AMT Atmospheric Measurement Techniques AMT Atmos. Meas. Tech. 1867-8548 Copernicus Publications Göttingen, Germany 10.5194/amt-8-3601-2015 Sensitivity analysis of polarimetric O<sub>2</sub> A-band spectra for potential cloud retrievals using OCO-2/GOSAT measurements Sanghavi S. 1 2 Lebsock M. 1 Stephens G. 1 2 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA Department of Atmospheric Science, Colorado State University, Fort Collins, USA 07 09 2015 8 9 3601 3616 Copyright: © 2015 S. Sanghavi et al. 2015 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://amt.copernicus.org/articles/8/3601/2015/amt-8-3601-2015.html The full text article is available as a PDF file from https://amt.copernicus.org/articles/8/3601/2015/amt-8-3601-2015.pdf

Clouds play a crucial role in Earth's radiative budget, yet their climate feedbacks are poorly understood. The advent of space-borne high resolution spectrometers probing the O<sub>2</sub> A band, like GOSAT and OCO-2, could make it possible to simultaneously retrieve vertically resolved cloud parameters that play a vital role in Earth's radiative budget, thereby allowing a reduction of the corresponding uncertainty due to clouds. Such retrievals would also facilitate air mass bias reduction in corresponding measurements of CO<sub>2</sub> columns. <br><br> In this work, the hyperspectral, polarimetric response of the O<sub>2</sub> A band to mainly three important cloud parameters, viz., optical thickness, top height and droplet size has been studied, revealing a different sensitivity to each for the varying atmospheric absorption strength within the A band. Cloud optical thickness finds greatest sensitivity in intensity measurements, the sensitivity of other Stokes parameters being limited to low cloud optical thicknesses. Cloud height had a negligible effect on intensity measurements at non-absorbing wavelengths but finds maximum sensitivity at an intermediate absorption strength, which increases with cloud height. The same is found to hold for cloud geometric thickness. The geometry-dependent sensitivity to droplet size is maximum at non-absorbing wavelengths and diminishes with increasing absorption strength. It has been shown that significantly more information on droplet size can be drawn from multi-angle measurements. We find that, in the absence of sunglint, the backscatter hemisphere (scattering angle larger than 90°) is richer in information on droplet size, especially in the glory and rainbow regions. It has been shown that <i>I</i> and <i>Q</i> generally have differing sensitivities to all cloud parameters. Thus, accurate measurements of two orthogonal components <i>I</i><sub>P</sub> and<i>I</i><sub>S</sub> (as in GOSAT) are expected to contain more information than measurements of only <i>I</i>, <i>I</i><sub>h</sub> or <i>I</i><sub>v</sub> (as in the case of OCO-2).

 References Abreu, L. and Anderson, G.: The MODTRAN 2/3 report and LOWTRAN 7 model, Contract, 19628, 0132, 1996. Ackerman, S., Holz, R., Frey, R., Eloranta, E., Maddux, B., and McGill, M.: Cloud detection with MODIS. Part II: validation, J. Atmos. Ocean. Tech., 25, 1073–1086, 2008. Anderson, G. P., Clough, S., Kneizys, F., Chetwynd, J., and Shettle, E. P.: AFGL atmospheric constituent profiles (0.120 km), Tech. rep., DTIC Document, 1986. Baker, M.: Cloud microphysics and climate, Science, 276, 1072–1078, 1997. Bodhaine, B. A., Wood, N. B., Dutton, E. G., and Slusser, J. R.: On Rayleigh optical depth calculations., J. Atmos. Ocean. Tech., 16, 1854–1861, 1999. Boesche, E., Stammes, P., and