岳阳市冬季暴雪和一般性降雪条件对比分析
A Comparison of Winter Blizzard and General Snowfall Conditions in Yueyang
中文摘要：
利用NCEP/NCAR 2.5°×2.5°再分析资料和常规气象观测资料，对1989—2018年岳阳市近30年的暴雪和一般降雪天气进行异同点归纳研究：1）频次差异：岳阳平均每年有0.4个暴雪日，一般降雪日平均每年出现3.8 d；2）环流形势差异：暴雪期间，500 hPa中高纬度阻塞形势明显，岳阳处于深厚的高空槽前，700 hPa为强盛西南低空急流、850 hPa为冷式切变线，地面1030 hPa表征线已南压过岳阳地区；而一般降雪高空环流平直，700 hPa西南风和850 hPa偏北风均偏弱，尤其是地面1030 hPa表征线还处于岳阳的北侧；3）温度层结差异：暴雪期间各层温度均低于0 ℃，700 hPa、850 hPa和近地面关键层的温度分别是－6 ℃、－5 ℃和－2 ℃左右，而一般降雪期间，700 hPa、850 hPa和近地面关键层的温度分别是－2 ℃、－1 ℃和1 ℃左右，虽然中层以上也表现为较明显的冷层，但关键层温度整体较一般暴雪偏高3 ℃以上；4）暴雪时近地面冷空气侵入，利于中层暖湿气流的强迫抬升，利于地面的降温和降雪天气的持续，散度、垂直速度和水汽条件等物理量均具有持续强降水特征。
中文关键词：
岳阳，暴雪，异同点归纳，温度层结
KeyWords：
Yueyang, blizzard, similarity and difference, temperature stratification
Abstract：
Based on NCEP/NCAR 2.5°×2.5° reanalysis data and conventional meteorological observation data, the similarities and differences between snowstorms and general snowfall weather in Yueyang City in the past 30 years from 1989 to 2018 were studied. Results show that: 1) frequency differences: Yueyang City had 0.4 snowstorm days and 3.8 general snowfall days each year; 2) circulation field differences: during the snowstorms, the blocking situation of 500 hPa in middle and high latitude was obvious, Yueyang was in front of a deep high trough, 700 hPa was the strong southwest low-altitude jet stream, 850 hPa was the cold shear line, and the surface 1030 hPa line had been southward over Yueyang. During the general snowfall weather condition, the upper air circulation was flat, and the southwest wind of 700hPa and the northerly wind of 850 hPa were weak. In particular, the ground 1030 hPa characterization line was still on the north side of Yueyang; 3) temperature differences of layer: during the snowstorms the temperature of each layer was lower than 0 ℃, and the temperature of 700 hPa, 850 hPa and the key layer near the ground was about 6 ℃, 5 ℃ and 2 ℃ respectively. During the normal snowfall period, the temperatures of 700 hPa, 850 hPa and the key layer near the ground were about 2 ℃, 1 ℃ and 1 ℃ respectively. It is worth noting that, during the normal snowfall period, although the middle layer and above also show obvious cold layer, the overall temperature of the key layer was over 3 ℃ higher than the snowstorms; 4) the invasion of cold air near the ground during snowstorm was conducive to the forced uplift of the middle layer warm and wet air flow, and the continued cooling and snowfall on the ground. Physical quantities such as divergence, vertical velocity and water vapor conditions had the characteristics of continuous heavy precipitation.