一次浓雾过程的观测分析

Observation and analysis of a dense fog process

利用DMTFM120雾滴谱仪(2-50μm)、VAISALAPWD22能见度仪和六要素自动气象站对2016年11月3日河北省中南部平原地区的一次浓雾天气进行了观测分析。这次浓雾过程主要由于夜间辐射降温形成,晴夜风速较弱,低空存在较强逆温,属于典型的辐射雾。观测表明,由于夜间长波辐射冷却作用的增强,温度迅速下降,雾滴浓度突增,导致能见度突降,出现了浓雾的爆发。这次浓雾过程的能见度最低为71m,相对湿度93%-99%;雾滴的平均浓度为89cm^-3,最小2cm^-3,最大403cm^-3;平均直径为3.9μm,最大直径13.5μm;平均含水量为0.0033gm^-3,最小含水量0.00002g·m^-3,最大含水量0.038g·m^-3。总体而言,这次过程雾滴浓度不高、含水量较低,各阶段的雾滴谱分布都偏向小滴一端,谱宽较窄,缺乏大滴,不利于向强浓雾发展。

Using DMT FM120 droplet spectrometer (2-50 um), VAISALA PWD22 visibility meter and six-element automatic weather station, a dense fog weather in the plain area of central and southern Hebei Province on November 3, 2016 was observed and analyzed. This dense fog process is mainly caused by the radiation cooling at night. The wind speed is weak on clear night and there is strong inversion at low altitude. It belongs to the typical radiation fog. Observations show that due to the enhanced cooling effect of long-wave radiation at night, the temperature drops rapidly and the droplet concentration increases sharply, resulting in a sudden drop in visibility and a dense fog eruption. The visibility of the dense fog process is 71 m, the relative humidity is 93%-99%;the average concentration of droplets is 89 cm^-3, the minimum is 2 cm^-3, the maximum is 403 cm^-3;the average diameter is 3.9 um, the maximum diameter is 13.5 um;the average water content is 0.0033 g m^-3, the minimum water content is 0.00002 g·m^-3, and the maximum water content is 0.038 g m^-3. Generally speaking, the droplet concentration is not high and the water content is low in this process. The distribution of droplet spectrum in each stage is inclined to one end of the droplet, and the spectrum width is narrow. The lack of large droplets is not conducive to the development of strong fog.