Coupled North Atlantic Subdecadal Variability in CMIP5 Models

Abstract Recent studies have hypothesized that Arctic amplification, the enhanced warming of the Arctic region compared to the rest of the globe, will cause changes in midlatitude weather over the twenty-first century. This study exploits the recently completed phase 5 of the Coupled Model Intercomparison Project (CMIP5) and examines 27 state-of-the-art climate models to determine if their projected changes in the midlatitude circulation are consistent with the hypothesized impact of Arctic amplification over North America and the North Atlantic. Under the largest future greenhouse forcing (RCP8.5), it is found that every model, in every season, exhibits Arctic amplification by 2100. At the same time, the projected circulation responses are either opposite in sign to those hypothesized or too widely spread among the models to discern any robust change. However, in a few seasons and for some of the circulation metrics examined, correlations are found between the model spread in Arctic amplification and the model spread in the projected circulation changes. Therefore, while the CMIP5 models offer some evidence that future Arctic warming may be able to modulate some aspects of the midlatitude circulation response in some seasons, the analysis herein leads to the conclusion that the net circulation response in the future is unlikely to be determined solely—or even primarily—by Arctic warming according to the sequence of events recently hypothesized.

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Statistical Projection of the North Atlantic Storm Tracks

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-17-0348.1 ◽

2019 ◽

Vol 58 (7) ◽

pp. 1509-1522 ◽

Cited By ~ 3

Author(s):

Kajsa M. Parding ◽

Rasmus Benestad ◽

Abdelkader Mezghani ◽

Helene B. Erlandsen

Keyword(s):

North Atlantic ◽

Geopotential Height ◽

Climate Model ◽

Global Climate ◽

Global Climate Model ◽

Storm Tracks ◽

Cmip5 Models ◽

The North ◽

The Future ◽

The North Atlantic

AbstractA method for empirical–statistical downscaling was adapted to project seasonal cyclone density over the North Atlantic Ocean. To this aim, the seasonal mean cyclone density was derived from instantaneous values of the 6-h mean sea level pressure (SLP) reanalysis fields. The cyclone density was then combined with seasonal mean reanalysis and global climate model projections of SLP or 500-hPa geopotential height to obtain future projections of the North Atlantic storm tracks. The empirical–statistical approach is computationally efficient because it makes use of seasonally aggregated cyclone statistics and allows the future cyclone density to be estimated from the full ensemble of available CMIP5 models rather than from a smaller subset. However, the projected cyclone density in the future differs considerably depending on the choice of predictor, SLP, or 500-hPa geopotential height. This discrepancy suggests that the relationship between the cyclone density and SLP, 500-hPa geopotential height, or both is nonstationary; that is, that the statistical model depends on the calibration period. A stationarity test based on 6-hourly HadGEM2-ES data indicated that the 500-hPa geopotential height was not a robust predictor of cyclone density.

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Dynamical Properties of the North Atlantic Atmospheric Circulation in the Past 150 Years in CMIP5 Models and the 20CRv2c Reanalysis

Journal of Climate ◽

10.1175/jcli-d-17-0176.1 ◽

2018 ◽

Vol 31 (15) ◽

pp. 6097-6111 ◽

Cited By ~ 12

Author(s):

David Rodrigues ◽

M. Carmen Alvarez-Castro ◽

Gabriele Messori ◽

Pascal Yiou ◽

Yoann Robin ◽

...

