Observation And Simulation Study Of Aerosol And Cloud Over Changjiang-Huaihe Region In Boreal Summer

The aircraft equipped with aerosol probe and cloud probe was used to detect spatial distribution characteristics of aerosol particles and cloud droplets over Changjiang-Huaihe Region during August 12-28,2014,together with meteorological data and GPS data,the vertical and horizontal distributions of aerosol and cloud are analyzed,and the relation between aerosol and cloud is discussed as well.WRF(Weather Research and Forecasting Model)model combined with aircraft observation data is used for simulating cloud over this region,characteristics of macro-microscopic parameters of cloud and variation of aerosol number concentration during cloud evolution process are analyzed.The parameterization scheme of WRF model is Thompson parameterization scheme which include the process of cloud-activated removal aerosol.The main results are as follows:(1)In Changjiang-Huaihe Region,the average number concentration of aerosol particles in the size range of 0.1-3.0??m was 481±199cm-3.Most of the aerosol particles were concentrated in the layer below 1km,where the number concentration decreased with the altitude.Cloud droplets number concentration and liquid water content was in the range of 24-297cm-3 and 0.04-0.13gm-3.The cloud number concentration decreaed with increasing height of cloud base,and cloud mean diameter increased with the increasing height of cloud.Cloud droplets were concentrated in the bottom of low clouds,and the cloud number concentration decreased with the altitude.A large fraction of aerosol particles was removed when clouds with cloud base lower than 2000m were present,the removal the cloud activation process removed a large number of aerosol particles.(2)WRF model was used to simulate a warm stratified cloud process on August 28,2014 in Anhui Province.The parameterization scheme was a Thompson scheme that included cloud droplet activation and collision scavenging of aerosols.Simulated radar reflectivity,precipitation distribution,and vertical distribution of cloud microphysical parameters are all correspond well with observation results.The simulation results show that there was a wide range of nimbostratus(Ns)below 1000m in the west of Anhui Province at 08:00.There were two peak centers of cloud number concentration in the north and south respectively.The coverage of cloud liquid water content coincided with the range of cloud number concentration.The Ns completed the transformation from development stage to mature stage within 1-1.5 hours,and it need to experience about 3 hours from the mature stage to complete dissipation.The height of cloud top and cloud base was about 1.1km and 0.1km,respectively,the thickness of cloud increased from west to east.During the development process,the cloud top gradually increased and the height of the cloud base increased slightly.The height of peak concentration of cloud droplets was below 0.8 km.The cloud has two development processes during 02:00-20:00.The slope of the decrease of aerosol number concentration was the largest in two developmental stages of the cloud,and the slope is smaller in the remaining period,indicating that cloud droplet activation process removed a large amount of aerosol.(3)In sensitivity experiments the initial aerosol number concentration was increased to 5,10,and 20 times of that in control experiment,respectively,the cloud case is a warm stratified cloud process on August 28,2014 in Anhui Province.Simulated cloud number concentration in sensitivity experiment was higher than that of the control experiment,while the coverage of the cloud layer in northern part did not change compared with control experiment.The peak concentration of cloud droplet was doubled,and the position of peak concentration center did not change.The coverage of the cloud in southern part has expanded a little and cloud number concentration increased.The increased cloud condensation nuclei(CCN)concentration led to an increase of the liquid water content in cloud center,The center value of the liquid water content did not change if CCN concentration exceeded a specific value.The Increasing concentration of CCN led to an increase of cloud number concentration below 1 km.The coverage height of cloud number concentration in value of 50 cm-3 increased from 0.5 km to about 0.7 km,and the coverage range expanded.Cloud liquid water content at different altitudes changed differently,the liquid water content increased in low level of cloud but decreased at high level in cloud.Increasing concentration of CCN promoted the second development of cloud,indicating that sufficient CCN is conducive to cloud development and will increase the height of cloud development.