Topographic forcing from East Asia and North America in the northern winter stratosphere and their mutual interference

2020 ◽  
Author(s):  
Rongcai Ren ◽  
Xin Xia ◽  
Jian Rao
Keyword(s):  
North America ◽  
East Asia ◽  
Climate Model ◽  
Polar Vortex ◽  
Wave Pattern ◽  
Mutual Interference ◽  
Mean Flow ◽  
Stratospheric Polar Vortex ◽  
Northern Winter ◽  
Topographic Forcing

<p>This study uses the stratosphere-resolved Whole Atmosphere Community Climate Model to demonstrate the “independent” and “dependent” topographic forcing from the topography of East Asia (EA) and North American (NA), and their “joint” forcing in the northern winter stratosphere. The mutual interference between the EA and NA forcing is also demonstrated. Specifically, without EA, an independent NA can also, like EA, induce a severe polar warming and weakening of the stratospheric polar vortex. While EA favors a displacement of the polar vortex toward Eurasia, NA favors a displacement toward the North America–Atlantic region. However, the independent-EA-forced weakening effect on the polar vortex can be largely decreased and changes to a location displacement when NA exists, and the interference the other way around is even more critical, being able to completely offset the independent-NA-forced effect, because EA can substantively obstruct NA’s effect on the tropospheric wave pattern over the Eurasia–Pacific region. The much stronger/weaker interference of EA/NA is associated with its stronger/weaker downstream weakening effect on the zonal flow that impinges on NA/EA. The mutual interference always tends to further destruct the upward wave fluxes over the eastern North Pacific and enhance the downward wave fluxes over NA. The overall changes in upward wave fluxes, as well as that in the Rossby stationary wavenumber responsible for the stratospheric changes, are related to changes in the zonal-mean flow pattern. The joint effects of EA and NA, rather than being a linear superimposition of their independent effects, are largely dominated by the effects of EA.</p>

scholarly journals Topographic Forcing from East Asia and North America in the Northern Winter Stratosphere and Their Mutual Interference

2019 ◽  
Vol 32 (24) ◽  
pp. 8639-8658 ◽  
Author(s):  
Rongcai Ren ◽  
Xin Xia ◽  
Jian Rao
Keyword(s):  
North America ◽  
East Asia ◽  
Climate Model ◽  
Polar Vortex ◽  
Wave Pattern ◽  
Mutual Interference ◽  
Mean Flow ◽  
Stratospheric Polar Vortex ◽  
Northern Winter ◽  
Topographic Forcing

Abstract This study uses the stratosphere-resolved Whole Atmosphere Community Climate Model to demonstrate the “independent” and “dependent” topographic forcing from the topography of East Asia (EA) and North America (NA), and their “joint” forcing in the northern winter stratosphere. The mutual interference between the EA and NA forcing is also demonstrated. Specifically, without EA, an independent NA can also, like EA, induce a severe polar warming and weakening of the stratospheric polar vortex. While EA favors a displacement of the polar vortex toward Eurasia, NA favors a displacement toward the North America–Atlantic region. However, the independent-EA-forced weakening effect on the polar vortex can be largely decreased and changes to a location displacement when NA exists, and the interference the other way around is even more critical, being able to completely offset the independent-NA-forced effect, because EA can substantively obstruct NA’s effect on the tropospheric wave pattern over the Eurasia–Pacific region. The much stronger (weaker) interference of EA (NA) is associated with its stronger (weaker) downstream weakening effect on the zonal flow that impinges on NA (EA). The mutual interference always tends to further destruct the upward wave fluxes over the eastern North Pacific and enhance the downward wave fluxes over North America. The overall changes in upward wave fluxes, as well as that in the Rossby stationary wavenumber responsible for the stratospheric changes, are related to changes in the zonal-mean flow pattern. The joint effects of EA and NA, rather than being a linear superimposition of their independent effects, are largely dominated by the effects of EA.

