scholarly journals Intermodel Spread in the Northern Hemisphere Stratospheric Polar Vortex Response to Climate Change in the CMIP5 Models

2019 ◽  
Vol 46 (22) ◽  
pp. 13290-13298 ◽  
Author(s):  
Yutian Wu ◽  
Isla R. Simpson ◽  
Richard Seager
Keyword(s):  
Climate Change ◽  
Northern Hemisphere ◽  
Polar Vortex ◽  
Cmip5 Models ◽  
Stratospheric Polar Vortex

scholarly journals The Downward Influence of Uncertainty in the Northern Hemisphere Stratospheric Polar Vortex Response to Climate Change

2018 ◽  
Vol 31 (16) ◽  
pp. 6371-6391 ◽  
Author(s):  
Isla R Simpson ◽  
Peter Hitchcock ◽  
Richard Seager ◽  
Yutian Wu ◽  
Patrick Callaghan
Keyword(s):  
Northern Hemisphere ◽  
General Circulation ◽  
Polar Vortex ◽  
General Circulation Models ◽  
Cmip5 Models ◽  
Regression Analyses ◽  
Stratospheric Polar Vortex ◽  
Wide Range ◽  
Tropospheric Circulation ◽  
Downward Influence

Abstract General circulation models display a wide range of future predicted changes in the Northern Hemisphere winter stratospheric polar vortex. The downward influence of this stratospheric uncertainty on the troposphere has previously been inferred from regression analyses across models and is thought to contribute to model spread in tropospheric circulation change. Here we complement such regression analyses with idealized experiments using one model where different changes in the zonal-mean stratospheric polar vortex are artificially imposed to mimic the extreme ends of polar vortex change simulated by models from phase 5 of the Coupled Model Intercomparison Project (CMIP5). The influence of the stratospheric vortex change on the tropospheric circulation in these experiments is quantitatively in agreement with the inferred downward influence from across-model regressions, indicating that such regressions depict a true downward influence of stratospheric vortex change on the troposphere below. With a relative weakening of the polar vortex comes a relative increase in Arctic sea level pressure (SLP), a decrease in zonal wind over the North Atlantic, drying over northern Europe, and wetting over southern Europe. The contribution of stratospheric vortex change to intermodel spread in these quantities is assessed in the CMIP5 models. The spread, as given by 4 times the across-model standard deviation, is reduced by roughly 10% on regressing out the contribution from stratospheric vortex change, while the difference between models on extreme ends of the distribution in terms of their stratospheric vortex change can reach up to 50% of the overall model spread for Arctic SLP and 20% of the overall spread in European precipitation.

scholarly journals Nonlinear response of Northern Hemisphere stratospheric polar vortex to the Indo–Pacific warm pool (IPWP) Niño

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Xin Zhou ◽  
Quanliang Chen ◽  
Fei Xie ◽  
Jianping Li ◽  
Minggang Li ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Temperature Response ◽  
Polar Vortex ◽  
Warm Pool ◽  
Boreal Winter ◽  
Linear Wave ◽  
Stationary Waves ◽  
Stratospheric Polar Vortex ◽  
Pacific Warm Pool ◽  
Tropical Sea

Abstract Variations in tropical sea surface temperatures (SST) have pronounced impacts on the stratospheric polar vortex, with the role of El Niño being the focus of much research interest. However, the Indo–Pacific warm pool (IPWP), which is the warmest body of seawater in the world, has received less attention. The IPWP has been warming in recent years. This paper presents for the first time the remarkable nonlinearity in Northern Hemisphere (NH) stratospheric circulation and temperature response to IPWP warming (the so-called IPWP Niño) in boreal winter. The magnitude of NH stratospheric vortex weakening is strong and significant in case of moderate IPWP Niño, but is weak and insignificant in strong IPWP Niño case. This phenomenon is robust in both the historical simulations and observations. An idealized model experiments forced with linear varying SST forcing in the IPWP region isolate the nonlinearities arising from IPWP Niño strength. Westward extension of precipitation into the Maritime Continent drives attenuation and westward shift of extratropical waves during strong IPWP Niño events. Linear wave interference analysis reveals this leads to weak interference between the climatological and anomalous stationary waves and thereby a weak response of the stratospheric vortex. These findings imply a distinct stratospheric vortex response to the IPWP Niño, and provide extended implications for the surface climate in the NH.

