Atmospheric CO _{Key Indicator 2} Remote Sensing Instruments And Sensitivity Analysis

Space based measurement of CO₂concentration in lower atmosphere by reflected sunlightin near infrared band has become a hot research topic at present. Associated with the detectionprecision requirement of TANSAT and the characteristics of grating spectrometer andarray-based detector, the effects of key specifications of the hyper spectral CO₂detector such asspectral resolution, sampling ratio and sign-to-noise ratio （SNR） on CO₂detection are analyzedusing high resolution atmosphere radiation transfer model. Meanwhile, sensitivities of aerosols,surface albedo, water vapor and temperature to spectra and aerosol-induced XCO₂（columnaveraged atmospheric CO₂dry air mole fraction） errors have also been investigated.The results show that hyper spectral CO₂detector should provide high resolution at first toresolve CO₂absorption lines from continuous spectra of reflected sunlight. Sampling ratioshould exceed2pixels/FWHM to ensure the accuracy of CO₂spectrum. The instrument SNR todetect1%change in XCO₂is attainable.Light path modification caused by aerosol scattering is closely related to the type, modeand vertical distribution of aerosols. Aerosols, urban aerosols and maritime aerosols in particular,have significant influences on measured spectrum. The structure of measured spectrum can bechanged by martime aerosols with strong scattering ability. When typical surface reflectance is0.15, the radiance change caused by aerosols mainly consist of coarse mode particles is negative,while tendency of radiance change caused by aerosols mainly consist of accumulation modeparticles varies with aerosol type and vertical distribution. However, no matter what the aerosolvertical distributions are, the radiance changes caused by coarse mode aerosols are alwaysnegative. In addition, the extent of negative radiance change decreases along with the increasedaerosol height distribution.Under typical observation geometry conditions （SZA=40°,nadir mode）, aerosol-inducedradiance change is negative when the surface is bright, and vice versa. There is a range of surfacealbedo from0.1to0.15, where continental aerosols have a vanishing net effect. Neglectingaerosol scattering yields XCO₂retrieval errors that can be substantial. Trial ensembles yieldaerosol-induced XCO₂errors mostly below4ppm up to aerosol optical thickness0.3if takingaerosol optical thickness and aerosol mode into consideration. Aerosol-induced XCO₂errors canbe further reduced with aerosol extinction profiles, and its sensitivities to surface albedo andaerosol mode can also be decreased. The influences of water vapour and temperature can beminimized by simultaneously modifying.