“海棠”台风（2005）结构对其降水影响的Q矢量分解研究

摘要： 基于WRF模式对2005年台风“海棠”登陆降水过程的成功模拟， 本文初步尝试利用修改后的非地转干Q矢量(QN矢量)PG分解， 定量揭示台风结构对台风降水和台风雨强差异形成的影响。结果表明： （1）在台风登陆过程的不同阶段， 对台风降水起主要贡献的台风结构因子是不同的。在台风登陆过程前12 h期间， 对降水贡献最为显著的为QNshdv， 其次是QNalst和QNcrst， 而QNcurv的贡献最小； 在后12 h期间， 对降水贡献最为显著的为QNcrst， 其次是QNcurv， QNshdv的贡献列第三， 而QNalst的贡献最小。（2）各台风结构因子QNalst、 QNcurv、 QNshdv及QNcrst对台风降水发生的贡献都存在明显的时、 空变化。（3）在台风登陆降水过程中， 对每个时刻暴雨雨强形成有贡献的台风结构因子是不同的。相对来讲， QNcurv对暴雨、 大暴雨及特大暴雨之间雨强差异形成的贡献最为显著， QNalst与QNcrst的贡献情况较为接近， 而QNshdv的贡献则相对最小。通过QN矢量PG分解， 可以定量揭示出登陆台风结构对台风降水的影响， 这也是总的QN矢量（即QN矢量）难以揭示的潜在物理机制。

Q Vector Partitioning Study on Effects of Typhoon Structures on Precipitation Associated with Typhoon Haitang (2005)

Based on simulation data associated with Typhoon Haitang (2005) from Weather and Research Forecasting (WRF) model,meanwhile,a modified dry ageostrophic Q vector (Q~N ) is partitioned into Q~N_(alst) (the "alongstream stretching" component that represents the intensification/weakening of the alongflow thermal gradient by contraction/stretchiong of isotherm spacing),Q~N_curv (the "curvature" component that represents the curvature effect according to which a downstream increase (decrease) in the cyclonic curvature of the isohypses induces subsidence (ascent)),Q~N_(shdv) (the "shear advection" component that represents the thermal advection by horizontal wind shear),and Q~N_crst (the "crosstream stretching" that represents the effect of confluence and diffluence of the wind,i.e.,the intensification/weakening of the cross-flow thermal gradient forced by confluence and diffluence of the wind) four components in a natural coordinate system that follows the isohypses (hereafter referred to as PG partitioning),it is the first time to conduct the Q~N PG partitioning analysis to quantitatively study impacts of typhoon structures on typhoon precipitation and differences in rainfall intensity. The results include:(1) Within 12 hours before the landfall,contribution to rainfall mainly comes from Q~N_(shdv ),and Q~N_(crst) as well as Q~N_(alst) ,while Q~N_(curv) is the smallest. Within 12 hours after the landfall,impacts on precipitation is from Q~N_(crst) ,Q~N_(curv) is secondary,and Q~N_(shdv )is third,while Q~N_(alst) shows the smallest effects;(2) impacts of Q~N_(alst) ,Q~N_(curv) ,Q~N_(shdv )and Q~N_(crst) on typhoon precipitation exhibit strong temporal and spatial changes;(3) Within 1～6 hours after the landfall,Q~N_(curv) ,Q~N_(shdv ) and Q~N_(crst) have main contributions to differences in rainfall intensity whereas within 7～12 hours after the landfall,Q~N_(alst) and Q~N_(curv) show major impacts. Among them,Q~N_(curv) has the largest impacts,while Q~N_(shdv ) is the smallest. The results indicate that the partitioning analysis do the better job in studying effects of typhoon structures on typhoon precipitation than the total Q~N does.