Establishment And Validation Of An Atmospheric Aerosol Model In China Coastal Seas

Atmospheric aerosols directly and indirectly change the radiation balance of the earth-atmosphere system by participating in atmospheric processes.Therefore,they significantly affect the global climate,regional weather and ecological environment.Atmospheric aerosols have diverse sources and complex compositions.There are great differences in the physical and chemical properties between different types of aerosols.In coastal areas,land-originated aerosols are transported here with air masses by wind act,and are mixed with marine aerosols.Compared with the atmospheric aerosols in open ocean environment,which is less affected by terrestrial sources,coastal aerosols are more complex and changeable.Based on in-depth analyses and statistics of atmospheric aerosol observations in the China coastal areas,this work develops a so-called Coastal Aerosol Model(CAM),which can obtain microphysical and optical parameters of coastal aerosols from the relative humidity(RH),wind speed and fetch.The main research contents of this work are as follows:1.The data of aerosols particle size distributions and meteorological parameters were collected at coasts of the South China Sea(SCS,Maoming)and the Yellow Sea(YS,Qingdao).Humidity can affect the aerosol particle size.In order to eliminate the influence of humidity on modeling,the observation condition is normalized to RH=80%through the relationship between aerosol particle radius and RH.After analysis of the processed observed data,it is found that the particle concentration has a certain relationship with wind speed and fetch.Using the lognormal distribution spectrum function,the atmospheric aerosol particle size distributions are calculated by a function of wind speed and fetch.Then CAM was developed for predicting the state of atmospheric aerosol in coastal aeras.The results show that CAM can better simulate the shape of aerosols particle size distributions in the Chinese coastal seas(the South Sea and the Yellow Sea).2.In order to quantify the performance of CAM,this work conducted two sets of comparative tests:1)the observed aerosol data were came from the scientific research ship Shenkuo while cruising in the South China Sea.In the coast area,comparing to cruise data,the modeled aerosols particle size distributions of CAM is consistent with the observed value.The correlation coefficient between the modeled value and the measured value is 0.93.2)Observations of aerosol extinction coefficient and scattering coefficient using extinction spectrometer CAPS-ALB at Qingdao.Compared to the modeled results by Navy Aerosol Model(NAM),CAM results can be seen to better predict the optical properties of aerosols in coast.3.Through the analysis of the one-year measured data(meteorological conditions)in the coast of the Yellow Sea(Qingdao),combining with the HYSPLIT backward trajectory model,it is found that the regional meteorological conditions and the source of air masses have obvious seasonal changes.And the particle concentrations of the four modes are also different in different seasons.The changing trends of the particles in the accumulation mode and the coarse particle mode are quite different.It indicates that the meteorological conditions have a greater impact on the particle size and concentration of atmospheric aerosols.Finally,the observational data of the four seasons are merged into the CAM model,so that CAM can more accurately predict the characteristics of atmospheric aerosol particles in the coastal areas of the Yellow Sea.4.By using the aerosol optical thickness(AOT)data of the ground-based observation network AERONET,the performance of the AOT products of the geostationary satellite Himawari-8(H-8)in the coast aeras was evaluated.After screening out the poor quality data,493 sets of samples were obtained through spatio-temporal matching.Through analysis,it is found that most of the H-8 products are underestimated with AOT greater than 0.2;when AOT is less than 0.2,there are more overestimations.As a geostationary satellite,H-8 can monitor the changing trend of AOT over time,laying a foundation for the application of H-8 aerosol products in the study of atmospheric aerosol modeling in coastal aeras.