Tropospheric Precursors of Anomalous Northern Hemisphere Stratospheric Polar Vortices

2010 ◽  
Vol 23 (12) ◽  
pp. 3282-3299 ◽  
Author(s):  
Chaim I. Garfinkel ◽  
Dennis L. Hartmann ◽  
Fabrizio Sassi
Keyword(s):  
Eastern Europe ◽  
Northern Hemisphere ◽  
North Pacific ◽  
Climate Model ◽  
Polar Vortex ◽  
Mean Flow ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
The North ◽  
The North Pacific

Abstract Regional extratropical tropospheric variability in the North Pacific and eastern Europe is well correlated with variability in the Northern Hemisphere wintertime stratospheric polar vortex in both the ECMWF reanalysis record and in the Whole Atmosphere Community Climate Model. To explain this correlation, the link between stratospheric vertical Eliassen–Palm flux variability and tropospheric variability is analyzed. Simple reasoning shows that variability in the North Pacific and eastern Europe can deepen or flatten the wintertime tropospheric stationary waves, and in particular its wavenumber-1 and -2 components, thus providing a physical explanation for the correlation between these regions and vortex weakening. These two pathways begin to weaken the upper stratospheric vortex nearly immediately, with a peak influence apparent after a lag of some 20 days. The influence then appears to propagate downward in time, as expected from wave–mean flow interaction theory. These patterns are influenced by ENSO and October Eurasian snow cover. Perturbations in the vortex induced by the two regions add linearly. These two patterns and the quasi-biennial oscillation (QBO) are linearly related to 40% of polar vortex variability during winter in the reanalysis record.

scholarly journals Robust asymmetry of the future Arctic polar vortex is driven by tropical Pacific warming

2020 ◽  
Author(s):  
Shinji Matsumura ◽  
Koji Yamazaki ◽  
Takeshi Horinouchi
Keyword(s):  
North America ◽  
Climate Model ◽  
Polar Vortex ◽  
Tropical Pacific ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Stratospheric Polar Vortex ◽  
Model Simulations ◽  
The Future ◽  
Stratospheric Cooling

Abstract The wintertime Arctic stratospheric polar vortex is characterized by a circumpolar westerly jet, confining the coldest temperatures over the Arctic. The future stratosphere is globally dominated by a strong radiative cooling due to the increase in greenhouse gases, enhancing the Arctic cooling. However, we find that over North America, the Arctic stratospheric cooling is suppressed or rather warming occurs, whereas over Eurasia stratospheric cooling is most pronounced, leading to an asymmetric polar vortex, based on 21st century climate model simulations. There are many causes that drive polar vortex variability, such as Arctic sea ice loss, and midlatitude and tropical Pacific warming, which make future projections highly uncertain. Our model simulations demonstrate that tropical warming induces the asymmetric polar vortex. The eastern equatorial Pacific warming causes eastward-shifted teleconnection, which strengthens the polar vortex over Eurasia and weakens over North America by enhancing the vertical wave propagation into the stratosphere. The asymmetric polar vortex is projected to markedly develop in the 2030s, and so could also affect winter surface climate over mid- to high-latitudes of Eurasia in the near future.

The Influence of the Quasi-Biennial Oscillation on the Troposphere in Winter in a Hierarchy of Models. Part I: Simplified Dry GCMs

2011 ◽  
Vol 68 (6) ◽  
pp. 1273-1289 ◽  
Author(s):  
Chaim I. Garfinkel ◽  
Dennis L. Hartmann
Keyword(s):  
Zonal Wind ◽  
Climate Model ◽  
Polar Vortex ◽  
Equation Model ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
The North ◽  
Subtropical Jet ◽  
Long Time ◽  
Biennial Oscillation

Abstract A dry primitive equation model is used to explain how the quasi-biennial oscillation (QBO) of the tropical stratosphere can influence the troposphere, even in the absence of tropical convection anomalies and a variable stratospheric polar vortex. QBO momentum anomalies induce a meridional circulation to maintain thermal wind balance. This circulation includes zonal wind anomalies that extend from the equatorial stratosphere into the subtropical troposphere. In the presence of extratropical eddies, the zonal wind anomalies are intensified and extend downward to the surface. The tropospheric response differs qualitatively between integrations in which the subtropical jet is strong and integrations in which the subtropical jet is weak. While fluctuation–dissipation theory provides a guide to predicting the response in some cases, significant nonlinearity in others, particularly those designed to model the midwinter subtropical jet of the North Pacific, prevents its universal application. When the extratropical circulation is made zonally asymmetric, the response to the QBO is greatest in the exit region of the subtropical jet. The dry model is able to simulate much of the Northern Hemisphere wintertime tropospheric response to the QBO observed in reanalysis datasets and in long time integrations of the Whole Atmosphere Community Climate Model (WACCM).

