浙江天目山背风坡对流触发个例的对比分析  

Comparative Analysis of Convective Initiation on the Lee Side of the Tianmu Mountain

作　　者：苏涛 董美莹 余贞寿 黎玥君 SU Tao;DONG Meiying;YU Zhenshou;LI Yuejun(Zhejiang Institute of Meteorological Sciences,Hangzhou 310008)

机构地区：[1]浙江省气象科学研究所

出　　处：《气象》2020年第2期158-168,共11页Meteorological Monthly

基　　金：浙江省气象局青年科技项目(2017QN05);浙江省气象科技计划重点项目(2017ZD04);浙江省科技计划项目(2017C03035);华东区域气象科技协同创新基金合作项目(QYIIZ201611)共同资助

摘　　要：针对夏季副热带高压背景下浙北天目山附近的强对流天气个例,利用中尺度实况资料,分析了天目山对触发对流的作用。结果表明:浙江省夏季位于副热带高压边缘时,低层处于西南背景风时,在低Froude数条件下,气流经过黄山、天目山后在背风侧形成一段辐合线,在有利的热力条件配合下,容易触发对流。山地的热力强迫作用使地形上空新生了很多积云,积云分布基本与地形一致。同时,天目山背风侧出现一条积云线,其形成的原因是天目山背风侧辐合线的辐合抬升作用。背风侧辐合线尺度有几十千米,方向随环境风向转变。对流触发的位置位于这条辐合线上靠近山地的一端。这可能是由于山地热力强迫作用产生的积云移到辐合线上继续发展产生对流云,即山地的动力和热力作用共同触发了对流。Mesoscale observations are used to study cases of severe convective weather that occurred near Tianmu Mountain in subtropical high synoptic situation in order to understand the impact of Tianmu Mountain on convective initiation(CI).The results show that,when Zhejiang Province is at the edge of subtropical high,the low-level flow is southwesterly and the Froude number is low,the upstream flow passing over the mountains forms a convergence line at the lee side of Huang Mountain and Tianmu Mountain,which factors CI in conjunction of thermal conditions.The thermal effect of the mountain causes cumulus clouds above the mountain area.The distribution of the cumulus clouds is consistent with the orography.Meanwhile,a belt of cumulus clouds forms at the lee side as a result of the convergence line.The convergence line extends tens of kilometers,and the direction changes with the ambient wind direction.Convective cells are initiated at the western end of the convergence line near the mountain.This suggests that CI may occur when the thermal-forced cumulus clouds move above the convergence line and continue to develop.In other words,thermal and dynamic effects of the mountain trigger the CI together.

关 键 词：天目山 对流触发 辐合线 强对流天气 

分 类 号：P445[天文地球—大气科学及气象学] P458