Anelastic semigeostrophic flow over a mountain ridge

Peter R. Bannon, Chu Pe-Cheng Chu

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Scale analysis indicates that five nondimensional parameters (R0 2, ε, μ, λ and kλ) characterize the disturbance generated by the steady flow of a uniform wind (U0, V0) incident on a mountain ridge of width a. Here μ = h0/HR is the ratio of the mountain height h0 to the deformation depth HR = fa/N where f is the Coriolis parameter and N is the static buoyancy frequency. The parameters λ = HR/H and kλ are the ratios of HR to the density scale height H and the potential temperature scale height H/k respectively. There are two Rossby numbers; ε = V0/fa, and R0 = U0/fa. If R0 2 ≤ 1, then the mountain-parallel flow is in approximate geostrophic balance and the flow is semigeostrophic. If the flow is anelastic (λ ≃ 1), no direct correspondence between the two approximations was found. However the anelastic effects are qualitatively similar for the two and lead to: i) an increase in the strength of the mountain anticyclone, ii) a reduction in the extent (and possible elimination) of the zone of blocked, cyclonic flow, iii) a permanent turning of the flow proportional to the mass of air displaced by the mountain, and iv) an increase in the ageostrophic cross-mountain flow. The last result implies an earlier breakdown of semigeostrophic theory for anelastic flow over topography. Apart from a strengthening of the cold potential temperature anomaly over the mountain, the presence of a finite potential temperature scale height (ie k nonzero) does not significantly alter the flow solution. -from Authors

Original languageEnglish (US)
Pages (from-to)1020-1029
Number of pages10
JournalJournal of the Atmospheric Sciences
Volume45
Issue number6
DOIs
StatePublished - Jan 1 1988

Fingerprint

mountain
potential temperature
Rossby number
anticyclone
steady flow
temperature anomaly
buoyancy
topography
disturbance
air
parameter

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Cite this

Bannon, Peter R. ; Pe-Cheng Chu, Chu. / Anelastic semigeostrophic flow over a mountain ridge. In: Journal of the Atmospheric Sciences. 1988 ; Vol. 45, No. 6. pp. 1020-1029.
@article{3181a4151df24428880feb0223f93564,
title = "Anelastic semigeostrophic flow over a mountain ridge",
abstract = "Scale analysis indicates that five nondimensional parameters (R0 2, ε, μ, λ and kλ) characterize the disturbance generated by the steady flow of a uniform wind (U0, V0) incident on a mountain ridge of width a. Here μ = h0/HR is the ratio of the mountain height h0 to the deformation depth HR = fa/N where f is the Coriolis parameter and N is the static buoyancy frequency. The parameters λ = HR/H and kλ are the ratios of HR to the density scale height H and the potential temperature scale height H/k respectively. There are two Rossby numbers; ε = V0/fa, and R0 = U0/fa. If R0 2 ≤ 1, then the mountain-parallel flow is in approximate geostrophic balance and the flow is semigeostrophic. If the flow is anelastic (λ ≃ 1), no direct correspondence between the two approximations was found. However the anelastic effects are qualitatively similar for the two and lead to: i) an increase in the strength of the mountain anticyclone, ii) a reduction in the extent (and possible elimination) of the zone of blocked, cyclonic flow, iii) a permanent turning of the flow proportional to the mass of air displaced by the mountain, and iv) an increase in the ageostrophic cross-mountain flow. The last result implies an earlier breakdown of semigeostrophic theory for anelastic flow over topography. Apart from a strengthening of the cold potential temperature anomaly over the mountain, the presence of a finite potential temperature scale height (ie k nonzero) does not significantly alter the flow solution. -from Authors",
author = "Bannon, {Peter R.} and {Pe-Cheng Chu}, Chu",
year = "1988",
month = "1",
day = "1",
doi = "10.1175/1520-0469(1988)045<1020:ASFOAM>2.0.CO;2",
language = "English (US)",
volume = "45",
pages = "1020--1029",
journal = "Journals of the Atmospheric Sciences",
issn = "0022-4928",
publisher = "American Meteorological Society",
number = "6",

}

Anelastic semigeostrophic flow over a mountain ridge. / Bannon, Peter R.; Pe-Cheng Chu, Chu.

