• Ackerman, S. A., and S. K. Cox, 1981: Comparison of satellite and all-sky camera estimates of cloud cover during GATE. J. Appl. Meteor., 20, 581587.

    • Search Google Scholar
    • Export Citation
  • Arthur, D. K., S. Lasher-Trapp, A. Abdel-Haleem, N. Klosterman, and D. S. Ebert, 2010: A new three-dimensional visualization system for combining aircraft and radar data and its application to RICO observations. J. Atmos. Oceanic Technol., 27, 811828.

    • Search Google Scholar
    • Export Citation
  • Berg, L. K., and R. B. Stull, 2005: A simple parameterization coupling the convective daytime boundary layer and fair-weather cumuli. J. Atmos. Sci., 62, 19761988.

    • Search Google Scholar
    • Export Citation
  • Betts, A. K., 1997: Trade cumulus: Observations and modeling. The Physics and Parameterization of Moist Atmospheric Convection, R. K. Smith, Ed., Kluwer Academic Publishers, 99–126.

  • Betts, A. K., and B. A. Albrecht, 1987: Conserved variable analysis of the convective boundary layer thermodynamic structure over the tropical oceans. J. Atmos. Sci., 44, 8399.

    • Search Google Scholar
    • Export Citation
  • Betts, A. K., and W. Ridgway, 1988: Coupling of the radiative, convective, and surface fluxes over the equatorial Pacific. J. Atmos. Sci., 45, 522536.

    • Search Google Scholar
    • Export Citation
  • Cuijpers, J. W. M., and P. G. Duynkerke, 1993: Large eddy simulation of trade wind cumulus clouds. J. Atmos. Sci., 50, 38943908.

  • Davison, J. L., R. M. Rauber, and L. Di Girolamo, 2013a: A revised conceptual model of the tropical marine boundary layer. Part II: Detecting relative humidity layers using Bragg scattering from S-band radar. J. Atmos. Sci., 70, 30253046.

    • Search Google Scholar
    • Export Citation
  • Davison, J. L., R. M. Rauber, L. Di Girolamo, and M. A. LeMone, 2013b: A revised conceptual model of the tropical marine boundary layer. Part III: Bragg scattering layer statistical properties. J. Atmos. Sci., 70, 30473062.

    • Search Google Scholar
    • Export Citation
  • de Roode, S. R., and C. S. Bretherton, 2003: Mass-flux budgets of shallow cumulus clouds. J. Atmos. Sci., 60, 137151.

  • de Rooy, W. C., and A. P. Siebesma, 2008: A simple parameterization for detrainment in shallow cumulus. Mon. Wea. Rev., 136, 560576.

  • Emanuel, K. A., 1994: Atmospheric Convection. Oxford University Press, 580 pp.

  • Fierro, A. O., J. Simpson, M. A. LeMone, J. M. Straka, B. F. Smull, 2009: On how hot towers fuel the Hadley cell: An observational and modeling study of line-organized convection in the equatorial trough from TOGA COARE. J. Atmos. Sci., 66, 27302746.

    • Search Google Scholar
    • Export Citation
  • Garstang, M. A., and C. I. Aspliden, 1974: Convective cloud code. Department of Environmental Science, University of Virginia, Charlottesville GATE International Experiment Rep., 20 pp.

  • Kim, D., and V. Ramanathan, 2008: Solar radiation budget and radiative forcing due to aerosols and clouds. J. Geophys. Res., 113, D02203, doi:10.1029/2007JD008434.

    • Search Google Scholar
    • Export Citation
  • Kloesel, K. A., and B. A. Albrecht, 1989: Low-level inversions over the tropical Pacific—Thermodynamic structure of the boundary layer and the above-inversion moisture structure. Mon. Wea. Rev., 117, 87101.

    • Search Google Scholar
    • Export Citation
  • Knight, C. A., L. J. Miller, and R. A. Rilling, 2008: Aspects of precipitation development in trade wind cumulus revealed by differential reflectivity at S band. J. Atmos. Sci., 65, 25632580.

    • Search Google Scholar
    • Export Citation
  • Malkus, J. S., 1958: On the structure of the trade wind moist layer. MIT and WHOI Papers in Physical Oceanography and Meteorology, Vol. 13, No. 2, 47 pp.

