Cloud Halos: Numerical Simulation of Dynamical Structure and Radiative Impact

Miao-Ling Lu California Institute of Technology, Pasadena, California

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Robert A. McClatchey Aerodyne Research, Inc., Billerica, Massachusetts

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John H. Seinfeld California Institute of Technology, Pasadena, California

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Abstract

Significant enhancements in humidity around cumulus clouds, that is, the “cloud halos” observed in many aircraft penetrations, are simulated using a three-dimensional dynamic model. Five case studies show that humidity halos occur mainly near lateral cloud boundaries and also occur at cloud top and base when the cloud dissipates. The humidity halo broadens as the cloud ages and is also broader in the presence of wind shear than in its absence, especially on the downshear side of the cloud. The broadband calculation over the solar spectrum (0.2–4.0 μm) shows that the shortwave (SW) heating rate in the halo is about 11%–18% larger than the ambient environmental heating rate. The strongest halo-induced surface SW radiative forcing for all cases studied is about −0.2 W m−2, which is approximately a 0.02% change from the forcing without a halo.

Corresponding author address: John H. Seinfeld, California Institute of Technology, 210-41, Pasadena, CA 91125. seinfeld@caltech.edu

Abstract

Significant enhancements in humidity around cumulus clouds, that is, the “cloud halos” observed in many aircraft penetrations, are simulated using a three-dimensional dynamic model. Five case studies show that humidity halos occur mainly near lateral cloud boundaries and also occur at cloud top and base when the cloud dissipates. The humidity halo broadens as the cloud ages and is also broader in the presence of wind shear than in its absence, especially on the downshear side of the cloud. The broadband calculation over the solar spectrum (0.2–4.0 μm) shows that the shortwave (SW) heating rate in the halo is about 11%–18% larger than the ambient environmental heating rate. The strongest halo-induced surface SW radiative forcing for all cases studied is about −0.2 W m−2, which is approximately a 0.02% change from the forcing without a halo.

Corresponding author address: John H. Seinfeld, California Institute of Technology, 210-41, Pasadena, CA 91125. seinfeld@caltech.edu

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  • Ackerman, B. 1958. Turbulence around tropical cumuli. J. Meteor. 15:6974.

  • Arking, A. 1996. Absorption of solar energy in the atmosphere: Discrepancy between model and observations. Science 273:779782.

  • Austin, G. R., R. M. Rauber, H. T. Ochs III, and L. J. Miller. 1996. Trade-wind clouds and Hawaiian rainbands. Mon. Wea. Rev. 124:21262151.

    • Search Google Scholar
    • Export Citation
  • Bretherton, C. S. and P. K. Smolarkiewicz. 1989. Gravity waves, compensating subsidence and detrainment around cumulus clouds. J. Atmos. Sci. 46:740759.

    • Search Google Scholar
    • Export Citation
  • Chen, Y-L. and A. Nash. 1994. Diurnal variation of surface airflow and rainfall frequencies on the island of Hawaii. Mon. Wea. Rev. 122:3456.

    • Search Google Scholar
    • Export Citation
  • Chylek, P. and V. Ramaswamy. 1982. Simple approximation for infrared emissivity of water clouds. J. Atmos. Sci. 39:171177.

  • Crisp, D. 1997. Absorption of sunlight by water vapor in cloudy conditions: A partial explanation for the cloud absorption anomaly. Geophys. Res. Lett. 24:571574.

    • Search Google Scholar
    • Export Citation
  • Davidson, B. 1968. The Barbados Oceanographic and Meteorological Experiment. Bull. Amer. Meteor. Soc. 49:928934.

  • Davies, R., W. L. Ridgway, and K-E. Kim. 1984. Spectral absorption of solar radiation in cloudy atmosphere: A 20 cm−1 model. J. Atmos. Sci. 41:21262137.

    • Search Google Scholar
    • Export Citation
  • Deardorff, J. W. 1970. A numerical study of three-dimensional turbulent channel flow at large Reynolds number. J. Fluid Mech. 41:453480.

    • Search Google Scholar
    • Export Citation
  • Evans, K. F. 1993. Two-dimensional radiative transfer in cloudy atmospheres: The spherical harmonic spatial grid method. J. Atmos. Sci. 50:31113124.

    • Search Google Scholar
    • Export Citation
  • Evans, K. F. . 1998. The spherical harmonic discrete ordinate method for three-dimensional atmospheric radiative transfer. J. Atmos. Sci. 55:429446.

    • Search Google Scholar
    • Export Citation
  • Fu, Q. and K. N. Liou. 1992. On the correlated k-distribution method for radiative transfer in nonhomogeneous atmospheres. J. Atmos. Sci. 49:21392156.

    • Search Google Scholar
    • Export Citation
  • GEWEX, 2000. GEWEX Global Cloud System Study (GCSS) Second Science and Implementation Plan. Int. GEWEX Project Office Series, Vol. 34, GEWEX, 52 pp.

    • Search Google Scholar
    • Export Citation
  • Harrington, J. Y. 1997. The effects of radiative and microphysical processes on simulated warm and transition season arctic stratus. Ph.D. dissertation, Dept. of Atmospheric Science, Colorado State University, 289 pp.

