Future Changes in the Hadley Circulation: The Role of Ocean Heat Transport

2021 ◽  
Vol 48 (4) ◽  
Author(s):  
R. Chemke
Keyword(s):  
Heat Transport ◽  
Hadley Circulation ◽  
Ocean Heat Transport

The Role of the Ocean in the Seasonal Cycle of the Hadley Circulation

2006 ◽  
Vol 63 (12) ◽  
pp. 3351-3365 ◽  
Author(s):  
Amy C. Clement
Keyword(s):  
Heat Transport ◽  
Seasonal Cycle ◽  
Climate Model ◽  
Hadley Circulation ◽  
Ocean Heat Transport ◽  
Complete Understanding ◽  
Atmospheric Processes ◽  
Summer Hemisphere ◽  
Hadley Cells

The influence of ocean heat transport on the seasonal cycle of the Hadley circulation is investigated using idealized experiments with a climate model. It is found that ocean heat transport plays a fundamental role in setting the structure and intensity of the seasonal Hadley cells. The ocean’s influence can be understood primarily via annual mean considerations. By cooling the equatorial regions and warming the subtropics in a year-round sense, the ocean heat transport allows for regions of SST maxima to occur off the equator in the summer hemisphere. This leads to large meridional excursions of convection over the ocean and a seasonal Hadley circulation that is strongly asymmetric about the equator. The broadening of the latitudinal extent of the SST maximum and the convecting regions by the ocean heat transport also weakens the annual mean Hadley circulation in a manner that is consistent with simpler models. The results are discussed in the context of prior studies of the controls on the strength and structure of the Hadley circulation. It is suggested that a complete understanding of the seasonal Hadley circulation must include both oceanic and atmospheric processes and their interactions.

Past climate and the role of ocean heat transport: Model simulations for the Cretaceous

1993 ◽  
Vol 8 (6) ◽  
pp. 785-798 ◽  
Author(s):  
Eric J. Barron ◽  
William H. Peterson ◽  
David Pollard ◽  
Starley Thompson
Keyword(s):  
Heat Transport ◽  
Transport Model ◽  
Ocean Heat Transport ◽  
Past Climate ◽  
Model Simulations

scholarly journals Response of the Hadley Circulation to Climate Change in an Aquaplanet GCM Coupled to a Simple Representation of Ocean Heat Transport

2011 ◽  
Vol 68 (4) ◽  
pp. 769-783 ◽  
Author(s):  
Xavier J. Levine ◽  
Tapio Schneider
Keyword(s):  
Heat Transport ◽  
General Circulation ◽  
Climate Models ◽  
Circulation Model ◽  
Hadley Circulation ◽  
Dynamical Regime ◽  
Ocean Heat Transport ◽  
Simple Representation ◽  
Wide Range ◽  
Momentum Fluxes

Abstract It is unclear how the width and strength of the Hadley circulation are controlled and how they respond to climate changes. Simulations of global warming scenarios with comprehensive climate models suggest the Hadley circulation may widen and weaken as the climate warms. But these changes are not quantitatively consistent among models, and how they come about is not understood. Here, a wide range of climates is simulated with an idealized moist general circulation model (GCM) coupled to a simple representation of ocean heat transport, in order to place past and possible future changes in the Hadley circulation into a broader context and to investigate the mechanisms responsible for them. By comparison of simulations with and without ocean heat transport, it is shown that it is essential to take low-latitude ocean heat transport and its coupling to wind stress into account to obtain Hadley circulations in a dynamical regime resembling Earth’s, particularly in climates resembling present-day Earth’s and colder. As the optical thickness of an idealized longwave absorber in the simulations is increased and the climate warms, the Hadley circulation strengthens in colder climates and weakens in warmer climates; it has maximum strength in a climate close to present-day Earth’s. In climates resembling present-day Earth’s and colder, the Hadley circulation strength is largely controlled by the divergence of angular momentum fluxes associated with eddies of midlatitude origin; the latter scale with the mean available potential energy in midlatitudes. The importance of these eddy momentum fluxes for the Hadley circulation strength gradually diminishes as the climate warms. The Hadley circulation generally widens as the climate warms, but at a modest rate that depends sensitively on how it is determined.

