九江市一次低温雨雪冰冻天气垂直温度层结分析

运用收集到的资料分析了2018年1月25～28日九江市阴雨雪和低温天气形成原因,分析了阴雨雪低温的恶劣天气的演变过程和水气环流特征,得出了江西地区冻雨的温度垂直分布特征结构和在九江地区具体应用情况的结论。结果表明:此次过程副高稳定,冷空气强盛500 hPa、700 hPa西南区域易产生逆温层,850 hPa东北气流使暖湿空气随着空气不断上升,更容易产生暴雪。水汽的输送过程非常频繁,同时该地区的辐合比较明显导致雨雪天气处于经常变化的情况;低层冷空气天气对冬天降水的形态起着非常关键的作用,此次过程冻雨灾害严重,经分析,25日为融化层位于850 hPa的情况,925～1 000 hPa区域迅速降温,850 hPa区域高于0℃,700 hPa和925 hPa区域温度低于0℃,1 000 hPa时温度在小于1℃,地面温度低于0℃,25日白天出现冻雨。27日融化层处于700 hPa左右温度大于0℃,925 hPa和850 hPa时温度低于-2℃,925～700 hPa有非常明显的温差;但由于1 000 hPa时温度在-3℃左右,所以27日白天九江地区降水相态复杂,大部分地区以降雪为主,部分地区出现冻雨。上述的阈值范围是九江地区冻雨的天气阈值。研究还表明,随着地面的温度降低,冻雨天气越容易产生,冻雨一般发生在最低气温低于0℃,同时一天的平均气温低于1.0℃。

Vertical Temperature Stratification Analysis of a Low Temperature Rain and Snow Freezing Weather in Jiujiang City

By using conventional observation data, the causes of the formation of low-temperature, rainy and snowy weather process in Jiujiang City from January 25 to 28, 2018 are analyzed. The circulation characteristics and evolution of continuous low-temperature, rainy and snowy weather in Jiujiang City are pointed out. The application indexes of vertical temperature stratification characteristics of freezing rain in Jiangxi Province are summarized. The results show that the location of snowfall area corresponds to the convergence area of 850 hPa-925 hPa under the stable circulation situation of 500 hPa and 700 hPa; active water vapor transport and strong convergence can maintain the rain and snow weather; low-level cold air plays a key role in the phase of winter precipitation; the occurrence of frozen rain in Jiangxi Province is usually accompanied by severe 1000-850 hPa cooling and 700 hPa warming, 925-700 hPa warming. There is obvious temperature inversion. The thawing layer is the necessary condition for the occurrence of freezing rain. The thawing layer of freezing rain is located at 700 hPa. Generally, the temperature of 1000 hPa < 1 C, 925 hPa and 850 hPa < 2 C and 700 hPa < 0 C are used as the threshold criteria for the prediction of freezing rain in Jiujiang. At the same time, attention should be paid to the situation that the thawing layer is located at 850 hPa. The lower the surface temperature is, the better the formation of frozen rain. The lowest temperature is below 0 and the average temperature is below 1.0 when the frozen rain occurs.