不同深厚气旋入海发展中环境因子作用对比研究

摘要

利用FNL再分析资料,统计2008—2012年入海发展江淮气旋并根据气旋不同深厚程度及季节特征分为:暖季深厚型、暖季浅薄型、冬季浅薄型和春初底层型.各类气旋的统计及合成分析表明四类气旋入海基本特征为:入海路径可分为东路和东北路;冬季与初春气旋入海发展增强幅度大于暖季;不同深厚气旋入海后均有下垫面摩擦力减小近海面风力增强,大风区扩大且由气旋偏东位置向东南偏移;暖季气旋入海降水强度增幅明显,并与气旋深厚程度成正比,冬季及春初气旋入海后降水增幅小,春初气旋后部有零散强降水.对入海发展机制的合成诊断显示,气旋中凝结潜热释放对暖季气旋起重要作用,并与气旋深厚程度成正比,对冬季气旋也有正贡献,但对春初底层型气旋无明显作用.春初底层型对海面动力热力影响更敏感,入海后正涡度区的垂直伸展较其它型更显著.而有利于气旋加深的上空辐散中心位置高度与气旋的深厚程度成正比.气旋入海发展中环境因子分析显示,下垫面非绝热加热对冬季和初春气旋作用显著,对暖季气旋影响不明显.高空急流动量下传与下垫面摩擦减弱促使各类气旋增强.湿位涡对暖季气旋有重要正贡献,对深厚气旋作用更强.冬季和初春风场的惯性稳定度和切变稳定度的共同作用有利于气旋增强.1000 hPa上湿斜压项MPV2显示的气旋区域温湿锋区位置及强度与入海气旋雨区及雨强对应较好,具有显著指示性.%Statistical classification of the intensification of different deep Changiang-Huaihe Cyclones (CHCs) over the East China and Yellow Seas (ECYSs) during 2008 to 2012 is studied using the FNL reanalysis data. Based on the penetration depth and the season of occurrence, the CHCs are divided into four categoriesincluding warm-season-deep (WSD), warm-season-shallow (WSS), winter-shallow(WTS) and early-spring-bottom (ESB). Statistics show the CHCs take either an eastward or a northeastward path after entering ECYSs. After moving to the seas, the intensification of CHCs is more significant in cold season than that in warm season.They all have the reduction of the friction of the underlying surface and the increase of the near surface winds. The area of strong winds extends and migrates from the east to the southeast of the CHCs. A significant increase of precipitation during the warm seasons is consistent with the penetration depth of the cyclones. While a slight increase of precipitation in cold season cyclones and scattered precipitation is observed behind the ESB cyclones in the early stage of spring. Synthetic diagnosis analysis of the CHC sover ECYSs shows that the latent heat release plays an important role in the amplification of cyclones during the warm season. The ESB cyclones are sensitive to the dynamic and thermal effects from the underlying surface. The vertical stretching of the positive vorticity volume is much more significant in ESB cyclones than that in other cyclones. The height of maximum upper level divergence is proportional to the penetration depth of the cyclone for all the categories. Diabatic heating from the underlying surface is more prominent in cold season cyclones. Downward transport of the kinetic energy from upper level jet and the reduced friction both have positive contributions to intensification of the CHCs. Moist Potential Vorticity (MPV) has more contribution to the intensification of warm season cyclones, especially WSD cyclones.The combined effects from inertial stability and shear stability are beneficial to theamplification of the cyclones in cold season. The position and strength of the temperature and moisture front from MPV2 term at 1000 hPa coincides with the area and intensity of precipitation, which shows that the MPV2 is an effective reference for CHCs rainfall forecast.