Development And Simulation Of A Fast High Spectral Resolution Infrared Radiative Transfer Algorithm For Dust-Storm Atmosphere

Dust storm is a kind of severe environmental hazard of global arid and semi-arid areas. It needs large-scale observation on occurrence and development of dust storm. In this viewpoint, the satellite remote sensing of dust storms has large potential in both temporal scale and spatial scale. Monitoring dust storm using satellite loaded high spectral resolution sounder is an orientation of remote sensing of dust storm. We have a rewarding trial in this paper, the calculation of single scattering properties of the dust aerosol using the Mie theory, the calculation of transmittance and reflectance of dust aerosol using the DISORT model, the development of the fast dusty sky high spectral resolution infrared radiative transfer model and the dust information extraction from the AIRS L1B data are performed.In the Mie scattering calculation, the paper analyzes the scattering properties of different aerosols, especially the scattering properties of water, ice and dust-like aerosol. The scattering properties of dust-like aerosol in different effective radius are also analyzed. The results show that the Mie scattering theory can exactly describe the scattering properties of dust-like aerosol. The extinction coefficients, single scattering albedo and asymmetry factors are functions of wavelength and effective radius. The extinction coefficients and asymmetry factors of dust-like aerosol increase with the increasing of effective radii. The single scattering albedo of dust-like aerosol increase with the increasing of effective radii when effective radius is less than 2 microns, but when the effective radius is more than 2 microns, the single scattering albedo of dust-like aerosol have no regularity.Based on Mie scattering calculations, we exploit the DISORT model to calculate the infrared transmittance and reflectance of the dust-like aerosol in 201 wavenumbers, 15 optical thicknesses, 19 effective radii and 50 zenith angles. The results show that the transmittance and reflectance can be expressed as a third order polynomial function of zenith angle cosine and effective radius for a certain wavenumber and optical thickness. In this assumption, using the calculated database, a couple groups of fitted coefficients for both transmittance and reflectance can be derived, with which we can rapidly interpolate the transmittance and reflectance for specified optical thickness, effective radius, zenith angle and wavenumber. And this is the key point for development of the fast infrared radiative transfer model for dust storms.The fast clear sky infrared radiative transfer model coupled with the transmittance and reflectance of dust can generate the model of the dusty condition. The sensitivity analyses show that the satellite detected brightness temperature of the dusty atmosphere is function of the dust optical thickness, effective radius, altitude and the surface temperature. 800～1000 cm?1 is the sensitive band for dust storms. The satellite detected brightness temperature decreases as the dust optical thickness, effective radius and altitude increase and as the surface temperature decreases. The optical thicknesses from 1 to 9 decrease the brightness temperature 10K for the most. The higher the altitude is, the more of brightness temperature's decreases in the 1000 cm?1 than 800 cm?1 . The When the effective radius increases, the brightness temperature of 800～1000 cm?1 decrease, but the extent is less than that of the optical thicknesses.To validate the dust model results, AIRS L1B data containing dust information are chosen. The analyses of the satellite data show that 830～1000 cm?1 is the sensitive band for dust storms and the light-dust brightness- temperature curves have steeper slope than the heavy one. These results correspond to our simulations, indicating the reliability of the fast dusty sky radiative transfer algorithm. In the infrared band, the clear sky, the dust storm and the cloud have different characteristics. The clear-sky atmosphere has the highest brightness temperature, and the cloudy atmosphere has the lowest brightness temperature. In the 1217～1613 cm?1 band, the clear-sky atmosphere brightness-temperature curve has the steepest slope, and the cloudy atmosphere brightness-temperature curve has the least steep slope; That of the dusty atmosphere locates in the middle. In the 800～1000 cm?1 , the cloudy atmosphere brightness temperature curve has the positive slope and the clear atmosphere curve has no slope. So, the high spectral resolution measurements provide a powerful way to choose the clear pixel.This research work could be a good base for the retrieval of dust physical properties using the high spectral resolution data and the practical applications of the dust monitoring..