scholarly journals Parallel Comparison of Major Sudden Stratospheric Warming Events in CESM1-WACCM and CESM2-WACCM

Atmosphere ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 679 ◽  
Author(s):  
Si-Ming Liu ◽  
Yuan-Hao Chen ◽  
Jian Rao ◽  
Can Cao ◽  
Si-Yu Li ◽  
...  
Keyword(s):  
North America ◽  
Climate Model ◽  
Polar Vortex ◽  
Statistical Characteristics ◽  
Stratospheric Warming ◽  
Sudden Stratospheric Warming ◽  
Near Surface ◽  
Eddy Heat Flux ◽  
General Statistical ◽  
Vortex Split

After the recent release of the historical runs by community Earth system model version 2–the whole atmosphere community climate model (CESM2-WACCM), the major sudden stratospheric warming (SSW) events in this model and in its previous version (CESM1-WACCM) are compared based on a modern reanalysis (JRA55). Using the World Meteorological Organization (WMO) definition of SSWs and a threshold-based classification method that can describe the polar vortex morphology, SSWs in models and the reanalysis are further classified into two types, vortex displacement SSWs and vortex split SSWs. The general statistical characteristics of the two types of SSW events in the two model versions are evaluated. Both CESM1-WACCM and CESM2-WACCM models are shown to reproduce the SSW frequency successfully, although the circulations differences between vortex displacement SSWs and vortex split SSWs in CESM2-WACCM are smaller than in CESM1-WACCM. Composite polar temperature, geopotential height, wind, and eddy heat flux anomalies in both the two models and the reanalysis show similar evolutions. In addition, positive Pacific–North America and negative Western Pacific patterns in the troposphere preceding vortex displacement and split SSWs are observed in both observations and the models. The strong negative North Atlantic oscillation-like pattern, especially after vortex split SSW onset, is also identified in models. The near-surface cold Eurasia–warm North America pattern before both types of SSW onset, the warm Eurasia–cold North America pattern after displacement SSW onset, and the cold Eurasia–cold North America pattern after split SSW onset are consistently identified in JRA55, CESM1-WACCM, and CESM2-WACCM, although the temperature anomalies after the split SSW onset in CESM2-WACCM are somewhat underestimated.

scholarly journals Seasonal Prediction Skill of Northern Extratropical Surface Temperature Driven by the Stratosphere

2017 ◽  
Vol 30 (12) ◽  
pp. 4463-4475 ◽  
Author(s):  
Liwei Jia ◽  
Xiaosong Yang ◽  
Gabriel Vecchi ◽  
Richard Gudgel ◽  
Thomas Delworth ◽  
...  
Keyword(s):  
Climate Model ◽  
Lower Troposphere ◽  
Polar Vortex ◽  
Seasonal Prediction ◽  
The Arctic ◽  
Northern Eurasia ◽  
Stratospheric Polar Vortex ◽  
Near Surface ◽  
Predictive Skill

This study explores the role of the stratosphere as a source of seasonal predictability of surface climate over Northern Hemisphere extratropics both in the observations and climate model predictions. A suite of numerical experiments, including climate simulations and retrospective forecasts, are set up to isolate the role of the stratosphere in seasonal predictive skill of extratropical near-surface land temperature. It is shown that most of the lead-0-month spring predictive skill of land temperature over extratropics, particularly over northern Eurasia, stems from stratospheric initialization. It is further revealed that this predictive skill of extratropical land temperature arises from skillful prediction of the Arctic Oscillation (AO). The dynamical connection between the stratosphere and troposphere is also demonstrated by the significant correlation between the stratospheric polar vortex and sea level pressure anomalies, as well as the migration of the stratospheric zonal wind anomalies to the lower troposphere.

