Raphael Köhler
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View article: The Arctic Beaufort Gyre in CMIP6 Models: Present and Future
The Arctic Beaufort Gyre in CMIP6 Models: Present and Future Open
The Beaufort Gyre (BG) is an important feature of the Arctic Ocean. By accumulating or releasing freshwater, it influences ocean properties both within the Arctic and as far as the North Atlantic. Yet, its future remains uncertain: the gyr…
View article: The Arctic Beaufort Gyre in CMIP6 Models: Present and Future
The Arctic Beaufort Gyre in CMIP6 Models: Present and Future Open
The Beaufort Gyre is an important feature of the Arctic Ocean. By accumulating or releasing freshwater, it influences ocean properties both within the Arctic and as far as the North Atlantic. Yet, its future remains uncertain: the gyre cou…
View article: The effect of model biases on the simulated future changes of the North Atlantic jet stream
The effect of model biases on the simulated future changes of the North Atlantic jet stream Open
Future projections of the European climate suffer from uncertainties in the changes of the North Atlantic jet stream. Previous studies of multi-model ensembles have suggested that the jet will shift poleward, and that the shift is anticorr…
View article: Influence of high-latitude blocking and the northern stratospheric polar vortex on cold-air outbreaks under Arctic amplification of global warming
Influence of high-latitude blocking and the northern stratospheric polar vortex on cold-air outbreaks under Arctic amplification of global warming Open
It is widely accepted that Arctic amplification (AA)—enhanced Arctic warming relative to global warming—will increasingly moderate cold-air outbreaks (CAOs) to the midlatitudes. Yet, some recent studies also argue that AA over the last thr…
View article: Storylines of summer Arctic climate change constrained by Barents–Kara seas and Arctic tropospheric warming for climate risk assessment
Storylines of summer Arctic climate change constrained by Barents–Kara seas and Arctic tropospheric warming for climate risk assessment Open
While climate models broadly agree on the changes expected to occur over the Arctic with global warming on a pan-Arctic scale (i.e. polar amplification, sea ice loss, and increased precipitation), the magnitude and patterns of these change…
View article: How do different pathways connect the stratospheric polar vortex to its tropospheric precursors?
How do different pathways connect the stratospheric polar vortex to its tropospheric precursors? Open
Processes involving troposphere–stratosphere coupling have been identified as important contributors to an improved subseasonal to seasonal prediction in the mid-latitudes. However, atmosphere models still struggle to accurately predict st…
View article: Storylines of Summer Arctic climate change constrained by Barents-Kara Sea and Arctic tropospheric warming for climate risks assessment
Storylines of Summer Arctic climate change constrained by Barents-Kara Sea and Arctic tropospheric warming for climate risks assessment Open
While climate models broadly agree on the changes expected to occur over the Arctic with global warming on a pan-Arctic scale (i.e., polar amplification, sea-ice loss, increased precipitation), the magnitude and patterns of those changes a…
View article: Evaluating Causal Arctic‐Midlatitude Teleconnections in CMIP6
Evaluating Causal Arctic‐Midlatitude Teleconnections in CMIP6 Open
To analyze links among key processes that contribute to Arctic‐midlatitude teleconnections we apply causal discovery based on graphical models known as causal graphs. First, we calculate the causal dependencies from observations during 198…
View article: Comment on wcd-2023-5
Comment on wcd-2023-5 Open
Abstract. Processes involving troposphere-stratosphere coupling have been identified as important contributors to an improved subseasonal to seasonal prediction in mid-latitudes. However, there is only a very vague understanding of the loc…
View article: Causal model evaluation of Arctic-midlatitude process during the boreal cold season in CMIP
Causal model evaluation of Arctic-midlatitude process during the boreal cold season in CMIP Open
Linked to increased sea ice loss, the Arctic region has warmed at least four times faster than the global average over the past 40 years. Mutual links between amplified Arctic warming with changes and variability in midlatitude weather hav…
View article: Fates of the Beaufort Gyre: Location, Extent and Strength
Fates of the Beaufort Gyre: Location, Extent and Strength Open
The Beaufort Gyre is a major reservoir of freshwater in the Arctic Ocean and plays an important role in shaping the sea ice distribution. The variations in Beaufort Gyre strength, and its capacity to accumulate or release freshwater, are p…
View article: How do different pathways connect the stratospheric polar vortex to its tropospheric precursors?
How do different pathways connect the stratospheric polar vortex to its tropospheric precursors? Open
Processes involving troposphere-stratosphere coupling have been identified as important contributors to an improved subseasonal to seasonal prediction in mid-latitudes. However, there is only a very vague understanding of the localised cou…
View article: Causal model evaluation of Arctic-midlatitude teleconnections in CMIP6
Causal model evaluation of Arctic-midlatitude teleconnections in CMIP6 Open
In this study, we apply causal discovery to analyse causal links among key processes that contribute to Arctic-midlatitude teleconnections. First, we calculate the causal dependencies from observations. We then evaluate climate models part…
View article: Causal evaluation of Arctic-midlatitude processes in CMIP6 model simulations
Causal evaluation of Arctic-midlatitude processes in CMIP6 model simulations Open
<p>The impact of various mechanisms that link Arctic and midlatitude processes occurring in conditions of amplified Arctic warming is still under debate. Observational and model studies lead to divergent conclusions. This has spurred…
View article: High vs. low latitude influence on seasonal stratospheric pathways in the atmospheric model ICON
High vs. low latitude influence on seasonal stratospheric pathways in the atmospheric model ICON Open
<p>Stratospheric pathways play an important role in connecting distant anomaly patterns to each other on seasonal timescales. As long-lived stratospheric extreme events can influence the large-scale tropospheric circulation on timesc…
View article: Improved Circulation in the Northern Hemisphere by Adjusting Gravity Wave Drag Parameterizations in Seasonal Experiments With ICON‐NWP
Improved Circulation in the Northern Hemisphere by Adjusting Gravity Wave Drag Parameterizations in Seasonal Experiments With ICON‐NWP Open
The stratosphere is one of the main potential sources for subseasonal to seasonal predictability in midlatitudes in winter. The ability of an atmospheric model to realistically simulate the stratospheric dynamics is essential in order to m…
View article: Towards seasonal prediction
Towards seasonal prediction Open
Stratospheric variability is one of the main potential sources for sub-seasonal to seasonal predictability in mid-latitudes in winter. Stratospheric pathways play an important role for long-range teleconnections between tropical phenomena,…
View article: Influence of gravity wave drag parametrisations on the stratospheric circulation of seasonal ICON-NWP experiments
Influence of gravity wave drag parametrisations on the stratospheric circulation of seasonal ICON-NWP experiments Open
<p>The stratospheric polar vortex is highly variable in winter and thus, models often struggle to capture its variability and strength. Yet, the influence of the stratosphere on the tropospheric circulation becomes highly important i…