Eddy Activity Response to Global Warming–Like Temperature Changes

2020 ◽  
Vol 33 (4) ◽  
pp. 1381-1404 ◽  
Author(s):  
Janni Yuval ◽  
Yohai Kaspi
Keyword(s):  
Global Warming ◽  
Temperature Gradient ◽  
Static Stability ◽  
The Arctic ◽  
Lower Latitude ◽  
Arctic Amplification ◽  
Meridional Temperature Gradient ◽  
Eddy Activity ◽  
Eddy Heat Flux ◽  
Upper Level

AbstractGlobal warming projections show an anomalous temperature increase both at the Arctic surface and at lower latitudes in the upper troposphere. The Arctic amplification decreases the meridional temperature gradient, and simultaneously decreases static stability. These changes in the meridional temperature gradient and in the static stability have opposing effects on baroclinicity. The temperature increase at the upper tropospheric lower latitudes tends to increase the meridional temperature gradient and simultaneously increase static stability, which have opposing effects on baroclinicity as well. In this study, a dry idealized general circulation model with a modified Newtonian cooling scheme, which allows any chosen zonally symmetric temperature distribution to be simulated, is used to study the effect of Arctic amplification and lower-latitude upper-level warming on eddy activity. Due to the interplay between the static stability and meridional temperature gradient on atmospheric baroclinicity changes, and their opposing effect on atmospheric baroclinicity, it is found that both the Arctic amplification and lower-latitude upper-level warming could potentially lead to both decreases and increases in eddy activity, depending on the exact prescribed temperature modifications. Therefore, to understand the effect of global warming–like temperature trends on eddy activity, the zonally symmetric global warming temperature projections from state-of-the-art models are simulated. It is found that the eddy kinetic energy changes are dominated by the lower-latitude upper-level warming, which tends to weaken the eddy kinetic energy due to increased static stability. On the other hand, the eddy heat flux changes are dominated by the Arctic amplification, which tends to weaken the eddy heat flux at the lower levels.

scholarly journals Equilibration of an Atmosphere by Adiabatic Eddy Fluxes

2013 ◽  
Vol 70 (9) ◽  
pp. 2948-2962 ◽  
Author(s):  
Malte Jansen ◽  
Raffaele Ferrari
Keyword(s):  
Temperature Gradient ◽  
Radiative Forcing ◽  
Static Stability ◽  
Meridional Temperature Gradient ◽  
Major Question ◽  
Full Characterization ◽  
Eddy Heat Flux ◽  
Eddy Fluxes ◽  
Mean State

Abstract A major question for climate studies is to quantify the role of turbulent eddy fluxes in maintaining the observed atmospheric mean state. Both the equator-to-pole temperature gradient and the static stability of the extratropical atmosphere are set by a balance between these eddy fluxes and the radiative forcing. Much attention has been paid to the adjustment of the isentropic slope, which relates the static stability and the meridional temperature gradient. It is often argued that the extratropical atmosphere always equilibrates such that isentropes leaving the surface in the subtropics reach the tropopause near the poles. However, recent work challenged this argument. This paper revisits scaling arguments for the equilibrated mean state of a dry atmosphere, which results from a balance between the radiative forcing and the along-isentropic eddy heat flux. These arguments predict weak sensitivity of the isentropic slope to changes in the radiative forcing, consistent with previous results. Large changes can, however, be achieved if other external parameters, such as the size and rotation rate of the planet, are varied. The arguments are also extended to predict both the meridional temperature gradient and the static stability independently. This allows a full characterization of the atmospheric mean state as a function of external parameters.

scholarly journals Interdecadal changes in synoptic transient eddy activity over the Northeast Pacific and their role in tropospheric Arctic amplification

2021 ◽  
Author(s):  
Dong Xiao ◽  
Hongli Ren
Keyword(s):  
Heat Flux ◽  
North Pacific ◽  
The Arctic ◽  
Transient Eddy ◽  
Arctic Amplification ◽  
Eddy Activity ◽  
The North ◽  
Eddy Heat Flux ◽  
Subtropical Jet ◽  
The North Pacific

