QX气象Meteorological Monthly1000-0526气象编辑部中国北京qx-40-6-73310.7519/j.issn.1000-0526.2014.06.010P458研究论文Articles台风海葵引发浙西山区大暴雨的成因Causation Analysis of Severe Torrential Rain Process in Mountain Areas of Western Zhejiang Triggered by Typhoon Haikui沈杭锋SHENHangfeng
The WRF (Advanced Weather Research and Forecasting modeling system) was employed to simulate the local severe rainstorm process caused by typhoon Haikui over the northwestern of Zhejiang Province from 6 to 9 August 2012. The analysis of the simulation result combined with Doppler radar data, TBB (Temperature of Black Body) data, and automatic weather station data shows that there are several mesoscale systems embedded in spiral cloud band of the landed typhoon. Mesoscale systems develop, reinforce and weaken after division from spiral cloud band. It brings the local severe rainstorms over the northwestern of Zhejiang Province due to the direct effect of mesoscale systems. There generates the mesoscale divergence line which is responsible for the rainstorm by northeasterly flow and northwesterly current under advantageous topography. The topography of the northwestern of Zhejiang Province can increase the intensity of rainfall but is not so related to typhoon track and range of rainfall.
热带气旋中经常会出现局地性强烈天气,在小范围地区内出现狂风暴雨,酿成灾害,它们的范围一般最大不超过200~300 km,是热带气旋内的中小尺度系统(陈联寿等,1979)。观测和研究发现,热带气旋环流中有明显的中尺度天气系统活动(Parrish et al,1982;Anthes et al,1982)。中尺度对流系统(MCS)不仅和暴雨对应出现,而且还是直接导致暴雨的原因(李志楠等,2000;Chen et al,2004a;李江南等,2005;孙建华等,2006;林毅等,2007;刘晓波等,2008;李英等,2010)。在对0505号台风海棠的研究中,周玲丽等(2009)发现台风海棠暴雨主要是由边界层强中尺度辐合带直接影响造成的,边界层顶的强东风急流和对流层低层强偏南气流在浙闽地区的交汇是强辐合带的成因;徐文慧等(2009)发现其外围云系有一个明显发展的中尺度对流云团,台风东南急流在低层受地形影响发生强烈辐合引起的垂直上升运动和冷暖空气相汇合产生的对流不稳定性是台风环流内中尺度对流系统的主要形成机制;徐文慧等(2010)进一步研究指出台风海棠中MCS形成的背景不稳定是对流不稳定,维持和发展的机制是条件对称不稳定。赵宇等(2011)研究表明台风海棠减弱的低压倒槽内发生发展的两个中尺度对流系统是暴雨的直接影响系统。
地形也是台风暴雨的重要影响因子。研究表明地形对台风暴雨会起到增幅作用,地形越高,对暴雨增幅越大(Chen et al,2004b;季亮等,2008;张陆等,2008;黄奕武等,2009;周玲丽等,2009)。地形对暴雨的增幅,除了地形抬升作用外,山地地形起伏还能够增强地面对大气的拖曳效应,使得台风环流滞留在原地,造成暴雨的持续过程(Chen et al,2004c)。冀春晓等(2007)还发现地形能激发螺旋云带中中尺度对流云团的发生发展,当除去地形以后,中尺度气旋性涡旋也随之消失。王晓芳等(2007)认为气流在有利地形条件下辐合上升,它的触发作用成为台风特大暴雨发生的重要原因。
Observed rainfall (a) from 08:00 BT 6 to 08:00 BT 9 August 2012 (shaded, unit:mm) and typhoon track (solid line), (b) hourly precipitation (unit: mm) at Shiling Station
Observed surface patterns of divergence (a, c, e, g, shaded, unit: 10-5 s-1) and next hourly precipitation (contour, unit: mm); CAPPI echo of East China (b, d, f, h, shaded, unit: dBz) at (a, b) 08:00, (c, d) 09:00, (e, f) 10:00, (g, h) 11:00 BT 8 August 2012
通过对台风海葵螺旋云带内中尺度系统的分析,可以看到在台风登陆后,螺旋云带内的中尺度系统与浙西北山区地形相互作用,从而导致山区出现大暴雨,虽然中尺度系统是直接导致暴雨的原因,但是大暴雨中心区域主要落在浙西北山区,因此地形也有重要的作用。为了进一步了解地形在本次特大暴雨中的作用,本文采用NCAR、NCEP和FSL/NOAA等联合开发研制的细网格中尺度Advanced Weather Research and Forecasting Model (ARW)数值模式(WRFV3.1.1) 进行模拟试验。模式采用全可压、非静力学方程,分为欧拉高度坐标和欧拉质量坐标两种坐标体系,水平格点采用Arakawa-C类格点(Skamarock et al,2008)。
模拟试验设计中的物理参数设置采用了如下的方案:WMS6类(Hong et al,2004;Hong et al,2006)的微物理过程方案,Dudhia(1989)的短波辐射方案,RRTM(Mlawer et al,1997)的长波辐射方案,YSU(Hong et al,2003)的边界层方案,Grell 3D(Grell et al,2002)的积云对流参数化方案。模拟过程中采用两重嵌套网格,第一重格距为30 km,第二重格距为10 km,模拟中心为28°N、118°E;模拟的初始时刻为2012年8月7日08时,积分48 h,使用了美国国家环境预报中心(NCEP)的1°×1°的全球预报系统(GFS)资料作为初始场资料。一共进行了两个模拟试验,一个是控制试验;另一个则是在相同参数和设置的前提下,将浙江西北部山区和安徽东南部山区地形(地形试验窗口参见图 6a中的方框)削减为200 m,从而与周边地区保持同等高度。
模拟结果
Numerical simulation results analysis of (a) terrain (shaded, uint: m) and observed typhoon track (filled circles) and simulated (empty circles) by control experiment, (b) observed (shaded, uint: mm) and simulated precipitation (contour, uint: mm) by control experiment from 08:00 BT 8 to 08:00 BT 9 August 2012
图 6a中的方框表示去掉地形的范围)
]]>Fig. 6a is the range of terrain cut in no terrain experiment)
]]>模拟结果分析
Surface analysis of control numerical simulation results of (a, c) divergence (shaded, uint: 10-5 s-1) and precipitation (contour, uint: mm) in the next 1hour, (b, d) radar reflectivity (shaded, unit: dBz); (a, b) at the 28th integral hour; (c, d) at the 29th integral hour
(a) Observed (shaded, uint: mm) and simulated precipitation (contour, uint: mm) by no terrain experiment from 08:00 BT 8 to 08:00 BT 9 August 2012, (b) the difference of precipition from 08:00 BT 8 to 08:00 BT 9 August 2012 between no terrain experiment and control experiment