scholarly journals Predictions of the boreal winter stratosphere with the C3S multi-model seasonal forecast system

2021 ◽  
Author(s):  
Alice Portal ◽  
Paolo Ruggieri ◽  
Froila M. Palmeiro ◽  
Javier Garcı́a-Serrano ◽  
Daniela I. V. Domeisen ◽  
...  
Keyword(s):  
Southern Oscillation ◽  
Polar Vortex ◽  
Seasonal Prediction ◽  
Seasonal Forecast ◽  
Wave Activity ◽  
Arctic Sea Ice ◽  
Mean Flow ◽  
Seasonal Forecasts ◽  
Stratospheric Polar Vortex ◽  
Prediction Systems

<p>As a result of the recent progress in the performance of seasonal prediction systems, forecasts of the mid-latitude weather at seasonal time scales are becoming increasingly important for societal decision making, as in risk estimate and management of meteorological extreme events. The predictability of the Northern-Hemisphere winter troposphere, especially in the Euro-Atlantic region, stems from the representation of a number of sources of predictability, notably El Nino Southern Oscillation, the stratospheric polar vortex, Arctic sea-ice extent, Eurasian snow cover. Among these, the stratospheric polar vortex is known to play a paramount role in seasonal forecasts of the winter tropospheric flow.</p><p>Here, we investigate the performance in the stratosphere of five seasonal prediction systems taking part in the Copernicus Climate Change Service (C3S), with a focus on the seasonal forecast skill and variability, and on the assessment of stratospheric processes. We show that dynamical forecasts of the stratosphere initialised at the beginning of November are considerably more skilful than empirical forecasts based on observed October or November anomalies. Advances in the representation of stratospheric seasonal variability and extremes, i.e. sudden stratospheric warming frequency, are identified with respect to previous generations of climate models running roughly a decade ago. Such results display, however, a large model dependence. Finally, we stress the importance of the relation between the stratospheric wave activity and the stratospheric polar vortex (i.e. the wave—mean-flow interaction), applied both to the variability and to the predictability of the stratospheric mean flow. Indeed, forecasts of the winter stratospheric polar vortex are closely connected to the prediction of November-to-February stratospheric wave activity, in particular in the Eurasian sector.</p>

scholarly journals Strengthened Impacts of November Snow Cover Over Siberia on the Out-of-phase Change in the Siberian High Between December and January Since 2000 and Implication for Intraseasonal Climate Prediction

2021 ◽  
Vol 9 ◽  
Author(s):  
Hongqing Yang ◽  
Ke Fan
Keyword(s):  
Phase Change ◽  
Snow Cover ◽  
Polar Vortex ◽  
Snow Accumulation ◽  
Arctic Sea Ice ◽  
Mean Flow ◽  
Stratospheric Polar Vortex ◽  
Siberian High ◽  
Arctic Sea ◽  
Reversal Frequency

This study investigates the out-of-phase change in the Siberian High (SH) between December and January (stronger than normal in December and weaker than normal in January, and vice versa). The results show that the monthly reversal frequency of the SH between December and January increases significantly after 2000 from 30% (1981–2000) to 63% (2001-2019). Correspondingly, the influence of November snow cover over Siberia on the phase reversal of the SH has intensified after 2000. The reasons may be as follows. Higher snow depth over Siberia (SSD) in November corresponds to stronger diabatic cooling and increased snow accumulation over Siberia in November and December, which may strengthen the SH in December via the positive feedback of snow albedo. The dynamic mechanisms between the higher SSD in November and weaker SH in January are further investigated from the perspective of troposphere–stratosphere interaction. Such anomalously higher SSD with strong upward heat flux induces the upward-propagating wave activity flux in November and December over the Urals and Siberia, leading to a weaker and warmer stratospheric polar vortex in January. Subsequently, the anomalies of the stratospheric polar vortex signal propagate downwards, giving rise to a negative Arctic Oscillation–like structure in the troposphere and a weakening of the SH in January. This mechanism can be partly reproduced in CMIP6. Additionally, the variability of the September–October Arctic sea ice mainly leads to coherent variations of the SH in December and January via the eddy–mean flow interaction before 2000. Furthermore, the preceding November snow cover over Siberia enhances the intraseasonal prediction skill for the winter SH after 2000. Meanwhile, considering the previous November SSD, the prediction accuracy for the out-of-phase change in the SH between December and January increases from 16% (outputs of the NCEP’s Climate Forecast System, version 2) to 75%.

