On the Influence of Released Latent Heat on Cyclone Development

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  • 1 Meteorological Service of Canada
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Abstract

The influences of release of latent heat on the vertical motion and production of kinetic energy and low- level vorticity in a major winter cyclone over the central United States have been investigated. The vertical velocity was obtained by solving the customary (diagnostic) ω-equation, and the results were compared with values determined by kinematical techniques. It proved necessary to make allowance for horizontal variations of the static stability and release of latent heat in order to obtain satisfactory agreement between the two sets of data.

Numerical solutions, with and without inclusion of released latent heat, were used to obtain ageostrophic wind components and their effect upon the production of kinetic energy and vorticity. The following results emerged: a) the influence of released latent heat was of the same order of magnitude as the effect of dry-adiabatic circulations; b) the amplification of the vertical motion that resulted from released latent heat was accompanied by intensification of the low-level convergence and high-level divergence; c) the ageostrophic winds associated with these fields of convergence and divergence had components toward lower pressure, thus giving positive contributions to the production of kinetic energy both at low and high levels; d) the computed rate of production of low-level vorticity exceeded the observed rate, and evidence suggests that frictional effects may be important.

Abstract

The influences of release of latent heat on the vertical motion and production of kinetic energy and low- level vorticity in a major winter cyclone over the central United States have been investigated. The vertical velocity was obtained by solving the customary (diagnostic) ω-equation, and the results were compared with values determined by kinematical techniques. It proved necessary to make allowance for horizontal variations of the static stability and release of latent heat in order to obtain satisfactory agreement between the two sets of data.

Numerical solutions, with and without inclusion of released latent heat, were used to obtain ageostrophic wind components and their effect upon the production of kinetic energy and vorticity. The following results emerged: a) the influence of released latent heat was of the same order of magnitude as the effect of dry-adiabatic circulations; b) the amplification of the vertical motion that resulted from released latent heat was accompanied by intensification of the low-level convergence and high-level divergence; c) the ageostrophic winds associated with these fields of convergence and divergence had components toward lower pressure, thus giving positive contributions to the production of kinetic energy both at low and high levels; d) the computed rate of production of low-level vorticity exceeded the observed rate, and evidence suggests that frictional effects may be important.

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