Research On Optical Absorption Properties Of Atmospheric Aerosol At 1064nm Wavelength

Atmospheric aerosol absorption is the most uncertain factor in the evaluation of atmospheric radiative forcing and also an important parameter in the evaluation of atmospheric transmission efficiency of laser.Atmospheric aerosols influence local weather and global climate through direct and indirect effects.At present,the technical methods and instruments for the direct measurement of aerosol absorption coefficient are still uncertain.At the same time,aerosol optical absorption characteristics are highly correlated with regional environment and meteorological factors.Aerosol absorption in different regions has significant differences in physical and chemical properties and optical properties due to different conditions such as source,composition,particle size and meteorological factors.Photoacoustic spectroscopy is considered as the most suitable method for measuring aerosol optical absorption due to its high sensitivity and in situ measurement.In this paper,a set of 1064 nm band aerosol photoacoustic spectrometer was developed based on photoacoustic spectroscopy.Long-term observations of aerosol optical absorption coefficient（OAC）in urban area（Hefei）,coastal area（Qingdao）and ocean area（South China Sea）were carried out by using this spectrometer.Combined with aerosol particle size characteristics,backward trajectory analysis method and AERONET data,the optical absorption properties and rules of different types of aerosols in the above areas are summarized.At the same time,there are few researches on aerosol absorption characteristics in marine areas,especially the lack of relevant measurement data in the South China Sea（SCS）.Therefore,the long-term observation data and relevant rules of aerosol absorption coefficient in this region obtained in this paper are of great significance for the study of aerosol characteristics in Chinese Marine areas.The main research content and innovation of this paper include:1.The overall structure of the aerosol absorption coefficient measuring instrument based on photoacoustic absorption spectroscopy measurement technology with a wavelength of 1064 nm was optimized,and the temperature control unit of the absorption cell was added to improve the measurement accuracy of the equipment2.Based on the aerosol absorption photoacoustic spectrometer and the scanning mobility particle sizer spectrometers（SMPS）,the dependence between the aerosol absorption coefficient and the aerosol particle size in Hefei was measured and analyzed,and the aerosol particle spectral characteristics and their effects on the absorption characteristics in different environments were summarized.3.Based on the long-term observation data of the aerosol absorption photoacoustic spectrometer in the coastal area of Qingdao,the aerosol source and its contribution to the absorption were analyzed by combining the backward trajectory model,and the correlation between the relevant factors and the atmospheric aerosol absorption was analyzed by combining the meteorological data and the pollution gas composition data.4.Based on the long-term observation data of the aerosol absorption photoacoustic spectrometer over the South China Sea,combined with the AERONET optical thickness data,the aerosol optical absorption characteristics and the spatial and temporal distribution characteristics of the aerosol in this region were analyzed.The main contents include:（1）Comparing the long-term variation of aerosol optical depth between Dongsha and Taiping and the surrounding Aeronet,it is clear that the aerosol imported from the coastal cities of southeast China and Singapore is the main source of the short-term and drastic increase of aerosol optical thickness over Dongsha and Taiping.（2）The influence of aerosol composition and meteorological parameters on aerosol absorption coefficient in Sansha area was summarized,and the classification of aerosol absorption coefficient by backward trajectory model was realized.The mean aerosol absorption coefficient over Sansha(2.8Mm^-1),the aerosol absorption coefficient over the southeast coast of China and the direction of Singapore(1.5-5 Mm^-1),and the direction of the Philippines(<1.5Mm^-1)were determined.（3）The diurnal variation of aerosol absorption coefficient in urban area（Hefei）,sea-land intersection area（Qingdao）,and ocean area（Sansha）was compared,and the differences in the absorption characteristics of atmospheric aerosols in different areas at 1064 nm were summarized.Atmospheric aerosol absorption is the most uncertain factor in the evaluation of atmospheric radiative forcing,and it is also an important parameter to evaluate the atmospheric transmission quality of laser.