Estimating Bolus Velocities from Data—How Large Must They Be?Source: Journal of Physical Oceanography:;2009:;Volume( 039 ):;issue: 001::page 70Author:Killworth, Peter D.
DOI: 10.1175/2008JPO3905.1Publisher: American Meteorological Society
Abstract: This paper examines the representation of eddy fluxes by bolus velocities. In particular, it asks the following: 1) Can an arbitrary eddy flux divergence of density be represented accurately by a nondivergent bolus flux that satisfies the condition of no normal flow at boundaries? 2) If not, how close can such a representation come? 3) If such a representation can exist in some circumstances, what is the size of the smallest bolus velocity that fits the data? The author finds, in agreement with earlier authors, that the answer to the first question is no, although under certain conditions, which include a modification to the eddy flux divergence, a bolus representation becomes possible. One such condition is when the eddy flux divergence is required to balance the time-mean flux divergence. The smallest bolus flow is easily found by solving a thickness-weighted Poisson equation on each density level. This problem is solved for the North Pacific using time-mean data from an eddy-permitting model. The minimum bolus flow is found to be very small at depth but larger than is usually assumed near the surface. The magnitude of this minimum flow is of order one-tenth of the mean flow. Similar but larger results are found for a coarse-resolution model.
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contributor author | Killworth, Peter D. | |
date accessioned | 2017-06-09T16:25:11Z | |
date available | 2017-06-09T16:25:11Z | |
date copyright | 2009/01/01 | |
date issued | 2009 | |
identifier issn | 0022-3670 | |
identifier other | ams-67517.pdf | |
identifier uri | http://onlinelibrary.yabesh.ir/handle/yetl/4208973 | |
description abstract | This paper examines the representation of eddy fluxes by bolus velocities. In particular, it asks the following: 1) Can an arbitrary eddy flux divergence of density be represented accurately by a nondivergent bolus flux that satisfies the condition of no normal flow at boundaries? 2) If not, how close can such a representation come? 3) If such a representation can exist in some circumstances, what is the size of the smallest bolus velocity that fits the data? The author finds, in agreement with earlier authors, that the answer to the first question is no, although under certain conditions, which include a modification to the eddy flux divergence, a bolus representation becomes possible. One such condition is when the eddy flux divergence is required to balance the time-mean flux divergence. The smallest bolus flow is easily found by solving a thickness-weighted Poisson equation on each density level. This problem is solved for the North Pacific using time-mean data from an eddy-permitting model. The minimum bolus flow is found to be very small at depth but larger than is usually assumed near the surface. The magnitude of this minimum flow is of order one-tenth of the mean flow. Similar but larger results are found for a coarse-resolution model. | |
publisher | American Meteorological Society | |
title | Estimating Bolus Velocities from Data—How Large Must They Be? | |
type | Journal Paper | |
journal volume | 39 | |
journal issue | 1 | |
journal title | Journal of Physical Oceanography | |
identifier doi | 10.1175/2008JPO3905.1 | |
journal fristpage | 70 | |
journal lastpage | 88 | |
tree | Journal of Physical Oceanography:;2009:;Volume( 039 ):;issue: 001 | |
contenttype | Fulltext |