地形对华北地区夏季降水影响的数值模拟研究

NUMERICAL SIMULATION STUDY FOR THE EFFECT OF TERRAIN ON NORTH CHINA SUMMER PRECIPITATION

行星大气中地形效应的研究一直是人们十分重视的问题。本文利用引进的ＮＣＡＲＲｅｇＣＭ２ 模式就地形对华北地区夏季降水的影响进行了数值模拟研究。结果表明，华北地区西部和北部的山脉地形对华北地区夏季降水有着非常重要的影响，尤其是对一些局地地区，甚至起到了决定性的作用。当降低地形高度时，华北地区夏季降水将明显减少。其物理机制可能主要有两点，一是降低地形高度后，使华北地区迎风坡地形抬升作用减弱，从而减少了山前降水；降低地形也减弱了背风槽或抑制了背风坡气旋的发展，因此也减少了山后降水。二是地形高度降低后，华北地区５００ ｈＰａ 高度场明显减弱，不利于夏季副热带高压的加强北跳，从而使华北地区夏季降水减少。

It is always a significant object to study the orographic effect on the planetary atmosphere. In this paper, a NCAR regional climate model is used to simulate the influence of terrain on North China summer precipitation. The results show that the summer precipitation of North China is greatly effected by the mountain over west and north parts of North China,especially over some part of it. When the terrain is removed, the precipitation over North China would be reduced. It may have two physical processes. First, when the mountain is removed, the terrain lifting effect would be weakened,precipitation on the windward side of the mountain would be reduced. At the same time, because of the weakening of leeward through or depression, precipitation on the leeward side of the mountain would be reduced too. Secondly, when the mountain is removed, 500 hPa height field over North China will be weakened and then the subtropical high would be weakened. This makes the precipitation more reduced.