乌鲁木齐一次暴雪过程地形敏感性试验
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摘要
以NCEP资料为初始场和侧边界条件,利用WRF模式对东、西天山地形对2015年12月9—12日大暴雪影响进行敏感性试验,从降水强度和分布等方面对比分析模拟结果,探讨地形在暴雪过程中的作用,对成因进行初步研究分析,结果表明:(1)此次强降雪发生是高空西南急流抽吸、低层风切变及风速辐合、偏北风与地形强迫抬升、地面冷锋移动缓慢等共同造成的。(2)此次暴雪天气过程,地形对强降雪的落区、强度影响很大,东、西天山高度与强降雪强度正相关,东、西天山高度降低、强降雪落区沿环流方向移动。(3)地形动力强迫整体上增强次级环流圈。近地面上升速度中心出现在迎风坡山脚至山腰区域,并向两侧递减,与此次大暴雪中心落区以及乌鲁木齐附近测站降雪量分布吻合,东、西天山地形高度降低50%,近地面上升速度中心值减少30%。地形强迫东、西天山峡谷近地面生成辐合中心和辐合线,辐合中心强度与地形高度正相关。(4)地形强迫抬升有加强水汽辐合汇聚的作用,东、西天山地形高度降低50%,水汽通量与水汽通量散度减少30%。
Using NCEP data as initial field and lateral boundary conditions,sensitivity experiments on the impact of terrain on the East and West Tianshan mountains during an extreme blizzard are performed with the WRF model.Comparing precipitation intensity,distribution and other aspects,results show that:(1) the occurrence of extreme blizzard is caused by upper southwest jet pumping,low-level wind shear,wind speed convergence,north wind,orographic forced uplift and slow movement of cold front.(2) The topography has a great influence on the falling area and intensity of heavy snowfall.The altitude of the East and West Tianshan Mountains is positively related to the intensity of heavy snowfall.The altitude of the East and West Tianshan Mountains decreases and the falling area of heavy snowfall move along the circulation direction.(3) The orographic forcing enhances the secondary circulation.The center of rising velocity near ground is on the windward slope from the foot of mountain to the mountainside,it coincides with the extreme blizzard center and the snowfall distribution nearby Urumqi station.The altitude of the East and West Tianshan Mountains decreases by 50%,the strength of rising velocity center near ground decreases by 30%.The terrain force produces the convergence center and convergence line near the ground in the Tianshan valley,and the intensity of convergence center is positively related to the terrain height.(4) The orographic forcing enhances the convergence of water vapor convergence.The altitude of the East and West Tianshan Mountains decreases by 50%,the water vapor flux and water vapor flux divergence decrease by 30%.
Using NCEP data as initial field and lateral boundary conditions,sensitivity experiments on the impact of terrain on the East and West Tianshan mountains during an extreme blizzard are performed with the WRF model.Comparing precipitation intensity,distribution and other aspects,results show that:(1) the occurrence of extreme blizzard is caused by upper southwest jet pumping,low-level wind shear,wind speed convergence,north wind,orographic forced uplift and slow movement of cold front.(2) The topography has a great influence on the falling area and intensity of heavy snowfall.The altitude of the East and West Tianshan Mountains is positively related to the intensity of heavy snowfall.The altitude of the East and West Tianshan Mountains decreases and the falling area of heavy snowfall move along the circulation direction.(3) The orographic forcing enhances the secondary circulation.The center of rising velocity near ground is on the windward slope from the foot of mountain to the mountainside,it coincides with the extreme blizzard center and the snowfall distribution nearby Urumqi station.The altitude of the East and West Tianshan Mountains decreases by 50%,the strength of rising velocity center near ground decreases by 30%.The terrain force produces the convergence center and convergence line near the ground in the Tianshan valley,and the intensity of convergence center is positively related to the terrain height.(4) The orographic forcing enhances the convergence of water vapor convergence.The altitude of the East and West Tianshan Mountains decreases by 50%,the water vapor flux and water vapor flux divergence decrease by 30%.
引文
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[12]庄晓翠,覃家秀,李博渊.2014年新疆西部一次暴雪天气的中尺度特征[J].干旱气象,2016,34(2):326-334.
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[2]庄晓翠,李博渊,李如琦,等.新疆北部强降雪天气研究若干进展[J].沙漠与绿洲气象.2016,1(1):1-7.
[3]赵军荣,郭金强.天山北坡中部一次罕见特大暴雪天气成因[J].干旱气象.2010,28(4):438-442.
[4]李如琦,牟欢,肉孜·阿基,等.2011年深秋北疆暴雪过程成因分析[J].沙漠与绿洲气象.2013,7(2):9-13.
[5]刘惠云,崔彩霞,李如琦.新疆北部一次持续暴雪天气过程分析[J].干旱区研究.2011,28(2):282-286.
[6]马玉芬,赵玲,赵勇.天山地形对新疆强降水天气影响的数值模拟研究[J].沙漠与绿洲气象.2012,6(5):40-44.
[7]朱莉莉,连钰,李梦婕等,天山天池一次强降水过程中的地形效应[J].科学技术与工程.2014,14(29):2-7.
[8]陶林科,杨侃,胡文东,等.“7.30”大暴雨的数值模拟及贺兰山地形影响分析[J].沙漠与绿洲气象.2014,8(4):32-38.
[9]朱红芳,王东勇,娄珊珊,等.地形对台风“海葵”降水增幅影响的研究[J].暴雨灾害.2015,34(2):160-167.
[10]李建华,崔宜少,杨成芳,等.太行山和山东半岛地形对冷流暴雪的影响分析[J].2014,30(3):18-24.
[11]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):310-315.
[12]庄晓翠,覃家秀,李博渊.2014年新疆西部一次暴雪天气的中尺度特征[J].干旱气象,2016,34(2):326-334.
[13]闫慧,赵桂香,张朝明,等.山西中部一次暴雪天气过程分析[J].干旱气象,2015,33(5):838-844.