高原东南缘大气近地层湍能特征与边界层动力、热力结构相关特征

Relationship Between Turbulent Energy in the Near-Surface Layer and Atmospheric Boundary Layer Thermodynamic Structure over the Southeastern Side of Tibetan Plateau

基于云南省大理2008年3、5、7月GPS加密探空试验时段(14和02时)资料,结合边界层铁塔综合观测资料,采用温度梯度法、逆温强度法和涡动相关法分别计算高原东南缘对流边界层(convective boundary layer,CBL)及稳定边界层(stable boundary layer,SBL)顶高度,通过计算获取感热通量、潜热通量、湍流动能、切变项以及浮力项与大气动力、热力过程垂直相关特征综合分析,可发现湍能方程中浮力项、感热、潜热通量与NCEP再分析资料计算获取的大气视热源相关特征显著,这某种程度反映了高原东南缘近地层大气湍流动量、热量输送对低层大气视热源Q_1的重要贡献。低层视热源Q_1亦表现出与湍能方程分量类似的日变化周期,此特征反映了高原东南缘大气热源变化与下垫面水热过程及其湍流输送日变化密切相关;浮力项与湍能等项对大气低层热源与涡动特征、热力混合结构的形成有重要作用;低层大气视热源、水汽汇均与边界层高度有显著相关,综合分析结果某种程度描述了青藏高原东南缘近地层湍流动量、热量输送状况与低层大气热源,热力混合边界层结构的综合相关物理图像,初步探索了高原东南缘对流活跃区大气湍流运动与大气动力、热力过程相互作用特征。研究表明近地层湍流通量变化某种程度可反映未来局地大气视热源垂直结构变化的"强信号"特征。本文上述研究结论也可启发我们进一步关注近地层湍流通量异常变化特征及其对局地降水过程大气热源结构演变的影响问题。

Based on the data observed from an intensive GPS sounding experiment and the comprehensive measurements of boundary layer in Dali of Yunnan Province during March,May and July 2008,the heights of CBL (convective boundary layer)and SBL (stable boundary layer)are calculated with approaches of temperature gradient and inversion layer strength and sensible heat flux,latent heat flux,turbulent kinetic energy,shear item and buoyancy item are obtained with eddy-correlation method.The apparent heat source Q1 ,which is calculated from the NCEP reanalysis data,presents the similar diurnal cycles to the turbulent energy components and turbulent flux,reflecting a close connection of the plateau’s heat source variations with the diurnal changes in turbulent transport of hydrothermal process in the underlying surface.The comprehensive analysis on the vertical profiles of variables about turbulence and thermody-namics reveals the significant correlations among sensible heat flux,latent heat flux,apparent heat source and buoyancy item,implying an important contribution of thermodynamic turbulence transport to the Q1 in the near-surface layer over the southeastern edges of the Tibetan Plateau.The buoyancy item and turbu-lent energy play an important role in formation of the near-surface Q1 ,vortex dynamics,thermodynamic mixing structure.The lower layer Q1 and moisture sink are closely associated with the boundary layer height.This comprehensive analysis describs a physical linkage of thermodynamic turbulence transport with atmospheric heat source,vortex dynamical process and thermodynamic mixing layer structure to un-derstand the interaction of turbulence-convection and atmospheric thermodynamic process in the active con-vection region over the southeastern edges of the Tibetan Plateau.