盆地涡是西南涡的一种类型， 是指在700 hPa等压面上生成于四川盆地， 连续有两次闭合等高线的低压或3个站风向为气旋性环流的低涡。它是造成四川盆地降水的主要系统， 而“西南型”盆地涡是盆地涡中发生频率最高、 强度较强的一类。本文利用ERA5（0.25°×0.25°）逐小时再分析资料、 GPM卫星降水资料以及《西南低涡年鉴》等， 探讨了2020年6月26 -28日发生于四川盆地的一次典型“西南型”盆地涡的特征和发生发展机制。结果表明： 此次盆地涡生成于四川盆地西南部， 随后向东北方向移动， 到达四川东北部后转向东行， 进入重庆后消亡， 生命史共计48 h。该盆地涡的形成发展与其位于200 hPa南亚高压东北侧及高空急流入口区右侧的辐散区， 以及500 hPa短波槽前正涡度平流造成低层减压密切相关。700 hPa上四川盆地西南部位于低空急流的左前方， 有利于辐合上升运动的发展和低涡形成。700 hPa盆地涡东北方向的锋生大值区、 低空急流的加强北上以及500 hPa高空槽前西南气流的引导作用， 是低涡向东北方向移动的主要因素。随着200 hPa南亚高压中心东移到江淮上空以及高空急流减弱， 500 hPa短波槽随之东移， 盆地涡位于槽后的负涡度平流区， 垂直方向转为下沉运动， 地面加压， 低涡逐渐减弱消亡。对涡度收支方程各项分析发现， 低空辐合是盆地涡强度增加的主要贡献项， 由低空辐合导致盆地涡正涡度的增加几乎贯穿了低涡整个生成发展阶段。此外高空正位涡大值区的存在、 盆地涡降水的凝结潜热释放等， 也对本次盆地涡的发展和移动起到了重要作用。

Basin Vortex is a type of Southwest Vortex， which refers to the vortex generated in the Sichuan Basin on the 700 hPa isobaric surface， with two consecutive low pressures with closed Contour line or cyclonic circulation in the wind direction of three stations.It is the main system that causes precipitation in the Sichuan Basin， and the "southwest type" Basin Vortex is the most frequent and strong type of Basin Vortex.This article utilizes ERA5 （0.25°×0.25°） hourly reanalysis data， GPM satellite precipitation data， and the Southwest Low Eddy Yearbook explored the characteristics and development mechanism of a typical “southwest type” Basin Vortex that occurred in the Sichuan Basin from June 26 to 28， 2020.The results indicate that the Basin Vortex was generated in the southwestern part of the Sichuan Basin， then moved towards the northeast direction， reached the northeastern part of Sichuan， turned eastward， and disappeared after entering Chongqing， with a total life history of 48 hours.The formation and development of the Basin Vortex are closely related to its divergence zone located on the northeast side of the 200 hPa South Asian High and on the right side of the entrance area of the high-altitude jet stream， as well as the low-level decompression caused by the positive vorticity advection in front of the 500 hPa short wave trough.The southwest part of the Sichuan Basin at 700 hPa is located to the left front of the low-level jet stream， which is conducive to the development of convergent upward motion and the formation of low eddies.The high value area of frontogenesis in the northeast direction of the 700 hPa Basin Vortex， the strengthening of the low-level jet and the guidance of the southwest airflow in front of the 500 hPa high altitude trough are the main factors for the movement of the Basin Vortex towards the northeast direction.As the center of the 200 hPa South Asian High moves eastward over the Yangtze-Huaihe River and the upper level jet weakens， the 500 hPa shortwave trough moves eastward， and the Basin Vortex is located in the negative vorticity advection zone behind the trough.The vertical direction turns into a sinking motion， with surface pressure increasing and the low vortex gradually weakening and disappearing.Analysis of the vorticity budget equation reveals that low-level convergence is the main contributor to the increase in the Basin Vortex intensity， and the increase in positive vorticity of the Basin Vortex caused by low-level convergence almost runs through the entire life cycle of the vortex.In addition， the existence of high-altitude orthonormal vortices and the release of condensation latent heat from the Basin Vortex precipitation also play an important role in the development and movement of the Basin Vortex.