AbstractArctic amplification refers to the greater surface warming of the Arctic than of other regions during recent decades. A similar phenomenon occurs in the troposphere and is termed “tropospheric Arctic amplification” (TAA). The poleward eddy heat flux and eddy moisture flux are critical to Arctic warming. In this study, we investigate the synoptic transient eddy activity over the North Pacific associated with TAA and its relationship with the subtropical jet stream, and propose the following mechanism. A poleward shift of the subtropical jet axis results in anomalies of the meridional gradient of zonal wind over the North Pacific, which drive a meridional dipole pattern of synoptic transient wave intensity over the North Pacific, referred to as the North Pacific Synoptic Transient wave intensity Dipole (NPSTD). The NPSTD index underwent an interdecadal shift in the late 1990s accompanying that of the subtropical jet stream. During the positive phase of the NPSTD index, synoptic eddy heat flux transports more heat to the Arctic Circle, and the eddy heat flux diverges, increasing Arctic temperature. This mechanism highlights the need to consider synoptic transient eddy activity over the North Pacific as the link between the mean state of the North Pacific subtropical upper jet and TAA.

scholarly journals Influence of Northern Hemispheric Winter Warming on the Pacific Storm Track

2021 ◽  
Author(s):  
Hyung-Ju Park ◽  
Kwang-Yul Kim
Keyword(s):  
Heat Flux ◽  
Global Warming ◽  
Energy Conversion ◽  
Storm Track ◽  
The Arctic ◽  
Late Winter ◽  
Turbulent Heat ◽  
Early Winter ◽  
Eddy Heat Flux ◽  
Northern Hemispheric

AbstractEffect of global warming on the sub-seasonal variability of the Northern Hemispheric winter (NDJFM) Pacific storm-track (PST) activity has been investigated. Previous studies showed that the winter-averaged PST has shifted northward and intensified, which was explained in terms of energy exchange with the mean field. Effect of global warming exhibits spatio-temporal heterogeneity with predominance over the Arctic region and in the winter season. Therefore, seasonal averaging may hide important features on sub-seasonal scales. In this study, distinct sub-seasonal response in storm track activities to winter Northern Hemispheric warming is analyzed applying cyclostationary empirical orthogonal function analysis to ERA5 data. The key findings are as follows. Change in the PST is not uniform throughout the winter; the PST shifts northward in early winter (NDJ) and intensifies in late winter (FM). In early winter, the combined effect of weakened baroclinic process to the south of the climatological PST and weakened barotropic damping to the north is responsible for the northward shift. In late winter, both processes contribute to the amplification of the PST. Further, change in baroclinic energy conversion is quantitatively dominated by eddy heat flux, whereas axial tilting of eddies is primarily responsible for change in barotropic energy conversion. A close relationship between anomalous eddy heat flux and anomalous boundary heating, which is largely determined by surface turbulent heat flux, is also demonstrated.

scholarly journals Influence of the SST Rise on Baroclinic Instability Wave Activity under an Aquaplanet Condition

2009 ◽  
Vol 66 (8) ◽  
pp. 2272-2287 ◽  
Author(s):  
Chihiro Kodama ◽  
Toshiki Iwasaki
Keyword(s):  
Global Warming ◽  
Temperature Gradient ◽  
Wave Energy ◽  
General Circulation ◽  
Baroclinic Instability ◽  
Lower Troposphere ◽  
Wave Activity ◽  
Instability Wave ◽  
Meridional Temperature Gradient ◽  
Poleward Shift

Abstract The influence of the sea surface temperature (SST) rise on extratropical baroclinic instability wave activity is investigated using an aquaplanet general circulation model (GCM). Two types of runs were performed: the High+3 run, in which the SST is increased by 3 K only at high latitudes, and the All+3 run, in which the SST is increased uniformly by 3 K all over the globe. These SST rises were intended to reproduce essential changes of the surface air temperature due to global warming. Wave activity changes are analyzed and discussed from the viewpoint of the energetics. In the High+3 run, midlatitude meridional temperature gradient is decreased in the lower troposphere and the wave energy is suppressed in the extratropics. In the All+3 run, although the large tropical latent heat release greatly enhances the midlatitude meridional temperature gradient in the upper troposphere, global mean wave energy does not change significantly. These results suggest that the low-level baroclinicity is much more important for baroclinic instability wave activity than upper-level baroclinicity. A poleward shift of wave energy, seen in global warming simulations, is evident in the All+3 run. Wave energy generation analysis suggests that the poleward shift of wave activity may be caused by the enhanced and poleward-shifted baroclinicity in the higher latitudes and the increased static stability in the lower latitudes. Poleward expansion of the high-baroclinicity region is still an open question.

