Simple Multicloud Models for the Diurnal Cycle of Tropical Precipitation. Part II: The Continental Regime

Yevgeniy Frenkel Courant Institute for Mathematical Sciences, New York University, New York, New York

Search for other papers by Yevgeniy Frenkel in
Current site
Google Scholar
PubMed
Close
,
Boualem Khouider Department of Mathematics and Statistics, University of Victoria, Victoria, British Columbia, Canada

Search for other papers by Boualem Khouider in
Current site
Google Scholar
PubMed
Close
, and
Andrew J. Majda Department of Mathematics, and Center for Atmosphere Ocean Science, Courant Institute of Mathematical Sciences, New York University, New York, New York

Search for other papers by Andrew J. Majda in
Current site
Google Scholar
PubMed
Close
Restricted access

Abstract

The variation of precipitation over land due to the diurnal cycle of solar heating is examined here in the context of a simple multicloud model for tropical convection with bulk atmospheric boundary layer (ABL) dynamics. The model utilizes three cloud types (congestus, deep, and stratiform) that are believed to characterize organized tropical convection based on the first two baroclinic modes of vertical structure in the free troposphere, coupled to the ABL through full bulk boundary layer (FBBL) dynamics, that allow a careful separation between sensible and latent heat surface fluxes. In a land parameter regime, characterized by a strong inversion profile, a large Bowen ratio of 0.4, and active mixing of sensible heat due to cumulus entrainment and downdraft fluxes at the top of the ABL, the model supports a stable 1-day periodic solution that is characterized by a pronounced (7 K day−1) afternoon peak in precipitation consistent with observations of tropical precipitation over continental regions. The current study suggests a division of the diurnal cycle of precipitation over land into a cycle of five phases: 1) an overnight phase of a radiative–convective equilibrium (RCE) state between 2000 and 0600 LST; 2) an early morning CAPE buildup accompanied by a sudden rise in precipitation that quickly dries the middle troposphere occurs between 0600 and roughly 1000 LST; 3) a moistening phase between roughly 1000 and 1600 LST; 4) a phase of maximum precipitation between 1600 and 1800 LST that dries the middle troposphere and quickly consumes CAPE; and 5) a rapid remoistening phase that restores the moisture level to sustain the overnight RCE precipitation and connects to phase 1 in the cycle. Sensitivity tests in the model confirm that the late afternoon precipitation maximum over land depends crucially on a strong inversion, the large Bowen ratio, and the active mixing of sensible heat due to cumulus entrainment and downdraft fluxes at the top of the ABL.

Corresponding author address: Boualem Khouider, Department of Mathematics and Statistics, University of Victoria, 3800 Finnerty Road, Victoria BC V8W 3P4, Canada. E-mail: khouider@uvic.ca

Abstract

The variation of precipitation over land due to the diurnal cycle of solar heating is examined here in the context of a simple multicloud model for tropical convection with bulk atmospheric boundary layer (ABL) dynamics. The model utilizes three cloud types (congestus, deep, and stratiform) that are believed to characterize organized tropical convection based on the first two baroclinic modes of vertical structure in the free troposphere, coupled to the ABL through full bulk boundary layer (FBBL) dynamics, that allow a careful separation between sensible and latent heat surface fluxes. In a land parameter regime, characterized by a strong inversion profile, a large Bowen ratio of 0.4, and active mixing of sensible heat due to cumulus entrainment and downdraft fluxes at the top of the ABL, the model supports a stable 1-day periodic solution that is characterized by a pronounced (7 K day−1) afternoon peak in precipitation consistent with observations of tropical precipitation over continental regions. The current study suggests a division of the diurnal cycle of precipitation over land into a cycle of five phases: 1) an overnight phase of a radiative–convective equilibrium (RCE) state between 2000 and 0600 LST; 2) an early morning CAPE buildup accompanied by a sudden rise in precipitation that quickly dries the middle troposphere occurs between 0600 and roughly 1000 LST; 3) a moistening phase between roughly 1000 and 1600 LST; 4) a phase of maximum precipitation between 1600 and 1800 LST that dries the middle troposphere and quickly consumes CAPE; and 5) a rapid remoistening phase that restores the moisture level to sustain the overnight RCE precipitation and connects to phase 1 in the cycle. Sensitivity tests in the model confirm that the late afternoon precipitation maximum over land depends crucially on a strong inversion, the large Bowen ratio, and the active mixing of sensible heat due to cumulus entrainment and downdraft fluxes at the top of the ABL.

Corresponding author address: Boualem Khouider, Department of Mathematics and Statistics, University of Victoria, 3800 Finnerty Road, Victoria BC V8W 3P4, Canada. E-mail: khouider@uvic.ca
Save
  • Casey, S. P. F., A. E. Dessler, and C. Schumacher, 2007: Frequency of tropical precipitating clouds as observed by the Tropical Rainfall Measuring Mission Precipitation Radar and ICESat/Geoscience Laser Altimeter System. J. Geophys. Res., 112, D14215, doi:10.1029/2007JD008468.

    • Search Google Scholar
    • Export Citation
  • Chapin, F. S., P. Matson, and H. Mooney, 2002: Principles of Terrestrial Ecosystem Ecology. Springer, 436 pp.

  • Dai, A., and K. E. Trenberth, 2004: The diurnal cycle and its depiction in the Community Climate System Model. J. Climate, 17, 930951.