Bennartz, R.: Aerosol influence on polarization and intensity in near-infrared O<sub>2</sub> and CO<sub>2</sub> absorption bands observed from space, J. Quant. Spectrosc. Ra., 110, 223–239, 2009. Bohren, C. F. and Huffman, D. R.: Absorption and scattering of light by small particles, Wiley, New York, 1983. Cairns, B., Russell, E. E., and Travis, L. D.: Research scanning polarimeter: calibration and ground-based measurements, in: SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, International Society for Optics and Photonics, 186–196, 1999. Chahine, M. T.: The hydrological cycle and its influence on climate, Nature, 359, 373–380, 1992. Crisp, D., Atlas, R., Breon, F.-M., Brown, L., Burrows, J., Ciais, P., Connor, B., Doney, S., Fung, I., Jacob, D., Miller, C., O'Brien, D., Pawson, S., Randerson, J., Rayner, P., Salawitch, R., Sander, S., Sen, B., Stephens, G., Tans, P., Toon, G., Wennberg, P., Wofsy, S., Yung, Y., Kuang, Z., Chudasama, B., Sprague, G., Weiss, B., Pollock, R., Kenyon, D., and Schroll, S.: The orbiting carbon observatory (OCO) mission, Adv. Space Res., 34, 700–709, 2004. Deirmendjian, D.: Electromagnetic Radiation Scattering by Spherical Polydispersed Particles, Elsevier, New York, 1969. Deschamps, P.-Y., Bréon, F.-M., Leroy, M., Podaire, A., Bricaud, A., Buriez, J.-C., and Seze, G.: The POLDER mission: Instrument characteristics and scientific objectives, IEEE T. Geosci. Remote, 32, 598–615, 1994. Dessler, A., Palm, S., and Spinhirne, J.: Tropical cloud-top height distributions revealed by the Ice, Cloud, and Land Elevation Satellite (ICESat)/Geoscience Laser Altimeter System (GLAS), J. Geophys. Res.-Atmos., 111, D12215, <a href="http://dx.doi.org/10.1029/2005JD006705">https://doi.org/10.1029/2005JD006705</a>, 2006. Diner, D. J., Beckert, J. C., Reilly, T. H., Bruegge, C. J., Conel, J. E., Kahn, R. A., Martonchik, J. V., Ackerman, T. P., Davies, R., Gerstl, S. A., Gordon, H., Muller, J.-P., Myneni, R., Sellers, P., Pinty, B., and Verstraete, M.: Multi-angle Imaging SpectroRadiometer (MISR) instrument description and experiment overview, IEEE T. Geosci. Remote, 36, 1072–1087, 1998. Diner, D. J., Mischna, M., Chipman, R. A., Davis, A., Cairns, B., Davies, R., Kahn, R. A., Muller, J.-P., and Torres, O.: WindCam and MSPI: two cloud and aerosol instrument concepts derived from Terra/MISR heritage, in: Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, vol. 7081, p. 25, 2008. Fischer, J. and Grassl, H.: Detection of cloud-top height from backscattered radiances within the oxygen A band. Part 1: Theoretical study, J. Appl. Meteorol., 30, 1245–1259, 1991. Fischer, J., Cordes, W., Schmitz-Peiffer, A., Renger, W., and Mörl, P.: Detection of cloud-top height from backscattered radiances within the oxygen A band. Part 2: Measurements, J. Appl. Meteorol., 30, 1260–1267, 1991. Fowler, L. D., Randall, D. A., and Rutledge, S. A.: Liquid and ice cloud microphysics in the CSU general circulation model. Part 1: Model description and simulated microphysical processes, J. Climate, 9, 489–529, 1996. Frankenberg, C., Hasekamp, O., O'Dell, C., Sanghavi, S., Butz, A., and Worden, J.: Aerosol information content analysis of multi-angle high spectral resolution measurements and its benefit for high accuracy greenhouse gas retrievals, Atmos. Meas. Tech., 5, 1809–1821, <a href="http://dx.doi.org/10.5194/amt-5-1809-2012">https://doi.org/10.5194/amt-5-1809-2012</a>, 2012. Gómez-Chova, L., Camps-Valls, G., Amorós-López, J., Guanter, L., Alonso, L., Calpe, J., and Moreno, J.: New cloud detection algorithm for