Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 8 5 2008 10.5194/acpd-8-17549-2008 http://www.atmos-chem-phys-discuss.net/8/17549/2008/ http://www.atmos-chem-phys-discuss.net/8/17549/2008/acpd-8-17549-2008.html http://www.atmos-chem-phys-discuss.net/8/17549/2008/acpd-8-17549-2008.pdf 17549 17580 2008-09-26 Physical interpretation of the spectral radiative signature in the transition zone between cloud-free and cloudy regions J. C. Chiu christine.chiu@nasa.gov A. Marshak Y. Knyazikhin P. Pilewskie W. J. Wiscombe University of Maryland Baltimore County, Baltimore, MD, USA NASA/Goddard Space Flight Center, Greenbelt, MD, USA Boston University, Boston, MA, USA University of Colorado at Boulder, Boulder, CO, USA Brookhaven National Laboratory, New York, NY, USA One-second-resolution zenith radiance measurements from the Atmospheric Radiation Measurement program's new shortwave spectrometer (SWS) provide a unique opportunity to analyze the transition zone between cloudy and cloud-free air, which has considerable bearing on the aerosol indirect effect. In the transition zone, we find a remarkable linear relationship between the sum and difference of radiances at 870 and 1640 nm wavelengths. The intercept of the relationship is determined primarily by aerosol properties, and the slope by cloud properties. We then show that this linearity can be predicted from simple theoretical considerations and furthermore that it supports the hypothesis of inhomogeneous mixing, whereby optical depth increases as a cloud is approached but the effective drop size remains unchanged. In addition, the width of transition zones from SWS data is in the range of 50–150 m, which differs from the width in satellite observations (a few kilometers) and in airborne lidar data (1–2 km). Ackerman, S. A., Strabala, K. I., Menzel, W. P., Frey, R. A., Moeller, C. C., and Gumley, L. E.: Discriminating clear sky from clouds with MODIS, J. Geophys. Res., 103, 32 141–32 158, 1998. Allan, J. D., Baumgardner, D., Raga, G. B., Mayol-Bracero, O. L., Morales-García, F., Garc\'ia-Garc\'ia, F., Montero-Mart\'inez, G., Borrmann, S., Schneider, J., Mertes, S., Walter, S., Gysel, M., Dusek, U., Frank, G. P., and Krämer, M.: Clouds and aerosols in Puerto Rico – a new evaluation, Atmos. Chem. Phys., 8, 1293–1309, 2008. Baker, M. B., Corbin, R. G., and Latham, J.: The influence of entrainment on the evolution of cloud droplet spectra: I. A model of inhomogeneous mixing. Q. J. Roy. Meteor. Soc., 106, 581–598, 1980. Berendes, T. A., Berendes, D. A., Welch, R. M., Dutton, E. G., Uttal, T., and Clothiaux, E. E.: Cloud cover comparisons of the MODIS daytime cloud mask with surface instruments at the North Slope of Alaska ARM site, IEEE T. Geosci. Remote, 42, 2584–2593, 2004. Blyth, A. M., Lasher-Trapp, S. G., and Cooper, W. A.: A study of thermals in cumulus clouds, Q. J. Roy. Meteor. Soc., 131, 1171–1190, 2005. Box, M. A., Gerstl, S. A. W., and Simmer, C.: Application of the adjoint formulation to the calculation of atmospheric radiative effects, Beitr. Phys. Atmos., 61, 303–311, 1988. Brenguier, J.-L., Bourrianne, T., Coelho, A. D., Isbert, J., Peytavi, R., Trevarin, D., and Weschler, P.: Improvements of droplet size distribution measurements with the Fast-FSSP (Forward Scattering Spectrometer Probe), J. Atmos. Ocean. Tech., 15, 1077–1090, 1998. Brennan, J. I., Kaufman, Y. J., Koren, I., and Li, R. R.: Aerosol-cloud interaction – Misclassification of MODIS clouds in heavy aerosol, IEEE T. Geosci. Remote, 43, 911–915, 2005. Charlson, R. J., Ackerman, A. S., Bender, F. A.