Polarization Effects on Column CO 2 Retrievals from GOSAT Measurements Vijay Natraj 1, Hartmut Bösch 2, Robert J.D. Spurr 3, Yuk L. Yung 4 1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA 2 Department of Physics and Astronomy, University of Leicester, Leicester, UK 3 RT Solutions, Inc., Cambridge, MA, USA 1 Department of Planetary Sciences, California Institute of Technology, Pasadena, CA, USA Contact: Vijay Natraj, Phone: , L-2OS Model Fast polarization correction algorithm Assume that only two scattering events contribute to polarization 2OS model used in conjunction with scalar RT model LIDORT (L) I sca, I cor : intensity with polarization neglected, scalar-vector intensity correction I, Q, U: Stokes parameters P, S: Polarized radiances measured by GOSAT References [1] T. Yokota, et al., Proc. Twenty-fourth Int. Symp. Space Technol. Sci., , 2004 [2] D. Crisp, et al., Adv. Space Res., 34(4), , [3] V. Natraj and R.J.D. Spurr, J. Quant. Spectrosc. Radiat. Transfer, 107(2), , [4] V. Natraj, et al., J. Geophys. Res., 113, D11212, [5] S. Chandrasekhar, Radiative Transfer, [6] C. D. Rodgers, Inverse Methods for Atmospheric Sounding, EGU Introduction Greenhouse Gases Observation Satellite (GOSAT): launched in 2009 Quantify sources and sinks of CO 2 using precise column abundance measurements Reflected sunlight at the top of the atmosphere (TOA) Spectrometers sensitive to atmospheric polarization. Need to consider polarization in modeling of atmospheric radiative transfer (RT). O 2 A-band CO  m CO  m Figure 1: GOSAT Near Infrared Spectral Regions Conclusions L-2OS model gives errors much smaller than 1 ppm and typically less than 0.1 ppm Scalar model errors could be as large as 3 ppm Scalar model performs better for southern hemisphere Lower solar zenith angle Fortuitous cancellation of polarization errors GOSAT sensitivity tests give an idea of errors for OCO-2 target mode Scenarios: Northern Hemisphere 3 cross-track angles (0°, 13° and 25°) SZA: 60° VZA: 1°, 15°, 29° Relative Azimuth Angle: 60° Aerosol/Cirrus: AOD = 0.05, 0.15, 0.3; COD = 0.1; AOD = 0.15, COD = 0.1 Surface types: conifer, desert, mix Scenarios: Southern Hemisphere 3 cross-track angles (0°, 13° and 25°) SZA: 25° VZA: 1°, 15°, 29° Relative Azimuth Angle: 123° Aerosol/Cirrus: AOD = 0.05, 0.15, 0.3; COD = 0.1; AOD = 0.15, COD = 0.1 Surface types: conifer, desert, mix X CO2 Errors: Northern Hemisphere Figure 2: X CO2 Errors for (left) scalar model (right) L-2OS model with aerosol and cirrus both present. The left and right panels in each plot are for P and S polarizations respectively. Figure 3: X CO2 Errors for L-2OS model for (left) aerosol and (right) cirrus only scenarios. X CO2 Errors: Southern Hemisphere Figure 4: X CO2 Errors for (left) scalar model (right) L-2OS model with aerosol and cirrus both present. The left and right panels in each plot are for P and S polarizations respectively. Figure 5: X CO2 Errors for L-2OS model for (left) aerosol and (right) cirrus only scenarios.