Long-term variability of Atlantic water temperature in the Svalbard fjords in conditions of past and recent global warming

2015 ◽  
Vol 5 (2) ◽  
pp. 134-142 ◽  
Author(s):  
Daniil I. Tislenko ◽  
Boris V. Ivanov
Keyword(s):  
Global Warming ◽  
Surface Air Temperature ◽  
Atlantic Water ◽  
The Arctic ◽  
Observation Data ◽  
Polar Regions ◽  
Arctic Amplification ◽  
The West ◽  
West Spitsbergen

Within last decades, the climate of our planet has underwent remarkable changes. The most notable are those called "Arctic amplification." is the changes comprise a decrease in the area of ​​multi-years ice in 2007 and 2012 in polar regions of the Northern hemisphere, accompanied by the temperature rise of intermediate Atlantic waters, increasing surface temperature. In this paper, an analysis of long-term variability of temperature transformed Atlantic waters (TAW) in the fjords of the West-Spitsbergen island (Isfjorden, Grnfjorden, Hornsund and Kongsfjorden) in the first period (1920–1940) and modern (1990–2009) warming in the Arctic is reported. It is shown that the instrumental observation data corresponds to the periods of rise in temperature in the layer of the TAW and surface air temperature (SAT) for the area of ​​the Svalbard.

scholarly journals Expansion of the Hadley Cell under Global Warming: Winter versus Summer

2012 ◽  
Vol 25 (24) ◽  
pp. 8387-8393 ◽  
Author(s):  
Sarah M. Kang ◽  
Jian Lu
Keyword(s):  
Global Warming ◽  
Outer Boundary ◽  
Coupled Model ◽  
Static Stability ◽  
Hadley Cell ◽  
Scaling Analysis ◽  
Zonal Winds ◽  
Scaling Relationship ◽  
Intercomparison Project ◽  
Upper Level

Abstract A scaling relationship is introduced to explain the seasonality in the outer boundary of the Hadley cell in both climatology and trend in the simulations of phase 3 of the Coupled Model Intercomparison Project (CMIP3). In the climatological state, the summer cell reaches higher latitudes than the winter cell since the Hadley cell in summer deviates more from the angular momentum conserving state, resulting in weaker upper-level zonal winds, which enables the Hadley cell to extend farther poleward before becoming baroclinically unstable. The Hadley cell can also reach farther poleward as the ITCZ gets farther away from the equator; hence, the Hadley cell extends farther poleward in solstices than in equinoxes. In terms of trend, a robust poleward expansion of the Hadley cell is diagnosed in all seasons with global warming. The scaling analysis indicates this is mostly due to an increase in the subtropical static stability, which pushes poleward the baroclinically unstable zone and hence the poleward edge of the Hadley cell. The relation between the trends in the Hadley cell edge and the ITCZ is also discussed.

Role of the Arctic Sea Ice melt on the lower latitude Climate

2020 ◽  
Author(s):  
Varunesh Chandra ◽  
Sandeep Sukumaran
Keyword(s):  
Global Warming ◽  
Sea Ice ◽  
Wave Train ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Lower Latitude ◽  
Sea Ice Concentration ◽  
Ice Melt ◽  
Arctic Sea ◽  
Ice Concentration

<p>The melting of polar ice caps and sea ice are of immediate concern in the context of global warming. The observations suggest that the thickness, as well as the areal extent of the Arctic sea ice, have been declining in the last three decades, in large part due to manmade global warming. The effect of faster sea ice melt on lower latitude climate is not well understood as compared to that of mid and high latitudes. It is reported that the mid-Pacific trough (MPT) can be influenced by a stationary wave train triggered in response to a melt of sea ice over the Bering strait (Deng et al., 2018, J. Clim).   The MPT is known to influence Pacific tropical cyclone (TC) activity.</p><p>         Here, we investigate the effect of the summer sea ice variability over the Arctic on Pacific TC activity. We have seen in the higher melting Sea Ice years showing the strong wave train toward the lower latitude over the northern pacific in comparison to the lower melting years and also affecting the pacific TCs. The summer Arctic sea ice concentration is regressed on TC track density and accumulated cyclone energy (ACE). Both track density and ACE show an increase with increased sea ice concentration. The wind shear over the tropical Pacific is found to have an opposite relation with the Arctic sea ice concentration that led to a more favorable environment for the TC development when the sea ice concentration is high.</p><p><strong>KEYWORDS: </strong>Climate Change; Tropical Cylone;</p>