    • Search Google Scholar
    • Export Citation
  • Hobbs, P. V. and L. F. Radke. 1992. Reply. J. Atmos. Sci. 49:15161517.

  • Jiang, H. and W. R. Cotton. 2000. Large eddy simulation of shallow cumulus convection during BOMEX: Sensitivity to microphysics and radiation. J. Atmos. Sci. 57:582594.

    • Search Google Scholar
    • Export Citation
  • Kogan, Y. L. 1991. The simulation of a convective cloud in a 3-D model with explicit microphysics. Part I: Model description and sensitivity experiments. J. Atmos. Sci. 48:11601189.

    • Search Google Scholar
    • Export Citation
  • Kollias, P., B. A. Albrecht, R. Lhermitte, and A. Savtchenko. 2001. Radar observations of updrafts, downdrafts, and turbulence in fair-weather cumuli. J. Atmos. Sci. 58:17501766.

    • Search Google Scholar
    • Export Citation
  • Li, J. and Y-L. Chen. 1999. A case study of nocturnal rain showers over the windward coastal region of the island of Hawaii. Mon. Wea. Rev. 127:26742692.

    • Search Google Scholar
    • Export Citation
  • Li, Z. and A. P. Trishchenko. 2001. Quantifying uncertainties in determining SW cloud radiative forcing and cloud absorption due to variability in atmospheric conditions. J. Atmos. Sci. 58:376389.

    • Search Google Scholar
    • Export Citation
  • Malkus, J. S. 1949. Effects of wind shear on some aspects of convection. Trans. Amer. Geophys. Union 30:1925.

  • Malkus, J. S. . 1954. Some results of a trade-cumulus investigation. J. Meteor. 11:220237.

  • McClatchey, R. A., R. W. Fenn, J. E. A. Selby, P. E. Volz, and J. S. Garing. 1972. Optical Properties of the Atmosphere. 3d ed. Air Force Cambridge Research Laboratory AFCRL-72-0497, 113 pp.

    • Search Google Scholar
    • Export Citation
  • Nakajima, T. and M. Tanaka. 1988. Algorithms for radiative intensity calculations in moderately thick atmospheres using a truncation approximation. J. Quant. Spectrosc. Radiat. Transfer 40:5169.

    • Search Google Scholar
    • Export Citation
  • O'Hirok, W. and C. Gautier. 1998. A three-dimensional radiative transfer model to investigate the solar radiation within a cloudy atmosphere. Part I: Spatial effects. J. Atmos. Sci. 55:21622179.

    • Search Google Scholar
    • Export Citation
  • Perry, K. D. and P. V. Hobbs. 1996. Influences of isolated cumulus clouds on the humidity of their surroundings. J. Atmos. Sci. 53:159174.

    • Search Google Scholar
    • Export Citation
  • Pielke, R. A. Coauthors,. 1992. A comprehensive meteorological modeling system—RAMS. Meteor. Atmos. Phys. 49:6991.

  • Podgorny, I. A., A. M. Vogelmann, and V. Ramanathan. 1998. Effects of cloud shape and water vapor distribution on solar absorption in the near infrared. Geophys. Res. Lett. 25:18991902.

    • Search Google Scholar
    • Export Citation
  • Radke, L. F. and P. V. Hobbs. 1991. Humidity and particle fields around some small cumulus clouds. J. Atmos. Sci. 48:11901193.

  • Takahashi, T. 1977. A study of Hawaiian warm rain showers based on aircraft observation. J. Atmos. Sci. 34:17331790.

  • Telford, J. W. and P. B. Wagner. 1980. The dynamical and liquid water structure of the small cumulus as determined from its environment. Pure Appl. Geophys. 118:935952.

    • Search Google Scholar
    • Export Citation
  • Trautmann, T., I. Podgorny, J. Landgraf, and P. J. Crutzen. 1999. Actinic fluxes and photodissociation coefficients in cloud fields embedded in realistic atmospheres. J. Geophys. Res. 104:3017330192.

    • Search Google Scholar
    • Export Citation
  • Tripoli, G. J. and W. R. Cotton. 1981. The use of ice-liquid water potential temperature as a thermodynamic variable in deep atmospheric models. Mon. Wea. Rev. 109:10941102.

    • Search Google Scholar
    • Export Citation
  • Walko, R. L., W. R. Cotton, M. P. Meyers, and J. Y. Harrington. 1995. New RAMS cloud microphysics parameterization. Part I: The single-moment scheme. Atmos. Res. 38:2962.

    • Search Google Scholar
    • Export Citation
  • Wang, J-J. and Y-L. Chen. 1998. A case study of trade-wind rainbands and their interaction with the island-induced airflow. Mon. Wea. Rev. 126:409423.

    • Search Google Scholar
    • Export Citation
  • Warner, J. 1977. Time variation of updraft and water content in small cumulus clouds. J. Atmos. Sci. 34:13061312.

  • Wendisch, M. and A. Keil. 1999. Discrepancies between measured and modeled solar and UV radiation within polluted boundary layer clouds. J. Geophys. Res. 104:2737327385.

    • Search Google Scholar
    • Export Citation
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