multispectral and hyperspectral images: Application to ENVISAT/MERIS and PROBA/CHRIS sensors, in: IEEE International Geoscience and Remote Sensing Symposium, IGARSS, 2757–2760, 2006. Hamazaki, T., Kaneko, Y., Kuze, A., and Kondo, K.: Fourier transform spectrometer for greenhouse gases observing satellite (GOSAT), in: Fourth International Asia-Pacific Environmental Remote Sensing Symposium 2004: Remote Sensing of the Atmosphere, Ocean, Environment, and Space, International Society for Optics and Photonics, 73–80, 2005. Hasekamp, O. P. and Butz, A.: Efficient calculation of intensity and polarization spectra in vertically inhomogeneous scattering and absorbing atmospheres, J. Geophys. Res.-Atmos., 113, 20309, <a href="http://dx.doi.org/10.1029/2008JD010379">https://doi.org/10.1029/2008JD010379</a>, 2008. Heidinger, A. K. and Stephens, G. L.: Molecular line absorption in a scattering atmosphere. Part II: Application to remote sensing in the O<sub>2</sub> A band, J. Atmos. Sci., 57, 1615–1634, 2000. Hovenier, J.: Multiple scattering of polarized light in planetary atmospheres, Astron. Astrophys., 13, 7, 1971. Key, J. and Barry, R.: Cloud cover analysis with Arctic AVHRR data: 1. Cloud detection, J. Geophys. Res.-Atmos., 94, 18521–18535, 1989. Koelemeijer, R. B., Stammes, P., Hovenier, J., and de Haan, J.: A fast method for retrieval of cloud parameters using oxygen A band measurements from the Global Ozone Monitoring Experiment, J. Geophys. Res.-Atmos., 106, 3475–3490, 2001. Kokhanovsky, A. A.: Cloud optics, vol. 34, Springer, 2006. Kuze, A. and Chance, K. V.: Analysis of cloud top height and cloud coverage from satellites using the O<sub>2</sub> A and B bands, J. Geophys. Res.-Atmos., 99, 14481–14491, 1994. Kuze, A., Suto, H., Nakajima, M., and Hamazaki, T.: Thermal and near infrared sensor for carbon observation Fourier-transform spectrometer on the Greenhouse Gases Observing Satellite for greenhouse gases monitoring, Appl. Optics, 48, 6716–6733, 2009. Lohmann, U. and Feichter, J.: Impact of sulfate aerosols on albedo and lifetime of clouds: A sensitivity study with the ECHAM4 GCM, J. Geophys. Res.-Atmos., 102, 13685–13700, 1997. Lohmann, U., Stier, P., Hoose, C., Ferrachat, S., Kloster, S., Roeckner, E., and Zhang, J.: Cloud microphysics and aerosol indirect effects in the global climate model ECHAM5-HAM, Atmos. Chem. Phys., 7, 3425–3446, <a href="http://dx.doi.org/10.5194/acp-7-3425-2007">https://doi.org/10.5194/acp-7-3425-2007</a>, 2007. Manolis, I., Grabarnik, S., Caron, J., Bézy, J.-L., Loiselet, M., Betto, M., Barré, H., Mason, G., and Meynart, R.: The MetOp second generation 3MI instrument, in: SPIE Remote Sensing, 88890J–88890J, International Society for Optics and Photonics, 2013. Mayer, B., Schröder, M., Preusker, R., and Schüller, L.: Remote sensing of water cloud droplet size distributions using the backscatter glory: a case study, Atmos. Chem. Phys., 4, 1255–1263, <a href="http://dx.doi.org/10.5194/acp-4-1255-2004">https://doi.org/10.5194/acp-4-1255-2004</a>, 2004. Nakajima, T. and King, M. D.: Determination of the optical thickness and effective particle radius of clouds from reflected solar radiation measurements. Part I: Theory, J. Atmos. Sci., 47, 1878–1893, 1990. Nakajima, T., King, M. D., Spinhirne, J. D., and Radke, L. F.: Determination of the Optical Thickness and Effective Particle Radius of Clouds from Reflected Solar Radiation Measurements. Part II: Marine Stratocumulus Observations, J. Atmos. Sci., 48, 728–751, 1991. Nakajima, T. Y. and Nakajma, T.: Wide-area determination of