Distribution Characteristic Analysis Of Visibility & Research Of Low Visibility Impact In Jiangsu Province

Visibility is an important factor affecting human production and life,especially for traffic safety and human health.This study was conducted based on the atmospheric visibility,surface meteorological data and atmospheric pollutant monitoring data of Jiangsu Province from 2014 to 2016,along with traffic accident data of Ningbo-Shanghai Expressway from2014 to 2015 and daily visits to the respiratory department of a third-level hospital in Nanjing from 2014 to 2015.The spatial and temporal distribution characteristics of atmospheric visibility in Jiangsu Province and its relationship with meteorological factors and air pollutant concentration were researched by statistical analysis.Additionally,this article discussed the influence of low visibility on highway traffic safety and the effect of fog-haze weather on the induction and aggravation of respiratory diseases.Firstly,the prediction index of low visibility fog was established with relative humidity,wind speed and inversion temperature of near surface layer as main factors,and its fitting rate reached 74%.The results also indicate that the average visibility of Jiangsu Province is generally 5-9km,characterized by east-high and low-lying distribution annually,while it is low south and high north in spring,on the contrary in summer,and high east and low west in autumn and winter.The visibility is higher from July to September and lower in January and December.The diurnal variation of visibility is obvious.Visibility is positively correlated with wind speed and air temperature,and the correlation coefficients are 0.87 and 0.61,respectively.Meanwhile,visibility is negatively correlated with relative humidity and PM2.5concentration,the correlation coefficients are-0.71 and-0.60,respectively.Further analysis of the low-visibility weather caused by fog and haze in Nanjing.The result showed that the circulation background was west airflow control at 500 hPa,uniform pressure field,large humidity,low wind speed,low mixing layer height and heavy pollution.At the same time,it is accompanied by weak sinking motion,weak negative vorticity,weak positive divergence and the temperature inversion.These factors contribute to the maintenance and enhancement of low-visibility weather.When the visibility is less than 500 m,it is easy to cause serious traffic accidents and death.The occurrence of fog accidents coincides well with the time of fogging.The diurnal variation characteristics of visibility are low in the morning(more accidents)and high in the afternoon(fewer accidents).The number of patients with respiratory diseases in fog-haze days is 12.8% higher than that of non-fog-haze days,with the increase rate more than 13.5% in winter and 21.0%among children(< 6 years old).There is an acute effect between PM2.5 and respiratory diseases,which is reflected in the high correlation between PM2.5 concentration and the number of patient visits on the day.In autumn and winter,the influence of environmental factors on respiratory diseases is persistent.The influence of environmental factors such as NO2,SO2 and O3 on the number of patients with respiratory diseases may last for 4 to 5 days.