寿县不同强度雾的微物理特征及其与能见度的关系

Microphysical Characteristics of Fog with Different Intensities and Their Relationship with Visibility in Shouxian County

雾对交通运输有不利影响,尤其是强浓雾。本文利用2019年1月上中旬在寿县国家气候观象台应用FM-100型雾滴谱仪测量的雾滴谱数据和常规气象观测数据,分析了不同强度雾的微物理特征,以及能见度与含水量、雾滴数浓度、相对湿度之间的关系,在此基础上建立了能见度参数化方案。结果表明:(1)随着雾的强度增强,雾中含水量显著增大,大雾、浓雾和强浓雾阶段含水量平均值分别为0.003 g m;、0.01 g m;和0.09 g m;当含水量大于0.02 g m;出现强浓雾的比例高达95%。(2)雾滴数浓度、雾滴尺度随着雾强度增强而增大,从大雾到浓雾,雾滴数浓度显著增加(增幅67%),而从浓雾到强浓雾,雾滴尺度显著增大,平均直径、平均有效半径分别增加62%、135%;当雾滴有效半径大于4.7μm,出现强浓雾的比例高达95%。(3)强浓雾、浓雾、大雾雾滴数浓度谱分布均为双峰结构,谱分布整体偏向小粒子一端,强浓雾谱型为Deirmendjian分布,浓雾、大雾均为Junge分布;强浓雾的雾水质量浓度谱呈现多峰特征,最大峰值出现在21.5μm处,浓雾雾水质量浓度谱为双峰分布,大雾为单峰型,最大峰值均出现在5μm处。(4)含水量、数浓度与能见度均呈反相关关系,含水量对能见度的影响最为显著;分别采用全样本和分段方式建立了四种能见度参数化方案,评估检验结果表明,基于含水量的能见度分段拟合方案对能见度的估算效果最好。

Fog,especially extremely dense fog,has adverse effects on transportation.This paper utilizes the fog droplet spectrum data measured using the FM-100 fog drop spectrometer at the Shouxian National Climate Observatory in January 2019 and the contemporary conventional meteorological observation data to investigate the microphysical characteristics of fog with different intensities.Based on the analysis of the relationships between the visibility(V)and liquid water content(L)and the number concentration(N)of fog droplets and RH(relative humidity),various visibility parameterization schemes were established.The results showed that:(1)With the increase of fog intensity,the water content in fog increased significantly,with average values of 0.003 g m;,0.01 g m;,and 0.09 g m;during the periods of fog,dense fog,and extremely dense fog,respectively.When the L was greater than 0.02 g m;,the proportion of extremely dense fog reached 95%.(2)The N and droplet size increased with the increase in fog intensity.From fog to dense fog,the N increased significantly by 67%,while from dense fog to extremely dense fog,the droplet size increased significantly,and the average diameter(D)and effective radius(R;)increased by 62%and 135%,respectively.When the R;was greater than 4.7μm,the proportion of extremely dense fog reached 95%.(3)All spectra distributions of the droplet number concentration for fog,dense fog,and extremely dense fog exhibited a bimodal structure with major peaks close to the end of the small particles.The spectrum type of the extremely dense fog was a Deirmendjian distribution,while that of the dense fog and fog was a Junge distribution.The fog water mass concentration spectrum was characterized by multipeaks for extremely dense fog with maximum peak appearing at 21.5μm,while the dense fog and fog exhibited a bimodal distribution and single peak type,respectively,with maximum peak at 5μm.(4)Both L and N were inversely correlated with visibility,with L showing the highest correlation coefficient with visibility.Four kinds of visibility parameterization schemes were established using the full sample and segmented method.Test results indicated that the visibility subsection fitting scheme based on L was the best.