| 基于客观判识的青藏高原横切变线结构及演变特征合成研究 |
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| 引用本文： | 张硕,姚秀萍,巩远发.基于客观判识的青藏高原横切变线结构及演变特征合成研究[J].气象学报,2019,77(6):1086-1106. |
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| 作者姓名： | 张硕 姚秀萍 巩远发 |
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| 作者单位： | 1.成都信息工程大学大气科学学院, 高原大气与环境四川省重点实验室, 成都, 610225 |
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| 基金项目： | 国家自然科学基金项目（91637105、41775048、41475041）、国家重点研发计划重点专项项目（2018YFC1507804）、第二次青藏高原综合科学考察项目（2019QZKK0105）。 |
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| 摘 要： | 利用1981—2016年6—8月每天4次，分辨率为1°×1°的ERA-Interim再分析资料，基于纬向风的经向切变、纬向风速0线和相对涡度3个参数，在计算机客观自动判识青藏高原横切变线（简称高原横切变线）基础上，选取位于33°—35°N的高原横切变线个例13个，采用合成分析技术，研究了高原横切变线结构及演变特征。表明高原横切变线位于青藏高原主体80°—100°E范围内，在500 hPa呈东西走向、水平尺度近2000 km，垂直方向在高原上空可伸展至480 hPa、厚度可达近2 km。高原横切变线出现的环流背景是:500 hPa高纬度两槽两脊，青藏高原两侧分别为带状分布的西太平洋副热带高压（西太副高）和伊朗高压。在动力场上，高原横切变线走向与500 hPa正涡度带轴线走向一致，切变线附近为带状的涡度正值区和上升运动区，对应于无辐散带，辐散/辐合带分布在高原横切变线北/南侧；高原横切变线附近正涡度带垂直可伸展到350 hPa，上升运动伸展至200 hPa，但高原横切变线仅至480 hPa左右，为浅薄的斜压性天气系统，呈现随高度升高向北倾斜的特征。在水汽热力场上，高原横切变线是水汽汇聚带；高原横切变线附近南侧的600—500 hPa存在高假相当位温中心，具有非常明显的高温、高湿特征。高原横切变线从初始产生到发展强盛再减弱的演变过程中，其生命期近4 d，伴随西太副高西移过程，随着高原横切变线附近正涡度带范围增大、强度增强，高原横切变线发展，干冷空气的侵入导致高原横切变线强度减弱甚至消亡。
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| 关 键 词： | 高原横切变线 合成 结构 演变 特征 客观判识 |
| 收稿时间： | 2018/9/17 0:00:00 |
| 修稿时间： | 2019/6/17 0:00:00 |
A synthetic study of the structure and evolution characteristics of a meridionally-oriented shearline over the Tibetan Plateau based on objective identification |
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| ZHANG Shuo,YAO Xiuping and GONG Yuanfa.A synthetic study of the structure and evolution characteristics of a meridionally-oriented shearline over the Tibetan Plateau based on objective identification[J].Acta Meteorologica Sinica,2019,77(6):1086-1106. |
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| Authors: | ZHANG Shuo YAO Xiuping and GONG Yuanfa |
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| Institution: | 1.School of Atmospheric Sciences, Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, Chengdu University of Information Technology, Chengdu 610225, China2.China Meteorological Administration Training Center, Beijing 100081, China |
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| Abstract: | Using the 4 times daily ERA-Interim reanalysis dataset on global 1°×1° grids for June-August from 1981 to 2016 the automatic method to identify meridionally-oriented shear lines over the Tibetan Plateau (MOSLs) is applied to determine shear lines based on three parameters, i.e. In total 13 cases of MOSLs between 33°-35°N are selected. Using synthetic analysis technique, the structure and evolution characteristics of the MOSLs are studied. The results show that MOSLs are largely located at the main body of the Tibetan Plateau within the scope of 80°-100°E, extending along the east-west direction with a quasi-horizontal distribution at 500 hPa, Its horizontal scale near 2000 km. In the vertical direction, the MOSL over the Tibetan Plateau can extend up to 480 hPa with a thickness of neary 2 km. The circulation background for the MOSL is characterized two-trough and two-ridge pattern in the high-latitude region at 500 hPa, while the western Pacific subtropical high (hereafter WPSH) and the Iran High are distributed on both sides of the Qinghai-Xizang Plateau respectively. On the dynamic field, the extension of MOSL is consistent with the axis of positive vorticity zone at 500 hPa; there are zonally distributed positive vorticity and ascending motion near the MOSL, corresponding to the non-divergence zone. Divergence and convergence zones are located on the northern and/southern sides of MOSL, respectively. The positive vorticity zone near the MOSL can vertivally extend to 350 hPa, and the ascending motion can reach 200 hPa. However, the shear line can only extend to about 480 hPa, suggesting that it is a shallow weather system with a certain baroclinic property and a northward inclination with height. On the water vapor and thermal fields, the MOSL corresponds to the water vapor convergence zone, and there is a high pseudo-equivalent temperature center between 600-500 hPa on the southern side of MOSL. It obviously has a clear feature of high temperature and high humidity. The evolution process of MOSL from its initial generation to strong development and then weakening takes about 4 d. Along with the westward shift of the WPSH, the range and intensity of positive vorticity zone near the MOSL increase, and the MOSL develops. With the invasion of dry cold air, the intensity of the MOSL decreases. Under certain extreme conditions, the MOSL even disappears. |
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| Keywords: | The meridionally-oriented shear lines over the Tibetan Plateau Synthesis Structure Evolution Characteristics Objective identification |
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