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ISSN 1006-9895

CN 11-1768/O4

基于ERA-5高分辨率资料的高原低涡客观识别方法研究
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成都信息工程大学高原大气与环境四川省重点实验室

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91937301


Objective Identification of the Tibetan Plateau Vortex Based on ERA-5 High Resolution Data
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1.Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, College of Atmospheric Sciences, Chengdu University of Information Technology;2.Nanjing Joint Institute for Atmospheric Sciences

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    摘要:

    利用ERA5的500hPa逐小时再分析资料(0.25°×0.25°),以高原低涡的天气学特征为依据,设计研究基于高时空分辨率网格资料的高原低涡客观识别算法,并对1990~2019年暖季的青藏高原低涡进行识别,建立高原低涡数据库。该算法通过客观标准提取低涡特征点、并采取DBSCAN算法进行特征点聚类分析,以相邻时次之间低涡的重合状况、临近程度和既往生命时长为依据对低涡进行追踪匹配,得到合理的低涡路径,将孤立的低涡连接成动态发展的低涡过程。利用《青藏高原低涡切变线年鉴》,针对2017年暖季(5~9月)低涡对比分析与本文的客观识别方法的异同,结果表明:客观识别低涡的月分布特征以及移出高原低涡的占比与《年鉴》相似,典型的长生命低涡能被正确识别,可见客观识别算法及其数据库具备一定的可靠性和实用性。但客观识别的低涡总数量多于《青藏高原低涡切变线年鉴》,并且源地为“西部型”的低涡也较多。究其原因,更精细的网格尺度能将低涡在更早的生命时期提取出来,可能会将《年鉴》中的“东部型”低涡进一步追溯到更靠西的位置。此外由于青藏高原西北部观测站点严重匮乏,导致生成于高原西北部的低涡在《年鉴》中未能体现出来,也是低涡数量存在差异的重要原因。

    Abstract:

    Using ERA5 500hPa hourly reanalysis data (0.25°×0.25°) and based on the synoptic characteristics of the Tibetan Plateau vortex(TPV), an objective identification algorithm based on the grid data with high spatial and temporal resolution was designed and researched to identify the TPV over the Qinghai-Tibet Plateau during the warm season from 1990 to 2019, and to establish the TPV database. The algorithm extracted the TPV feature points by objective criteria, and adopted DBSCAN algorithm for feature point clustering analysis. Based on the coincidence, proximity and previous lifetime of the TPV between adjacent time periods, a reasonable path of the TPV was obtained to connect the isolated TPV into a dynamic vortex process. Using the Qinghai-Tibet Plateau Low Vortex Shear Line Yearbook, the comparison of the TPV in the warm season of 2017 (from May to September) and the objective identification method in this paper are compared. The results show:the monthly distribution characteristics of the objective identification TPV and the proportion of the TPV moving out of the plateau are similar to those in the Yearbook, and the typical long-life TPV can be correctly identified, which shows that the objective identification algorithm and its database have certain reliability and practicability. However, the total number of the objective identification TPV is more than that in the Yearbook of Low Vortex Shear Line over the Qinghai-Tibet Plateau, and there are also more TPV originating from "western type". The reason for this is that finer grid scale can extract the eddies from earlier lifetimes, possibly tracing the "eastern type" eddies in the Almanac further to the west. In addition, due to the serious lack of observation stations in the northwest part of the Qinghai-Tibet Plateau, the TPV generated in the northwest part of the Plateau are not reflected in the Yearbook, which is also an important reason for the difference in the number of the TPV.

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  • 收稿日期:2022-07-05
  • 最后修改日期:2022-08-19
  • 录用日期:2022-10-09
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