Contrastive Analysis of the Freezing Rain and Heavy Snow Processes in 2008
Contrastive Analysis of the Freezing Rain and Heavy Snow Processes in 2008
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发表时间：
2008
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通讯作者：
Zheng Jing
中科院分区：
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作者：
Zheng Jing
基于NCEP 1°×1° 6 h间隔再分析资料和逐日观测，对江西省2008年1月25—28日区域性冻雨和2月1—2日大雪进行了环流形势、热力结构、动力抬升和水汽条件等方面的对比。结果表明，两个过程具有相似的环流背景，但大雪比冻雨具有更深的水汽饱和层、更强的冷空气、更强的辐合和垂直风切变。对流层中层气温快速升高是冻雨转为大雪的关键，两个过程均在925—700 hPa之间出现逆温现象。但冻雨时锋面逆温较强，800 hPa以上有1～2公里暖层，最高气温2～7℃，大雪时整个对流层温度在0℃以下。大雪伴随着湿位涡而发展。 MPV1正中心附近的高梯度区域、斜压中心附近的密集等斜线区域以及深部强烈的上升运动可以指示冻雨和大雪。两个过程均存在下层辐散、中层辐合和上层辐散，且辐合和辐散从上层到下层均由北向南倾斜。大雪有更显着的上层辐散和抽吸作用。
Based on NCEP 1°×1° 6 h interval reanalyzed data and daily observation, the Jan. 25—28 regional freezing rain and Feb. 1-2 heavy snow in 2008 in Jiangxi province were contrasted at the aspects of circulation situation, thermodynamic structure, dynamic lifting and vapor condition. The results show that the two processes had the similar circulation background, but the heavy snow had deeper vapor-saturated layer and stronger cold air, stronger convergence and vertical wind shear than the freezing rain. The temperature increasing quickly in the middle troposphere was the key for freezing rain changing into heavy snow, both of the two processes had temperature inversions between 925—700 hPa. However, for the freezing rain the frontal inversion was stronger, with a 1—2 km warm layer above 800 hPa, in which the highest temperature was 2—7 ℃, while for the heavy snow the temperature was below 0 ℃ in the whole troposphere. The heavy snow developed with the moist potential vorticity. High gradient region near the MPV1 positive center, dense isoclines area near the baroclinic center, and deep strong ascending motion can indicate freezing rain and heavy snow. Both of the two processes had lower-layer divergence, mid-level convergence and upper-layer divergence, with the convergence and divergence inclining northward to the southward from upper to lower layer. The heavy snow had more significant upper-layer divergence and pumping action.