scholarly journals The effect of interactive ozone chemistry on weak and strong stratospheric polar vortex events

2020 ◽  
Author(s):  
Jessica Oehrlein ◽  
Gabriel Chiodo ◽  
Lorenzo M. Polvani
Keyword(s):  
Climate Variability ◽  
Northern Hemisphere ◽  
North Atlantic ◽  
Climate Model ◽  
Stratospheric Ozone ◽  
Polar Vortex ◽  
Late Winter ◽  
Stratospheric Polar Vortex ◽  
Winter Climate ◽  
The Impact

Abstract. Modeling and observational studies have reported effects of stratospheric ozone extremes on Northern Hemisphere spring climate. Recent work has further suggested that the coupling of ozone chemistry and dynamics amplifies the surface response to midwinter sudden stratospheric warmings (SSWs). Here, we study the importance of interactive ozone chemistry in representing the stratospheric polar vortex and Northern Hemisphere winter surface climate variability. We contrast two simulations from the interactive and specified chemistry (and thus ozone) versions of the Whole Atmosphere Community Climate Model, designed to isolate the impact of interactive ozone on polar vortex variability. In particular, we analyze the response with and without interactive chemistry to midwinter SSWs, March SSWs, and strong polar vortex events (SPVs). With interactive chemistry, the stratospheric polar vortex is stronger, and more SPVs occur, but we find little effect on the frequency of midwinter SSWs. At the surface, interactive chemistry results in a pattern resembling a more negative North Atlantic Oscillation following midwinter SSWs, but with little impact on the surface signatures of late winter SSWs and SPVs. These results suggest that including interactive ozone chemistry is important for representing North Atlantic and European winter climate variability.

scholarly journals Impact of Reduced Arctic Sea Ice on Northern Hemisphere Climate and Weather in Autumn and Winter

2021 ◽  
pp. 1-61
Author(s):  
Svenya Chripko ◽  
Rym Msadek ◽  
Emilia Sanchez-Gomez ◽  
Laurent Terray ◽  
Laurent Bessières ◽  
...  
Keyword(s):  
North America ◽  
Sea Ice ◽  
Central Asia ◽  
Northern Hemisphere ◽  
Climate Model ◽  
Polar Vortex ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Arctic Sea ◽  
Autumn And Winter

AbstractThe Northern Hemisphere transient atmospheric response to Arctic sea decline is investigated in autumn and winter, using sensitivity experiments performed with the CNRMCM6-1 high-top climate model. Arctic sea ice albedo is reduced to the ocean value, yielding ice-free conditions during summer and a more moderate sea ice reduction during the following months. A strong ampli_cation of temperatures over the Arctic is induced by sea ice loss, with values reaching up to 25°C near the surface in autumn. Signi_cant surface temperature anomalies are also found over the mid-latitudes, with a warming reaching 1°C over North America and Europe, and a cooling reaching 1°C over central Asia. Using a dynamical adjustment method based on a regional reconstruction of circulation analogs, we show that the warming over North America and Europe can be explained both by changes in the atmospheric circulation and by the advection of warmer oceanic air by the climatological ow. In contrast, we demonstrate that the sea-ice induced cooling over central Asia is solely due to dynamical changes, involving an intensi_cation of the Siberian High and a cyclonic anomaly over the Sea of Okhotsk. In the troposphere, the abrupt Arctic sea ice decline favours a narrowing of the subtropical jet stream and a slight weakening of the lower part of the polar vortex that is explained by a weak enhancement of upward wave activity toward the stratosphere. We further show that reduced Arctic sea ice in our experiments is mainly associated with less severe cold extremes in the mid-latitudes.

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