Surface Arctic Amplification Factors in CMIP5 Models: Land and Oceanic Surfaces and Seasonality

2016 ◽  
Vol 29 (9) ◽  
pp. 3297-3316 ◽  
Author(s):  
Alexandre Laîné ◽  
Masakazu Yoshimori ◽  
Ayako Abe-Ouchi
Keyword(s):  
Global Warming ◽  
Arctic Ocean ◽  
Kernel Method ◽  
The Arctic ◽  
Cmip5 Models ◽  
Primary Role ◽  
Arctic Amplification ◽  
Surface Warming ◽  
The Arctic Ocean ◽  
The Tropics

Abstract Arctic amplification (AA) is a major characteristic of observed global warming, yet the different mechanisms responsible for it and their quantification are still under investigation. In this study, the roles of different factors contributing to local surface warming are quantified using the radiative kernel method applied at the surface after 100 years of global warming under a representative concentration pathway 4.5 (RCP4.5) scenario simulated by 32 climate models from phase 5 of the Coupled Model Intercomparison Project. The warming factors and their seasonality for land and oceanic surfaces were investigated separately and for different domains within each surface type where mechanisms differ. Common factors contribute to both land and oceanic surface warming: tropospheric-mean atmospheric warming and greenhouse gas increases (mostly through water vapor feedback) for both tropical and Arctic regions, nonbarotropic warming and surface warming sensitivity effects (negative in the tropics, positive in the Arctic), and warming cloud feedback in the Arctic in winter. Some mechanisms differ between land and oceanic surfaces: sensible and latent heat flux in the tropics, albedo feedback peaking at different times of the year in the Arctic due to different mean latitudes, a very large summer energy uptake and winter release by the Arctic Ocean, and a large evaporation enhancement in winter over the Arctic Ocean, whereas the peak occurs in summer over the ice-free Arctic land. The oceanic anomalous energy uptake and release is further studied, suggesting the primary role of seasonal variation of oceanic mixed layer temperature changes.

scholarly journals Effects of Global Warming on the Poleward Heat Transport by Non-Stationary Large-Scale Atmospheric Eddies, and Feedbacks Affecting the Formation of the Arctic Climate

2021 ◽  
Vol 9 (8) ◽  
pp. 867
Author(s):  
Sergei Soldatenko
Keyword(s):  
Global Warming ◽  
Heat Transport ◽  
Large Scale ◽  
Arctic Sea Ice ◽  
Arctic Climate ◽  
The Arctic ◽  
Arctic Amplification ◽  
Near Surface ◽  
Feedback Mechanisms ◽  
Arctic Sea

It is a well-known fact that the observed rise in the Arctic near-surface temperature is more than double the increase in global mean temperature. However, the entire scientific picture of the formation of the Arctic amplification has not yet taken final shape and the causes of this phenomenon are still being discussed within the scientific community. Some recent studies suggest that the atmospheric equator-to-pole transport of heat and moisture, and also radiative feedbacks, are among the possible reasons for the Arctic amplification. In this paper, we highlight and summarize some of our research related to assessing the response of climate in the Arctic to global warming and vice versa. Since extratropical transient eddies dominate the meridional transport of sensible and latent heat from low to high latitudes, we estimated the effect of climate change on meridional heat transport by means of the β-plane model of baroclinic instability. It has been shown that the heat transport from low and middle latitudes to the Arctic by large scale transient eddies increases by about 9% due to global warming, contributing to the polar amplification—and thereby a decrease in the extent—of the Arctic sea, which, in turn, is an important factor in the formation of the Arctic climate. The main radiative feedback mechanisms affecting the formation of the Arctic climate are also considered and discussed. It was emphasized that the influence of feedbacks depends on a season since the total feedback in the winter season is negative, while in the summer season, it is positive. Thus, further research is required to diminish the uncertainty regarding the character of various feedback mechanisms in the shaping of the Artic climate and, through that, in predicting the extent of Arctic sea ice.

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