Vertical section of divergence (shaded, uint:10-5 s-1) and vertical velocity (contour, uint: Pa·s-1) along line CD in Fig. 7a at the (a, c) 28th integral hour, (b, d) 29th integral hour; (a, b) control experiment, (c, d) no terrain experiment
Vertical cross-sections along line AB in Fig. 7a of (a, c) wind speed paralleled with the cross section (contour, unit: m·s-1) and divergence (shaded, unit: 10-5s-1); (b, d) wind speed perpendicular to the cross section (contour, unit: m·s-1) and vorticity (shaded, unit: 10-5s-1); (a, b) at the 28th integral hour; (c, d) at the 29th integral hour
AnthesR AKuoY RBenjaminS GThe evolution of the mesoscale environment of severe local storms: Preliminary modeling results198211091187121310.1175/1520-0493(1982)110<1187:TEOTME>2.0.CO;2
Anthes R A, Kuo Y R, Benjamin S G, et al. 1982. The evolution of the mesoscale environment of severe local storms: Preliminary modeling results. Mon Wea Rev, 110(9):1187-1213.
ChenL SLuoH BDuanY HAn overview of tropical cyclone and tropical meteorology research progress2004a21350551410.1007/BF02915577
Chen L S, Luo H B, Duan Y H, et al. 2004a. An overview of tropical cyclone and tropical meteorology research progress. Adv Atmos Sci, 21(3):505-514.
ChenL SLuoZ XA study of the effect of topography on the merging of vortices2004b211132210.1007/BF02915676
Chen L S, Luo Z X. 2004b. A study of the effect of topography on the merging of vortices.Adv Atmos Sci, 21(1):13-22.
ChenL SLuoZ XInteraction of typhoon and mesoscale vortex2004c21451552810.1007/BF02915719
Chen L S, Luo Z X. 2004c. Interaction of typhoon and mesoscale vortex. Adv Atmos Sci, 21(4):515-528.
DudhiaJNumerical study of convection observed during the winter monsoon experiment using a mesoscale two-dimensional model1989463077310710.1175/1520-0469(1989)046<3077:NSOCOD>2.0.CO;2
Dudhia J. 1989. Numerical study of convection observed during the winter monsoon experiment using a mesoscale two-dimensional model.J Atmos Sci, 46:3077-3107.
GrellG ADevenyiDA generalized approach to parameterizing convection combining ensemble and data assimilation techniques2002291416931697
Grell G A, Devenyi D. 2002. A generalized approach to parameterizing convection combining ensemble and data assimilation techniques. Geophys Res Lett, 29(14):1693-1697.
Hong S Y, Dudhia J. 2003. Testing of a new non-local boundary layer vertical diffusion scheme in numerical weather prediction applications, 20th Conference on Weather Analysis and Forecasting/16th Conference on Numerical Weather Prediction, Seattle, WA, USA.
HongS YDudhiaJChenS HA revised approach to ice microphysical processes for the bulk parameterization of clouds and precipitation200413210312010.1175/1520-0493(2004)132<0103:ARATIM>2.0.CO;2
Hong S Y, Dudhia J, Chen S H. 2004. A revised approach to ice microphysical processes for the bulk parameterization of clouds and precipitation.Mon Wea Rev, 132:103-120.
HongS YLimJ O JThe WRF single-moment 6-class microphysics scheme (WSM6)200642129151
Hong S Y, Lim J O J. 2006. The WRF single-moment 6-class microphysics scheme (WSM6).J Korean Meteor Soc, 42:129-151.
MlawerE JTaubmanS JBrownP DRadiative transfer for inhomogeneous atmosphere: RRTM, a validated correlated-k model for the longwave1997102D14166631668210.1029/97JD00237
Mlawer E J, Taubman S J, Brown P D, et al. 1997. Radiative transfer for inhomogeneous atmosphere: RRTM, a validated correlated-k model for the longwave.J Geophys Res, 102(D14):16663-16682.
ParrishJ RBurpeeR WMarksJ F DRainfall patterns observed by digitized radar during landfall of Hurricane Frederic (1979)1982110121933194410.1175/1520-0493(1982)110<1933:RPOBDR>2.0.CO;2
Parrish J R, Burpee R W, Marks J F D, et al. 1982. Rainfall patterns observed by digitized radar during landfall of Hurricane Frederic (1979).Mon Wea Rev, 110(12):1933-1944.
SchumacherR SJohnsonR HMesoscale processes contributing to extreme rainfall in a midlatitude warm-season flash flood20081363964398610.1175/2008MWR2471.1
Schumacher R S, Johnson R H. 2008. Mesoscale processes contributing to extreme rainfall in a midlatitude warm-season flash flood.Mon Wea Rev, 136:3964-3986.