Quantitative Remote Sensing Inversion Of Absorbing Aerosols Based On Satellite Ultraviolet Spectral Information

Absorbing aerosols are complicated and unstable in components,and they are on the list of the extremely uncertain factors in climate simulation and prediction,as well as a difficulty for atmospheric corrections of ocean color remote sensing.After predecessors’ research for decades,the study on absorbing aerosol remote sensing is from qualitative,then semi-quantitative to quantitative;but at present researchers commonly use Lidar active remote sensing approach to quantitatively obtain absorbing aerosols,and using passive satellite remote sensing method to retrieve absorbing aerosols qualitatively is challenging.Nevertheless,applying satellite remote sensing technique to large-scale retrieve absorbing aerosols can offer benefits,such as reducing the uncertainties for global climate change prediction,monitoring the pollution air more precisely,and improve the accuracy of atmospheric correction for satellite ocean color remote sensing.Since some types of absorbing aerosols have significant difference in optical properties of ultraviolet bands,though they are similar with traditional scattering aerosols with visible bands,utilizing spectral information of satellite’s ultraviolet bands provides great application potential.This paper aims at quantitative retrieval of absorbing aerosols over ocean with remote sensing method.Based on ocean-atmosphere radiative transfer theory and analysis of the optical properties for absorbing aerosols,optical look-up-tables are constructed and generated for 4 types absorbing aerosols,and an ultraviolet algorithm to quantitative retrieve absorbing aerosols is developed.The algorithm is applied to monitoring of dust storm and volcano eruptions.The principal results are as follows:(1)The improvement of the current ocean-atmosphere radiative transfer model OSOAA gets the calculation precision better than 0.5% for Rayleigh scattering,10%for aerosol scattering,5% for diffuse transmittance;(2)Based on OPAC aerosol data base,improved ocean-atmosphere radiative transfer model is used to generate optical parameter look-up-tables for 4 types of absorbing aerosols,and the corresponding diffused transmittance look-up-tables with varied geometry angles are also calculated and generated;(3)Inversion algorithm utilizing ultraviolet spectral information of satellite(UVAA)is developed.Compared with standard NSAC algorithm,the UVAA algorithm developed in this paper shows better accuracy for retrieval of aerosols.With the benchmark of ground measured data from AERONET-OC,the corresponding fitting coefficients of aerosol optical thickness at 412、443、490、532、551 and 667 nm are0.872、0.865、0.897、0.930、0.919 and 0.946 for UVAA algorithm,higher than the fitting coefficients of NSAC algorithm;the RMSE for UVAA algorithm are0.034、0.032、0.024、0.018、0.017 and 0.010,less than that of NSAC algorithm;(4)Aerosol Angstrom index and remote sensing reflectance can be also obtained using UVAA algorithm.Since UVAA algorithm takes account of the absorbing aerosols,the Angstrom index of absorbing aerosols can be calculated more precisely,and the“over correction” for aerosol scattering at short and ultraviolet bands for NSAC algorithm can be avoided to get more accurate remote sensing reflectance at blue-violet and ultraviolet bands;(5)The UVAA algorithm in this paper is developed originally for HICO,with the sensitive wavebands of 393 nm and 510 nm.Additionally,more results show that nice products can also be obtained when applying the UVAA algorithm to OLCI.So this algorithm can be applied to other ultraviolet ocean color remote sensors,and shows great application potential.