scholarly journals The Importance of Ocean Dynamical Feedback for Understanding the Impact of Mid–High-Latitude Warming on Tropical Precipitation Change

2018 ◽  
Vol 31 (6) ◽  
pp. 2417-2434 ◽  
Author(s):  
Masakazu Yoshimori ◽  
Ayako Abe-Ouchi ◽  
Hiroaki Tatebe ◽  
Toru Nozawa ◽  
Akira Oka
Keyword(s):  
Heat Transport ◽  
General Circulation ◽  
Circulation Model ◽  
Hadley Circulation ◽  
Precipitation Change ◽  
Meridional Overturning Circulation ◽  
Climate Projections ◽  
Ocean Heat Transport ◽  
Tropical Precipitation ◽  
The Impact

It has been shown that asymmetric warming between the Northern and Southern Hemisphere extratropics induces a meridional displacement of tropical precipitation. This shift is believed to be due to the extra energy transported from the differentially heated hemisphere through changes in the Hadley circulation. Generally, the column-integrated energy flux in the mean meridional overturning circulation follows the direction of the upper, relatively dry branch, and tropical precipitation tends to be intensified in the hemisphere with greater warming. This framework was originally applied to simulations that did not include ocean dynamical feedback, but was recently extended to take the ocean heat transport change into account. In the current study, an atmosphere–ocean general circulation model applied with a regional nudging technique is used to investigate the impact of extratropical warming on tropical precipitation change under realistic future climate projections. It is shown that warming at latitudes poleward of 40° causes the northward displacement of tropical precipitation from October to January. Warming at latitudes poleward of 60° alone has a much smaller effect. This change in the tropical precipitation is largely explained by the atmospheric moisture transport caused by changes in the atmospheric circulation. The larger change in ocean heat transport near the equator, relative to the atmosphere, is consistent with the extended energy framework. The current study provides a complementary dynamical framework that highlights the importance of midlatitude atmospheric eddies and equatorial ocean upwelling, where the atmospheric eddy feedback modifies the Hadley circulation resulting in the northward migration of precipitation and the ocean dynamical feedback damps the northward migration from the equator.

The role of ocean heat transport in climatic change

1988 ◽  
Vol 24 (6) ◽  
pp. 429-445 ◽  
Author(s):  
Curt Covey ◽  
Eric Barron
Keyword(s):  
Climatic Change ◽  
Heat Transport ◽  
Ocean Heat Transport

scholarly journals Convection Parameterization, Tropical Pacific Double ITCZ, and Upper-Ocean Biases in the NCAR CCSM3. Part II: Coupled Feedback and the Role of Ocean Heat Transport

2010 ◽  
Vol 23 (3) ◽  
pp. 800-812 ◽  
Author(s):  
Guang J. Zhang ◽  
Xiaoliang Song
Keyword(s):  
Surface Energy ◽  
Heat Transport ◽  
Energy Flux ◽  
Ocean Model ◽  
Tropical Pacific ◽  
Ocean Heat Transport ◽  
Surface Energy Flux ◽  
Double Itcz ◽  
Slab Ocean

Abstract This study investigates the coupled atmosphere–ocean feedback and the role of ocean dynamic heat transport in the formation of double ITCZ over the tropical Pacific in the NCAR Community Climate System Model, version 3 (CCSM3) and its alleviation when a revised Zhang–McFarlane (ZM) convection scheme is used. A hierarchy of coupling strategy is employed for this purpose. A slab ocean model is coupled with the atmospheric component of the Community Atmosphere Model, version 3 (CAM3) to investigate the local feedback between the atmosphere and the ocean. It is shown that the net surface energy flux differences in the southern ITCZ region between the revised and original ZM scheme seen in the stand-alone CAM3 simulations can cool the SST by up to 1.5°C. However, the simulated SST distribution is very sensitive to the prescribed ocean heat transport required in the slab ocean model. To understand the role of ocean heat transport, the fully coupled CCSM3 model is used. The analysis of CCSM3 simulations shows that the altered ocean dynamic heat transport when the revised ZM scheme is used is largely responsible for the reduction of SST bias in the southern ITCZ region, although surface energy flux also helps to cool the SST in the first few months of the year in seasonal variation. The results, together with those from Part I, suggest that the unrealistic simulation of convection over the southern ITCZ region in the standard CCSM3 leads to the double-ITCZ bias through complex coupled interactions between atmospheric convection, surface winds, latent heat flux, cloud radiative forcing, SST, and upper-ocean circulations. The mitigation of the double-ITCZ bias using the revised ZM scheme is achieved by altering this chain of interactions.

