西北太平洋热带气旋强度变化对雨带分布特征的影响

IMPACT OF TC INTENSITY CHANGE ON PRECIPITATION DISTRIBUTION OVER THE NORTHWESTERN PACIFIC

关键词:  热带气旋  强度变化  雨带分布  降水变化

Key words:  tropical cyclone  intensity change  rainband distribution  precipitation change

摘要:

已有研究表明热带气旋强度变化与雨带分布间存在紧密联系，然而其在西北太平洋区域的量化特征尚待揭示。利用2000—2018年6—9月的中国气象局（CMA）热带气旋最佳路径数据集和全球测雨计划（GPM）格点级降水数据（IMERG）降水数据，建立了西北太平洋区域热带气旋移动坐标系，并根据气旋中心气压变化将热带气旋分为初生、缓慢增强、快速增强、稳定和消散共五类，在此基础上研究了各类气旋的降水分布及变化特征。结果表明，初生型气旋的降水率在距离气旋中心10 km和40 km处分别存在两个峰值；快速增强型气旋也存在两个峰值，分别出现在10 km和30 km处；缓慢增强和减弱型气旋的降水率随径向距离的变化均呈现出单峰分布，峰值分别出现在40 km和60 km处。气旋内雨带降水变化与气旋强度变化间存在显著的正相关关系；而外雨带降水变化与气旋强度变化间则存在负相关关系。气旋各个方位降水变化对强度变化的响应不同，减弱型热带气旋的降水率减小主要发生在气旋西侧，应与热带气旋登陆过程有关。研究结果可为西北太平洋热带气旋强度及降水模拟提供事实依据。

Abstract:

Previous studies have revealed the close relationships between the intensity change and rainband distributions of tropical cyclones. However, their quantitative characteristics over the northwestern Pacific are yet to be revealed. In this paper, we used the CMA best track dataset and the GPM IMERG precipitation data from June to September 2000-2018. The tropical cyclones over the northwestern Pacific were classified into five categories, namely initiating, slowly strengthening, rapidly strengthening, stable, and weakening typhoons, respectively. The precipitation distribution as well as its changes for various types of tropical cyclones was studied based on a mobile cyclonic coordinate system. It is shown that the radial rainfall of initiating cyclones peaks at 10 km and 40 km away from cyclonic centers, respectively; the radial rainfall of rapidly strengthening cyclones peaks at 10 km and 30 km away from cyclonic centers, respectively; the radial precipitation distributions for both the slowly strengthening and weakening cyclones present a unimodal distribution, with the peaks appearing at 40 km, and 60 km to the centers, respectively. A significant positive correlation exists between the rainfall change of the inner rainband and cyclonic intensity change, whereas a negative correlation exists between the change of the outer rainband and cyclonic intensity change. Moreover, the precipitation changes in various azimuths of cyclonic centers respond differently to intensity change. Specifically, the decrease of precipitation in weakening cyclones mainly occurs on the west side, which is likely related to the cyclonic landing process. These findings could provide observational evidence for the model of tropical cyclones over the northwestern Pacific.