Idealized Modeling of the Atmospheric Boundary Layer Response to SST Forcing in the Western Indian OceanSource: Journal of the Atmospheric Sciences:;2019:;volume 076:;issue 007::page 2023DOI: 10.1175/JAS-D-18-0303.1Publisher: American Meteorological Society
Abstract: AbstractThe atmospheric response to sea surface temperature (SST) variations forced by oceanic downwelling equatorial Rossby waves is investigated using an idealized convection-resolving model. Downwelling equatorial Rossby waves sharpen SST gradients in the western Indian Ocean. Changes in SST cause the atmosphere to hydrostatically adjust, subsequently modulating the low-level wind field. In an idealized cloud model, surface wind speeds, surface moisture fluxes, and low-level precipitable water maximize near regions of strongest SST gradients, not necessarily in regions of warmest SST. Simulations utilizing the steepened SST gradient representative of periods with oceanic downwelling equatorial Rossby waves show enhanced patterns of surface convergence and precipitation that are linked to a strengthened zonally overturning circulation. During these conditions, convection is highly organized, clustering near the maximum SST gradient and ascending branch of the SST-induced overturning circulation. When the SST gradient is reduced, as occurs during periods of weak or absent oceanic equatorial Rossby waves, convection is much less organized and total rainfall is decreased. This demonstrates the previously observed upscale organization of convection and rainfall associated with oceanic downwelling equatorial Rossby waves in the western Indian Ocean. These results suggest that the enhancement of surface fluxes that results from a steepening of the SST gradient is the leading mechanism by which oceanic equatorial Rossby waves prime the atmospheric boundary layer for rapid convective development.
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contributor author | Rydbeck, Adam V. | |
contributor author | Jensen, Tommy G. | |
contributor author | Igel, Matthew R. | |
date accessioned | 2019-10-05T06:51:46Z | |
date available | 2019-10-05T06:51:46Z | |
date copyright | 4/24/2019 12:00:00 AM | |
date issued | 2019 | |
identifier other | JAS-D-18-0303.1.pdf | |
identifier uri | http://yetl.yabesh.ir/yetl1/handle/yetl/4263656 | |
description abstract | AbstractThe atmospheric response to sea surface temperature (SST) variations forced by oceanic downwelling equatorial Rossby waves is investigated using an idealized convection-resolving model. Downwelling equatorial Rossby waves sharpen SST gradients in the western Indian Ocean. Changes in SST cause the atmosphere to hydrostatically adjust, subsequently modulating the low-level wind field. In an idealized cloud model, surface wind speeds, surface moisture fluxes, and low-level precipitable water maximize near regions of strongest SST gradients, not necessarily in regions of warmest SST. Simulations utilizing the steepened SST gradient representative of periods with oceanic downwelling equatorial Rossby waves show enhanced patterns of surface convergence and precipitation that are linked to a strengthened zonally overturning circulation. During these conditions, convection is highly organized, clustering near the maximum SST gradient and ascending branch of the SST-induced overturning circulation. When the SST gradient is reduced, as occurs during periods of weak or absent oceanic equatorial Rossby waves, convection is much less organized and total rainfall is decreased. This demonstrates the previously observed upscale organization of convection and rainfall associated with oceanic downwelling equatorial Rossby waves in the western Indian Ocean. These results suggest that the enhancement of surface fluxes that results from a steepening of the SST gradient is the leading mechanism by which oceanic equatorial Rossby waves prime the atmospheric boundary layer for rapid convective development. | |
publisher | American Meteorological Society | |
title | Idealized Modeling of the Atmospheric Boundary Layer Response to SST Forcing in the Western Indian Ocean | |
type | Journal Paper | |
journal volume | 76 | |
journal issue | 7 | |
journal title | Journal of the Atmospheric Sciences | |
identifier doi | 10.1175/JAS-D-18-0303.1 | |
journal fristpage | 2023 | |
journal lastpage | 2042 | |
tree | Journal of the Atmospheric Sciences:;2019:;volume 076:;issue 007 | |
contenttype | Fulltext |