Upward Momentum Transfer in the Marine Boundary LayerSource: Journal of Physical Oceanography:;2001:;Volume( 031 ):;issue: 007::page 1698DOI: 10.1175/1520-0485(2001)031<1698:UMTITM>2.0.CO;2Publisher: American Meteorological Society
Abstract: This paper focuses on the study of momentum flux between ocean and atmosphere in light winds and is based on the data collected during several field campaigns, the Atlantic Stratocumulus Transition Experiment, the Tropical Ocean Global Atmosphere Coupled Ocean?Atmosphere Response Experiment, and the San Clemente Ocean Probing Experiment. Weak wind at sea is frequently accompanied by the presence of fast-traveling ocean swell, which dramatically affects momentum transfer. It is found that the mean momentum flux (uw covariance) decreases monotonically with decreasing wind speed, and reaches zero around a wind speed U ≈ 1.5?2 m s?1, which corresponds to wave age cp/U ≈ 10 for wave/swell conditions of the experiments in this study. Further decrease of the wind speed (i.e., increase of the wave age) leads to a sign reversal of the momentum flux, implying negative drag coefficient. Upward momentum transfer is associated with fast-traveling swell running in the same direction as the wind, and this regime can be treated as swell regime or mature sea state. In the swell regime the surface stress vector is nearly opposite to wind and swell directions, and the wind is roughly aligned in the swell direction. Thus, a weak wind over ocean swell can be frequently associated with upward momentum transfer (i.e., from ocean to atmosphere).
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contributor author | Grachev, A. A. | |
contributor author | Fairall, C. W. | |
date accessioned | 2017-06-09T14:54:35Z | |
date available | 2017-06-09T14:54:35Z | |
date copyright | 2001/07/01 | |
date issued | 2001 | |
identifier issn | 0022-3670 | |
identifier other | ams-29458.pdf | |
identifier uri | http://onlinelibrary.yabesh.ir/handle/yetl/4166687 | |
description abstract | This paper focuses on the study of momentum flux between ocean and atmosphere in light winds and is based on the data collected during several field campaigns, the Atlantic Stratocumulus Transition Experiment, the Tropical Ocean Global Atmosphere Coupled Ocean?Atmosphere Response Experiment, and the San Clemente Ocean Probing Experiment. Weak wind at sea is frequently accompanied by the presence of fast-traveling ocean swell, which dramatically affects momentum transfer. It is found that the mean momentum flux (uw covariance) decreases monotonically with decreasing wind speed, and reaches zero around a wind speed U ≈ 1.5?2 m s?1, which corresponds to wave age cp/U ≈ 10 for wave/swell conditions of the experiments in this study. Further decrease of the wind speed (i.e., increase of the wave age) leads to a sign reversal of the momentum flux, implying negative drag coefficient. Upward momentum transfer is associated with fast-traveling swell running in the same direction as the wind, and this regime can be treated as swell regime or mature sea state. In the swell regime the surface stress vector is nearly opposite to wind and swell directions, and the wind is roughly aligned in the swell direction. Thus, a weak wind over ocean swell can be frequently associated with upward momentum transfer (i.e., from ocean to atmosphere). | |
publisher | American Meteorological Society | |
title | Upward Momentum Transfer in the Marine Boundary Layer | |
type | Journal Paper | |
journal volume | 31 | |
journal issue | 7 | |
journal title | Journal of Physical Oceanography | |
identifier doi | 10.1175/1520-0485(2001)031<1698:UMTITM>2.0.CO;2 | |
journal fristpage | 1698 | |
journal lastpage | 1711 | |
tree | Journal of Physical Oceanography:;2001:;Volume( 031 ):;issue: 007 | |
contenttype | Fulltext |