In: Journal of the Atmospheric Sciences, Vol. 45, No. 6, 01.01.1988, p. 1020-1029.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Anelastic semigeostrophic flow over a mountain ridge

AU - Bannon, Peter R.

AU - Pe-Cheng Chu, Chu

PY - 1988/1/1

Y1 - 1988/1/1

N2 - Scale analysis indicates that five nondimensional parameters (R0 2, ε, μ, λ and kλ) characterize the disturbance generated by the steady flow of a uniform wind (U0, V0) incident on a mountain ridge of width a. Here μ = h0/HR is the ratio of the mountain height h0 to the deformation depth HR = fa/N where f is the Coriolis parameter and N is the static buoyancy frequency. The parameters λ = HR/H and kλ are the ratios of HR to the density scale height H and the potential temperature scale height H/k respectively. There are two Rossby numbers; ε = V0/fa, and R0 = U0/fa. If R0 2 ≤ 1, then the mountain-parallel flow is in approximate geostrophic balance and the flow is semigeostrophic. If the flow is anelastic (λ ≃ 1), no direct correspondence between the two approximations was found. However the anelastic effects are qualitatively similar for the two and lead to: i) an increase in the strength of the mountain anticyclone, ii) a reduction in the extent (and possible elimination) of the zone of blocked, cyclonic flow, iii) a permanent turning of the flow proportional to the mass of air displaced by the mountain, and iv) an increase in the ageostrophic cross-mountain flow. The last result implies an earlier breakdown of semigeostrophic theory for anelastic flow over topography. Apart from a strengthening of the cold potential temperature anomaly over the mountain, the presence of a finite potential temperature scale height (ie k nonzero) does not significantly alter the flow solution. -from Authors

AB - Scale analysis indicates that five nondimensional parameters (R0 2, ε, μ, λ and kλ) characterize the disturbance generated by the steady flow of a uniform wind (U0, V0) incident on a mountain ridge of width a. Here μ = h0/HR is the ratio of the mountain height h0 to the deformation depth HR = fa/N where f is the Coriolis parameter and N is the static buoyancy frequency. The parameters λ = HR/H and kλ are the ratios of HR to the density scale height H and the potential temperature scale height H/k respectively. There are two Rossby numbers; ε = V0/fa, and R0 = U0/fa. If R0 2 ≤ 1, then the mountain-parallel flow is in approximate geostrophic balance and the flow is semigeostrophic. If the flow is anelastic (λ ≃ 1), no direct correspondence between the two approximations was found. However the anelastic effects are qualitatively similar for the two and lead to: i) an increase in the strength of the mountain anticyclone, ii) a reduction in the extent (and possible elimination) of the zone of blocked, cyclonic flow, iii) a permanent turning of the flow proportional to the mass of air displaced by the mountain, and iv) an increase in the ageostrophic cross-mountain flow. The last result implies an earlier breakdown of semigeostrophic theory for anelastic flow over topography. Apart from a strengthening of the cold potential temperature anomaly over the mountain, the presence of a finite potential temperature scale height (ie k nonzero) does not significantly alter the flow solution. -from Authors

UR - http://www.scopus.com/inward/record.url?scp=0024190186&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0024190186&partnerID=8YFLogxK

U2 - 10.1175/1520-0469(1988)045<1020:ASFOAM>2.0.CO;2

DO - 10.1175/1520-0469(1988)045<1020:ASFOAM>2.0.CO;2

M3 - Article

VL - 45

SP - 1020

EP - 1029

JO - Journals of the Atmospheric Sciences

JF - Journals of the Atmospheric Sciences

SN - 0022-4928

IS - 6

ER -