scholarly journals Influence of Arctic Wetlands on Arctic Atmospheric Circulation

2007 ◽  
Vol 20 (16) ◽  
pp. 4243-4254 ◽  
Author(s):  
William J. Gutowski ◽  
Helin Wei ◽  
Charles J. Vörösmarty ◽  
Balázs M. Fekete
Keyword(s):  
Boundary Conditions ◽  
Atmospheric Circulation ◽  
Land Surface ◽  
Lower Boundary ◽  
Internal Variability ◽  
Surface Fluxes ◽  
Arctic Climate ◽  
The Arctic ◽  
Energy And Momentum ◽  
Circulation Changes

Abstract The Arctic’s land surface has large areas of wetlands that exchange moisture, energy, and momentum with the atmosphere. The authors use a mesoscale, pan-Arctic model simulating the summer of 1986 to examine links between the wetlands and arctic atmospheric dynamics and water cycling. Simulations with and without wetlands are compared to simulations using perturbed initial and lateral boundary conditions to delineate when and where the wetlands influence rises above nonlinear internal variability. The perturbation runs expose the temporal variability of the circulation’s sensitivity to changes in lower boundary conditions. For the wetlands cases examined here, the period of the most significant influence is approximately two weeks, and the wetlands do not introduce new circulation changes but rather appear to reinforce and modify existing circulation responses to perturbations. The largest circulation sensitivity, and thus the largest wetlands influence, occurs in central Siberia. The circulation changes induced by adding the wetlands appear as a propagating, equivalent barotropic wave. The wetlands anomaly circulation spreads alterations of surface fluxes to other locations, which undermines the potential for the wetlands to present a distinctive, spatially fixed forcing to atmospheric circulation. Using the climatology of artic synoptic-storm occurrence to indicate when the arctic circulation is most sensitive to altered forcing, the results suggest that the circulation is susceptible to the direct influence of wetlands for a limited time period extending from spring thaw of wetlands until synoptic-storm occurrence diminishes in midsummer. Sensitivities in arctic circulation uncovered through this work occur during a period of substantial transition from a fundamentally frozen to thawed state, a period of major concern for impacts of greenhouse warming on pan-Arctic climate. Changing arctic climate could alter the behavior revealed here.

scholarly journals Effects of sea ice change on the Arctic climate: insights from experiments with a polar atmospheric regional climate model

2021 ◽  
Author(s):  
Xiying Liu ◽  
Chenchen Lu
Keyword(s):  
Sea Ice ◽  
Boundary Conditions ◽  
Regional Climate Model ◽  
Air Temperature ◽  
Climate Model ◽  
Regional Climate ◽  
Lower Boundary ◽  
Arctic Climate ◽  
The Arctic ◽  
Sea Ice Concentration

Abstract To get insights into the effects of sea ice change on the Arctic climate, a polar atmospheric regional climate model was used to perform two groups of numerical experiments with prescribed sea ice cover of typical mild and severe sea ice. In experiments within the same group, the lateral boundary conditions and initial values were kept the same. The prescribed sea ice concentration (SIC) and other fields for the lower boundary conditions were changed every six hours. 10-year integration was completed, and monthly mean results were saved for analysis in each experiment. It is shown that the changes in annual mean surface air temperature have close connections with that in SIC, and the maximum change of temperature surpasses 15 K. The effects of SIC changes on 850 hPa air temperature is also evident, with more significant changes in the group with reduced sea ice. The higher the height, the weaker the response in air temperature to SIC change. The annual mean SIC change creates the pattern of differences in annual mean sea level pressure. The degree of significance in pressure change is modulated by atmospheric stratification stability. In response to reduction/increase of sea ice, the intensity of polar vortex weakens/strengthens.

scholarly journals Late Twenty-First-Century Changes in the Midlatitude Atmospheric Circulation in the CESM Large Ensemble

2017 ◽  
Vol 30 (15) ◽  
pp. 5943-5960 ◽  
Author(s):  
Y. Peings ◽  
J. Cattiaux ◽  
S. Vavrus ◽  
Gudrun Magnusdottir
Keyword(s):  
Atmospheric Circulation ◽  
Extreme Temperature ◽  
Internal Variability ◽  
First Century ◽  
The Arctic ◽  
Arctic Amplification ◽  
Large Ensemble ◽  
Longitudinal Sector ◽  
Twenty First Century ◽  
Projected Changes

