• Bergman, J. W., and H. H. Hendon, 1998: Calculating monthly radiative fluxes and heating rates from monthly observations of cloud cover. J. Atmos. Sci.,55, 3471–3491.

  • ——, and ——, 2000: The impact of clouds on the seasonal cycle of radiative heating over the Pacific. J. Atmos. Sci.,57, 545–566.

  • Bony, S., Y. Sud, K. M. Lau, J. Susskind, and S. Saha, 1997: Comparison and satellite assessment of NASA/DAO and NCEP–NCAR reanalyses over tropical ocean: Atmospheric hydrology and radiation. J. Climate,10, 1441–1462.

  • Cess, R. D., and Coauthors, 1995: Absorption of solar radiation by clouds: Observations versus models. Science,267, 496–499.

  • ECMWF Research Department, 1992: Research manual 1: ECMWF data assimilation scientific documentation. ECMWF, 88 pp. [Available from ECMWF, Shinfield Park, Reading, Berkshire RG2 9AX, United Kingdom.].

  • Gill, A., 1980: Some simple solutions for heat induced tropical circulation. Quart. J. Roy. Meteor. Soc.,106, 447–462.

  • ——, 1982: Atmosphere–Ocean Dynamics. Academic Press, 662 pp.

  • Hoskins, B. J., H. H. Hsu, I. N. James, M. Matsutani, P. D. Sardeshmukh, and G. H. White, 1989: Diagnostics of the global atmospheric circulation based on ECMWF analyses 1979–1989. WCRP-27, WMO/TD-326, 217 pp. [Available from WMO, Case Postale No. 2300, CH-1211 Geneva 2, Switzerland.].

  • Kalnay, E. M., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc.,77, 432–471.

  • Kessler, W. S., L. M. Rothstein, and D. Chen, 1998: The annual cycle of SST in the eastern tropical Pacific diagnosed in an ocean GCM. J. Climate,11, 777–799.

  • Kiehl, J. T., J. J. Hack, M. H. Zhang, and R. D. Cess, 1995: Sensitivity of a GCM climate to enhanced shortwave cloud absorption. J. Climate,8, 2200–2212.

  • ——, ——, G. B. Bonan, B. A. Boville, B. P. Briegleb, D. L. Williamson, and P. J. Rasch, 1996: Description of the NCAR community climate model (CCM3). NCAR Tech. Note NCAR/TN-420+STR, National Center for Atmospheric Research, Boulder, CO, 152 pp.

  • Lau, N.-C., 1979: The observed structure of tropospheric stationary waves and the balance of vorticity and heat. J. Atmos. Sci.,36, 996–1016.

  • Li, Z., L. Moreau, and A. Arking, 1997: On the solar energy disposition: A perspective from observation and modeling. Bull. Amer. Meteor. Soc.,78, 53–70.

  • Liu, A. Z., M. Ting, and H. Wang, 1998: Maintenance of circulation anomalies during the 1988 drought and 1993 floods over the United States. J. Atmos. Sci.,55, 2810–2832.

  • Ma, C.-C., C. R. Mechoso, A. W. Robertson, and A. Arakawa, 1996:Peruvian stratus clouds and the tropical Pacific circulation: A coupled ocean–atmosphere GCM study. J. Climate,9, 1635–1645.

  • Mechoso, C. R., and Coauthors, 1995: The seasonal cycle over the tropical Pacific in coupled ocean–atmosphere general circulation models. Mon. Wea. Rev.,123, 2825–2838.

  • Mitchell, T. P., and J. M. Wallace, 1992: The annual cycle in equatorial convection and sea surface temperature. J. Climate,5, 1140–1156.

  • Newell, R. E., J. W. Kidson, D. G. Vincent, and G. J. Boer, 1974: The General Circulation of the Tropical Atmosphere. Vol. 2. The MIT Press, 371 pp.

  • Nigam, S., 1994: On the dynamical basis for the Asian summer monsoon rainfall–El Niño relationship. J. Climate,7, 1750–1771.

  • ——, 1997: The annual warm to cold phase transition in the eastern equatorial Pacific: Diagnosis of the role of stratus cloud-top-cooling. J. Climate,10, 2447–2467.

  • Ramanathan, V., 1987: The role of Earth radiation budget studies in climate and general circulation research. J. Geophys. Res.,92, 4075–4095.

  • ——, and W. C. Collins, 1991: Thermodynamic regulation of ocean warming by cirrus clouds deduced from observations of the 1987 El Nino. Nature,351, 27–32.

  • ——, B. Subasilar, G. J. Zhang, W. Conant, R. D. Cess, J. T. Kiehl, H. Grassl, and L. Shi, 1995: Warm pool heat budget and shortwave cloud forcing: A missing physics? Science,267, 499–503.

  • Randall, D. A., Harshvardhan, D. A. Dazlich, and T. G. Corsetti, 1989: Interactions among radiation, convection, and large-scale dynamics in a general circulation model. J. Atmos. Sci.,46, 1943–1970.

  • Ridout, J. A., and T. E. Rosmond, 1996: Global modeling of cloud radiative effects using ISCCP cloud data. J. Climate,9, 1479–1496.

  • Rossow, W. B., and R. A. Schiffer, 1991: ISCCP cloud data products. Bull. Amer. Meteor. Soc.,72, 2–20.

