Retrieval Of Atmospheric Aerosol Optical Properties From Dual-angle Dual-channel Remote Sensing Datas

Atmospheric aerosols are the research highlight of quantitative remote sensing and atmospheric correction,and has significant effects on Earth observation satellite data quality,and the content distribution has obvious spatial and temporal variation.The effects of aerosol on electromagnetic radiation transfer can be analyzed through parameters such as optical depth,size distribution and aerosol complex refractive index(ACRI).Despite the ground-based measurements can acquire high accuracy aerosol optical,physical even chemistry characteristics,single point measurement can not satisfy the actual demands in consideration of the aerosol spatial distribution.However,the Earth observation satellite can obtain widespread near real time data that including atmospheric aerosol distribution information.Compared with the traditional ground-based measurement,the aerosol remote sensing has great advantages.We carried detail research on aerosol optical depth(AOD),exponent of Junge power-law distribution and the imaginary part of ACRI in this thesis,using radiation transfer model simulated the effects of these parameters,and proposed a dual-channel,dual-angle iterative algorithm that can determining these parameters simultaneously above salty waters.And,the algorithm feasibilities are proved through numerical simulations and satellite retrieval experiments.The main research work and innovation are listed as follows:(1).In order to study the effects of aerosol optical parameters,we use the radiative transfer model 6S to simulate the atmospheric reflectance of VIIRS channels under different Junge power-law exponent and ACRI over ocean waters,based on control variate technique.Through the simulation,the effects of Junge power-law exponent are mainly in the visible and NIR spectrum of wavelength less than 1.24?m.the larger Junge exponent,the larger difference between the reflectance of red and near-infrared bands.In addition,the change of real part of ACRI with wavelength has little influence on reflectance that can be omitted,however the changes of imaginary part are relatively larger.(2).We use 6S model to simulate the dual-angle apparent reflectance of the two SeaWiFS NIR bands and the AATSR NIR and SWIR bands under the Junge power-law and lognormal distribution,then inverse the three aerosol parameters utilize the dual-angle iterative algorithm and compare the inverse values with the input values.The results show that when the aerosol satisfies the Junge power-law distribution,the dual-angle iterative algorithm can obtain high accuracy aerosol optical parameters.If the aerosol satisfies the lognormal distribution,our algorithm can still obtain high accuracy AOD with the Junge power-law assumption.(3).To further testify the feasibility of our dual-angle,dual-channel algorithm,we inverse the three aerosol parameters from the NIR-SWIR channels of Terra-Aqua dual MODIS,AATSR,SLSTR satellite data over salty waters such as Bohai,HuangHai,Taiwan Strait and Qinghai Lake and freshwaters like Taihu and Chaohu.As the lack of in-situ measured datas,we used the MODIS aerosol products as the reference values.Besides that,we compare the retrieval imaginary part of ACRI with that from POLDER data.The experiments show that our dual-angle,dual-channel algorithm can retrieve the aerosol information over coastal,oceanic seawater and inland salty waters from NIR-SWIR channels.However,only few freshwater pixels can be successfully retrieved and there are great difficulties in operation for freshwaters.For MODIS,we obtain the LIB data onboard Terra and Aqua of the same area to construct the dual-angle data.Then,the aerosols are retrieved over the pixels that have little variation in Terra-Aqua MODIS AOD product at 550nm.The retrieved AOD is acceptable compared with the two Terra-Aqua product values and their average.The dual-angle data constructed from Terra-Aqua also indicate that dual and multi satellite synergy can be used to monitor the atmospheric environment.(4).We calculate the water-leaving reflectance spectrum from MODIS and CHRIS data using the aerosol information obtained by previously proposed dual?channel iterative algorithm,and compare with the MODIS ocean color products to validate the spectrum.But we discover that there is negative water-leaving reflectance in NIR bands.In other words,MODIS products have overcorrection problems and the aerosol content is larger than practical situation.Furthermore,we inverse the three ocean color components from the water-leaving reflectance of sentinel-3A using bio-optical models.As the lack of measured values onboard,we compared the inverse values with the historical values measured by China maritime agencies.However,the retrieval Yellow Substance is greatly different with the law of historical data.(5).Influenced by the dual-angle,dual-channel theory,we use the structure function method to retrieve the AOD over Beijing area from Sentinel-3 A&B LIB datas,and introduce different angles and channels.The results show that dual-channel LIB datas can not improve the AOD accuracy,and the AOD retrieved through dual-angle is worse than single angle except the 865nm channel.We also calculate the 532nm depolarization ratio and the color ratio from the signal of ground-based micro-pulse lidar which equipped 532nm and 1064nm dual wavelength for the validation of the echo signal of satellite borne lidar.It is found that there is distinct difference between the ground-based and satellite-based lidar of atmosphere under 2km through comparison.