cloud microphysical properties from NOAA AVHRR measurements for FIRE and ASTEX regions, J. Atmos. Sci., 52, 4043–4059, 1995. Nakajima, T. Y., Suzuki, K., and Stephens, G. L.: Droplet growth in warm water clouds observed by the A-Train. Part I: Sensitivity analysis of the MODIS-derived cloud droplet sizes, J. Atmos. Sci., 67, 1884–1896, 2010. O'Brien, D. and Mitchell, R.: Error estimates for retrieval of cloud-top pressure using absorption in the A band of oxygen, J. Appl. Meteorol., 31, 1179–1192, 1992. O'Brien, D. M., Polonsky, I., O'Dell, C., Kuze, A., Kikuchi, N., Yoshida, Y., and Natraj, V.: Testing the Polarization Model for TANSO-FTS on GOSAT Against Clear-Sky Observations of Sun Glint Over the Ocean, IEEE T. Geosci. Remote, 51, 5199–5209, 2013. Peng, Y. and Lohmann, U.: Sensitivity study of the spectral dispersion of the cloud droplet size distribution on the indirect aerosol effect, Geophys. Res. Lett., 30, 1507, <a href="http://dx.doi.org/10.1029/2003GL017192">https://doi.org/10.1029/2003GL017192</a>, 2003. Peralta, R. J., Nardell, C., Cairns, B., Russell, E. E., Travis, L. D., Mishchenko, M. I., Fafaul, B. A., and Hooker, R. J.: Aerosol polarimetry sensor for the Glory Mission, in: International Symposium on Multispectral Image Processing and Pattern Recognition, 67865L–67865L, International Society for Optics and Photonics, 2007. Pfeilsticker, K., Erle, F., Funk, O., Veitel, H., and Platt, U.: First geometrical pathlengths probability density function derivation of the skylight from spectroscopically highly resolving oxygen A-band observations: 1. Measurement technique, atmospheric observations and model calculations, J. Geophys. Res.-Atmos., 103, 11483–11504, 1998. Platnick, S. and Valero, F. P.: A validation of a satellite cloud retrieval during ASTEX, J. Atmos. Sci., 52, 2985–3001, 1995. Pollock, R., Haring, R. E., Holden, J. R., Johnson, D. L., Kapitanoff, A., Mohlman, D., Phillips, C., Randall, D., Rechsteiner, D., Rivera, J., Rodriguez, J. I., Schwochert, M. A., and Sutin, B. M.: The Orbiting Carbon Observatory Instrument: performance of the OCO instrument and plans for the OCO-2 instrument, in: Remote Sensing, 78260W–78260W, International Society for Optics and Photonics, 2010. Rodgers, C. D.: Inverse methods for atmospheric sounding: theory and practice, vol. 2, World scientific Singapore, 2000. Rothman, L. S., Gordon, I. E., Barbe, A., Benner, D. C., Bernath, P. F., Birk, M., Boudon, V., Brown, L. R., Campargue, A., Champion, J.-P., Chance, K., Coudert, L., Dana, V., Devi, V., Fally, S., Flaud, J.-M., Gamache, R., Goldman, A., Jaquemart, D., Kleiner, I., Lacome, N., Lafferty, W., Mandin, J.-Y., Massie, S., Mikhailenko, S., Miller, C., Moazzen-Ahmadi, N., Naumenko, O., Nikitin, A., Orphal, J., Perevalov, V., Perrin, A., Predoi-Cross, A., Rinsland, C., Rotger, M., Simeckova, M., Smith, M., Sung, K., and Tashkun, S.: The HITRAN 2008 molecular spectroscopic database, J. Quant. Spectrosc. Ra., 110, 533–572, 2009. Rozanov, V. V. and Kokhanovsky, A. A.: Semianalytical cloud retrieval algorithm as applied to the cloud top altitude and the cloud geometrical thickness determination from top-of-atmosphere reflectance measurements in the oxygen A band, J. Geophys. Res.