-M., Anderson, T. L., and Liu, Z.: On the climate forcing consequences of the albedo continuum between cloudy and clear air, Tellus B, 59, 715–727, 2007. Chiu, J. C., Marshak, A., Knyazikhin, Y., Wiscombe, W. J., Barker, H. W., Barnard, J. C., and Luo, Y.: Remote sensing of cloud properties using ground-based measurements of zenith radiance, J. Geophys. Res., 111, D16201, doi:10.1029/2005JD006843, 2006. Clarke, A. D., Howell, S., Quinn, P. K., Bates, T. S., Ogren, J. A., Andrews, E., Jefferson, A., Massling, A., Mayol-Bracero, O., Maring, H., Savoie, D., and Cass, G.: INDOEX aerosol: A comparison and summary of chemical, microphysical, and optical properties observed from land, ship, and aircraft, J. Geophys. Res., 107(D19), 8033, doi:10.1029/2001JD00572, 2002. Clothiaux, E. E., Ackerman, T. P., Mace, G. G., Moran, K. P., Marchand, R. T., Miller, M. A., and Martner, B. E.: Ojbective determination of cloud heights and radar reflectivities using a combination of active remote sensors at the ARM CART sites, J. Appl. Meteorol., 39, 645–665, 2000. Coakley, J. A., Friedman, M. A., and Tahnk, W. R.: Retrieval of cloud properties for partly cloudy imager pixels, J. Atmos. Ocean. Tech., 22, 3–17, 2005 Davis, A., Marshak, A., Gerber, H., and Wiscombe, W. J.: Horizontal structure of marine boundary layer clouds from centimeter to kilometer scales, J. Geophys. Res., 104, 6123–6144, 1999. Diner, D. J., Ackerman, T. P., Anderson, T. L., Bosenberg, J., Braverman, A. J., Charlson, R. J., Collins, W. D., Davies, R., Holben, B. N., Hostetler, C. A., Kahn, R. A., Martonchik, J. V., Menzies, R. T., Miller, M. A., Ogren, J. A., Penner, J. E., Rasch, P. J., Schwartz, S. E., Seinfeld, J. H., Stephens, G. L., Torres, O., Travis, L. D., Wielicki, B. A., and Yu, B.: PARAGON – an integrated approach for characterizing aerosol climate impacts and environmental interactions, B. Am. Meteorol. Soc., 85, 1491–1501, 2004. Freud, E., Rosenfeld, D., Andreae, M. O., Costa, A. A., and Artaxo, P.: Robust relations between CCN and the vertical evolution of cloud drop size distribution in deep convective clouds, Atmos. Chem. Phys., 8, 1661–1675, 2008. Gomez-Chova, L., Camps-Valls, G., Calpe-Maravilla, J., Guanter, L., and Moreno, J.: Cloud-screening algorithm for ENVISAT/MERIS multispectral images, IEEE T. Geosci. Remote, 45, 4105–4118, 2007. Holben, B. N., Eck, T. F., Slutsker, I., Tanré, D., Buis, J. P., Setzer, A., Vermote, E., Reagan, J. A., Kaufman, Y. J., Nakajima, T., Lavenu, F., Jankowiak, I., and Smirnov, A.: AERONET – a federated instrument network and data archive for aerosol characterization, Remote Sens. Environ. 66, 1–16, 1998. Joseph, J. H. and Cahalan, R. F.: Nearest neighbor spacing of fair weather cumulus, J. Appl. Meteor., 29, 793–805, 1990. Knyazikhin, Y., Miessen, G., Panfyorov, O., and Gravenhorst, G.: Small-scale study of three-dimensional distribution of photosynthetically active radiation in a forest, Agr. Forest Meteorol., 88, 215–239, 1997. Koren, I., Oreopoulos, L., Feingold, G., Remer, L. A., and Altaratz, O.: How small is a small cloud?, Atmos. Chem. Phys., 8, 3855–3864, 2008. Koren, I., Remer, L. A., Kaufman, Y. J., Rudich, Y., and Martins, J. V.: On the twilight zone between clouds and aerosols, Geophys. Res. Lett., 34, L08805, doi:10.1029/2007GL029253, 2007. Kotchenruther, R. A., Hobbs, P. V., and Hegg, D. A.: Humidification factors for atmospheric aerosols off the mid-Atlantic coast of the United States, J. Geophys. Res., 104(D2), 2239–2251, 1999. Lane, D. E., Goris, K., and Somerville, R. C. J.: Radiative transfer through broken clouds: observations and model validation, J. Climate, 15, 2921–2933, 2002. Loeb, N. G. and Manalo-Smith, N.: Top-of-atmosphere direct radiative effect of aerosols over global oceans from merged CERES and MODIS observations, J. Climate, 18, 3506–3526, 2005. Long, C. N. and Ackerman, T. P.: Identification of clear skies from broadband pyranometer measurements and calculation of downwelling shortwave cloud effects, J. Geophys. Res., 105(D12), 15 609–15 626, 2000. Long, C. N., Slater, D. W., and Tooman, T.: Total Sky Imager Model 880 status and testing results, ARM Technical Report ARM TR-006, U.S. Department of Energy, Washington, D.C., 2001. Long, C. N., Ackerman, T. P., Gaustad, K. L., and Cole, J. N. S.: Estimation of fractional sky cover