中国北方一次沙尘天气环流特征及其强度与感热通量的关系

Characteristics of A Dust Storm Circulation in Northern China and Its Relationship with Sensible Heat Flux

利用2020年5月2—3日地面常规观测资料,采用天气学分析法和分类统计学,研究中国北方大范围沙尘天气环流特征及其强度与感热通量的关系。研究结果表明:高空槽加强为冷涡,冷空气沿偏西气流南下,有强冷平流。地面沙尘区域内形成北有冷高压、南有低压倒槽对峙的形式。等压线密集区的气压梯度力大,形成偏东大风,产生沙尘天气。在蒙古冷高压底部形成准静止锋,使得天气系统移动缓慢,沙尘天气持续时间较长;沙尘天气发生期间,总体上平均感热通量大于0,地表放热,空气吸热。从感热通量绝对值的平均值看,强沙尘暴是沙尘暴的2~3倍,扬沙、浮尘是沙尘暴的2~4倍。在夜间,由于沙尘的保温作用,使得地表温度大于地面2 m温度,感热通量为正值,沙尘保温作用对沙尘天气发展起正反馈作用。

Based on the conventional ground observation data from May 2 to 3,2020,the synoptic analysis method and classified statistics were used to study the circulation characteristics and the relationship between the intensity and sensible heat flux of large scale dust weather in northern China.The results show that the high trough was strengthened into a cold vortex,and the cold air flows southward along the westerly flow,with a strong cold advection.In the surface sand dust area,there was a cold high in the north and a low pressure trough in the south.The pressure gradient force in the concentrated area of isobars was large,forming a strong wind to the east,resulting in dust weather.A quasi-static front was formed at the bottom of Mongolia cold high,which makes the weather system move slowly and the dust weather lasts longer;During the sand dust weather,the average sensible heat flux was greater than 0 on the whole,the surface emits heat and the air absorbs heat.From the average value of the absolute value of sensible heat flux,the strong sandstorm was 2~3 times of the sandstorm,and the blowing sand and floating dust were 2~4 times of the sandstorm.At night,due to the heat preservation effect of sand dust,the surface temperature was 2m higher than the ground temperature,and the sensible heat flux was positive.The heat preservation effect of sand dust has a positive feedback effect on the development of sand dust weather.