青海省寒潮天气过程中的气温变化影响因素分析

利用常规气象观测资料,分析了2011年3月13—14日青海省一次大范围的寒潮天气过程的成因,并在此基础上根据局地温度方程,定量分析了过程中影响温度变化的主要因子和各自的贡献,结论如下:(1)此次过程是青海省一次典型的横槽转竖型寒潮天气,并且自西向东爆发。过程前期形成典型的寒潮中期倒大“Ω”流型。上游有强冷平流输送,500 hPa冷中心-44℃,700 hPa冷中心-28℃。青海上空西北风风速26 m/s,300 hPa高空西风急流入口区的横向非地转正次级环流也利于地面降温。(2)地面蒙古冷高压中心1060 hPa,影响青海的冷高压达1050 hPa。过程中青海西部的24 h最大正变压18 hPa,24 h负变温最大为-18℃,最低气温平均下降10~13℃,格尔木站下降幅度最大,达到16℃。东部的24 h最大正变压18 hPa,24 h时负变温最大-11℃,最低气温平均下降6~8℃,河南站下降幅度最大,达到16℃。同时东部和西部的地面风速在13日、14日白天都增大,并以偏西风为主。(3)此次过程中的温度变化主要由温度平流项和对流变化项决定,且这2项对青海西部的降温贡献大于青海东部。冷气团的个别变化项对降温也有一定贡献,对东部和西部的贡献基本相等。非绝热项对西部起增温作用,对东部的温度变化没有作用。(4)由强冷空气引起的寒潮天气过程中,温度平流变化和对流变化对降温起主导作用,过程前期应关注温度平流变化的影响,过程结束时应关注对流变化。个别变化项的影响程度依赖于冷空气强度和冷气团变性程度。非绝热项的影响决定于大气中发生相态变化的水汽含量,对温度变化有约束效应。

Analysis on Influencing Factors of Temperature Variety in the Process of Cold Wave Weather over Qinghai

Based on the conventional meteorological observation,data,this paper analyzed the causes of the large-scale cold wave weather process over Qinghai Province from March 13 to 14,2011.According to the local temperature equation,the main factors affecting the temperature variety and their respective contributions in the process were quantitatively analyzed.The conclusions were as follows:(1)This process was a typical horizontal trough to vertical cold wave weather in Qinghai Province,and it erupted from west to east.In the early stage of the process,the typical“Ω”flow pattern occurred in the middle of cold wave was formed.There was strong cold advection in the upper reaches,the cold center at 500 hPa was-44℃,at 700 hPa was-28℃.The northwest wind speed over Qinghai was 26 m/s,and the transverse Non-Geostrophic positive secondary circulation in the entrance area of 300 hPa upper westerly jet was also conducive to surface cooling.(2)The center of ground Mongolia cold high pressure reached 1060 hPa,and the cold high pressure affecting Qinghai was up to 1050 hPa.During the process,the 24-hour positive pressure in the western part of Qinghai was 18 hPa,the maximum negative temperature variety in 24 hour was-18°C,the minimum temperature dropped by 10-13℃on average,and the maximum reduction was 16℃at Golmud station.In the eastern part,the 24-hour positive pressure was 18 hPa,the 24-hour negative temperature was-11℃,the minimum temperature fallen 10-13℃ on average,and the maximum reduction was 16℃ at Henan station.At the same time,the surface wind speed in the east and west increased on the 13th and 14th,and the dominant wind direction was westerly wind.(3)The temperature variety during the process was mainly determined by the temperature advection term and the convective term,and these two terms contributed more to the cooling for the western part than the eastern part of Qinghai.The individual variety of the cold air mass also contributed to the cooling,and the contributions to the eastern and the western were basically equal.The diabatic heating term played warming role for the western part and had no effect on temperature changes for the eastern.(4)For the cold wave weather caused by strong cold air,temperature advection change and convective change played a leading role in cooling.The influence of temperature advection change should be concerned in the early stage of the process,and convective change should be concerned at the end of the process.The extent of the impact of individual change depended on the intensity of the cold air and the degree of denaturation of the cold air mass.The influence of diabatic heating term was determined by the water vapor content of the phase change in the atmosphere,which had a constraining effect on temperature changes.