Judah Cohen
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View article: The tropospheric response to zonally asymmetric momentum torques: implications for the downward response to wave reflection and SSW events
The tropospheric response to zonally asymmetric momentum torques: implications for the downward response to wave reflection and SSW events Open
The role of zonal structure in the stratospheric polar vortex for the surface response to weak vortex states is isolated using an intermediate-complexity moist general circulation model. Zonally asymmetric wave-1 momentum torques with vary…
View article: Cold-air outbreaks in the continental US: Connections with stratospheric variations
Cold-air outbreaks in the continental US: Connections with stratospheric variations Open
Mid-latitude Northern Hemisphere extreme cold events continue to occur despite overall winter warming trends. These events have been linked to weakened stratospheric polar vortex (SPV) states. In this study, we analyze both the upper and l…
View article: On Risk of Rain on Snow Over High‐Latitude Coastal Areas in North America
On Risk of Rain on Snow Over High‐Latitude Coastal Areas in North America Open
Extreme floods and landslides in high‐latitude watersheds have been associated with rain‐on‐snow (ROS) events. Yet, the risks of changing precipitation phases on a declining snowpack under a warming climate remain unclear. Normalizing the …
View article: Author Correction: No detectable trend in mid-latitude cold extremes during the recent period of Arctic amplification
Author Correction: No detectable trend in mid-latitude cold extremes during the recent period of Arctic amplification Open
View article: Teleconnection from Arctic warming suppresses long-term warming in central Eurasia
Teleconnection from Arctic warming suppresses long-term warming in central Eurasia Open
Whether the rapid warming of the Arctic, particularly the Barents-Kara Sea (BKS), substantially affects the Eurasian winter climate has been debated for over a decade. Here, we use an extended dynamical adjustment method to separate the ef…
View article: Lessened projections of Arctic warming and wetting after correcting for model errors in global warming and sea ice cover
Lessened projections of Arctic warming and wetting after correcting for model errors in global warming and sea ice cover Open
Credible projections of Arctic warming and wetting (AWW) are essential for informed decision-making in a changing climate. However, current AWW projections from state-of-the-art climate models carry uncertainties. Using observational datas…
View article: A process-based evaluation of biases in extratropical stratosphere–troposphere coupling in subseasonal forecast systems
A process-based evaluation of biases in extratropical stratosphere–troposphere coupling in subseasonal forecast systems Open
Two-way coupling between the stratosphere and troposphere is recognized as an important source of subseasonal-to-seasonal (S2S) predictability and can open windows of opportunity for improved forecasts. Model biases can, however, lead to a…
View article: Structural fluctuations of the Arctic Oscillation tied to the Atlantic Multidecadal Oscillation
Structural fluctuations of the Arctic Oscillation tied to the Atlantic Multidecadal Oscillation Open
The Arctic Oscillation (AO) has been observed to undergo distinct decadal structural fluctuations that significantly influence regional weather and climate. Understanding the drivers and mechanisms behind the AO’s spatial nonstationarity i…
View article: Anomalous Arctic warming linked with severe winter weather in Northern Hemisphere continents
Anomalous Arctic warming linked with severe winter weather in Northern Hemisphere continents Open
We have extended a recently developed metric that ingests United States station data—the accumulated winter season severity index—to a global indicator based on temperature and snowfall from reanalysis output. The expanded index is analyze…
View article: Development of the signal‐to‐noise paradox in subseasonal forecasting models: When? Where? Why?
Development of the signal‐to‐noise paradox in subseasonal forecasting models: When? Where? Why? Open
Subseasonal forecast models are shown to suffer from the same inconsistency in the signal‐to‐noise ratio evident in climate models. Namely, predictable signals in these models are too weak, yet there is a relatively high level of agreement…
View article: The Predictability of the Downward Versus Non‐Downward Propagation of Sudden Stratospheric Warmings in S2S Hindcasts
The Predictability of the Downward Versus Non‐Downward Propagation of Sudden Stratospheric Warmings in S2S Hindcasts Open
Roughly one‐third of sudden stratospheric warming (SSW) events lack a strong canonical surface response, and this can lead to a forecast bust if a strong response was predicted. Hence, it is desirable to predict before SSW onset if an even…
View article: Supplementary material to "A process-based evaluation of biases in extratropical stratosphere-troposphere coupling in subseasonal forecast systems"
Supplementary material to "A process-based evaluation of biases in extratropical stratosphere-troposphere coupling in subseasonal forecast systems" Open
View article: A process-based evaluation of biases in extratropical stratosphere-troposphere coupling in subseasonal forecast systems
A process-based evaluation of biases in extratropical stratosphere-troposphere coupling in subseasonal forecast systems Open
Two-way coupling between the stratosphere and troposphere is recognized as an important source of subseasonal-to-seasonal (S2S) predictability and can open windows of opportunity for improved forecasts. Model biases can, however, lead to a…
View article: Boreal Winter Extratropical Weather Regime Changes During 1979–2019 and Their Weather Impacts and Possible Linkages to Sea‐Ice in the Nordic Seas
Boreal Winter Extratropical Weather Regime Changes During 1979–2019 and Their Weather Impacts and Possible Linkages to Sea‐Ice in the Nordic Seas Open
Previous studies have suggested possible connections between the decreasing Arctic sea‐ice and long‐duration (>5 days, LD) cold weather events in Eurasia and North America. Here we document the occurrences of weather regimes in winter by t…
View article: The predictability of the downward vs. non-downward propagation of sudden stratospheric warmings in S2S hindcasts
The predictability of the downward vs. non-downward propagation of sudden stratospheric warmings in S2S hindcasts Open
Roughly one-third of sudden stratospheric warming (SSW) events lack a strong canonical surface impact, and this can lead to a forecast bust if a strong impact had been predicted. Hence, it is important to predict before the SSW onset if an…
View article: Development of the signal-to-noise paradox in subseasonal forecasting models: After how long? Where? Why?
Development of the signal-to-noise paradox in subseasonal forecasting models: After how long? Where? