• Anthes, R. A., 1977: Hurricane model experiments with a cumulus parameterization scheme. Mon. Wea. Rev., 105 , 287300.

  • Arakawa, A., 1969: Parameterization of cumulus convection. Proc. WMO/IUGG Symp. on Numerical Weather Prediction, Tokyo, Japan,. Japan Meteor. Agency IV, 8 , 16.

    • Search Google Scholar
    • Export Citation
  • Arakawa, A., , and W. H. Schubert, 1974: Interaction of a cumulus cloud ensemble with the large-scale environment, Part I. J. Atmos. Sci., 31 , 674701.

    • Search Google Scholar
    • Export Citation
  • Baik, J-J., , M. DeMaria, , and S. Raman, 1990: Tropical cyclone simulations with the Betts convective adjustment scheme. Part I: Model description and control simulation. Mon. Wea. Rev., 118 , 513528.

    • Search Google Scholar
    • Export Citation
  • Betts, A. K., 1975: Parametric interpretation of trade-wind budget studies. J. Atmos. Sci., 32 , 19341945.

  • Betts, A. K., . 1976: The thermodynamic transformation of the tropical subcloud layer by precipitation and downdrafts. J. Atmos. Sci., 33 , 10081020.

    • Search Google Scholar
    • Export Citation
  • Betts, A. K., . 1986: A new convective adjustment scheme. I. Observational and theoretical basis. Quart. J. Roy. Meteor. Soc., 112 , 677691.

    • Search Google Scholar
    • Export Citation
  • DeMaria, M., , and J. D. Pickle, 1988: A simplified system of equations for simulating tropical cyclones. J. Atmos. Sci., 45 , 15421554.

    • Search Google Scholar
    • Export Citation
  • Dengler, K., , and M. J. Reeder, 1997: The effects of convection and baroclinicity on the motion of tropical-cyclone-like vortices. Quart. J. Roy. Meteor. Soc., 123 , 699727.

    • Search Google Scholar
    • Export Citation
  • Emanuel, K. A., 1989: The finite-amplitude nature of tropical cyclogenesis. J. Atmos. Sci., 46 , 34313456.

  • Emanuel, K. A., . 1995: The behavior of a simple hurricane model using a convective scheme based on subcloud-layer entropy equilibrium. J. Atmos. Sci., 52 , 39603968.

    • Search Google Scholar
    • Export Citation
  • Emanuel, K. A., . 1997: Overview of atmospheric convection. The Physics and Parameterization of Moist Atmospheric Convection, R. K. Smith, Ed., Kluwer, 1–28.

    • Search Google Scholar
    • Export Citation
  • Gregory, D., , J-J. Morcrette, , C. Jakob, , A. C. M. Beljaars, , and T. Stockdale, 2000: Revision of convection, radiation, and cloud schemes in the ECMWF Integrated Forecasting System. Quart. J. Roy. Meteor. Soc., 126 , 16851710.

    • Search Google Scholar
    • Export Citation
  • Jordan, C. L., 1957: Mean soundings for the West Indies area. J. Meteor., 15 , 9197.

  • Moncrieff, M. W., 1997: Momentum transport by organized convection. The Physics and Parameterization of Moist Atmospheric Convection, R. K. Smith, Ed., Kluwer, 231–253.

    • Search Google Scholar
    • Export Citation
  • Ooyama, K. V., 1969: Numerical simulation of the life cycle of tropical cyclones. J. Atmos. Sci., 26 , 340.

  • Raymond, D. J., 1995: Regulation of moist convection over the West Pacific warm pool. J. Atmos. Sci., 52 , 39453959.

  • Raymond, D. J., . 1997: Boundary layer quasi-equilibrium (BLQ). The Physics and Parameterization of Moist Atmospheric Convection, R. K. Smith, Ed., Kluwer, 387–397.

    • Search Google Scholar
    • Export Citation
  • Shapiro, L. J., 1992: Hurricane vortex motion and evolution in a three-layer model. J. Atmos. Sci., 49 , 140153.

  • Smith, R. K., , W. Ulrich, , and G. Dietachmayer, 1990: A numerical study of tropical cyclone motion using a barotropic model. Part I: The role of vortex asymmetries. Quart. J. Roy. Meteor. Soc., 116 , 337362.

    • Search Google Scholar
    • Export Citation
  • Wada, M., 1979: Numerical experiments of the tropical cyclone model by use of the Arakawa–Schubert parameterization. J. Meteor. Soc. Japan, 57 , 505530.