  • Minor, H. A., R. M. Rauber, S. Göke, and L. Di Girolamo, 2011: Trade wind cloud evolution observed by polarization radar: Relationship to giant condensation nuclei concentrations and cloud organization. J. Atmos. Sci., 68, 10751096.

    • Search Google Scholar
    • Export Citation
  • Neggers, R. A. J., A. P. Siebesma, and H. J. J. Jonker, 2002: A multiparcel model for shallow cumulus convection. J. Atmos. Sci., 59, 16551668.

    • Search Google Scholar
    • Export Citation
  • Neggers, R. A. J., H. J. J. Jonker, and A. P. Siebesma, 2003: Size statistics of cumulus cloud populations in large-eddy simulations. J. Atmos. Sci., 60, 10601074.

    • Search Google Scholar
    • Export Citation
  • Neggers, R. A. J., B. Stevens, and J. D. Neelin, 2006: A simple equilibrium model for shallow cumulus topped mixed layers. Theor. Comput. Fluid Dyn., 20, 305322, doi:10.1007/s00162-006-0030-1.

    • Search Google Scholar
    • Export Citation
  • Nitta, T., and S. Esbensen, 1974: Diurnal variations in the Western Atlantic trades during the BOMEX. J. Meteor. Soc. Japan, 52, 254257.

    • Search Google Scholar
    • Export Citation
  • Nuijens, L., B. Stevens, and A. P. Siebesma, 2009: The environment of precipitating shallow cumulus convection. J. Atmos. Sci., 66, 19621979.

    • Search Google Scholar
    • Export Citation
  • Pennell, W. T., and M. A. LeMone, 1974: An experimental study of turbulence structure in the fair-weather trade wind boundary layer. J. Atmos. Sci., 31, 13081323.

    • Search Google Scholar
    • Export Citation
  • Rauber, R. M., and Coauthors, 2007: Rain in shallow cumulus over the ocean. Bull. Amer. Meteor. Soc., 88, 19121928.

  • Reiche, C. K. H., and S. G. Lasher-Trapp, 2010: The minor importance of giant aerosol to precipitation development within small trade wind cumuli observed during RICO. Atmos. Res., 95, 386399.

    • Search Google Scholar
    • Export Citation
  • Riehl, H., T. C. Yeh, J. S. Malkus, and N. E. Laseur, 1951: The northeast trade of the Pacific Ocean. Quart. J. Roy. Meteor. Soc., 77, 598626.

    • Search Google Scholar
    • Export Citation
  • Roberts, R. D., and Coauthors, 2008: REFRACTT 2006. Bull. Amer. Meteor. Soc., 89, 15351548.

  • Ruttenberg, S., 1975: GATE Information Bulletin. No. 8, GATE Project Office, Rockville, MD, 43 pp. [Available online at http://nldr.library.ucar.edu/repository/assets/gate/GATE-000-000-000-008.pdf.]

  • Siebesma, A. P., 1998: Shallow cumulus convection. Buoyant Convection in Geophysical Flows, E. J. Plate et al., Eds., Kluwer, 441–486.

  • Siebesma, A. P., and J. W. M. Cuijpers, 1995: Evaluation of parametric assumptions for shallow cumulus convection. J. Atmos. Sci., 52, 650666.

    • Search Google Scholar
    • Export Citation
  • Siebesma, A. P., and A. A. M. Holtslag, 1996: Model impacts of entrainment and detrainment rates in shallow cumulus convection. J. Atmos. Sci., 53, 23542364.

    • Search Google Scholar
    • Export Citation
  • Siebesma, A. P., and Coauthors, 2003: A large eddy simulation intercomparison study of shallow cumulus convection. J. Atmos. Sci., 60, 12011219.

    • Search Google Scholar
    • Export Citation
  • Snodgrass, E. R., L. Di Girolamo, and R. M. Rauber, 2009: Precipitation characteristics of trade wind clouds during RICO derived from radar, satellite, and aircraft measurements. J. Appl. Meteor. Climatol., 48, 464483.

