Research On The Boundary Layer Flow Field Structure Under Typical Weather Based On Lidar Data

The atmospheric boundary layer is the main layer which is composed of human life and various ecological circles,besides,it is the most closely related layer of human relations.The atmospheric boundary layer is an important atmosphere for the exchange of material,energy,heat and water vapor between the surface and the free atmosphere,and its height is generally distance from the ground 1-2km.The conventional methods for detecting the atmospheric boundary layer include the tethered balloon detection,the wind tower and the remote sensing detection.The remote sensing detection can detect the characteristics of the boundary layer systematically and continuously.In particular,the laser radar to study the characteristics of the boundary layer is the main research content of this paper.In this paper,we use the data of ground-based remote sensing equipment including laser radar,microwave radiation and their Inversion of secondary products in Shanhaiguan,K unming and Xi'a n to analyze the characteristics of weather situation,wind field,temperature and humidity field,boundary layer physical quantity field and so on,after selecting cases by using the ground by time observation of the synoptic data.Finally,we use lidar data,wind profile radar data and ground-based microwave radiometer data to analyse the difference of Shanhaiguan,K unming and Xi'an boundary layer and introduce the application of laser radar scanning mode in addition to wind profile scanning mode in the boundary layer.The conclusion is as follows:(1)When the concentration of PM2.5 increases gradually in fog and haze day at Shanhaiguan,the turbulence dissipation rate increases gradually,and the height of maximum turbulence dissipation rate decreases except surface boundary layer.This indicates that the higher the maximum turbulence dissipation rate is,the more favorable for the diffusion of pollutants.In cloudy days,when there are more low clouds and lower heights of cloud,the turbulence dissipation rate is stronger,and the maximum height of turbulence dissipation rate is lower.There are more obvious boundary layers in cloudy days,and the height of the boundary layer has obvious diurnal change and the height extremum of the boundary layer appears at noon.In clear day,After sunrise,the mixed layer began to thicken gradually,and after sunset,the peak of turbulence appeared.The turbulence dissipation rate developed strongly,was slightly later than the height of the boundary layer and the heights is lower the height of boundary layer.(2)In the K unming,the height of the boundary layer is unstable before the precipitation, and gradually increases with time.Until the beginning of precipitation,The height of the boundary layer begins to gradually decrease,and gradually changes from the unstable boundary layer to the stable boundary layer.After precipitation,the unstable boundary layer gradually began to establish.In windy days,the boundary layer is the unstable boundary layer,and there is a clear change in the height of the boundary layer when high wind occurs,and the height of the boundary layer increases.At the time of precipitation and high wind,the wind speed and direction detected by laser wind radar change greatly and the temperature advection is large.(3)By analyzing the boundary layer characteristics of different locations in the same weather condition,we can know that in sunny days,the average horizontal wind speed in the offshore area Shanhaiguan is higher than in the plateau area K unming,and there is a large wind area in Shanhaiguan after nightfall.The main wind direction of the two places is the west wind,and the wind direction changes little.In the cloudy day,the horizontal wind speed in Shanhaiguan is large,which is mainly controlled by the north wind and the northeast wind.The horizontal wind speed in K unming is relatively large,and the wind direction changes greatly,which is mainly controlled by the westerly wind and the southwest wind.There is a high-pressure center abo ve the C hangshui Airport.In fog and haze day,the horizontal wind speed is small,and the wind direction is almost unchanged,which is mainly controlled by the west wind in Kunming.At Xi'an,during the transit of the system,there was flooding and trembling precipitation,with large wind speeds appearing on the ground,followed by a whole gale,and finally a large wind speed.In rainy day at Kunming and Xi'an,the changes in wind direction are relatively large,and there is a wind shear.The temperature starts to decrease gradually and after precipitation,it increase.The relative humidity increases to more than 80% at 3-4km before precipitation,and the relative humidity 100% begins to descend from high altitude to the ground.(4)According to the analysis o f the data obtained,use PPI scanning mode boundary layer can analyze the range and intensity of cold and warm advection.Using the current unique lidar's mode take-off and landing channels to scan the boundary layer can getting the evolution of the boundary layer along the wind glide slope and it is more suitable for aeronautical meteorological service work.The high spatio-temporal resolution data obtained by the Lidar's RHI profile scan of the boundary layer along the runway can be used to analyze aircraft vortices.