山脉地形对云南冷锋切变型强降水的影响
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摘要
利用多种资料对2014年6月28—29日云南省冷锋切变型强降水进行诊断分析,并利用WRF中尺度模式,对此次过程进行地形敏感性数值试验.结果表明去除山脉地形后,全省区域降水量明显减弱,大雨、暴雨的落区急剧缩减;降水量的变化差异主要由降水强度的变化引起.山脉对低层冷空气的引导和阻挡作用最为显著,四川东部到贵州一带的东北气流经乌蒙山加速进入到滇中地区,受哀牢山、无量山和横断山脉的阻挡,与青藏高原东南侧沿横断山脉南下的冷平流汇合,在滇中及以东、以北地区盘踞;夏季来自南海的东南气流及来自孟加拉湾的偏西气流均具有高温高湿性质,在山脉的引导和阻挡作用下,与南下受阻的冷空气交汇,形成锋面降水;山脉的强迫抬升机制迫使其周边出现显著的垂直上升运动,强度约0.4~0.7 m/s;在山谷相间的区域,特别是山脉的迎风坡处,水汽通量辐合,其增量可达(0.02~0.07)×10-6g·s-1·cm-2·h Pa-1,有利于当地大雨、暴雨的发生.
Based on the observed data and output data form WRF,the causes and the influence of mountain terrain on the formation of cold front shear heavy rain in Yunnan Province from June 28 to 29 in 2014 have been analyzed. The results show that taking no consideration of mountain terrain,the precipitation decreased significantly,the heavy rain fall area shrank. The change of precipitation difference is mainly caused by the change of precipitation intensity. The mountains' guiding and blocking effect of cold air is significantly apparent. The airflow from Sichuan and Guizhou Province accelerate into the region of Yunnan by Wumeng Mountain,then it is blocked by the Ailao Mountain,Wuliang Mountain and Hengduan Mountains,converging with the cold advection from Qinghai-Tibet Plateau along the Hengduan Mountains,occupying the areas in the east,the north and the middle of Yunnan Province. In summer,the southeast air current from the south China Sea and the west airflow from Bay of Bengal presents properties of high temperature and high humidity,under the guidance and blocking in the mountains,their moving speed slows down and converges with the cold air aforementioned,resulting in frontal precipitation. Mountains' forced lifting mechanism forced its surrounding a marked vertical upward movement,intensity of 0. 4 to 0. 7 m / s. In the valleys,especially in the windward side of mountain,water vapor convergence will build up by the effect of mountains,resulting in the increment of(0. 02—0. 07) × 10-6g·s-1·cm-2·h Pa-1.
Based on the observed data and output data form WRF,the causes and the influence of mountain terrain on the formation of cold front shear heavy rain in Yunnan Province from June 28 to 29 in 2014 have been analyzed. The results show that taking no consideration of mountain terrain,the precipitation decreased significantly,the heavy rain fall area shrank. The change of precipitation difference is mainly caused by the change of precipitation intensity. The mountains' guiding and blocking effect of cold air is significantly apparent. The airflow from Sichuan and Guizhou Province accelerate into the region of Yunnan by Wumeng Mountain,then it is blocked by the Ailao Mountain,Wuliang Mountain and Hengduan Mountains,converging with the cold advection from Qinghai-Tibet Plateau along the Hengduan Mountains,occupying the areas in the east,the north and the middle of Yunnan Province. In summer,the southeast air current from the south China Sea and the west airflow from Bay of Bengal presents properties of high temperature and high humidity,under the guidance and blocking in the mountains,their moving speed slows down and converges with the cold air aforementioned,resulting in frontal precipitation. Mountains' forced lifting mechanism forced its surrounding a marked vertical upward movement,intensity of 0. 4 to 0. 7 m / s. In the valleys,especially in the windward side of mountain,water vapor convergence will build up by the effect of mountains,resulting in the increment of(0. 02—0. 07) × 10-6g·s-1·cm-2·h Pa-1.
引文
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[2]林必元,张维恒.地形对降水影响的研究[M].北京:气象出版社,2001.LI B Y,ZHANG W H.Orographic influences on surface precipitation[M].Beijing:China Meteorological Press,2001.