    • Search Google Scholar
    • Export Citation
  • Sommeria, G., and M. A. LeMone, 1978: Direct testing of a three-dimensional model of the planetary boundary layer against experimental data. J. Atmos. Sci., 35, 2539.

    • Search Google Scholar
    • Export Citation
  • Stevens, B., 2005: Atmospheric moist convection. Annu. Earth Planet. Sci., 32, 605643.

  • Stevens, B., 2006: Bulk boundary layer concepts for simplified models of tropical dynamics. Theor. Comput. Fluid Dyn., 20, 279304.

  • Stevens, B., and J.-L. Brenguier, 2009: Cloud-controlling factors: Low clouds. Clouds in the Perturbed Climate System: Their Relationship to Energy Balance, Atmospheric Dynamics, and Precipitation, J. Heintzenberg and R. Charlson, Eds., MIT Press, 173–196.

  • Stevens, B., and Coauthors, 2001: Simulations of trade wind cumuli under a strong inversion. J. Atmos. Sci., 58, 18701891.

  • Stull, R. B., 1988: An Introduction to Boundary Layer Meteorology. Kluwer Academic Publishers, 670 pp.

  • Trenberth, K. E., and Coauthors, 2007: Observations: Surface and atmospheric climate change. Climate Change 2007: The Physical Science Basis, S. Solomon et al., Eds., Cambridge University Press, 235–336.

  • Vaisala, 2010: Vaisala radiosonde RS-92-SGP. Vaisala Reference Doc. B210358EN-E, 2 pp. [Available online at http://www.vaisala.com/Vaisala%20Documents/Brochures%20and%20Datasheets/RS92SGP-Datasheet-B210358EN-F-LOW.pdf.]

  • vanZanten, M. C., and Coauthors, 2011: Controls on precipitation and cloudiness in simulations of trade-wind cumulus as observed during RICO. J. Adv. Model. Earth Syst., 3, M06001, doi:10.1029/2011MS000056.

    • Search Google Scholar
    • Export Citation
  • von Salzen, K., and N. A. McFarlane, 2002: Parameterization of the bulk effects of lateral and cloud-top entrainment in transient shallow cumulus clouds. J. Atmos. Sci., 59, 14051430.

    • Search Google Scholar
    • Export Citation
  • Währn, J., I. Rekikoski, H. Jauhiainen, and J. Hirvensalo, 2004: New Vaisala radiosonde RS92: Testing and results from the field. Preprints, Eighth Symp. on Integrated Observing and Assimilation Systems for Atmosphere, Oceans, and Land Surface, Seattle, WA, Amer. Meteor. Soc., 4.13. [Available online at http://ams.confex.com/ams/84Annual/techprogram/paper_72134.htm.]

  • Weckwerth, T. M., and Coauthors, 2004: An overview of the International H2O Project (IHOP_2002) and some preliminary highlights. Bull. Amer. Meteor. Soc., 85, 253277.

    • Search Google Scholar
    • Export Citation
  • Xue, H., and G. Feingold, 2006: Large-eddy simulations of trade wind cumuli: Investigation of aerosol indirect effects. J. Atmos. Sci., 63, 16051622.

    • Search Google Scholar
    • Export Citation
  • Xue, H., G. Feingold, and B. Stevens, 2008: Aerosol effects on clouds, precipitation, and the organization of shallow cumulus convection. J. Atmos. Sci., 65, 392406.

    • Search Google Scholar
    • Export Citation
  • Yanai, M., S. Esbensen, and J. Chu, 1973: Determination of bulk properties of tropical cloud clusters from large-scale heat and moisture budgets. J. Atmos. Sci., 30, 611627.

    • Search Google Scholar
    • Export Citation
  • Yin, B., and B. Albrecht, 2000: Spatial variability of atmospheric boundary layer structure over the eastern equatorial Pacific. J. Climate, 13, 15741592.

    • Search Google Scholar
    • Export Citation
  • Yuter, S. E., and R. A. Houze, 1995: Three-dimensional kinemetic and microphysical evolution of Florida cumulonimbus. Part II: Frequency distributions of vertical velocity, reflectivity, and differential reflectivity. Mon. Wea. Rev., 123, 19411963.