    • Search Google Scholar
    • Export Citation
  • Fisch, G., J. Tota, L. A. T. Machado, M. A. F. Silva Dias, R. F. da F. Lyra, C. A. Nobre, A. J. Dolman, and J. H. C. Gash, 2004: The convective boundary layer over pasture and forest in Amazonia. Theor. Appl. Climatol., 78, 4759.

    • Search Google Scholar
    • Export Citation
  • Frenkel, Y., B. Khouider, and A. J. Majda, 2011: Simple multicloud models for the diurnal cycle of tropical precipitation. Part I: Formulation and the case of the tropical oceans. J. Atmos. Sci., 68, 21692190.

    • Search Google Scholar
    • Export Citation
  • Fu, R., B. Zhu, and R. E. Dickinson, 1999: How do atmosphere and land surface influence seasonal changes of convection in the tropical Amazon? J. Climate, 12, 13061321.

    • Search Google Scholar
    • Export Citation
  • Hsu, S. A., 1998: A relationship between the Bowen ratio and sea–air temperature difference under unstable conditions at sea. J. Phys. Oceanogr., 28, 22222226.

    • Search Google Scholar
    • Export Citation
  • Johnson, R. H., T. M. Rickenbach, S. A. Rutledge, P. E. Ciesielski, and W. H. Schubert, 1999: Trimodal characteristics of tropical convection. J. Climate, 12, 23972418.

    • Search Google Scholar
    • Export Citation
  • Khouider, B., and A. J. Majda, 2006: A simple multicloud parameterization for convectively coupled tropical waves. Part I: Linear analysis. J. Atmos. Sci., 63, 13081323.

    • Search Google Scholar
    • Export Citation
  • Khouider, B., and A. J. Majda, 2007: A simple multicloud parameterization for convectively coupled tropical waves. Part II: Nonlinear simulations. J. Atmos. Sci., 64, 381400.

    • Search Google Scholar
    • Export Citation
  • Khouider, B., and A. J. Majda, 2008a: Equatorial convectively coupled waves in a simple multicloud model. J. Atmos. Sci., 65, 33763397.

    • Search Google Scholar
    • Export Citation
  • Khouider, B., and A. J. Majda, 2008b: Multicloud models for organized tropical convection: Enhanced congestus heating. J. Atmos. Sci., 65, 895914.

    • Search Google Scholar
    • Export Citation
  • Khouider, B., A. St-Cyr, A. J. Majda, and J. Tribbia, 2011: The MJO and convectively coupled waves in a coarse-resolution GCM with a simple multicloud parameterization. J. Atmos. Sci., 68, 240264.

    • Search Google Scholar
    • Export Citation
  • Kikuchi, K., and B. Wang, 2008: Diurnal precipitation regimes in the global tropics. J. Climate, 21, 26802696.

  • Lin, X., D. A. Randall, and L. D. Fowler, 2000: Diurnal variability of the hydrologic cycle and radiative fluxes: Comparisons between observations and a GCM. J. Climate, 13, 41594179.

    • Search Google Scholar
    • Export Citation
  • Machado, L. A. T., H. Laurent, N. Dessay, and I. Miranda, 2004: Seasonal and diurnal variability of convection over the Amazonia: A comparison of different vegetation types and large scale forcing. Theor. Appl. Climatol., 78, 6177.

    • Search Google Scholar
    • Export Citation
  • Randall, D. A., Harshvardhan, and D. A. Dazlich, 1991: Diurnal variability of the hydrological cycle in a general circulation model. J. Atmos. Sci., 48, 4062.

    • Search Google Scholar
    • Export Citation
  • Raymond, D. J., 1995: Regulation of moist convection over the west Pacific warm pool. J. Atmos. Sci., 52, 39453959.

  • Sadhuram, Y., T. V. Ramana Murthy, Y. V. B. Sarma, and V. S. N. Murty, 2001: Comments on “On the estimation of overwater Bowen ratio from sea–air temperature difference.” J. Phys. Oceanogr., 31, 19331934.

    • Search Google Scholar
    • Export Citation
  • Schumacher, C., and R. Houze, 2003: Stratiform rain in the tropics as seen by the TRMM precipitation radar. J. Climate, 16, 17391756.

    • Search Google Scholar
    • Export Citation
  • Stevens, B., 2006: Bulk boundary-layer concepts for simplified models of tropical dynamics. Theor. Comput. Fluid Dyn., 20, 279304.

  • Stull, R., 1988: An Introduction to Boundary Layer Meteorology. Springer, 380 pp.

  • Takayabu, Y. N., S. Shige, W.-K. Tao, and N. Hirota, 2010: Shallow and deep latent heating modes over tropical oceans observed with TRMM PR spectral latent heating data. J. Climate, 23, 20302046.

    • Search Google Scholar
    • Export Citation
  • Tian, B., B. J. Soden, and X. Wu, 2004: Diurnal cycle of convection, clouds, and water vapor in the tropical upper troposphere: Satellites versus a general circulation model. J. Geophys. Res. Lett., 109, D10101, doi:10.1029/2003JD004117.

    • Search Google Scholar
    • Export Citation
  • Waite, M. L., and B. Khouider, 2009: Boundary layer dynamics in a simple model for convectively coupled gravity waves. J. Atmos. Sci., 66, 27802795.

    • Search Google Scholar
    • Export Citation
  • Yang, G., and J. Slingo, 2001: The diurnal cycle in the tropics. Mon. Wea. Rev., 129, 784801.

  • Yang, S., and E. A. Smith, 2006: Mechanisms for diurnal variability of global tropical rainfall observed from TRMM. J. Climate, 19, 51905226.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 126 30 3
PDF Downloads 92 24 2