Keyword(s):

Dynamical Systems ◽

Atmospheric Circulation ◽

North Atlantic ◽

Large Scale ◽

Cmip5 Models ◽

Historical Period ◽

Local Dimension ◽

The North ◽

The North Atlantic ◽

Over Time

It is of fundamental importance to evaluate the ability of climate models to capture the large-scale atmospheric circulation patterns and, in the context of a rapidly increasing greenhouse forcing, the robustness of the changes simulated in these patterns over time. Here we approach this problem from an innovative point of view based on dynamical systems theory. We characterize the atmospheric circulation over the North Atlantic in the CMIP5 historical simulations (1851–2000) in terms of two instantaneous metrics: local dimension of the attractor and stability of phase-space trajectories. We then use these metrics to compare the models to the Twentieth Century Reanalysis version 2c (20CRv2c) over the same historical period. The comparison suggests that (i) most models capture to some degree the median attractor properties, and models with finer grids generally perform better; (ii) in most models the extremes in the dynamical systems metrics match large-scale patterns similar to those found in the reanalysis; (iii) changes in the attractor properties observed for the ensemble-mean 20CRv2c are artifacts resulting from inhomogeneities in the standard deviation of the ensemble over time; and (iv) the long-term trends in local dimension observed among the 56 members of the 20CR ensemble have the same sign as those observed in the CMIP5 multimodel mean, although the multimodel trend is much weaker.

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Trends and characteristics of winter storms in CMIP6

10.5194/egusphere-egu21-15487 ◽

2021 ◽

Author(s):

Mareike Schuster ◽

Uwe Ulbrich

Keyword(s):

Climate Change ◽

North Atlantic ◽

Life Time ◽

Storm Tracks ◽

The Arctic ◽

Cmip5 Models ◽

Atlantic Basin ◽

North Atlantic Basin ◽

The North ◽

The North Atlantic

Windstorms are considered the most devastating natural peril in many regions around the globe. For insurance associations in Europe for example, the damages generated by windstorms make up to about 90% of the claims in the category of natural hazards. The interannual variability of windstorms can be quite strong and thus research has recently focused on this topic.However, storm risk and its changes under anthropogenically induced climate change are so far rather little discussed in literature. Thus, there are still large uncertainties about how climate change will affect the extratropical circulation. CMIP5 models showed at times opposing signals regarding number and strength of windstorm generating cyclones and storm tracks. In more detail, the latest IPCC AR5 states that substantial uncertainty and low confidence remains in projecting changes in NH storm tracks, especially for the North Atlantic basin.With the lately released CMIP6 simulations, providing model output of increased spatial and temporal resolution, there is potential for new insights and enhanced confidence regarding future trends of storminess.In our study, we assess characteristics and trends of windstorm diagnostics in an ensemble of the latest CMIP6 climate scenario simulations, with a focus to the North Atlantic basin and winterstorms affecting Europe.In the CMIP6 model ensemble the trends of winter windstorm frequencies appear to be overall weaker in an anthropogenically changed climate than in the preceding CMIP5 scenarios; yet, first results indicate that they are somewhat more consistent amongst models. All CMIP6 models exhibit a windstorm frequency increase locally confined over the Arctic, while in the mid and high latitudes a wide-ranging decrease of windstorm activity is simulated. In our study we will also assess what this entails for characteristics like life time, intensity and size.

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A Further Investigation of the Simulation of North Atlantic Storm Track Activity in CMIP5 Models

Journal of Coastal Research ◽

10.2112/si99-058.1 ◽

2020 ◽

Vol 99 (sp1) ◽

pp. 428

Author(s):

Kun Yu ◽

Peilong Yu ◽

Yun-Ge Chen ◽

Yang Lu ◽

Wenning Hao

Keyword(s):

North Atlantic ◽

Storm Track ◽

Cmip5 Models ◽

Storm Track Activity

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Evaluation of CMIP5 models over the northern North Atlantic in the context of forthcoming paleoclimatic reconstructions

Climate Dynamics ◽

10.1007/s00382-017-3536-x ◽

2017 ◽

Vol 49 (11-12) ◽

pp. 3673-3691 ◽

Cited By ~ 4

Author(s):

Maria Pyrina ◽

Sebastian Wagner ◽

Eduardo Zorita

Keyword(s):

North Atlantic ◽

Cmip5 Models

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The role of the North Atlantic overturning and deep-ocean for multi-decadal global-mean-temperature variability