from broadband shortwave radiometer measurements, J. Geophys. Res., 111, D11204, doi:10.1029/2005JD006475, 2006a. Long, C. N., Sabburg, J. M., Calbo, J., and Pages, D.: Retrieving cloud characteristics from ground-based daytime color all-sky images, J. Atmos. Ocean. Tech., 23, 633–652, 2006b. Marshak, A., Knyazikhin, Y., Evans, K. D., and Wiscombe, W. J.: The "RED versus NIR" plane to retrieve broken-cloud optical depth from ground-based measurements, Cloud-vegetation interaction: Use of normalized difference cloud index for estimation of cloud optical thickness, J. Atmos. Sci., 61, 1911–1925, 2004. Marshak, A., Wen, G., Coakley, J., Remer, L., Loeb, N. G., and Cahalan, R. F.: A simple model for the cloud adjacency effect and the apparent bluing of aerosols near clouds, J. Geophys. Res., 113, D14S17, doi:10.1029/2007JD009196, 2008. Martins, J. V., Tanré, D., Remer, L. A., Kaufman, Y. J., Mattoo, S., and Levy, R.: MODIS cloud screening for remote sensing of aerosol over oceans using spatial variability, Geophys. Res. Lett., 29(12), 8009, doi:10.1029/2001GL013252, 2002. Miller, M. A., Johnson, K. L., Troyan, D. T., Clothiaux, E. E., Mlawer, E. J., and Mace, G. G.: ARM value-added cloud products: description and status, Proceedings of the 13th ARM Science Team Meeting, 31 March to 4 April 2003, Broomfield, Colorado, available at: http://www.arm.gov/publications/proceedings/conf13/extended_abs/miller-ma.pdf, 2003. Paluch, I. R. and Baumgardner, D. G.: Entrainment and find-scale mixing in a continental convective cloud, J. Atmos. Sci., 46, 261–278, 1989. Pilewskie, P., Pommier, J., Bergstrom, R., Gore, W., Howard, S., Rabbette, M., Schmid, B., Hobbs, P. V., and Tsay, S. C.: Solar spectral radiative forcing during the Southern African Regional Science Initiative, J. Geophys. Res., 108(D13), 8486, doi:10.1029/2002JD002411, 2003. Schaaf, C. B., Gao, F., Strahler, A. H., Lucht, W., Li, X .W., Tsang, T., Strugnell, N, C., Zhang, X. Y., Jin, Y. F., Muller, J. P., Lewis, P., Barnsley, M., Hobson, P., Disney, M., Roberts, G., Dunderdale, M., Doll, C., d'Entremont, R. P., Hu, B. X., Liang, S. L., Privette, J. L., and Roy, D.: First operational BRDF, albedo nadir reflectance products from MODIS, Remote Sens. Environ., 83, 135–148, 2002. Stephens, G. L., Vane, D. G., Boain, R. J., Mace, G. G., Sassen, K., Wang, Z. E., Illingworth, A. J., O'Connor, E. J., Rossow, W. B., Durden, S. L., Miller, S. D., Austin, R. T., Benedetti, A., and Mitrescu, 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. Stith, J. L.: Observations of cloud-top entrainment in cumuli, J. Atmos. Sci., 49, 1334–1347, 1992. Taylor, T. E., L'Ecuyer, T. S., Slusser, J. R., Stephens, G. L., and Goering, C. D.: An operational retrieval algorithm for determining aerosol optical properties in the ultraviolet, J. Geophys. Res., 113, D03201, doi:10.1029/2007JD008661, 2008. Thomas, G. E. and Stamnes, K.: Radiative transfer in the atmosphere and ocean, Cambridge University Press, 517 pp., 2002. Turner, D. D., Clough, S. A., Lijegren, J. C., Clothiaux, E. E., Cady-Pereira, K. E., and Gaustad, K. L.: Retrieving liquid water path and precipitable water vapor from the atmospheric radiation measurement (ARM) microwave radiometers, IEEE T. Geosci. Remote, 45, 3680–3690, 2007. Walte-Shea, E. A. and Norman, J. M.: Leaf optical properties, in: Photon-vegetation interactions: applications in plant physiology and optical remote sensing, edited by: Myneni, R. B. and Ross, J., Springer Verlag, 229–251, 1991. Wen, G., Marshak, A., Cahalan, R. F., Remer, L. A., and Kleidman, R. G.: 3-D aerosol-cloud radiative interaction observed in collocated MODIS and ASTER images of cumulus cloud fields, J. Geophys. Res., 112, D13204, doi:10.1029/2006JD008267, 2007. Zhang, J. L., Reid, J. S., and Holben, B. N.: An analysis of potential cloud artifacts in MODIS over ocean aerosol optical thickness products, Geophys. Res. Lett., 32, L15803, doi:10.1029/2005GL023254, 2005.