scholarly journals Modulation of Monsoon Circulations by Cross-Equatorial Ocean Heat Transport

2019 ◽  
Vol 32 (12) ◽  
pp. 3471-3485 ◽  
Author(s):  
Nicholas J. Lutsko ◽  
John Marshall ◽  
Brian Green
Keyword(s):  
Heat Transport ◽  
Vertical Wind Shear ◽  
Atmospheric Model ◽  
Mean Value ◽  
Meridional Overturning Circulation ◽  
Ocean Heat Transport ◽  
Meridional Overturning ◽  
Static Energy ◽  
Monsoon Winds

Abstract Motivated by observations of southward ocean heat transport (OHT) in the northern Indian Ocean during summer, the role of the ocean in modulating monsoon circulations is explored by coupling an atmospheric model to a slab ocean with an interactive representation of OHT and an idealized subtropical continent. Southward OHT by the cross-equatorial cells is caused by Ekman flow driven by southwesterly monsoon winds in the summer months, cooling sea surface temperatures (SSTs) south of the continent. This increases the reversed meridional surface gradient of moist static energy, shifting the precipitation maximum over the land and strengthening the monsoonal circulation, in the sense of enhancing the vertical wind shear. However, the atmosphere’s cross-equatorial meridional overturning circulation is also weakened by the presence of southward OHT, as the atmosphere is required to transport less energy across the equator. The sensitivity of these effects to varying the strength of the OHT, fixing the OHT at its annual-mean value, and to removing the land is explored. Comparisons with more realistic models suggest that the idealized model used in this study produces a reasonable representation of the effect of OHT on SSTs equatorward of subtropical continents, and hence can be used to study the role of OHT in shaping monsoon circulations on Earth.

Why Tropical Sea Surface Temperature is Insensitive to Ocean Heat Transport Changes

2013 ◽  
Vol 26 (18) ◽  
pp. 6742-6749 ◽  
Author(s):  
Daniel D. B. Koll ◽  
Dorian S. Abbot
Keyword(s):  
Heat Transport ◽  
Climate Models ◽  
Global Climate ◽  
Hadley Circulation ◽  
Global Climate Models ◽  
Sea Surface ◽  
Ocean Heat Transport ◽  
Additional Degree ◽  
Tropical Sea ◽  
Do So

AbstractPrevious studies have shown that increases in poleward ocean heat transport (OHT) do not strongly affect tropical SST. The goal of this paper is to explain this observation. To do so, the authors force two atmospheric global climate models (GCMs) in aquaplanet configuration with a variety of prescribed OHTs. It is found that increased OHT weakens the Hadley circulation, which decreases equatorial cloud cover and shortwave reflection, as well as reduces surface winds and evaporation, which both limit changes in tropical SST. The authors also modify one of the GCMs by alternatively setting the radiative effect of clouds to zero and disabling wind-driven evaporation changes to show that the cloud feedback is more important than the wind–evaporation feedback for maintaining constant equatorial SST as OHT changes. This work highlights the fact that OHT can reduce the meridional SST gradient without affecting tropical SST and could therefore serve as an additional degree of freedom for explaining past warm climates.

Quantifying the role of geographic change in Cenozoic ocean heat transport using uncoupled atmosphere and ocean models

2000 ◽  
Vol 161 (3-4) ◽  
pp. 295-310 ◽  
Author(s):  
Karen L. Bice ◽  
Christopher R. Scotese ◽  
Dan Seidov ◽  
Eric J. Barron
Keyword(s):  
Heat Transport ◽  
Ocean Heat Transport ◽  
Ocean Models
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