    • Search Google Scholar
    • Export Citation
  • Zhao, G., and L. Di Girolamo, 2007: Statistics on the macrophysical properties of trade wind cumuli over the tropical western Atlantic. J. Geophys. Res., 112, D10204, doi:10.1029/2006JD007371.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 45 45 45
PDF Downloads 28 28 28

A Revised Conceptual Model of the Tropical Marine Boundary Layer. Part I: Statistical Characterization of the Variability Inherent in the Wintertime Trade Wind Regime over the Western Tropical Atlantic

View More View Less
  • 1 Department of Atmospheric Sciences, University of Illinois at Urbana–Champaign, Urbana, Illinois
  • | 2 National Center for Atmospheric Research, Boulder, Colorado
Restricted access

Abstract

This paper investigates wintertime tropical marine boundary layer (TMBL) statistical characteristics over the western North Atlantic using the complete set of island-launched soundings from the Rain in Cumulus over the Ocean (RICO) experiment. The soundings are subdivided into undisturbed and disturbed classifications using two discriminators: 1) dates chosen by Global Energy and Water Cycle Experiment (GEWEX) Cloud System Studies (GCSS) investigators to construct the mean RICO sounding and 2) daily average rain rates.

A wide range of relative humidity (RH) values was observed between the surface and 8.0 km. At 2.0 km, half the RH values were within 56%–89%; at 4.0 km, half were within 13%–61%. The rain-rate method of separating disturbed and undisturbed soundings appears more meaningful than the GCSS method. The median RH for disturbed conditions using the rain-rate method showed moister conditions from the surface to 8.0 km, with maximum RH differences of 30%–40%. Moist air generally extended higher on disturbed than undisturbed days.

Based on equivalent potential temperature, wind direction, and RH analyses, the most common altitude marking the TMBL top was about 4.0 km. Temperature inversions (over both 50- and 350-m intervals) were observed at every altitude above 1.2 km; there were no dominant inversion heights and most of the inversions were weak. Wind direction analyses indicated that winds within the TMBL originated from more tropical latitudes on disturbed days.

The analyses herein suggest that the RICO profile used to initialize many model simulations of this environment represents only a small subset of the broad range of possible conditions characterizing the wintertime trades.

Corresponding author address: Jennifer L. Davison, Department of Atmospheric Sciences, University of Illinois at Urbana–Champaign, 105 S. Gregory St., Urbana, IL 61801. E-mail: jdavison@earth.uiuc.edu

Abstract

This paper investigates wintertime tropical marine boundary layer (TMBL) statistical characteristics over the western North Atlantic using the complete set of island-launched soundings from the Rain in Cumulus over the Ocean (RICO) experiment. The soundings are subdivided into undisturbed and disturbed classifications using two discriminators: 1) dates chosen by Global Energy and Water Cycle Experiment (GEWEX) Cloud System Studies (GCSS) investigators to construct the mean RICO sounding and 2) daily average rain rates.

A wide range of relative humidity (RH) values was observed between the surface and 8.0 km. At 2.0 km, half the RH values were within 56%–89%; at 4.0 km, half were within 13%–61%. The rain-rate method of separating disturbed and undisturbed soundings appears more meaningful than the GCSS method. The median RH for disturbed conditions using the rain-rate method showed moister conditions from the surface to 8.0 km, with maximum RH differences of 30%–40%. Moist air generally extended higher on disturbed than undisturbed days.

Based on equivalent potential temperature, wind direction, and RH analyses, the most common altitude marking the TMBL top was about 4.0 km. Temperature inversions (over both 50- and 350-m intervals) were observed at every altitude above 1.2 km; there were no dominant inversion heights and most of the inversions were weak. Wind direction analyses indicated that winds within the TMBL originated from more tropical latitudes on disturbed days.

The analyses herein suggest that the RICO profile used to initialize many model simulations of this environment represents only a small subset of the broad range of possible conditions characterizing the wintertime trades.

Corresponding author address: Jennifer L. Davison, Department of Atmospheric Sciences, University of Illinois at Urbana–Champaign, 105 S. Gregory St., Urbana, IL 61801. E-mail: jdavison@earth.uiuc.edu
Save