-Atmos., 109, D05202, <a href="http://dx.doi.org/10.1029/2003JD004104">https://doi.org/10.1029/2003JD004104</a>, 2004. Rozanov, V. V., Kokhanovsky, A. A., and Burrows, J. P.: The determination of cloud altitudes using GOME reflectance spectra: multilayered cloud systems, IEEE T. Geosci. Remote, 42, 1009–1017, 2004. Sanghavi, S., Martonchik, J. V., Landgraf, J., and Platt, U.: Retrieval of the optical depth and vertical distribution of particulate scatterers in the atmosphere using O<sub>2</sub> A- and B-band SCIAMACHY observations over Kanpur: a case study, Atmos. Meas. Tech., 5, 1099–1119, <a href="http://dx.doi.org/10.5194/amt-5-1099-2012">https://doi.org/10.5194/amt-5-1099-2012</a>, 2012. Sanghavi, S., Davis, A. B., and Eldering, A.: vSmartMOM: A vector matrix operator method-based radiative transfer model linearized with respect to aerosol properties, J. Quant. Spectrosc. Ra., 133, 412–433, 2014. Sanghavi, S. V., Martonchik, J. V., Davis, A. B., and Diner, D. J.: Linearization of a scalar matrix operator method radiative transfer model with respect to aerosol and surface properties, J. Quant. Spectrosc. Ra., 116, 1–16, 2013. Sassen, K., Wang, Z., and Liu, D.: Global distribution of cirrus clouds from CloudSat/Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) measurements, J. Geophys. Res.-Atmos., 113, D00A12, 2008. Schutgens, N., Tilstra, L., Stammes, P., and Bréon, F.-M.: On the relationship between Stokes parameters Q and U of atmospheric ultraviolet/visible/near-infrared radiation, J. Geophys. Res.-Atmos., 109, D09205, <a href="http://dx.doi.org/10.1029/2003JD004081">https://doi.org/10.1029/2003JD004081</a>, 2004. Slingo, A.: Sensitivity of the Earth's radiation budget to changes in low clouds, Nature, 343, 49–51, 1990. Slingo, A. and Slingo, J.: The response of a general circulation model to cloud longwave radiative forcing. I: Introduction and initial experiments, Q. J. Roy. Meteor. Soc., 114, 1027–1062, 1988. Stephens, G.: Radiation profiles in extended water clouds. II: Parameterization schemes, J. Atmos. Sci., 35, 2123–2132, 1978. Stephens, G. L.: Cloud feedbacks in the climate system: A critical review, J. Climate, 18, 237–273, 2005. Stephens, G. L. and Platt, C.: Aircraft observations of the radiative and microphysical properties of stratocumulus and cumulus cloud fields, J. Climate and applied meteorology, 26, 1243–1269, 1987. Stephens, G. L., Vane, D. G., Boain, R. J., Mace, G. G., Sassen, K., Wang, Z., Illingworth, A. J., O'Connor, E. J., Rossow, W. B., Durden, S. L., Miller, S., RT, A., Benedetti, A., and Mirescu, C.: The CloudSat mission and the A-Train: A new dimension of space-based observations of clouds and precipitation, B. Am. Meteorol. Soc., 83, 1771–1790, 2002. Stephens, G. L., Vane, D. G., Tanelli, S., Im, E., Durden, S., Rokey, M., Reinke, D., Partain, P., Mace, G. G., Austin, R., Benedetti, A., and Mitrescu, C.: CloudSat mission: Performance and early science after the first year of operation, J. Geophys. Res.-Atmos., 113, D00A18, <a href="http://dx.doi.org/10.1029/2008JD009982">https://doi.org/10.1029/2008JD009982</a>, 2008. Tran, H. and Hartmann, J.-M.: An improved O<sub>2</sub> A band absorption model and its consequences for retrievals of photon paths and surface pressures, J. Geophys. Res.-Atmos., 113, 18104, <a href="http://dx.doi.org/10.1029/2008JD010011">https://doi.org/10.1029/2008JD010011</a>, 2008. van de Hulst, H. C.: Light scattering by small particles, Courier Dover Publications, New York, 1957. Van Diedenhoven, B., Hasekamp, O., and Landgraf, J.: Retrieval of cloud parameters from satellite-based reflectance measurements in the ultraviolet and the oxygen A-band, J. Geophys. Res.-Atmos., 112, 15208, <a href="http://dx.doi.org/10.1029/2006JD008155">https://doi.org/10.1029/2006JD008155</a>, 2007. Wiscombe, W. J.: Improved Mie scattering algorithms, Appl. Optics, 19, 1505–1509, 1980.