第二类热成风螺旋度对登陆台风降水的诊断能力分析台风泰利个例研究  

Relation of the second type thermal helicity(H_2) to precipitation of landfalling typhoons:A case study of typhoon Talim.

作　　者：喻自凤[1] 余晖[1] 

机构地区：[1]中国气象局上海台风研究所,中国气象局台风预报技术重点开放实验室,上海200030

出　　处：《气象学报》2009年第5期851-863,共13页Acta Meteorologica Sinica

基　　金：国家重点基础研究发展计划项目(2009CB421505);国家科技部公益研究专项(2005DIB3J104);国家自然科学基金项目(40405012,40830958,40705024)

摘　　要：文中利用中尺度数值模式MM5模拟了台风泰利的登陆过程,模拟的台风路径、天气形势和降水都与观测基本一致,能够很好地反映出真实的天气过程。再利用数值模拟结果,研究了第二类热成风螺旋度(H_2)对登陆台风泰利降水的诊断能力,结果表明它对深入内陆的台风强降水具有较好的诊断能力,而对刚登陆前后的台风降水诊断能力不如经典螺旋度。特别地,H_2在提前1 h时与泰利降水达到最高相关系数,且在提前1—5 h时,它与降水的相关性比经典螺旋度的高,表现出十分显著的预示降水增幅的能力。进一步分析表明,在刚登陆前后,泰利台风中心850-200 hPa的风场垂直切变较小(约5 m/s),其最强降水出现在路径右侧300 km半径范围以内,与低空的正温度平流、低空辐合、高空辐散等无明显的关系,而低空相对涡度能够很好地反映降水的变化,这是经典螺旋度与降水在这一阶段相关性优于H_2的主要原因。而在深入内陆后,台风泰利本体环流减弱,受北部西风槽的影响逐渐增强,环境风场垂直切变迅速增大,发生强降水的庐山和大别山区处于顺垂直风切变方向左侧。在东北向的垂直风切变情况下,庐山和大别山强降水区上空有向东的高空急流出流,强高空辐散诱发垂直次级环流,从而激发对流,形成强上升运动区,因此H_2的诊断优势在这一阶段表现得最清楚。This study utilizes the MM5 mesoscale model to simulate the landfalling process of the Typhoon Talim. The simulated typhoon track, weather patterns, and rainfall process could well represent the observation. Using the numerical simulation outputs, the relation of the second type thermal helicity （H2） to rainfall caused by the landfalling typhoon Talim is analyzed. The results show that H 2 can reflect the heavy inland rainfall well while the relation was not as goo d as that of helicity to rainfall during the beginning landfalling stage. In par ticular, H2 had the highest correlation coefficient with rainfall of Talim 1 h in advance. For 1-5 h prediction times, it had a higher correlation with ra infall than helicity, and thus it showed a better potential in forecasting rainf all intensification. Further analyses have found that when Talim was in the begi nning stage of landfall, the 850-200 hPa vertical wind shear around the Talim ce nter was quite small （about 5 m/s）. The highest rainfall was to the right of the Talim track and in the 300 km radius area around the Talim center, and it had no obvious relation with lowlevel temperature advection, low-level air converg ence, or upper-level divergence. But the lowlevel relative vorticity could re flect the rainfall change quite well, which was the main reason why helicity ha d a better performance than （H2） in this period. But after Talim moved inlan d further, it weakened gradually and was affected increasingly by the northern trough, and the vertical wind shear was increasing as well. The left side of the down vertical wind shear direction lies the Lushan and Dabieshan mountain area, which could have contributed to intriguing a secondary vertical circulation, and thus heavy rainfall was produced over there. Hence, H2 showed a better ca pacity to reflect the rainfall change during this stage.

关 键 词：第二类热成风螺旋度 台风 降水诊断 

分 类 号：P457.8[天文地球—大气科学及气象学]