A Comprehensive Analysis Of Remote Sensing Observation On Aerosol Physical Radiation Characteristics In China

Since the industrial revolution,the scope of human activities has been steadily growing,and the concentration of aerosols has been increasing,which has had a significant impact on global climate and the environment.Aerosols affect the earth-atmospheric system through direct,indirect,and semi-direct effects,and they contribute to the degradation of the atmospheric environment by participating in atmospheric chemical processes and seriously endanger human health.China has a complex terrain and a large population,it has a wide variety of aerosol,which physical and chemical characteristics are more complex,from a wide range of aerosol sources.Thorough research on the physical radiation characteristics of aerosols in China is therefore essential.At present,there is relatively little research on the long-term comprehensive analysis on physical properties and types of aerosols.Therefore,in this paper,we use ground-based,satellite and other comprehensive data to explore the characteristics of aerosol distribution in China from 2005-2016,the typical region of aerosol distribution was then accurately divided by rotating experience orthogonal decomposition method.The physical characteristics and types of aerosols in the typical regional stations were explored.Finally the research targets were locked in arid and semi-arid regions of the Loess Plateau and study the physical radiation characteristics of a typical daily absorbing aerosol in this area,the main results are as follows:（1）The analysis on multi-year mean value and standard deviation change of aerosol physical properties indicate that the aerosol optical thickness in China has changed from 0.1 to 1.1 in the past decade,and the optical thickness of absorption has ranged from 0.01 to 0.06.The high value areas of the them are mainly located in the northwestern desert area（AOD up to 0.6,AAOD up to 0.05）centered on the Taklimakan Desert,Beijing-Tianjin-Hebei region,the middle and lower reaches of the Yangtze River,the Pearl River Delta,and the Sichuan Basin（AOD up to about 1.1 AAOD can reach a maximum of 0.03）,of which the aerosol absorption in the southwest of the Qinghai-Tibet Plateau and south-western Yunnan and Guangxi is very obvious（AAOD up to 0.06⁰.08）.The regions with large changes in aerosol optical thickness are located in the Taklimakan Desert,Beijing-Tianjin-Hebei region,and the Sichuan Basin.The standard deviation varies from 0.5 to 0.8,indicating that there is a high degree of time inhomogeneity in aerosols in these regions.With the exception of the Taklimakan Desert,the temporal change for the absorption optical thickness was small overall,suggesting that the absorptive aerosol exists in a specific area and is relatively stable.（2）Seasonal analysis on aerosol physical characteristics showed that the AOD in Taklimakan Desert and its downstream areas was the largest in spring,reaching about 1.0,and gradually decreasing in summer,autumn and winter;except for the northwestern desert areas,AOD was the largest in summer,and the high value areas included the Beijing-Tianjin-Hebei region,the middle and lower reaches of the Yangtze River,the Sichuan Basin,and the Pearl River Delta,the high-value center can reach about 1.2,followed by spring and autumn.The absorption optical thickness is the largest in spring,followed by winter,and is smaller in summer and autumn.（3）The EOF and REOF analysis on aerosols in China shows that aerosols have large spatial and temporal variations and do not have obvious modalities.The contribution of the first mode is 14%,and the first principal component shows that the distribution of aerosol has an obvious annual cycle,and the cumulative contribution variance of the first 20 modes is 60%.According to the REOF results,typical areas for the distribution of aerosols include the Taklamakan Desert,the Qaidam Desert,the Kumutag Desert and the surrounding Gobi region,the Horqin Sandy Land,the Hulun Buir Sandy Land,the Sichuan Basin,the North China Plain,and the middle and lower reaches of the Yangtze River.（4）Aerosol physical characteristics of representative sites represent that the aerosol absorption（characterized by the imaginary part of the multi-refractive index）,Hong Kong’s strongest（0.012）,followed by Beijing（0.0105）,followed by SACOL（0.008）The Taihu Lake’s weakest（0.007）;the scattering of aerosols（characterized by the real part of the multi-refractive index）,SACOL is the strongest（1.517）,followed by Beijing（1.490）,followed by Taihu Lake（1.440）,Hong Kong’s weakest（1.420）;single scattering albedo,largest in Lake Tai（0.938）,followed by SACOL（0.915）,followed by Hong Kong（0.915）,Beijing minimum（0.910）;absorbed optical thickness,Beijing largest（0.095）,followed by Hong Kong（0.060）,followed by Taihu Lake（0.060）,and finally SACOL（0.050）.SACOL has the smallest lidar ratio,averaging（56.99±10.44）sr,mainly concentrated in 50-60 sr.SACOL is mainly dust aerosol in spring,and there are anthropogenic aerosols in other seasons.With the exception of SACOL,the Lidar ratios at other sites were all greater than 60,were mainly anthropogenic aerosols.The largest in Hong Kong was（76.51±9.93）sr,mainly distributed in 70⁸0 sr;in Beijing（62.24±10.15）sr,mainly distributed in 60⁷0 sr;in Taihu Lake（69.04±10.77）sr,mainly distributed in 60⁷0 sr.（5）The correlation analysis between lidar ratio and other aerosol physical parameters shows that there is a negative correlation between the lidar ratio and the depolarization ratio,the absorption wavelength index,and the real index of the complex index of refraction,and the correlation coefficients are-0.365 and-0.237,-0.682,respectively;There is a weak positive correlation with the imaginary part of the complex refractive index,and the correlation coefficient is 0.166.For dust aerosols,the lidar ratio varies from 40 to60 sr;the absorption wavelength index is a good indicator of dust and man-made pollutants,and the absorption wavelength index is between 2 and 3,increased absorption mainly caused by dust aerosols.DP=0.15 and RER=1.5 can be used as a threshold to distinguish between dust and anthropogenic aerosols.Through correlation analysis,we can seek a new way to obtain the laser radar ratio,that is,by establishing the regression equation of the lidar ratio and other related physical quantities,obtain the observable physical quantity and find the lidar ratio.（6）The comprehensive analysis of the physical radiation characteristics of the absorbing aerosol on September 3,4,21,and 28,September 2012 in the arid and semi-arid region of the Loess Plateau shows that the research period is mainly mixed aerosols between local dust and anthropogenic pollution.Absorption is obvious and the scale is small.The northwesterly winds strengthened on the 4th,and dust and aerosols were transmitted over long distances,thus the optical thickness was greatest,and the particle size was significantly increased.Attempts to determine the reference altitude using the grey correlation method,which are 7.41 km,8.47 km,7.13 km,and 7.66 km,respectively,invert the aerosol extinction coefficient.The correlation between the optical thickness and the solar photometer observation obtained by this integral can reach 0.975.The inversion effect is better.During the study period,the uplift of aerosols was mainly caused by thermal turbulence during the day,the development of the boundary layer,and the upward transmission of aerosols.At 12 o’clock（local time,the same below）to 14 o’clock,the maximum height of aerosols was lifted.The height of aerosol lift corresponded to the high value area of atmospheric heating rate.The heating rate in the lower layer can reach 1 K·d^-1.Aerosols caused negative radiative forcing at the top of the atmosphere and ground,-12.707 W·m^-2,-25.398 W·m^-2,respectively,and positive radiative forcing in the atmosphere,12.692 W·m^-2.The radiative forcing at the top is most sensitive to the physical properties of aerosols.When the aerosol absorption is significant,the instantaneous radiative forcing at the top of the atmosphere will appear positive.