2020年春季中国北方一次扬沙天气过程微气象学与沙尘输送特征

利用内蒙古科尔沁沙地和沈阳地区同步气象要素梯度观测和地面大气颗粒物(PM_2.5和PM₁₀)质量浓度观测资料, 分析了中国北方地区2020年5月10日一次大范围扬沙天气过程微气象学和沙尘输送特征。结果表明: 受大尺度天气系统影响, 此次沙尘天气过程中科尔沁沙地不同高度(< 20 m)风速均明显增加, 各层相对湿度和浅层地表含水量有所降低, 较强湍流动力作用配合干燥的土壤和大气环境有利于沙源地区地表大量的沙尘粒子释放到大气中。此后这些沙尘粒子随较强的西北气流集中在2—3 km以下高度向下游地区输送。受沙尘输送的影响, 沈阳地区10日小时平均PM₁₀浓度最高达817 μg·m^-3, 能见度减小至3.7 km。此外, 科尔沁沙地起沙过程中能见度与摩擦速度存在明显的反相关关系(相关系数R²=0.93), 与湍流动力学热通量相关性相对较小, 表明湍流动力作用在此次起沙过程占主导作用。

Micrometeorological characteristics and dust transport during a blowing sand event in the spring of 2020 over northern China

Based on multilevel observations of meteorological variables and surface atmospheric particulate matter (i.e.PM_2.5 and PM₁₀ in this study) mass concentration in Horqin Sandy Land area and Shenyang, we analyzed the characteristics of micro-meteorology and dust transportation during a blowing dust event on May 10, 2020, in northern China.The results indicate that during the blowing dust event affected by large-scale synoptic systems, wind speed at different heights (< 20 m) over the Horqin Sandy Land area increases significantly and ambient relative humidity at each level and surface water content both decrease.Enhanced turbulent dynamic activity along with dry air and soil conditions is conducive to the release of massive dust particles from the surface of sand source areas into the atmosphere.Thereafter, these dust particles are transported to the downstream areas with the strong northwesterly airflow, concentrating at altitudes below 2 km.Due to the long-range transport of dust particles, the hourly mean PM₁₀ concentration in Shenyang on May 10 increased up to 817 μg·m^-3, and the visibility decreased to 3.7 km.During the dust emission period in the Horqin Sandy Land area, visibility exhibits a significant negative correlation with friction velocity (correlation coefficient R²=0.93) and a weaker negative correlation with kinetic turbulent vertical heat flux, meaning that the turbulent dynamic effect plays a leading role in the dust emission process.