摘要
采用宇如聪等研制开发的η坐标有限区域中尺度暴雨数值预报模式AREM,对2004年7月16—17日发生在河南的一次特大暴雨过程进行了数值模拟。模拟结果表明:凝结潜热促使对流层中层大气在β中尺度水平范围的气柱内得到加热,中高层大气的等压面抬高并形成β中尺度高压,中低层大气的等压面降低并形成β中尺度低压,上下层的共同作用促进了垂直运动的迅速发展。当上升运动强烈发展时,在其四周有明显的补偿下沉气流出现:在强上升运动南侧,对流层高层辐散气流向南回流导致对流层高层出现中尺度垂直环流圈,它的下沉支融入上升运动区南侧的补偿下沉气流中,并将高空的水平动量带到对流层低层形成一支新的β中尺度急流;在强上升运动北侧,对流层低层发展出了一支中尺度垂直环流圈,其下沉支向南的辐散气流与低层西南暖湿气流汇合,形成β中尺度辐合线,加强了暴雨区上空低层的辐合;在强上升运动东侧,对流层低层也有一支中尺度垂直环流发展,其下沉支中向西的辐散气流使该区域原来较为一致的西南气流出现向东的偏转,从而在西南气流中形成气旋性弯曲,更进一步加强了β中尺度辐合线上的辐合。对流层低层非地转涡度的强烈发展是β中尺度气旋形成的重要原因。最后给出了强暴雨β中尺度流场发展机理的三维空间示意图。
Numerical simulation of a heavy rain case in Henan area during 16-17 July, 2004 is performed by the LASG mesoscale model AREM developed by Yu Rucong, etc. As shown by the results： the air in the middle troposphere within the horizontal range of the meso-β scale convective system is heated by latent heat release, leading to the upward convex of the isobaric surface in the middle and upper troposphere, i. e the formation of meso-β scale high, and the downward concave of the isobaric surface in the lower troposphere, i.e. the genesis of meso-β scale low, and the joint effect of the meso-β scale systems in the upper and lower troposphere promotes the rapid development of vertical motion. When the ascending motion develops vigorously, the obvious compensation descending motion appears around it. On the south side and part of the ascending motion region, the divergent air flow in the upper troposphere flows backwards to the south, forming a mesoscale vertical circulation cell, whose descending leg merges into the compensation descending current on the south side of the ascending motion and carries the horizontal momentum of upper air to the lower troposphere, resulting in the formation of a new meso-β scale jet. On the north side of the ascending motion region, a mesoscale vertical circulation cell develops in the lower troposphere, whose descending leg southward divergent flow meets the low level southwest warm/moist flow, forming a meso-β scale convergence line, which further strengthens the low level convergence in the heavy rain area. On the east side of the ascending motion, a mesoscale vertical circulation cell also develops in the low troposphere, and its westward divergent flow makes the original southwest flow turn northwards, resulting in the cyclonic curvature of streamlines, and thus further strengthening the convergence along the meso-β scale convergence line. The rapid development of ageostrophic vorticity in the lower troposphere is the major factor responsible for the formation of the meso-β scale cyclone. At last, the three-dimensional structure chart for the development of heavy rain meso-β scale flow is given.
出处
《气象学报》
CAS
CSCD
北大核心
2006年第4期500-509,i0001,共11页
Acta Meteorologica Sinica
基金
科技部科研院所社会公益研究专项资金"我国南方致洪暴雨预测预警系统研究"
关键词
特强暴雨
Β中尺度
三维空间结构
垂直环流圈
数值模拟
Heavy rain, Meso-β scale, Three-dimensional structure, Vertical circulation cell, Numerical simulation
