即重庆东北部);盆地东部地形高度由于对中低层影响系统移动路径的影响,从而对三峡地区的降雨量级和落区有较明显的影响.

Mesoscale Numerical Model WRF was used to test the effects of underlying surface changes in the Three Gorges Reservoir area on the meteorological elements of Chongqing, through changing surface water cover and terrain height of two representative strong rainfall processes over the area. The results showed that the impact of changes in the underlying surface water cover on temperature of Three Gorges Reservoir area was not obvious, except for the temperature around the river during daytime. Surface wind speed had a slight decrease when the water body of the Three Gorges Area was removed, meanwhile the wind speed around the water had a little increase when the area of surface water was enlarged. The water body of the underlying surface layer was very important for the local water vapor source. When it was removed, the specific humidity of reservoir hinterland decreased significantly. When its area doubled, however, it induced no obvious changes. The changes in the underlying surface water cover had a great influ- ence on the rainfall around the reservoir area, especially for its hinterland （northeast of Chongqing area）. Terrain height of eastern basin had a great influence on the precipitation intensity and location of thr area by affecting the moving path of middle and low level systems.