scholarly journals Impacts of regional climate and teleconnection on hydrological change in the Bosten Lake Basin, arid region of northwestern China

2017 ◽  
Vol 9 (1) ◽  
pp. 74-88 ◽  
Author(s):  
Huaijun Wang ◽  
Yingping Pan ◽  
Yaning Chen
Keyword(s):  
Climate Change ◽  
Northern Hemisphere ◽  
Air Temperature ◽  
Large Scale ◽  
Southern Oscillation ◽  
Polar Vortex ◽  
Circulation Index ◽  
Lake Basin ◽  
Area Index ◽  
Bosten Lake

Abstract This investigation examined effects of climate change, measured as annual, seasonal, and monthly air temperature and precipitation from 1958 to 2010, on water resources (i.e., runoff) in the Bosten Lake Basin. Additionally, teleconnections of hydrological changes to large-scale circulation indices including El Nino Southern Oscillation (ENSO), Arctic Oscillation (AO), North Atlantic Oscillation (NAO), Tibetan High (XZH), westerly circulation index (WI), and northern hemisphere polar vortex area index (VPA) were analyzed in our study. The results showed the following. (1) Annual and seasonal air temperature increased significantly in the Bosten Lake Basin. Precipitation exhibited an increasing trend, while the significance was less than that of temperature. Abrupt changes were observed in 1996 in mountain temperature and in 1985 in plain temperature. (2) Runoff varied in three stages, decreasing before 1986, increasing from 1987 to 2003, and decreasing after 2003. (3) Precipitation and air temperature have significant impacts on runoff. The hydrological processes in the Bosten Lake Basin were (statistically) significantly affected by the northern hemisphere polar vortex area index (VPA) and the Tibetan High (XZH). The results of this study are good indicators of local climate change, which can enhance human mitigation of climate warming in the Bosten Lake Basin.

The stratospheric response and surface influence in a bias-corrected model.

2020 ◽  
Author(s):  
Nicholas Tyrrell ◽  
Alexey Karpechko ◽  
Sebastian Rast
Keyword(s):  
Northern Hemisphere ◽  
Polar Vortex ◽  
Atmospheric Model ◽  
Quasi Biennial Oscillation ◽  
Stratospheric Polar Vortex ◽  
Surface Response ◽  
Model Biases ◽  
Increased Strength ◽  
And Control ◽  
Bias Corrections

<p>We investigate the effect of systematic model biases on teleconnections influencing the Northern Hemisphere wintertime circulation. We perform a two-step nudging and bias-correcting scheme for the dynamic variables of the ECHAM6 atmospheric model to reduce errors in the model climatology relative to ERA-Interim. The developed scheme is efficient in removing errors in model’s climatology. In particular, large negative bias in December-February mean zonal stratospheric winds is reduced by up to 75%, significantly increasing the strength of the Northern Hemisphere wintertime stratospheric polar vortex. <!-- I think calling increase in vortex strength ”a result” somewhat shifts the focus. The result is reduced error, not increased strength. I mean technically it is the same, but perception of the result is a bit different. What do you think? -->The bias-corrections are applied to the full atmosphere or stratosphere only.</p><p>We compare the response of bias-corrected and control runs to internal stratospheric variability and surface forcings that are important on seasonal timescales: Siberian snow cover in October; the Quasi-Biennial Oscillation (QBO); and ENSO. We find the bias-corrected model has the potential for a strengthened and more realistic response to the teleconnections, either in the stratospheric or surface response. In particular, the bias-corrected model has a strong QBO teleconnection which modulates the extratropical polar vortex and sea level pressure variability in a manner similar to that seen in observations. The Siberian snow forcing with the stratosphere-only bias-corrections also leads to an enhanced surface response relative to the control.<!-- Given considerable remaining biases in tropospheric waves in the stratosphere-only bias corrected run I would not overemphasize the results in this particular run especially because full bias-corrected run does not show large surface response. But it is Ok to mention this result in the abstract. --> The mechanism behind the sensitivity of the teleconnections to model biases is discussed.</p>

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.

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