Algorithm development for atmospheric gas remote sensing by measuring the high resolution spectrum and polarization

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1.A few methods to use the polarization have been developed for correcting the scattering of light by cloud and aerosols in remote sensing atmospheric gases from space. Simulations of retrieval of gases have been performed assuming the observation of Earth-reflected solar radiation is made in the 1.6 μ band with a FTS (Fourier Transform Spectrometer) having a spectral resolution 0.2cm^<-1>. It has been shown that the retrieval error of CO_2 column amount is reduced by about 0.5 % when the polarization was used compared with non-use of polarization.2.Incomplete performance of IMC (Image Motion Compensation) mechanism generates a fluctuation of the position of IFOV (Instantaneous Field of View) of satellite borne FTS. It has been shown, by using satellite-observed image data, that this fluctuation of IFOV generates large retrieval error of CO_2 column amount. To correct the effect of IFOV fluctuation, a method has been developed by using the low frequency spectrum out side the band pass filter of FTS. It has been found that the error is greatly reduced by applying this method.3.The effect of Doppler shift of spectral lines due to the Earth revolution around the sun, spin motion of the Earth and satellite motion has been investigated.4.A program has been developed to estimate the extra-terrestrial solar spectrum from ground-based high spectral-resolution FTS.5.A long term monitor of CO_2 amount from ground-based high spectral-resolution FTS has been initiated. The preliminary test of accuracy showed a good coincidence with the tower observation and air borne observation, showing the accuracy of relative value of CO_2 better than 0.2 %.