scholarly journals Global meridional eddy heat transport inferred from Argo and altimetry observations

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Bowen Sun ◽  
Chuanyu Liu ◽  
Fan Wang
2017 ◽  
Vol 47 (6) ◽  
pp. 1281-1289 ◽  
Author(s):  
A. M. Treguier ◽  
C. Lique ◽  
J. Deshayes ◽  
J. M. Molines

AbstractCorrelations between temperature and velocity fluctuations are a significant contribution to the North Atlantic meridional heat transport, especially at the northern boundary of the subtropical gyre. In satellite observations and in a numerical model at ⅞° resolution, a localized pattern of positive eddy heat flux is found northwest of the Gulf Stream, downstream of its separation at Cape Hatteras. It is confined to the upper 500 m. A simple kinematic model of a meandering jet can explain the surface eddy flux, taking into account a spatial shift between the maximum velocity of the jet and the maximum cross-jet temperature gradient. In the Gulf Stream such a spatial shift results from the nonlinear temperature profile and the vertical tilting of the velocity profile with depth. The numerical model suggests that the meandering of the Gulf Stream could account, at least in part, for the large eddy heat transport (of order 0.3 PW) near 36°N in the North Atlantic and for its compensation by the mean flow.


2014 ◽  
Vol 32 (4) ◽  
pp. 431-442 ◽  
Author(s):  
M. N. Vlasov ◽  
M. C. Kelley

Abstract. The turbopause region is characterized by transition from the mean molecular mass (constant with altitude) to the mean mass (dependent on altitude). The former is provided by eddy turbulence, and the latter is induced by molecular diffusion. Competition between these processes provides the transition from the homosphere to the heterosphere. The turbopause altitude can be defined by equalizing the eddy and molecular diffusion coefficients and can be located in the upper mesosphere or the lower thermosphere. The height distributions of chemical inert gases very clearly demonstrate the transition from turbulent mixing to the diffusive separation of these gases. Using the height distributions of the chemical inert constituents He, Ar, and N2 given by the MSIS-E-90 model and the continuity equations, the height distribution of the eddy diffusion coefficient in the turbopause region can be inferred. The eddy diffusion coefficient always strongly reduces in the turbopause region. According to our results, eddy turbulence above its peak always cools the atmosphere. However, the cooling rates calculated with the eddy heat transport coefficient equaled to the eddy diffusion coefficient were found to be much larger than the cooling rates corresponding to the neutral temperatures given by the MSIS-E-90 model. The same results were obtained for the eddy diffusion coefficients inferred from different experimental data. The main cause of this large cooling is the very steep negative gradient of the eddy heat transport coefficient, which is equal to the eddy diffusion coefficient if uniform turbulence takes place in the turbopause region. Analysis of wind shear shows that localized turbulence can develop in the turbopause region. In this case, eddy heat transport is not so effective and the strong discrepancy between cooling induced by eddy turbulence and cooling corresponding to the temperature given by the MSIS-E-90 model can be removed.


2007 ◽  
Vol 64 (2) ◽  
pp. 608-620 ◽  
Author(s):  
Seok-Woo Son ◽  
Sukyoung Lee ◽  
Steven B. Feldstein

Abstract The physical processes that drive the fluctuations of the extratropical tropopause height are examined with the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis data. A composite zonal-mean heat budget analysis for the Northern Hemisphere winter shows that fluctuations in the extratropical tropopause height result not only from a warming of the troposphere but also from an even stronger cooling of the lower stratosphere. While the tropospheric warming is caused by a poleward eddy heat transport associated with baroclinic eddies, the stratospheric cooling is driven primarily by planetary-scale waves. The results from analyses of synoptic- and planetary-scale eddy kinetic energy and Eliassen–Palm fluxes are consistent with the planetary waves first gaining their energy within the troposphere, and then propagating vertically into the stratosphere. For the Southern Hemisphere, while lower-stratospheric temperature anomalies still play an important role for the fluctuations in the tropopause height, the temperature anomalies are accounted for primarily by a poleward eddy heat transport associated with synoptic-scale eddies, and by diabatic heating. These results indicate that, although the height of the extratropical tropopause is modulated by baroclinic eddies, which is consistent with existing theories, the amount of the modulation is highly influenced by stratospheric processes.


2013 ◽  
Vol 70 (10) ◽  
pp. 3288-3301 ◽  
Author(s):  
Hyo-Seok Park ◽  
Shang-Ping Xie ◽  
Seok-Woo Son

Abstract The orographic effect of the Tibetan Plateau on atmospheric poleward heat transport is investigated using an atmospheric general circulation model. The linear interference between the Tibetan Plateau–induced winds and the eddy temperature field associated with the land–sea thermal contrast is a key factor for enhancing the poleward stationary eddy heat transport. Specifically, Tibetan Plateau–induced stationary waves produce northerlies over the cold eastern Eurasian continent, leading to a poleward heat transport. In another hot spot of stationary eddy heat transport over the eastern North Pacific, Tibetan Plateau–induced stationary waves transport relatively warm marine air northward. In an experiment where the Tibetan Plateau is removed, the poleward heat transport is mostly accomplished by transient eddies, similar to the Southern Hemisphere. In the presence of the Tibetan Plateau, the enhanced stationary eddy heat transport is offset by a comparable reduction in transient eddy heat transport. This compensation between stationary and transient eddy heat transport is seen in observed interannual variability. Both the model and observations indicate that an enhanced poleward heat transport by stationary waves weakens transient eddies by decreasing the meridional temperature gradient and the associated westerlies in midlatitudes.


2021 ◽  
Vol 10 (1) ◽  
pp. 33
Author(s):  
Dmitry Stepanov ◽  
Vladimir Fomin ◽  
Anatoly Gusev ◽  
Nikolay Diansky

The driving mechanisms of mesoscale processes and associated heat transport in the Japan/East Sea (JES) from 1990 to 2010 were examined using eddy-resolving ocean model simulations. The simulated circulation showed correctly reproduced JES major basin-scale currents and mesoscale dynamics features. We show that mesoscale eddies can deepen isotherms/isohalines up to several hundred meters and transport warm and low salinity waters along the western and eastern JES boundaries. The analysis of eddy kinetic energy (EKE) showed that the mesoscale dynamics reaches a maximum intensity in the upper 300 m layer. Throughout the year, the EKE maximum is observed in the southeastern JES, and a pronounced seasonal variability is observed in the southwestern and northwestern JES. The comparison of the EKE budget components confirmed that various mechanisms can be responsible for the generation of mesoscale dynamics during the year. From winter to spring, the baroclinic instability of basin-scale currents is the leading mechanism of the JES mesoscale dynamics’ generation. In summer, the leading role in the generation of the mesoscale dynamics is played by the barotropic instability of basin-scale currents, which are responsible for the emergence of mesoscale eddies, and in autumn, the leading role is played by instabilities and the eddy wind work. We show that the meridional heat transport (MHT) is mainly polewards. Furthermore, we reveal two paths of eddy heat transport across the Subpolar Front: along the western and eastern (along 138∘ E) JES boundaries. Near the Tsugaru Strait, we describe the detected intensive westward eddy heat transport reaching its maximum in the first half of the year and decreasing to the minimum by summer.


2014 ◽  
Vol 33 (1) ◽  
pp. 42-47 ◽  
Author(s):  
Zhiwei Zhang ◽  
Yisen Zhong ◽  
Jiwei Tian ◽  
Qingxuan Yang ◽  
Wei Zhao

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