Scattering And Radiation Study Of Nonspherical Dust Aerosols Above The Sea Based On T-Matrix Algorithm

Atmospheric aerosols are particles with diameter in the range of about 10-3 to 102 ?m suspended in the atmosphere.Natural aerosols are nearly irregular particles.The application of spherical particle model in early researches makes it easy to deal with aerosols scattering.Recently,increasingly enhanced researches testify that there exists large differences in scattering property between non-spherical and spherical particles.To deal with aerosols scattering in marine radiative transfer model and atmospheric correction,Mie scattering based on spherical particles hypothesis is used,which definitely have defects on accuracy in both remote sensing inversion and atmospheric correction.Scattering and radiation of nonspherical aerosols plays a significant role in remote sensing inversion and atmospheric correction.Dust aerosols,a typical nonspherical aerosols,have both semi-spherical and irregular shapes.Thus,this paper regards irregular dust aerosols as study objects to discuss non-spherical particles scattering property.The development of nonspherical particles scattering algorithms provides a useful tool to make a further study of irregular aerosols scattering.Based on T-matrix algorithm,we discussed the effect particles shape have on their scattering property and concluded that particle size,shape and deformation degree were indispensable aspects in aerosols scattering.According to the above,we designed an spheroids simulation program about dust aerosols.Results showed that spheroids can be used as a model to study the scattering property of nonspherical dust aerosols.As the simulation program did not consider deformation of real dust particles,we proposed an improved method to better simulate non-spherical dust aerosols scattering based on distribution of aspect ratio.Validation results showed that the improved method could improve the precision of back scattering,which plays an important role in satellite observation.Using improved method,we simulated scattering properties of nonspherical dust aerosols in different wavelengths,size distribution and relative humidity.Simulation results represented that satellite observations differed a lot under different observing conditions.To study radiation properties of nonspherical dust aerosols above the sea,we used the PolRadTran radiative transmission model to respectively simulate the radiation of ideal spherical dust particles and real non-spherical dust particles under various wavelengths,solar zenith angles and relative humidity.After the comparison and analysis of radiative simulations,we found that the atmospheric radiance is sensitive to aerosols shapes under different wavelengths and solar zeniths,instead of relative humidity.Finally,we selected the day with strong influence from dust aerosols.Based on the improved scattering method,we simulated radiations under different solar zenith angles and wavelengths.Comparing with satellite data from GOCI,we validated the reliability of simulation results.Results showed that simulations could well express the radiation tendency under different wavelengths and solar zenith angles.