    • Search Google Scholar
    • Export Citation
  • Zhu, H., , R. K. Smith, , and W. Ulrich, 2001: A minimal three-dimensional tropical cyclone model. J. Atmos. Sci., 58 , 19241944.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 104 104 85
PDF Downloads 16 16 3

The Importance of Three Physical Processes in a Minimal Three-Dimensional Tropical Cyclone Model

View More View Less
  • 1 Meteorological Institute, University of Munich, Munich, Germany
© Get Permissions Rent on DeepDyve
Restricted access

Abstract

The minimal three-dimensional tropical cyclone model developed by Zhu et al. is used to explore the role of shallow convection, precipitation-cooled downdrafts, and the vertical transport of momentum by deep convection on the dynamics of tropical cyclone intensification. The model is formulated in σ coordinates and has three vertical levels, one characterizing a shallow boundary layer, and the other two representing the upper and lower troposphere, respectively. It has three options for treating cumulus convection on the subgrid scale and a simple scheme for the explicit release of latent heat on the grid scale.

In the model, as in reality, shallow convection transports air with low moist static energy from the lower troposphere to the boundary layer, stabilizing the atmosphere not only to itself, but also to deep convection. Also it moistens and cools the lower troposphere. For realistic parameter values, the stabilization in the vortex core region is the primary effect: it reduces the deep convective mass flux and therefore the rate of heating and drying in the troposphere. This reduced heating, together with the direct cooling of the lower troposphere by shallow convection, diminishes the buoyancy in the vortex core and thereby the vortex intensification rate.

The effects of precipitation-cooled downdrafts depend on the closure scheme chosen for deep convection. In the two closures in which the deep cloud mass flux depends on the degree of convective instability, the downdrafts do not change the total mass flux of air that subsides into the boundary layer, but they carry air with a lower moist static energy into this layer than does subsidence outside downdrafts. As a result they decrease the rate of intensification during the early development stage. Nevertheless, by reducing the deep convective mass flux and the drying effect of compensating subsidence, they enable grid scale saturation, and therefore rapid intensification, to occur earlier than in calculations where they are excluded. In the closure in which the deep cloud mass flux depends on the mass convergence in the boundary layer, downdrafts reduce the gestation period and increase the intensification rate.

Convective momentum transport as represented in the model weakens both the primary and secondary circulations of the vortex. However, it does not significantly reduce the maximum intensity attained after the period of rapid development. The weakening of the secondary circulation impedes vortex development and significantly prolongs the gestation period.

Where possible the results are compared with those found in other studies.

Corresponding author address: Prof. Roger K. Smith, Meteorological Institute, University of Munich, Theresienstr. 37, 80333 Munich, Germany. Email: roger@meteo.physik.uni-muenchen.de

Abstract

The minimal three-dimensional tropical cyclone model developed by Zhu et al. is used to explore the role of shallow convection, precipitation-cooled downdrafts, and the vertical transport of momentum by deep convection on the dynamics of tropical cyclone intensification. The model is formulated in σ coordinates and has three vertical levels, one characterizing a shallow boundary layer, and the other two representing the upper and lower troposphere, respectively. It has three options for treating cumulus convection on the subgrid scale and a simple scheme for the explicit release of latent heat on the grid scale.

In the model, as in reality, shallow convection transports air with low moist static energy from the lower troposphere to the boundary layer, stabilizing the atmosphere not only to itself, but also to deep convection. Also it moistens and cools the lower troposphere. For realistic parameter values, the stabilization in the vortex core region is the primary effect: it reduces the deep convective mass flux and therefore the rate of heating and drying in the troposphere. This reduced heating, together with the direct cooling of the lower troposphere by shallow convection, diminishes the buoyancy in the vortex core and thereby the vortex intensification rate.

The effects of precipitation-cooled downdrafts depend on the closure scheme chosen for deep convection. In the two closures in which the deep cloud mass flux depends on the degree of convective instability, the downdrafts do not change the total mass flux of air that subsides into the boundary layer, but they carry air with a lower moist static energy into this layer than does subsidence outside downdrafts. As a result they decrease the rate of intensification during the early development stage. Nevertheless, by reducing the deep convective mass flux and the drying effect of compensating subsidence, they enable grid scale saturation, and therefore rapid intensification, to occur earlier than in calculations where they are excluded. In the closure in which the deep cloud mass flux depends on the mass convergence in the boundary layer, downdrafts reduce the gestation period and increase the intensification rate.

Convective momentum transport as represented in the model weakens both the primary and secondary circulations of the vortex. However, it does not significantly reduce the maximum intensity attained after the period of rapid development. The weakening of the secondary circulation impedes vortex development and significantly prolongs the gestation period.

Where possible the results are compared with those found in other studies.

Corresponding author address: Prof. Roger K. Smith, Meteorological Institute, University of Munich, Theresienstr. 37, 80333 Munich, Germany. Email: roger@meteo.physik.uni-muenchen.de

Save