Projected changes in the midlatitude atmospheric circulation at the end of the twenty-first century are investigated using coupled ocean–atmosphere simulations from the Community Earth System Model Large Ensemble (CESM-LENS). Different metrics are used to describe the response of the midlatitude atmospheric dynamics in 40 ensemble members covering the 1920–2100 period. Contrasted responses are identified depending on the season and longitudinal sector that are considered. In winter, a slowdown of the zonal flow and an increase in waviness is found over North America, while the European sector exhibits a reinforced westerly flow and decreased waviness. Extreme temperature events in midlatitudes are more sensitive to thermodynamical than dynamical changes, and a general decrease in the intensity of wintertime cold spells is found. Analyses of individual ensemble members reveal a large spread in circulation changes due to internal variability. Causes for this spread are found to be tied to the Arctic amplification in the Pacific–North American sector and to the polar stratosphere in the North Atlantic. A competition mechanism is also discussed between the midlatitude response to polar versus tropical changes. While the upper-tropospheric tropical warming pushes the jet stream poleward, in winter, Arctic amplification and the weaker polar vortex exert an opposite effect. This competition results in a narrowing of the jet path in the midlatitudes, leading to decreased/unchanged waviness/blockings. This interpretation somewhat reconciles conflicting results between the hypothesized effect of Arctic amplification and projected changes in midlatitude flow characteristics. This study also illustrates that further understanding of regional processes is critical for anticipating changes in the midlatitude dynamics.

scholarly journals Advances in understanding and parameterization of small-scale physical processes in the marine Arctic climate system: a review

2014 ◽  
Vol 14 (17) ◽  
pp. 9403-9450 ◽  
Author(s):  
T. Vihma ◽  
R. Pirazzini ◽  
I. Fer ◽  
I. A. Renfrew ◽  
J. Sedlar ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Sea Ice ◽  
Surface Fluxes ◽  
Climate System ◽  
Arctic Climate ◽  
The Arctic ◽  
Small Scale ◽  
Climate Modelling ◽  
Physical Processes ◽  
Made In

Abstract. The Arctic climate system includes numerous highly interactive small-scale physical processes in the atmosphere, sea ice, and ocean. During and since the International Polar Year 2007–2009, significant advances have been made in understanding these processes. Here, these recent advances are reviewed, synthesized, and discussed. In atmospheric physics, the primary advances have been in cloud physics, radiative transfer, mesoscale cyclones, coastal, and fjordic processes as well as in boundary layer processes and surface fluxes. In sea ice and its snow cover, advances have been made in understanding of the surface albedo and its relationships with snow properties, the internal structure of sea ice, the heat and salt transfer in ice, the formation of superimposed ice and snow ice, and the small-scale dynamics of sea ice. For the ocean, significant advances have been related to exchange processes at the ice–ocean interface, diapycnal mixing, double-diffusive convection, tidal currents and diurnal resonance. Despite this recent progress, some of these small-scale physical processes are still not sufficiently understood: these include wave–turbulence interactions in the atmosphere and ocean, the exchange of heat and salt at the ice–ocean interface, and the mechanical weakening of sea ice. Many other processes are reasonably well understood as stand-alone processes but the challenge is to understand their interactions with and impacts and feedbacks on other processes. Uncertainty in the parameterization of small-scale processes continues to be among the greatest challenges facing climate modelling, particularly in high latitudes. Further improvements in parameterization require new year-round field campaigns on the Arctic sea ice, closely combined with satellite remote sensing studies and numerical model experiments.

scholarly journals Internal Variability in Projections of Twenty-First-Century Arctic Sea Ice Loss: Role of the Large-Scale Atmospheric Circulation

2014 ◽  
Vol 27 (2) ◽  
pp. 527-550 ◽  
Author(s):  
Justin J. Wettstein ◽  
Clara Deser
Keyword(s):  
Sea Ice ◽  
Atmospheric Circulation ◽  
Large Scale ◽  
Wave Train ◽  
Internal Variability ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Arctic Sea ◽  
Rossby Wave Train ◽  
Arctic Sea Ice Loss

Abstract Internal variability in twenty-first-century summer Arctic sea ice loss and its relationship to the large-scale atmospheric circulation is investigated in a 39-member Community Climate System Model, version 3 (CCSM3) ensemble for the period 2000–61. Each member is subject to an identical greenhouse gas emissions scenario and differs only in the atmospheric model component's initial condition. September Arctic sea ice extent trends during 2020–59 range from −2.0 × 106 to −5.7 × 106 km2 across the 39 ensemble members, indicating a substantial role for internal variability in future Arctic sea ice loss projections. A similar nearly threefold range (from −7.0 × 103 to −19 × 103 km3) is found for summer sea ice volume trends. Higher rates of summer Arctic sea ice loss in CCSM3 are associated with enhanced transpolar drift and Fram Strait ice export driven by surface wind and sea level pressure patterns. Over the Arctic, the covarying atmospheric circulation patterns resemble the so-called Arctic dipole, with maximum amplitude between April and July. Outside the Arctic, an atmospheric Rossby wave train over the Pacific sector is associated with internal ice loss variability. Interannual covariability patterns between sea ice and atmospheric circulation are similar to those based on trends, suggesting that similar processes govern internal variability over a broad range of time scales. Interannual patterns of CCSM3 ice–atmosphere covariability compare well with those in nature and in the newer CCSM4 version of the model, lending confidence to the results. Atmospheric teleconnection patterns in CCSM3 suggest that the tropical Pacific modulates Arctic sea ice variability via the aforementioned Rossby wave train. Large ensembles with other coupled models are needed to corroborate these CCSM3-based findings.

