摘要
基于WRF模式,在模式下垫面中嵌入长江水体以及改变地形高度,研究了三峡地区长江水体和局地地形在有降水和无降水事件中的局地效应。结果表明,在有降水事件中,水体下垫面为降水提供了局地水汽,同时在局地喇叭口和峡谷地形动力强迫作用下,近地面河谷风增加,偏南气流携带水汽北上,三峡地区下游段在峡谷地形的"狭管"效应作用下,河谷风偏东风增加,增加水汽向西输送并与偏南风北上水汽在喇叭口地形末端汇合,下垫面变化的同时也为降水提供了充分的潜热能量,夹带水汽气流在局地地形的强迫抬升作用下,促使水汽辐合上升,与高空的干冷空气造成了层结不稳定,潜热不稳定能量的释放,导致了该地区的降水量增加;在无降水事件中,长江水体在白天(夜晚)具有相应的降温(保温)作用,进而呈现出冷(暖)湖效应,在水体下垫面和地形作用下,潜热在喇叭口末端聚集,没有地形对气流阻挡作用,偏南气流、偏东气流加强;在有、无降水事件中,环流特征变化表明局地水体下垫面和局地地形对三峡地区天气均有不可忽视的重要性。
Based on WRF model,the local effect of the Yangtze River and local topography were studied between precipitation and non-precipitation events in the Three Gorges area.The results showed that in the process of precipitation event,the underlying surface water bodies provided the local water vapor for precipitation,and the near-surface valley wind that was forced dynamically by the local bell mouth and canyon terrain increased.The southerly airstream affected by the bell topography carried moisture northward,and the valley easterly wind compelled by ＇narrow pipe＇ effect of the canyon terrain increased in the downstream section of the Three Gorges area,which enhanced westerly water vapor transportation that converged on the northward moisture affected by northerly wind in the end of the bell mouth terrain.Meanwhile,the changed underlying surface provided latent heat energy for rainfall.The airflow with water vapor was uplifted compulsorily by local terrain and converged with the dry and cold air caused by the unstable stratification from the height,the latent heat energy released instability to lead to precipitation increasing in the region.On the other hand,in the process of non-precipitation event,the Yangtze River can cool/warm at the day/night accordingly,and had cold/warm lake effect.The latent heat concentrated in the end of bell mouth with the water underlying surface imbedding and the terrain action.There was no terrain blocking effect on flow,and the southerly flow and the easterly flow enhanced.The variations of circulation characteristic suggested that both of the water underlying surface and the local terrain were ineligibly important for the weather in the Three Gorges area in different events.
出处
《高原气象》
CSCD
北大核心
2011年第1期83-93,共11页
Plateau Meteorology
基金
重庆市自然科学基金计划重点项目(CSTC
2008BA0022)
中国气象局成都高原气象研究所开放基金项目(LPM200814)
重庆市气象局2010年科技计划项目(zl201003)共同资助
关键词
三峡地区
下垫面
地形
数值试验
Three Gorges area
Underlying surface
Topography
Numerical experimentation
