海洋温带气旋爆发性发展数值试验

利用PSU/NCARMM4对5个西北太平洋温带气旋的爆发性发展进行了一系列数值模拟和敏感性试验,并对重要的物理过程进行了分析和诊断.采用相同物理过程及边界条件的控制试验成功地模拟出了主要的爆发性气旋加深率,为海洋爆发性气旋的业务数值预报提供了可能.敏感性试验获得了湿物理过程、能量频散、SST和海面能通量、日本岛地形及初、边值条件等影响气旋加深率的定量认识,分析表明水的微物理过程,特别是网格尺度的水汽凝结、未饱和层的云滴和雨滴蒸发,是气旋爆发性发展中最重要的物理过程;在高空200～300hPa层的云滴蒸发效应可能是形成相应层气旋中心非绝热冷却峰值的主要原因;由内在热力-动力学过程所决定的潜热释放比对流参数化任意规定的加热分布更接近实际并能产生更好的模拟结果;没有能量频散效应时可减小模拟加深的30%;海面能通量在初始时刻比在爆发性发展时更重要,不计初始时海面能通量将影响模拟加深约25%,而不计爆发性发展时的海面能通量,这种影响不及前者的一半;爆发性发展时的海面能通量呈不均匀分布并能诱导反锋面热力环流在局部抑制气旋的加深;大气模式对海-气边界层能通量交换的变化和海洋增暖产生了显着的热力学响.试验还得出了日本岛地形及初、边值条件影响的重要结论.

NUMERICAL SIMULATION AND EXPERIMENT STUDY ON EXPLOSIVE MARINE CYCLONES

A series of numerical simulations and sensitivity tests for five explosive cyclones over the Northwestern Pacific were performed using PSU/NCAR MM4.The primary deepening rates can be simulated successfully by the control experiments including the same full physics processes and boundary conditions,thereby exhibiting an ability to forecast explosive marine cyclones by operationally numerical prediction.The quantitative numerical experiments were designed to test the sensitivity of deepening rate to moisture processes,energy dispersion,SST,surface energy fluxes,topographic forcing of Japan Island,boundary conditions and initialization.It has been shown that the microphysical processes,especially grid scale condensation of vapor,evaporation of cloud and rain drops,are predominant ones during the explosive development.The cloud drops evaporation effects at 200-300 hPa levels caused likely a diabatic cooling peak of corresponding levels above the cyclone center.A more realistic simulation can be produced by the model involving the latent heat release determined by interior thermodynamic dynamics than involving the heating profile given by cumulus convective parameterization.The removed energy dispersion will result in about 30% reduction of simulated deepening rate whereas the absent initial surface energy fluxes will impact about 25% of deepening rate.The initial surface energy fluxes are more vital than those in explosive halfway with the latter effect less than 1/2 of former one.The surface energy fluxes at explosive time inhibit moderately the deepening via inducing anti fontal circulation in local areas.The model dynamics responds remarkably to both the air sea exchange variation and marine warming.Several important conclusions about the sensitivity of development to topography,initial and boundary conditions were also reached.