| 辽宁东南部一次强降雪天气的成因分析 |
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| 引用本文： | 李燕,赛瀚,刘晓初,张彩凤.辽宁东南部一次强降雪天气的成因分析[J].山东气象,2021,41(3):84-93. |
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| 作者姓名： | 李燕 赛瀚 刘晓初 张彩凤 |
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| 作者单位： | （大连市气象台，辽宁 大连 116001） |
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| 基金项目： | 环渤海区域科技协同创新基金项目（QYXM201615）；大连市山洪地质灾害防治气象保障工程2017年建设项目-城市山洪地质灾害防御能力建设项目 |
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| 摘 要： | 利用常规观测资料、NCEP再分析资料、多普勒雷达资料等对2015年2月25日辽宁东南部一次强降雪过程进行分析。结果表明：此次强降雪过程发生在低空切变线东侧暖湿区对应高空急流出口区左侧的辐散区内，有强的水汽辐合中心；地面偏南气流受山前地形抬升作用在强降水区形成风向辐合和850 hPa以下急流中心，是造成强降雪的主要原因之一；暴雪过程开始前6 h出现温度平流随高度减小的配置，假相当位温空间分布上锋区的形成，有利于不稳定层结的建立；8～12 h前正涡度平流、中低层风向辐合带、近地面冷空气层的建立以及次级环流的形成加强了上升运动，对强降雪预报具有很好的指示作用；在降水相态是雨或雨夫雪时，雷达回波最大强度达到40～45 dBZ，而强降雪时回波强度为20～25 dBZ；当大连本站850 hPa温度以及1 000 hPa与850 hPa两层等压面之间的厚度处于雨雪转换临界值时，大连南部为雨或雨夹雪，北部为雪，此时出现强降雪，回波高度基本在6 km以下，最强回波25～35 dBZ维持在1 km以下，近地层为弱偏北风，与其上的西南风在边界层形成切变层，将暖湿气流抬升，为强降水提供动力条件。
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| 关 键 词： | 暴雪 不稳定层结 冷垫 雷达回波 相态 |
Analysis on causes of a heavy snowfall event in the southeast of Liaoning |
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| LI Yan,SAI Han,LIU Xiaochu,ZHANG Caifeng.Analysis on causes of a heavy snowfall event in the southeast of Liaoning[J].Journal of Shandong Meteorology,2021,41(3):84-93. |
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| Authors: | LI Yan SAI Han LIU Xiaochu ZHANG Caifeng |
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| Institution: | (Dalian Meteorological Observatory, Dalian 116001, China) |
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| Abstract: | The heavy snowfall event in the southeast of Liaoning on 25 February 2015 is analyzed by using conventional observation data, NCEP reanalysis data, and Doppler radar data. The results are as follows. The heavy snowfall event occurs in the warm moist area on the east of the low-level shear line, which corresponds to the divergence area on the left of the outflow area of the upper-level jet stream, and there is a strong water vapor convergence center; under the uplifting effect of mountains, the surface southerly airflow introduces the wind direction convergence and jet stream center below 850 hPa in the heavy precipitation area, which is one of the main causes of the heavy snowfall. Six hours before the snowstorm process, the temperature advection decreases with height and the frontal zone is formed on the field of pseudo-equivalent potential temperature, which contributes to the development of vertically unstable stratification; 8-12 hours before the process, the development of the positive vorticity advection, wind direction convergence zone in the middle and lower level, and near-surface cold air layer and the formation of the secondary circulation strengthen the ascending motion, and these conditions are useful indicators for forecasting the heavy snowfall. The maximum radar echo intensity reaches between 40 dBZ and 45 dBZ when the precipitation phase shows rain or sleet, while the echo intensity is between 20 dBZ and 25 dBZ during heavy snowfall phase. When the temperature at 850 hPa and the thickness between 1 000 hPa and 850 hPa reach the conversion thresholds between rain and snow at Dalian station, rain or sleet appears in the north of Dalian, snow appears in the north, and the heavy snowfall occurs at this time. During the heavy snowfall, the echo height is basically below 6 km, the maximum echo intensity between 25 dBZ and 35 dBZ maintains below 1 km, the weak northerly winds prevail near surface layer, together with the southwesterly winds above, the shear layer is formed at the boundary layer, which lifts the wam moist air and provides dynamic conditions for the heavy precipitation. |
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| Keywords: | snowstorm unstable stratification cold air cushion radar echo phase |
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