Mechanism of Diabatic Heating on Precipitation and the Track of a Tibetan Plateau Vortex over the Eastern Slope of the Tibetan Plateau

Abstract

Existing studies contend that latent heating (LH) will replace sensible heating (SH) to become the dominant factor affecting the development of the Tibetan Plateau vortex (TPV) after it moves off the Tibetan Plateau (TP). However, in the process of the TPV moving off the TP requires that the airmass traverse the eastern slope of the Tibetan Plateau (ESTP) where the topography and diabatic heating (DH) conditions rapidly change. How LH gradually replaces SH to become the dominant factor in the development of the TPV over the ESTP is still not very clear. In this paper, an analysis of a typical case of a TPV with a long life history over the ESTP is performed by using multi-sourced meteorological data and model simulations. The results show that SH from the TP surface can change the TPV-associated precipitation distribution by temperature advection after the TPV moves off the TP. The LH can then directly promote the development of the TPV and has a certain guiding effect on the track of the TPV. The SH can control the active area of LH by changing the falling area of the TPV-associated precipitation, so it still plays a key role in the development and tracking of the TPV even though it has moved out of the main body of the TP.

摘 要

现有研究认为潜热加热将在高原低涡移出高原后接替感热加热成为影响其发展的主导因素. 然而在高原低涡移出高原的过程中, 涡旋气团需要穿越地形和非绝热加热条件都将发生急剧变化的高原东坡地带. 目前尚不清楚感热加热和潜热加热在高原东坡地带如何实现主导作用的转变以及这种转变对高原低涡发展的影响机制. 本文结合多源气象数据和数值模拟方法分析了一次活动于青藏高原东坡的长生命史高原低涡典型个例发现: 高原地面感热加热在高原低涡移出高原后仍旧可以通过温度平流改变高原低涡的降水分布. 与降水相关的潜热加热则可直接加强高原低涡的发展并对低涡移动路径有明确的引导作用. 由于感热加热可以通过改变高原低涡降水落区的方式限制潜热加热的作用区域, 因此即便高原低涡已经移出高原主体, 高原地面感热加热仍能对高原低涡的发展和移动路径起到关键作用.