Variation Characteristics Of Meteorological Elements And Their Relationship With Particulate Matter Concentration During Heavy Pollution In Guanzhong Region

Atmospheric diffusion is usually determined by meteorological conditions.In order to study the relationship between meteorological conditions and air pollution in Guanzhong region,the test points in Baoji and Xi'an(the test point in Baoji is No.1,and the Xi'an point is No.2)are set up to represent the border and the central of Guanzhong.The particle concentration and ground meteorological data of the two test points are obtained by ground observation.The upper air meteorological data in Guanzhong region are obtained by using the WRF/CALMET coupling system.Combined with the monitoring data collected from Baoji Chencang point and Xi'an Xiao Zhai point(national control point),from the perspective of Guanzhong region,the evolution characteristics of meteorological conditions during the formation,continuous,dissipation and after dissipation of a heavy pollution process are analyzed.The relationship between the meteorological factors of two test points and the concentration of particulates in different particle sizes is also analyzed.The main conclusions are as follows:(1)During the formation and continuous stage of pollution,along the Qinling Mountains mountains,there is an updraft but attenuates to 0m/s at 850 hPa,and the vertical wind speed is zero in most regions of the basin.The stage of pollution dissipation,along the two sides of the mountain,has strong downdraft into the basin,and the updraft in the basin begins to appear at a speed of about 0.03m/s.During the after dissipation stage.The upward and downward wind speeds of the basin are about 0.12m/s and-0.05m/s,and the convection is strong at the surface and upper air.(2)During the continuous stage of pollution,temperature gradient in the basin is very small,and the temperature difference between the 700 m and the ground is 2?.The formation stage of pollution,there are many high temperature regions in the basin,and the height of the heat island group is about 300-500 m.During the stage of pollution dissipation,the temperature distribution in the basin is more uniform and the heat island group disappear.There is no heat island phenomenon in the test period during the no pollution stage,and the average temperature of 10 m at point No.1 is 271.38�2.83 K,and the point No.2 is 273.60+3.06 K,which is the lowest in all stages.(3)In the continuous stage of pollution,the height of mixed layer in Guanzhong region is obviously lower than that after pollution dissipation.At the time of pollution formation,the average height of the mixed layer at two points is about 300 m.When the pollution dissipated,the average height of mixed layer height of point No.1 and point No.2 increased to 527.48+353.08 m and 425.16+283.71 m respectively.(4)Under the condition of high humidity(RH>60%),the concentrations of particulate matter at two test points were all bimodal distribution.The number concentration of large particles at high humidity is higher than that at low humidity,and the number concentration of small particles is higher in low humidity.When Dp<0.1?m,the total concentration of particulate matter in RH<60% situation,No.1 and No.2 test points is 1.05 times and 1.06 times respectively when RH?60%.When Dp?0.1?m,the total concentration of particulate matter at No1 point and No.2 point in RH<60% situation is 0.35 times and 0.68 times respectively when RH?60%.(5)The correlation between temperature and particulate matter of different particle sizes is different,humidity also has a similar phenomenon.Temperature was negatively correlated with particulate matter with a median particle size of about 0.01?m,and positively correlated with the particulate matter with a median particle size greater than 0.121?m.Humidity is negatively correlated with the median particle size of 0.010-0.072?m,which is positively related to the particle which the median particle size is in 0.199-1.242?m,and the particles with the median particle size of more than 2.007?m are negatively correlated in the high humidity condition,and are positively correlated in the low humidity environment in No.1 test point,and the correlation is not obvious in the low humidity environment of No.2 test point.