2006年6月北大西洋上热带风暴Alberto变性后爆发性发展机理分析

本文利用欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)的ERA5客观再分析资料、气象卫星合作研究所(Cooperative Institute for Meteorological Satellite Studies,CIMSS)提供的红外卫星云图资料,对2006年6月14~20日发生在北大西洋上的一个爆发性气旋进行分析。该气旋由热带风暴阿尔贝托(Tropical Storm Alberto)变性后发展而来,是2000—2016年的17个夏季(6、7和8月)发生在北大西洋上的中心气压加深率最大的爆发性气旋个例。该气旋的演变过程可划分为初始、发展、成熟和衰亡四个阶段。本文旨在分析气旋演变过程中的云系特点、气旋爆发前后的高低空环流形势和高低空相互作用。分析显示,低层强烈的温度平流导致的大气斜压性是利于气旋发展的重要环境条件;500 hPa槽前的正涡度平流可为气旋发展提供动力强迫;高层异常PV的下传对气旋发展有促进作用;潜热释放(Q2/CP)主要位于对流层的中低层,这有利于气旋发展。利用Zwack-Okossi方程进行诊断分析发现,在该气旋发展过程中绝对涡度平流项和非绝热项的贡献为正,且非绝热加热对气旋快速发展的贡献最大,而温度平流项和绝热项对气旋发展起阻碍作用。

Analyses of the Explosive Development of Tropical Storm Alberto After Its Extratropical Transition over the Northern Atlantic in June,2006

In this paper,an explosive extratropical cyclone(EC)over the Northern Atlantic from 14 to 20 June 2006 was investigated by using the ERA5 reanalysis data provided by European Centre for Medium-Range Weather Forecasts(ECMWF),as well as the infrared satellite imagery provided by Cooperative Institute for Meteorological Satellite Studies(CIMSS).Tropical Storm Alberto underwent an extratropical transition(ET)process and then developed into an explosive cyclone.It was the EC case with maximum deepening rate of central pressure among the ECs that occurred over the Northern Atlantic during the 17 summers from 2000 to 2016.The evolutionary process of this cyclone might be classified into four stages initial,developing,mature and decaying stages.The cloud characteristics associated with this EC at its different stages were documented.The upper-and lower-level circulations as well as the interaction between upper-and lower-level during the explosive intensification of this cyclone were also investigated.It is shown that lower-level atmospheric baroclinicity caused by intense cold and warm advections was a significant environmental condition for the cyclone’s intensification.The positive advection of relative vorticity in the front of 500 hPa trough might provide dynamic forcing for the development of this cyclone.The downward transmission of anomalous upper-level potential vorticity might contribute to the rapid deepening of this cyclone.The latent heat release(Q2/CP)which was mainly located in the middle and lower troposphere,seemed to be conducive to the development of this cyclone.In terms of the Zwack-Okossi equation,the contribution of the absolute vorticity advection term and the diabatic term was always positive during the development of this cyclone.Diabatic heating was the dominan factor which promoted the rapid development of this cyclone.While the temperature advection term and the adiabatic term acted to inhibit development.