[3]廖菲,洪延超,郑国光.地形对降水的影响研究概述[J].气象科技,2007,35(3):309-316.LIAO F,HONG Y C,ZHENG G G.Review of orographic influences on surface precipitation[J].Meteorological Science and Technology,2007,35(3):309-316.
[4]陶诗言.中国之暴雨[M].北京:科学出版社,1980.TAO S Y.China heavy rains[M].Beijing:Science Press,1980.
[5]臧增亮,张铭,沈洪卫,等.江淮地区中尺度地形对一次梅雨锋暴雨的敏感性试验[J].气象科学,2004,24(1):26-34.ZANG Z L,ZHANG M,SHEN H W,et al.Experiments on the sentivity of mesoscale terrains in Jiang-Huai area to a heavy mold rain[J].Scientia Meteorologlca Sinica,2004,24(1):26-34.
[6]COTTON W R,ANTHES R A.风暴和云动力学[M].叶家东,等,译.北京:气象出版社,1993:885-919.COTTON W R,ANTHES R A.Strom and cloud dynamics[M].YE J D,et al.Translate.Beijing:Meteorological Press,1993:885-919.
[7]朱民,余志豪,陆汉城.中尺度地形背风坡的作用及其应用[J].气象学报,1999,57(6):795-804.ZHU M,YU Z H,LU H C.The meso-scale lee wave function and its application[J].Acta Meteorologica Sinica,1999,57(6):795-804.
[8]余锦华,傅抱璞.山谷地形对盛行气流影响的数值模拟[J].气象学报,1995,53(1):50-61.YU J H,FU B P.Numerical simulation for the impact of prevailing airflow by valley terrain[J].Acta Meteorologica Sinica,1995,53(1):50-61.
[9]胡伯威,崔春光,房春花.1998年7月21—22日鄂东沿江连日特大暴雨成因探讨[J].大气科学,2001,25(4):479-491.HU B W,CUI C G,FANG C H.Causes of a two-day successively extremely heavy rain along the Changjiang valley in the eastern hubei province during 21~22 July1998[J].Chinese Journal of Atmospheric Sciences,2001,25(4):479-491.
[10]董海萍,赵思雄,曾庆存.低纬高原地形对强降水过程影响的数值试验研究[J].气候与环境研究,2007,12(3):381-396.DONG H P,ZHAO S X,ZENG Q C.A numerical simulation of topography on heavy rainfall in lower latitude plateau[J].Climatic and Environmental Research,2007,12(3):381-396.
[11]徐国强,胡欣,苏华.太行山地形对“96-8”暴雨影响的数值试验研究[J].气象,1999,25(7):3-7.XU G Q,HU X,SU H.Simulation study of Taihang mountain terrain effects on heavy rain in august 1996[J].Meteorological Monthly,1999,25(7):3-7.
[12]周天军,钱永甫.地形效应影响数值预报结果的试验研究[J].大气科学,1996,20(4):452-462.ZHOU T J,QIAN Y P.An experimental study on the effects of topography on numerical prediction[J].Chinese Journal of Atmospheric Sciences,1996,20(4):452-462.
[13]RIPHAGEN H A,BRUYERE C L,JORDAAN W,et al.Experiments with the NCEP regional Eta model at the south African weather Bu-reau,with emphasis on terrain representation and it effect on pre-cipitation predictions[J].Mon Wea Rev,2002,130:1 246-1263.
[14]王曼,李华宏,段旭,等.WRF模式三维变分中背景误差协方差估计[J].应用气象学报,2011,22(4):482-492.WANG M,LI H H,DUAN X,et al.Estimating background error covariance in regional 3DVAR of WRF[J].Journal of Applied Meteorological Science,2011,22(4):482-492.
[15]李华宏,王曼,曹杰,等.WRF模式在云南一次强降水过程中的应用[J].云南大学学报:自然科学版,2014,36(4):538-545.LI H H,WANG M,CAO J,et al.The application of WRF numerical model in a torrential rain case occurred in Yunnan[J].Journal of Yunnan University:Natural Sciences Edition,2014,36(4):538-545.