Research On Atmospheric Correction Of Bright Temperature Of Spaceborne Microwave Radiometer

The spaceborne microwave radiometer has all-weather and all-day characteristics.A series of satellites equipped with spaceborne microwave radiometer have been launched at home and abroad,and a number of quantitative remote sensing studies have also been carried out for spaceborne microwave radiometers.Due to the influence of the atmosphere,the accuracy of quantitatively retrieving the parameters of the Earth system is limited.According to the radiation transfer equation,the effect of the atmosphere on the brightness of the earth's surface is mainly reflected in the atmospheric transmittance and the atmospheric upward radiation brightness.It is the absorption and discharge of the atmosphere.And the atmospheric transmittance is mainly related to atmospheric factors such as atmospheric water vapor and cloud liquid water.Therefore,this paper will study the atmospheric temperature correction of the bright temperature received by the spaceborne microwave radiometer,establish a parametric inversion model of atmospheric factors and atmospheric influences,remove the atmospheric influences from the principle.Finally,an atmospheric correction parametric model of a spaceborne microwave radiometer that does not depend on auxiliary data is established.Based on MonoRTM(Monochromatic Radiative Transfer Model)microwave radiation transmission model,the atmospheric radiation transmission process of spaceborne microwave radiometer is simulated for the microwave frequency commonly(6.9GHz,10.7GHz,18.7GHz,23.8GHz,36.5GHz and 89GHz)used in spaceborne microwave radiometer under different atmospheric profiles and different surface environments,and establish a simulation database.Based on the simulation database,the parameterization model of atmospheric factors is established by parameterizing the liquid water and atmospheric water vapor content in the cloud.Then,the parametric model of atmospheric influence is established,and the parametric equation of atmospheric transmittance and atmospheric upward radiation brightness is obtained from the principle.Finally,through the principle of radiation transmission,combined with the parametric model of atmospheric factors and atmospheric effects,it is brought into the bright-temperature atmospheric correction model of the spaceborne microwave radiometer to establish a parametric model of atmospheric correction.Based on the simulation database,the correlation between the content of liquid water and atmospheric water vapor in the cloud and the value of the verification data in the database is analyzed by using the parametric equation.The R-square of the liquid water parameterization inversion in the cloud is 0.9877,the R-square of the atmospheric water vapor parameter inversion is 0.9439,which indicates that the parametric equation is applied to the simulation database with high precision,which also indicates that the developed algorithm can achieve higher precision under a series of changes in surface and atmosphere.Inversion of liquid water and atmospheric water vapor in the cloud also reveals that this algorithm can be used for the inversion of liquid water and atmospheric water vapor in the cloud of a spaceborne microwave radiometer.The atmospheric data correction is performed by selecting some data in the simulation database that are not involved in the calibration model.The root mean square error RMSE of the brightness temperature and the actual surface brightness temperature of each frequency is obtained.The results show that the parametric atmospheric correction model is at 6.9 GHz,10.7 GHz,18.7.The GHz and 36.5 GHz channels achieve high accuracy with a ground temperature rms error of less than 1K,and high accuracy at 23.8 GHz and 89.0 GHz channels,with RMSE of 1.57 K and 3.87 K,respectively.The parameterized atmospheric correction model established by the database is used to correct the 18.7 GHz brightness temperature data of AMSR-E_L2A,and the obtained calibration result is compared with the correction result based on sounding data.The Rsquare is 0.6732.Because the atmospheric correction model formula is more complicated,coupled with the error transmission and accumulation of liquid water and atmospheric water vapor parameter inversion in the cloud,the obtained R-square is within the effective error range,so the parameterization established in this paper does not depend on any auxiliary data.The atmospheric correction model has certain feasibility.