| 摘要: |
| 利用常规的地面观测资料、micaps卫星资料以及NCEP再分析资料，对2016年11月7到9日发生在湖北西南山区一次大范围暴雨转暴雪灾害天气的成因进行了分析。结果表明：此次极端雨雪灾害天气，是东移南下强冷空气与西南强暖湿气流共同作用的结果。低空急流的形成与维持，南支槽前正涡度的加强，以及中层正好处于冷暖气流交汇区，这种高层辐散、低层辐合的有利配置，是7到8日产生大范围大雨，局部暴雨的主要天气背景。8日夜间到9日的暴雪产生，除中层西南暖湿气流加强对降雪增幅的贡献外，还主要受东、西两路冷空气汇合加强共同影响；动力锋生产生的正、反两支锋面次级环流是造成降雪最直接的中尺度系统；此次雨雪持续期间，水汽充沛，并伴有强的水汽辐合上升运动，在强降雪影响期间，影响区上空存在NE-SW带状动力结构，这种锋面斜压性特征，加强了暖湿气流沿冷空气垫的爬升；针对秋季雨雪转换的温度层结特点，重点关注中层逆温和近地层气温变化。综合相关文献及本次研究结果，针对湖北地区降雪，850 hPa在0℃或以下，地面气温在2℃或以下，可作为雨转雪或雨夹雪的温度指标。中层逆温不是降雪必备条件，但对于产生强降雪需要适宜的中层逆温，本次降雪逆温出现在-1℃附近，该指标也可作为秋季降雪的参考指标。 |
| 关键词: 暴雪灾害；雨转雪；中尺度系统；中层逆温 |
| DOI： |
| 投稿时间：2020-10-15修订日期：2021-05-04 |
| 基金项目:中国气象局预报员专项（CMAYBY2020-083）：雷达估算降水在山洪灾害预警中的应用研究；湖北省气象局重点项目（2021Z01）：鄂西南山地极端强降水成因分析及预报概念模型建立。 |
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| Analysis on the Causes of the Tranformation of a Rare Autumn Rainstorm to Blizzard in the Mountain Area of Southwest Hubei Province |
| Luojuying,Tanyanli,Yuliehui |
| (Enshi Region Meteorological Bureau,Enshi Hubei) |
| Abstract: |
| Based on conventional ground observations, MICAPS satellite data and NCEP reanalysis data, the causes of a large-scale rainstorm to blizzard disaster in the mountainous area of southwest Hubei Province from 7 to 9 November 2016 are analyzed. The results show that: This extreme rain and snow disaster weather is the result of the interaction of south-flowing strong cold air and southwest strong warm moisture airflow. Formation and maintenance of a low-level jet streams, the enhancement of positive vorticity in front of the southern branch trough, and the middle level is in the cold and warm airflow cross zone, these conditions became the high-level divergence and low-level convergence of a favorable configuration, which is the main weather background of massive rain and local rainstorm from November 7th to 8th . From the night of 8th to 9th, in addition to the contribution of the strong warm and humid air flow in the middle southwest to the increase of snowfall, it is also mainly affected by the strong confluence of the cold air from east and west. The positive and negative secondary circulation produced by dynamic frontal is the most direct mesoscale system for snowfall. During the continuous rain and snow, there''s plenty of water, accompanied by strong water vapor convergence and upward motion, During heavy snowfall, there was a NE-SW banded dynamic structure over the affected area, and this front baroclinic feature strengthened the flowing of the warm and wet air along the cold air cushion climb; in view of the characteristics of temperature stratification of rain-snow conversion in autumn, the temperature changes in the middle and near strata are focused. Based on the relevant literature and the results of this study, for the snowfall in Hubei Province, 850 hPa at 0℃ or below, and the ground temperatures are 2℃ or below, which can be used as a temperature index for rain to snow or sleet. The temperature inversion of middle-air layer is not a prerequisite for snowfall, But for the appropriate mid-air layer’s temperature inversion is required for heavy snowfall, the snow''s reverse temperature appears near ℃-1, this index can also be used as a reference index for snowfall in autumn. |
| Key words: blizzard disaster; rain to snow; mesoscale system; mesoscale inversion |
