摘要
利用NCEP FNL(1°×1°)全球分析资料,采用动能梯度的定义和扰动动能方程,对2014年8月25—27日初生于青海省东南部之后东移到四川省中部产生天气影响过程的高原切变线进行了能量诊断分析。结果表明:在高原切变线发生发展时,切变线的位置和强的地转偏差及动能梯度大值区相对应,动能梯度模值的水平、垂直分布和相应的散度分布一致,可以反映切变线的基本结构特征;引入动能梯度有助于从能量变化视角来理解高原切变线的发展演变。扰动动能大值区的分布和切变线的走向一致,在切变线发展初期,扰动动能明显增大。扰动动能平流项和正压转换项的值都比较小,不足以反映切变线演变过程中的能量变化,而斜压转换项和扰动位势平流项是扰动动能收支的主导项;在切变线成熟阶段,扰动有效位能向扰动动能的转换最大,斜压转换项是高原切变线发展过程中能量转换的重要途径,有利于切变线上的上升运动加强。扰动动能趋势项可以较好预示切变线的发展态势,扰动非地转位势通量及其散度对高原切变线的生消及移动具有较好的指示意义。
Using NCEP FNL (1°×1°)global analysis data, with the definition of kinetic energy gradient and eddy kinetic energy equation, a plateau shear line was diagnostically analyzed in the aspect of energy from August 25 to August 27, 2014. The plateau shear line first occurs in the southeast of Qinghai Province and then move eastward to the central of Sichuan Province, affecting the weather. The results show that: when the plateau shear line occurs and evolves, the location of it corresponds with the strong geostrophic deviation and large-value area of kinetic energy gradient, and the horizontal and vertical distribution of the kinetic energy gradient are consistent with the corresponding distribution of divergence, which reflect the basic structure of the shear line. The introduction of kinetic energy gradient is conducive to understanding the development and evolution of plateau shear line from the perspective of energy change. The distribution of large-value area of eddy kinetic energy is consistent with the direction of the shear line. During the early stage of shear line development, the eddy kinetic energy increases obviously. The values of the eddy kinetic energy advection and the barotropic transformation are too small to explain the transformation of the eddy kinetic energy during the evolution of the shear line. The baroclinic transformation and the eddy potential advection dominate the eddy kinetic energy budget. During the mature period of the shear line, the most available eddy potential energy is converted to the eddy kinetic energy. The baroclinic conversion is an important way of energy conversion during the development of plateau shear line, and it is conducive to the intensification of the ascending motion on the shear line. Eddy kinetic energy trend item can better predict the development trend of the shear line. Eddy ageostrophic geopotential flux and its divergence have good implications of the formation, disappearance and movement of the plateau shear line.
作者
罗潇
李国平
LUO Xiao;LI Guoping(School of Atmospheric Sciences, Chengdu University of Information Technology, Chengdu 610225, China;Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters,Nanjing University of Information Science & Technology,Nanjing 210044, China)
出处
《气象科学》
北大核心
2019年第2期226-236,共11页
Journal of the Meteorological Sciences
基金
国家自然科学基金资助项目(41675057
41765003
41675042)
国家重点研发计划项目(2018YFC1507200)
关键词
切变线
地转偏差
动能梯度
扰动动能
shear line
geostrophic deviation
kinetic energy gradient
eddy kinetic energy
