河北冬奥赛区一次夜间增温过程的数值模拟及诊断

Numerical Simulation and Diagnosis of a Nocturnal Warming Process in the Hebei Winter Olympic Games Area

夜间增温是河北冬奥赛区冬季频发的天气现象,对其进行准确的模拟与预报对赛区建设及比赛保障至关重要。本文针对河北冬奥赛区2020年2月8日夜间至9日凌晨发生的一次夜间增温过程,通过引入高分辨率地形数据,利用中尺度区域数值模式WRF4.1.5精细化再现了此次夜间增温过程,并探究了此次过程的气象特征及成因。研究结果表明:此次夜间增温过程受东北冷涡影响,中高空冷平流显著,高低层风切变较强,有明显的平流差异,同时,近地面气象要素变化特征明显,包括相对湿度降低、风速增大、海平面气压降低、地表热通量及长波辐射增强等;增温发生时,强冷平流在范围及强度上均明显增加,导致强烈的下沉运动,使得低层大气温度升高,并且高低层强风切变以及平流差异容易产生垂直混合,等熵面波动明显,湍流加强,进一步加强湍流垂直混合运动,运动热通量输送增强,产生夜间温度异常升高现象。

Nocturnal warming is a frequent weather phenomenon in the Hebei Winter Olympic Games area,and its accurate simulation and forecast are very important for the construction of the competition area and guarantee of the competition.By introducing the higher resolution terrain data,the mesoscale regional numerical model WRFv4.1.5 was used to reproduce the nocturnal warming process,and the meteorological characteristics and causes of the process were explored.Results show that:(1)the process is affected by the northeast cold vortex,(2)the cold advection is significant at the middle and upper levels,(3)the wind shear is strong at the high and low levels,and(4)there are obvious advection differences.At the same time,the variation characteristics of meteorological elements near the surface are obvious,including the decrease in relative humidity,increase in wind speed,decrease in sea level pressure,and enhancement of surface heat flux and long-wave radiation.In addition,the strong wind shear and advection difference between the upper and lower levels easily produces vertical mixing.The isentropic surface fluctuation is obvious and the turbulence is strengthened,which further strengthens the turbulent vertical mixing movement,enhances the moving heat flux transport,and produces the abnormal increase of night temperature.