skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Vertical heat fluxes generated by mesoscale atmospheric flow induced by thermal inhomogeneities in the PBL

Abstract

An analytical evaluation of the vertical heat fluxes associated with the mesoscale flow generated by thermal inhomogeneities in the PBL in the absence of a synoptic wind is presented. Results show that the mesoscale fluxes are of the same order as the diabatic beat fluxes. In the sea-breeze case, results show that in the lower layer of the atmosphere the heat flux is positive over the land and negative over the sea with an overall positive horizontal average. In the free atmosphere above the PBL, the mesoscale vertical heat flux is negative over the land and over the sea. The mesoscale flow contributes to the weakening of the atmospheric stability within a region that extends a Rossby radius distance from the coastline and up to an altitude larger than twice the depth of the convective PBL. The average momentum flux equals zero. Sinusoidally periodic thermal inhomogeneities induce periodic atmospheric cells of the same horizontal scale. The intensity of mesoscale cells increases for increasing values of the wavenumber, maximizes 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. The intensity of the vertical velocity andmore » vertical fluxes is only a weak function of the wavenumber, at large wavenumber. The intensity of the mesoscale heat flux does not decrease substantially at high wavenumbers; however, the transport of cool air over small heated patches of land may cut off the temperature gradient in the atmosphere between the land and water early in the day, thereby reducing the duration of the mesoscale activity. Horizontal diffusion of heat in the convective boundary layer can significantly weaken horizontal temperature gradients for large wavenumbers. Periodic square-wave thermal inhomogeneities are more effective than sinusoidal waves in generating mesoscale cells. When dealing with low resolution models the mesoscale heat fluxes have to be introduced in a parametric form.« less

Authors:
 [1];  [2]
  1. Colorado State Univ., Fort Collins (United States) IFA-CNR, Rome (Italy)
  2. Colorado State Univ., Fort Collins (United States)
Publication Date:
OSTI Identifier:
6534660
Resource Type:
Journal Article
Journal Name:
Journal of the Atmospheric Sciences; (United States)
Additional Journal Information:
Journal Volume: 50:6; Journal ID: ISSN 0022-4928
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; EARTH ATMOSPHERE; HEAT FLUX; EVALUATION; ATMOSPHERIC CIRCULATION; DIFFUSION; METEOROLOGY; RESOLUTION; TEMPERATURE GRADIENTS; WIND; 540110*

Citation Formats

Dalu, G A, and Pielke, R A. Vertical heat fluxes generated by mesoscale atmospheric flow induced by thermal inhomogeneities in the PBL. United States: N. p., 1993. Web. doi:10.1175/1520-0469(1993)050<0919:VHFGBM>2.0.CO;2.
Dalu, G A, & Pielke, R A. Vertical heat fluxes generated by mesoscale atmospheric flow induced by thermal inhomogeneities in the PBL. United States. https://doi.org/10.1175/1520-0469(1993)050<0919:VHFGBM>2.0.CO;2
Dalu, G A, and Pielke, R A. 1993. "Vertical heat fluxes generated by mesoscale atmospheric flow induced by thermal inhomogeneities in the PBL". United States. https://doi.org/10.1175/1520-0469(1993)050<0919:VHFGBM>2.0.CO;2.
@article{osti_6534660,
title = {Vertical heat fluxes generated by mesoscale atmospheric flow induced by thermal inhomogeneities in the PBL},
author = {Dalu, G A and Pielke, R A},
abstractNote = {An analytical evaluation of the vertical heat fluxes associated with the mesoscale flow generated by thermal inhomogeneities in the PBL in the absence of a synoptic wind is presented. Results show that the mesoscale fluxes are of the same order as the diabatic beat fluxes. In the sea-breeze case, results show that in the lower layer of the atmosphere the heat flux is positive over the land and negative over the sea with an overall positive horizontal average. In the free atmosphere above the PBL, the mesoscale vertical heat flux is negative over the land and over the sea. The mesoscale flow contributes to the weakening of the atmospheric stability within a region that extends a Rossby radius distance from the coastline and up to an altitude larger than twice the depth of the convective PBL. The average momentum flux equals zero. Sinusoidally periodic thermal inhomogeneities induce periodic atmospheric cells of the same horizontal scale. The intensity of mesoscale cells increases for increasing values of the wavenumber, maximizes 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. The intensity of the vertical velocity and vertical fluxes is only a weak function of the wavenumber, at large wavenumber. The intensity of the mesoscale heat flux does not decrease substantially at high wavenumbers; however, the transport of cool air over small heated patches of land may cut off the temperature gradient in the atmosphere between the land and water early in the day, thereby reducing the duration of the mesoscale activity. Horizontal diffusion of heat in the convective boundary layer can significantly weaken horizontal temperature gradients for large wavenumbers. Periodic square-wave thermal inhomogeneities are more effective than sinusoidal waves in generating mesoscale cells. When dealing with low resolution models the mesoscale heat fluxes have to be introduced in a parametric form.},
doi = {10.1175/1520-0469(1993)050<0919:VHFGBM>2.0.CO;2},
url = {https://www.osti.gov/biblio/6534660}, journal = {Journal of the Atmospheric Sciences; (United States)},
issn = {0022-4928},
number = ,
volume = 50:6,
place = {United States},
year = {Mon Mar 15 00:00:00 EST 1993},
month = {Mon Mar 15 00:00:00 EST 1993}
}