山东04.28强飑线过程重力波结构的分析

ANALYSIS OF GRAVITY WAVE CHARACTERISTICS OF A STRONG SQUALL LINE PROCESS IN APRIL 2006 IN SHANDONG PROVINCE

利用卫星、雷达及山东省中尺度自动站网获取的多种观测资料分析了2006年4月28日主要发生在山东境内的一次飑线（squall line）过程。利用PSU／NCAR中尺度大气非静力模式MM5对这次飑线过程进行了数值模拟分析。分析结果表明，高空冷槽叠加在低空暖空气上，形成上冷下暖的大气热力层结，积累了大量的对流有效位能。由于太行山地形影响而产生的下坡风与地面低压槽前的西南暖湿气流相汇合，形成中尺度辐合线，触发了不稳定能量的释放，产生对流并由中尺度辐合线组成飑线。用小波分析的方法对数值模拟的结果进行连续小波变换，对变换后的结果进行分析表明：太行山的背风波是此次过程的激发机制之一，并且在这次过程中有明显的中尺度重力波结构，其主要波长约为50—100km，波包传播速度为14．28m／s，但50km波相速略大于100km波。

A squall line that occurred on 28 April 2006 in Shandong province is investigated by using multiple observations of satellite, radar and data measured at mesoscale automatic weather stations. The PSU/NCAR mesoscale nonhydrostatic model MM5 is used to simulate and analyze the process. The result of the analysis shows that large amount of Convective Available Potential Energy（CAPE） is accumulated from an atmospheric thermal stratification that is warmer at lower levels than at higher ones because of the superimposition of a cold upper-level trough over warm lower-level air. A mesoscale convergence line, which is formed by downslope wind from the Taihang Mts. Converging with southwest warm humid wind in front of a surface trough, induces the release of the CAPE and initiates convection and organizes the convective cells into a squall line. The wavelet analysis method is used to transform the simulation results into continuous wave structures. The analysis of the transformed result shows that the lee waves generated from the Taihang Mts. are one of the initiation mechanisms of this process, during which there are obvious mesosclae gravity wave structures with the main wavelengths about 50-100 km, the group velocity about 14-28 m/s, but with a slightly faster phase velocity with the 50 km wave than with the 100 km wave.