高级检索
高媛, 姚秀萍, 李山山, 等. 2022. 影响夏季青藏高原横切变线演变的动力和热力作用分析[J]. 大气科学, 46(2): 486−500. doi: 10.3878/j.issn.1006-9895.2108.21053
引用本文: 高媛, 姚秀萍, 李山山, 等. 2022. 影响夏季青藏高原横切变线演变的动力和热力作用分析[J]. 大气科学, 46(2): 486−500. doi: 10.3878/j.issn.1006-9895.2108.21053
GAO Yuan, YAO Xiuping, LI Shanshan, et al. 2022. Dynamic and Thermodynamic Effects on the Evolution of the Transverse Shear Line over the Tibetan Plateau in Boreal Summer [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 46(2): 486−500. doi: 10.3878/j.issn.1006-9895.2108.21053
Citation: GAO Yuan, YAO Xiuping, LI Shanshan, et al. 2022. Dynamic and Thermodynamic Effects on the Evolution of the Transverse Shear Line over the Tibetan Plateau in Boreal Summer [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 46(2): 486−500. doi: 10.3878/j.issn.1006-9895.2108.21053

影响夏季青藏高原横切变线演变的动力和热力作用分析

Dynamic and Thermodynamic Effects on the Evolution of the Transverse Shear Line over the Tibetan Plateau in Boreal Summer

  • 摘要: 青藏高原横切变线(简称切变线)是引发青藏高原夏季暴雨的主要天气系统之一。本文基于欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,简称ECMWF)提供的ERA-5再分析资料,选取14个生成于6~8月、生命史为38小时且引发高原暴雨的切变线个例进行合成分析,探究动力和热力作用对夏季切变线生成和强度演变的影响。结果表明:(1)500 hPa切变线生成于伊朗高压和西太平洋副热带高压两高之间的鞍形场中,处于580 dagpm闭合低值中心和272 K高温中心内,比湿大值区的北侧;200 hPa南亚高压北部边缘、西风急流入口区南侧。(2)切变线强度表现出明显的日变化特征,在当地时间(LT=UTC+6h)23时最强,13时最弱。(3)涡度收支诊断表明,青藏高原上空高低层散度变化对切变线强度变化具有指示意义,500 hPa涡度最大值(最小值)出现时间滞后于辐合作用最大值(最小值)3小时。(4)切变线演变过程中,切变线发展时位涡随之增大。位涡收支诊断表明,青藏高原上空的水汽和非绝热加热对切变线的生成和发展演变起到重要作用。当边界层感热加热增强时,低层辐合增强,上升运动增强,在充足的水汽配合下,凝结潜热释放使非绝热加热中心抬高至大气中层,从而有利于切变线生成及发展。

     

    Abstract: One of the major weather systems over the Tibetan Plateau is the Tibetan Plateau transverse shear line (TPTSL). Fourteen cases of TPTSLs that cause heavy rainfall and generated between June and August with a lifetime of 38 h were selected and composited using the ERA-5 reanalysis datasets provided by the European Centre for Medium-Range Weather Forecasts in order to reveal the effect of dynamic and thermodynamic forces on the intensity evolution of TPTSLs. The following are the results. (1) At 500 hPa, the TPTSL is generated in the saddle field between the Iran high and the western Pacific subtropical high, and it is located at the low-pressure center contoured by 584 dagpm and the warm center contoured by 272K, to the north of the specific humidity center. At 200 hPa, the TPTSL is located at the northern margin of the South Asian High and the south of the entrance region of the westerly jet stream. (2) The TPTSL intensity at 500 hPa exhibits a noticeable diurnal variation, with the highest intensity at 23 LT and the lowest at 13 LT (LT=UTC+6 h). (3) According to the vorticity budget, the divergence variation at the upper layers and the convergence at the lower layers over the Tibetan Plateau are indicative of the TPTSL intensity. The vorticity at 500 hPa reaches a maximum of 3 h later than that of the convergence. (4) As the TPTSL develops, the potential vorticity (PV) increases. According to the PV budget, water vapor and diabatic heating play important roles in TPTSL generation and evolution. The enhanced sensible heating results in an intensified ascent. When the water supply is sufficient, the latent heating is released, and the diabatic heating center rises to the middle layer, which is favorable for TPTSL generation and development.

     

/

返回文章
返回