Atmospheric processes in the Central Arctic during MOSAiC

2021 ◽  
Author(s):  
Matthew Shupe ◽  
Markus Rex ◽  
Keyword(s):  
Sea Ice ◽  
Large Scale ◽  
Model Development ◽  
Surface Fluxes ◽  
Climate System ◽  
Assessment Model ◽  
Arctic Climate ◽  
The Arctic ◽  
Model Assessment ◽  
Research Activities

<p>The atmosphere plays a central role in the Arctic climate system and its recent changes. Enhanced Arctic atmospheric warming over the past decades is linked with many key processes, including variability in large-scale circulation patterns, changes in fluxes of heat, sea-ice decline, impacts on the ecosystem, and many more. It is this collection of interdependent processes, and their recent changes, that has motivated the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC, 2019-2020) expedition. Based on the Polarstern icebreaker, an international and interdisciplinary team of scientists conducted an intensive, year-long scientific exploration of the Central Arctic climate system while drifting with the sea ice. This presentation highlights the atmospheric components of this scientific expedition. These include the most comprehensive set of field observations to ever be made of the Central Arctic atmosphere, spanning from the stratosphere to the surface. Specific research activities examine atmospheric structure, winds, clouds, precipitation, aerosols, and surface fluxes of heat, momentum, gases, and moisture. Complementing these observational aspects are numerous modeling activities, including observation-based model assessment, model development, and regional process studies, among others. Finally, key links between the atmosphere and the sea ice, snow, and ocean through a variety of physical, chemical, and biological processes are discussed.</p>

Local Advection of Momentum, Heat, and Moisture during the Melt of Patchy Snow Covers

1995 ◽  
Vol 34 (7) ◽  
pp. 1705-1715 ◽  
Author(s):  
Glen E. Liston
Keyword(s):  
Energy Balance ◽  
Snow Cover ◽  
Land Surface ◽  
Lower Boundary ◽  
Conservation Equation ◽  
Surface Fluxes ◽  
Balance Model ◽  
Snow Covered Area ◽  
Covered Area ◽  
Heat And Moisture

Abstract A numerical atmospheric boundary layer model, based on higher-order turbulence closure assumptions, is developed and used to simulate the local advection of momentum, heat, and moisture during the melt of patchy snow covers over a 10-km horizontal domain. The coupled model includes solution of the mass continuity equation, the horizontal and vertical momentum equations, an E−ε turbulence model, an energy equation, and a water vapor conservation equation. Atmospheric buoyancy is accounted for, and a land surface energy balance model is implemented at the lower boundary. Model integrations indicate that advective processes occurring at local scales produce nonlinear horizontal variations in surface fluxes. Under conditions of the numerical experiments, the energy available to melt snow-covered regions has been found to increase by as much as 30% as the area of exposed vegetation increases upwind of the snow cover. The melt increase is found to vary in a largely linear fashion with decreasing snow-covered area for snow-covered areas greater than 25% and in a strongly nonlinear fashion below that value. Decreasing the ratio of patch size to total area, or increasing the patchiness, of the snow cover also leads to nonlinear increases in the energy available to melt the snow. In the limit of a snow cover composed of small patches, melt energy is found to increase linearly as the fractional snow-covered area decreases. In addition, for the purpose of computing grid-average surface fluxes during snowmelt in regional atmospheric models, the results of this study indicate that separate energy balance computations can be performed over the snow-covered and vegetation-covered regions, and the resulting fluxes can be weighted in proportion to the fractional snow cover to allocate the total energy flux partitioning within each surface grid cell.

scholarly journals A regime view of future atmospheric circulation changes in Northern mid-latitudes

2020 ◽  
Author(s):  
Federico Fabiano ◽  
Virna Meccia ◽  
Paolo Davini ◽  
Paolo Ghinassi ◽  
Susanna Corti
Keyword(s):  
Atmospheric Circulation ◽  
North Atlantic ◽  
The Arctic ◽  
The North ◽  
The Pacific ◽  
General Improvement ◽  
Polar Stratosphere ◽  
The North Atlantic ◽  
Different Levels ◽  
Circulation Changes