Earth System Dynamics Discussions ◽

10.5194/esdd-4-967-2013 ◽

2013 ◽

Vol 4 (2) ◽

pp. 967-1003 ◽

Cited By ~ 3

Author(s):

C. F. Schleussner ◽

J. Runge ◽

J. Lehmann ◽

A. Levermann

Keyword(s):

Sea Ice ◽

North Atlantic ◽

Heat Content ◽

Deep Ocean ◽

Meridional Overturning Circulation ◽

Cmip5 Models ◽

Global Mean Temperature ◽

Mean Temperature ◽

Global Mean

Abstract. Earth's climate exhibits internal modes of variability on various time scales. Here we investigate multi-decadal variability of the Atlantic meridional overturning circulation (AMOC) in the control runs of an ensemble of CMIP5 models. By decomposing global-mean-temperature (GMT) variance into contributions of the AMOC and Northern Hemisphere sea-ice extent using a graph-theoretical statistical approach, we find the AMOC to contribute 8% to GMT variability in the ensemble mean. Our results highlight the importance of AMOC sea-ice feedbacks that explain 5% of the GMT variance, while the contribution solely related to the AMOC is found to be about 3%. As a consequence of multi-decadal AMOC variability, we report substantial variations in North Atlantic deep-ocean heat content with trends of up to 0.7 × 1022 J decade−1 that are of the order of observed changes over the last decade and consistent with the reduced GMT warming trend over this period. Although these temperature anomalies are largely density-compensated by salinity changes, we find a robust negative correlation between the AMOC and North Atlantic deep-ocean density with density lagging the AMOC by 5 to 11 yr in most models. While this would in principle allow for a self-sustained oscillatory behavior of the coupled AMOC–deep-ocean system, our results are inconclusive about the role of this feedback in the model ensemble.

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Evaluation of Extratropical Cyclone Precipitation in the North Atlantic Basin: An Analysis of ERA-Interim, WRF, and Two CMIP5 Models

Journal of Climate ◽

10.1175/jcli-d-17-0308.1 ◽

2018 ◽

Vol 31 (6) ◽

pp. 2345-2360 ◽

Cited By ~ 17

Author(s):

James F. Booth ◽

Catherine M. Naud ◽

Jeff Willison

Keyword(s):

Wind Speed ◽

North Atlantic ◽

Surface Wind ◽

Wrf Model ◽

Surface Wind Speed ◽

Convective Precipitation ◽

Cmip5 Models ◽

Convection Scheme ◽

The North ◽

The North Atlantic

The representation of extratropical cyclone (ETC) precipitation in general circulation models (GCMs) and the Weather Research and Forecasting (WRF) Model is analyzed. This work considers the link between ETC precipitation and dynamical strength and tests if parameterized convection affects this link for ETCs in the North Atlantic basin. Lagrangian cyclone tracks of ETCs in ERA-Interim (ERAI), GISS and GFDL CMIP5 models, and WRF with two horizontal resolutions are utilized in a compositing analysis. The 20-km-resolution WRF Model generates stronger ETCs based on surface wind speed and cyclone precipitation. The GCMs and ERAI generate similar composite means and distributions for cyclone precipitation rates, but GCMs generate weaker cyclone surface winds than ERAI. The amount of cyclone precipitation generated by the convection scheme differs significantly across the datasets, with the GISS model generating the most, followed by ERAI and then the GFDL model. The models and reanalysis generate relatively more parameterized convective precipitation when the total cyclone-averaged precipitation is smaller. This is partially due to the contribution of parameterized convective precipitation occurring more often late in the ETC’s life cycle. For reanalysis and models, precipitation increases with both cyclone moisture and surface wind speed, and this is true if the contribution from the parameterized convection scheme is larger or not. This work shows that these different models generate similar total ETC precipitation despite large differences in the parameterized convection, and these differences do not cause unexpected behavior in ETC precipitation sensitivity to cyclone moisture or surface wind speed.

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