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Title: Effective buoyancy at the surface and aloft

Abstract

Here, it is shown here that a wide, buoyant parcel of air at the surface accelerates far less rapidly than it does aloft. In particular, analytical formulae are derived for the effective buoyancy (i.e. the net vertical acceleration due to parcel buoyancy and environmental response) of idealized cylinders of diameter D and height H, located in free space and at the surface. These formulae quantify the decrease of effective buoyancy with increasing aspect ratio D/H, and show that this effect is more pronounced for surface cylinders, especially when D/H > 1. We gain intuition for these results by considering the pressure fields generated by these buoyant parcels, and we test our results with large-eddy simulations. Our formulae can inform parametrizations of the vertical velocity equation for clouds, and also provide a quantitative map of the 'grey zone' in numerical modelling between hydrostatic and non-hydrostatic regimes.

Authors:
 [1];  [2]
  1. Univ. of California, Berkeley, CA (United States). Dept. of Physics; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Climate and Ecosystem Sciences Division
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Climate and Ecosystem Sciences Division; Univ. of California, Berkeley, CA (United States). Dept. of Earth and Planetary Sciences
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1471000
DOE Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Quarterly Journal of the Royal Meteorological Society
Additional Journal Information:
Journal Volume: 142; Journal Issue: 695; Journal ID: ISSN 0035-9009
Publisher:
Royal Meteorological Society
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES

Citation Formats

Jeevanjee, Nadir, and Romps, David M. Effective buoyancy at the surface and aloft. United States: N. p., 2015. Web. doi:10.1002/qj.2683.
Jeevanjee, Nadir, & Romps, David M. Effective buoyancy at the surface and aloft. United States. doi:10.1002/qj.2683.
Jeevanjee, Nadir, and Romps, David M. Mon . "Effective buoyancy at the surface and aloft". United States. doi:10.1002/qj.2683.
@article{osti_1471000,
title = {Effective buoyancy at the surface and aloft},
author = {Jeevanjee, Nadir and Romps, David M.},
abstractNote = {Here, it is shown here that a wide, buoyant parcel of air at the surface accelerates far less rapidly than it does aloft. In particular, analytical formulae are derived for the effective buoyancy (i.e. the net vertical acceleration due to parcel buoyancy and environmental response) of idealized cylinders of diameter D and height H, located in free space and at the surface. These formulae quantify the decrease of effective buoyancy with increasing aspect ratio D/H, and show that this effect is more pronounced for surface cylinders, especially when D/H > 1. We gain intuition for these results by considering the pressure fields generated by these buoyant parcels, and we test our results with large-eddy simulations. Our formulae can inform parametrizations of the vertical velocity equation for clouds, and also provide a quantitative map of the 'grey zone' in numerical modelling between hydrostatic and non-hydrostatic regimes.},
doi = {10.1002/qj.2683},
journal = {Quarterly Journal of the Royal Meteorological Society},
issn = {0035-9009},
number = 695,
volume = 142,
place = {United States},
year = {2015},
month = {11}
}

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