一类青藏高原低涡异常路径的环境场分析

Environmental Fields Analysis of a Kind of Qinghai-Tibetan Plateau Vortex Abnormal Tracks

利用NCEP/NCAR再分析资料、历史天气图,在分析1998-2015年移出高原后持续活动2天以上的高原低涡(简称持续高原涡)活动情况基础上,分析了在河套地区打转的持续高原涡的对流层中层高度场特征,并且利用WRF3.5.1模式,对2002年7月1-5日在河套地区打转的久治涡活动的环境场进行了模拟与台风或热带低压强度增强、减弱的数值试验。结果发现,在中国大陆以东、140°E以西洋面上台风或热带低压向北活动,会造成持续高原涡在河套地区打转的异常路径;其环流背景,主要是台风或热带低压向北活动,使副热带高压(简称副高)北抬,会使蒙古高压与副高之间的切变环境场或青海高压和副高与蒙古东部高压打通的高压之间的切变环境场持续,从而使持续高原涡处在相对较弱的切变环境场中东移受阻;数值试验表明,热带低压强度变化,会影响副高位置,从而会影响低涡打转活动的切变环境场,造成低涡打转位置与次数的变化。

By using the NCEP/NCAR reanalysis data, historical weather graphs, on the base of 2 days or more sustained departure Tibetan Plateau Vortexes （SDPVs） activities analysis during 1998 --2015, the geopotential height characters at middle troposphere levels of SDPVs spinning over Hetao region were analyzed. By using the numerical WRF 3. 5. 1 model, the simulation of environmental field of the spinning Hetao region Jiuzhi Plateau vortex process during July 1 to 5, 2002, and stronger tropical low and weaker tropical low numerical experiments were carded out. The results show that the northward moving typhoon or tropical low between the mainland of eastern China and west 140°E will lead to the abnormal track spinning SDPVs over Hetao region. The circulation background of spinning Hetao region SDPVs, which is mainly the northward moving of typhoon or tropical low that will make the subtropical high go north, can lead to the sustaining of Mongolia High and subtropical high shearing field or sustaining Qinhai High and subtropical high-Mongolia High shearing field, which will block the eastward moving of the SDPVs in the shearing field. The numerical experiments demonstrate that the intensity changing of the tropical low will influence the position of the western Pacific subtropical high, which will affect the shear environment field of the spinning SDPV, resulting in the changes of the position and frequency of the low vortex.