Abstract. Future wintertime atmospheric circulation changes in the Euro-Atlantic (EAT) and Pacific-North American (PNA) sectors are studied from a Weather Regimes perspective. The CMIP5 and CMIP6 historical simulations performance in reproducing the observed regimes is first evaluated, showing a general improvement of CMIP6 models, more evident for EAT. The circulation changes projected by CMIP5 and CMIP6 scenario simulations are analyzed in terms of the change in the frequency and persistence of the regimes. In the EAT sector, significant positive trends are found for the frequency and persistence of NAO+ for SSP245, SSP370 and SSP585 scenarios, with a concomitant decrease in the frequency of the Scandinavian Blocking and Atlantic Ridge regimes. For PNA, the Pacific Through regime shows a significant increase, while the Bering Ridge is predicted to decrease in all scenarios analyzed. The spread among the model responses is linked to different levels of warming in the Polar Stratosphere, the North Atlantic and the Arctic.

A regime view of future atmospheric circulation changes in Northern mid-latitudes

2021 ◽  
Author(s):  
Federico Fabiano ◽  
Virna L. Meccia ◽  
Paolo Davini ◽  
Paolo Ghinassi ◽  
Susanna Corti
Keyword(s):  
Atmospheric Circulation ◽  
Winter Season ◽  
Model Performance ◽  
The Arctic ◽  
Historical Period ◽  
Weather Regimes ◽  
The North ◽  
The Pacific ◽  
General Improvement ◽  
Circulation Changes

<p>Future changes in the mid-latitude wintertime atmospheric circulation are studied from a weather regimes perspective. The analysis is based on daily geopotential height at 500 hPa during the extended winter season (NDJFM) from both CMIP5 and CMIP6 historical and scenario simulations. The model performance in reproducing the observed weather regimes during the historical period in the Euro-Atlantic (EAT) and Pacific-North American (PAC) sectors is first evaluated, showing a general improvement of CMIP6 models in terms of regime patterns, frequencies and variance ratio. The projected circulation changes in the future climate (2050-2100) under the different scenarios are analysed in terms of the change in the frequency and persistence of the regimes. Significant positive trends are found for the frequency of NAO+ and negative trends for the Scandinavian Blocking and Atlantic Ridge regimes. This confirms the tendency for the zonalization of the circulation in the EAT sector, with decreased latitudinal variability of the jet stream. For the PAC sector, significant changes are seen for the Pacific Trough regime (increase) and the Bering Ridge (decrease), while there is no agreement in the response of the two PNA regimes. The spread among the model responses in the most extreme scenarios is analysed through a multi-linear regression approach and linked to different levels of warming in the polar stratosphere, the tropical upper troposphere, the North Atlantic and the Arctic.</p>

Increased Variability in the Early Winter Subarctic North American Atmospheric Circulation*

2015 ◽  
Vol 28 (18) ◽  
pp. 7297-7305 ◽  
Author(s):  
James E. Overland ◽  
Muyin Wang
Keyword(s):  
Atmospheric Circulation ◽  
Probabilistic Approach ◽  
State Dependence ◽  
Internal Variability ◽  
Circulation Pattern ◽  
Cold Weather ◽  
The Arctic ◽  
Eastern United States ◽  
Seasonal Forecasts ◽  
Atmospheric Variability

Abstract The last decade shows increased variability in the Arctic Oscillation (AO) index for December. Over eastern North America such increased variability depended on amplification of the climatological longwave atmospheric circulation pattern. Recent negative magnitudes of the AO have increased geopotential thickness west of Greenland and cold weather in the central and eastern United States. Although the increased variance in the AO is statistically significant based on 9-yr running standard deviations from 1950 to 2014, one cannot necessarily robustly attribute the increase to steady changes in external sources (sea temperatures, sea ice) rather than a chaotic view of internal atmospheric variability; this is due to a relatively short record and a review of associated atmospheric dynamics. Although chaotic internal variability dominates the dynamics of atmospheric circulation, Arctic thermodynamic influence can reinforce the regional geopotential height pattern. Such reinforcement suggests a conditional or state dependence on whether an Arctic influence will impact subarctic severe weather, based on different circulation regimes. A key conclusion is the importance of recent variability over potential trends in Arctic and subarctic atmospheric circulation. Continued thermodynamic Arctic changes are suggested as a Bayesian prior leading to a probabilistic approach for potential subarctic weather linkages and the potential for improving seasonal forecasts.

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