  • ——, and L. C. Garder, 1993: Validation of ISCCP cloud detections. J. Climate,6, 2370–2393.

  • ——, A. Walker, D. Beuschel, and M. Roiter, 1996: International Satellite Cloud Climatology Project (ISCCP) documentation of new cloud dataset. WMO/TD-No. 737, World Meteorological Organization, 115 pp. [Available online at http://isccp.giss.nasa.gov/documents.html].

  • Sherwood, S. C., V. Ramanathan, T. P. Barnett, M. K. Tyree, and E. Roeckner, 1994: Response of an atmospheric general circulation model to radiative forcing of tropical clouds. J. Geophys. Res.,99, 20 829–20 845.

  • Slingo, J. M., and A. Slingo, 1991: The response of a general circulation model to cloud longwave radiative forcing: II Further studies. Quart. J. Roy. Meteor. Soc.,117, 333–364.

  • Stephens, G. L., 1996: How much solar radiation do clouds absorb? Science,271, 1131–1133.

  • Weare, B. C., 1997: Comparison of NCEP–NCAR cloud radiative forcing reanalyses with observations. J. Climate,10, 2200–2209.

  • Webster, P. J., 1994: The role of hydrological processes in ocean–atmosphere interactions. Rev. Geophys.,32, 427–476.

  • Yanai, M., S. Esbensen, and J. H. Chu, 1973: Determination of bulk properties of tropical cloud clusters from large-scale heat and moisture budgets. J. Atmos. Sci.,30, 611–627.

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Cloud Radiative Forcing of the Low-Latitude Tropospheric Circulation: Linear Calculations

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  • 1 NOAA–CIRES Climate Diagnostics Center, Boulder, Colorado
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Abstract

The role of clouds for low-latitude atmospheric circulations is examined in a linearized calculation forced by diabatic heating rates. A comparison of the circulation calculated from total diabatic heating, obtained from reanalysis data, with observed fields determines which aspects of the calculation are realistic and which are not. The role of clouds is quantified by the circulation calculated from atmospheric cloud radiative forcing, which, in turn, has been calculated with the National Center for Atmospheric Research radiative transfer model using cloud properties observed in the International Satellite Cloud Climatology Project.

In general, cloud radiative forcing contributes about 20% to the magnitude of low-latitude circulations. It typically reinforces the circulation that is driven by convective latent heating. Cloud radiative forcing tends to have a stronger influence in the lower troposphere than at upper levels. It influences local circulations more than remote ones. In particular, cloud radiative forcing from local low cloud cover is the dominant source of diabatic heating influencing subtropical circulations over the eastern oceans. Cloud radiative forcing from low clouds is also found to be important for seasonal variations of meridional winds over the cold tongue in the eastern Pacific. This indicates that atmospheric cloud radiative forcing, and not just surface forcing, is important for ocean–atmospheric coupling there.

Additional calculations are performed that test the sensitivity of the atmospheric circulation to different sources of diabatic heating rates. These sources include radiative heating rates that have been calculated from different cloud data, different cloud overlap assumptions, and enhanced cloud short-wave absorptivity. The principal conclusions of this investigation are unchanged by these calculations. However, enhanced short-wave absorption by clouds systematically reduces the impact of clouds on atmospheric circulations.

Corresponding author address: John W. Bergman, CIRES–NOAA Climate Diagnostics Center, R/E/CD1, 325 Broadway, Boulder, CO 80309-0449.

Email: jwb@cdc.noaa.gov

Abstract

The role of clouds for low-latitude atmospheric circulations is examined in a linearized calculation forced by diabatic heating rates. A comparison of the circulation calculated from total diabatic heating, obtained from reanalysis data, with observed fields determines which aspects of the calculation are realistic and which are not. The role of clouds is quantified by the circulation calculated from atmospheric cloud radiative forcing, which, in turn, has been calculated with the National Center for Atmospheric Research radiative transfer model using cloud properties observed in the International Satellite Cloud Climatology Project.

In general, cloud radiative forcing contributes about 20% to the magnitude of low-latitude circulations. It typically reinforces the circulation that is driven by convective latent heating. Cloud radiative forcing tends to have a stronger influence in the lower troposphere than at upper levels. It influences local circulations more than remote ones. In particular, cloud radiative forcing from local low cloud cover is the dominant source of diabatic heating influencing subtropical circulations over the eastern oceans. Cloud radiative forcing from low clouds is also found to be important for seasonal variations of meridional winds over the cold tongue in the eastern Pacific. This indicates that atmospheric cloud radiative forcing, and not just surface forcing, is important for ocean–atmospheric coupling there.

Additional calculations are performed that test the sensitivity of the atmospheric circulation to different sources of diabatic heating rates. These sources include radiative heating rates that have been calculated from different cloud data, different cloud overlap assumptions, and enhanced cloud short-wave absorptivity. The principal conclusions of this investigation are unchanged by these calculations. However, enhanced short-wave absorption by clouds systematically reduces the impact of clouds on atmospheric circulations.

Corresponding author address: John W. Bergman, CIRES–NOAA Climate Diagnostics Center, R/E/CD1, 325 Broadway, Boulder, CO 80309-0449.

Email: jwb@cdc.noaa.gov

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