Accession Number:

ADA244147

Title:

Linear Impact of Thermal Inhomogeneities on Mesoscale Atmospheric Flow with Zero Synoptic Wind

Descriptive Note:

Corporate Author:

COOPERATIVE INST FOR RESEARCH IN THE ATMOSPHERE FORT COLLINS CO

Report Date:

1991-07-15

Pagination or Media Count:

22.0

Abstract:

This paper presents an analytical evaluation of the perturbations to mesoscale atmospheric flows induced by thermal inhomogeneities in the convective boundary layer. The time evolution of these perturbations is studies as a function of the intensity and of the horizontal and vertical scales of the diabatic forcing. The problem is approached using Laplace transform theory for the time behavior and Green function theory for the spatial structure. Results show that the growth of the atmospheric perturbations closely follows the growth of the convective boundary layer the transient being characterized by a number of inertia-gravity oscillations of decreasing intensity. The vertical scale is determined by the depth of the convective boundary layer and the transient being characterized by a number of inertia-gravity oscillations of decreasing intensity. The vertical scale is determined by the depth of the convective boundary layer and the horizontal scale is determined by the local Rossby deformation radius. Sinusoidally periodic thermal forcing induce periodic atmospheric cells of the same horizontal scale. The intensity of mesoscale cells increases for increasing values of the wave number, reaches its maximum value when the wavelength of the forcing is of the order of the local Rossby radius, and then decreases as the wavelength of the forcing decreases. However, because of the destructive interference between mesoscale cells, the intensity of the vertical velocity is only a weak function of the wave numbers, for large wave numbers. Periodic square wave surface thermal inhomogeneities are more effective than sinusoidal waves in generating mesoscale cells, i.e. the intensity of the flow is generally stronger.

Subject Categories:

  • Meteorology

Distribution Statement:

APPROVED FOR PUBLIC RELEASE