2008年初江西低温雨雪冰冻天气过程成因探讨

利用T213资料以及常规观测资料,对2008年初江西省持续性低温雨雪冰冻天气过程进行了分析。结果表明,乌拉尔山高压脊稳定维持,副高持续偏北、偏强,地面冷空气不断南下,850hPa层气温始终维持在0℃以下,是造成江西2008年低温雨雪冰冻天气的直接原因。副高和乌拉尔山高压的强度均在不断增强,控制范围不断扩大,导致江西出现三种性质截然不同的降水。700hPa层气温的变化与江西降水性质关系密切,气温为0℃以上时,水汽呈液相态,主要为雨或雨夹雪天气;气温为0℃以下时,水汽呈固相态,以降雪天气为主。中层和低层的水汽输送均可产生冻雨和大雪天气,江西1月25-26日冻雨天气的水汽主要来源于低层输送,28日晚-29日大雪天气的水汽来源于中层和低层的输送,31日晚-2月2日大雪天气的水汽则来源于中层的输送。

CAUSES OF JIANGXI LOW-TEMPERATURE AND FREEZING RAIN PROCESS IN EARLY 2008

Based on the T213 and conventional observation data, the Jiangxi low-temperature and freezing rain process in early 2008 was studied. The results showed that the direct causes of this process were that the ridge of Ural high remained stably, the subtropical high was northward and stronger, the cold air continued moving southward, and the 850 hPa temperature was lower than 0℃. That both the subtropical high and the Ural high strengthened and expanded continuously led to the simultaneous occurrence of three entirely different kinds of precipitations. The type of precipitation was decided by 700 hPa temperature. When the 700 hPa temperature was higher than 0 ℃, the water vapor was in the liquid state, which is associated with rain or sleet. While it was lower than 0℃, the water vapor was in the solid state with snow. Both the middle-level and low-level water vapors could produce freezing rain and snow. The freezing rain was caused by the low-level water vapor during Jan. 25--26, and the Jan. 28--29 snow was associated with both middle-level and low-level water vapor. However, the San. 31 to Feb. 2 snow was connected with the middle-level.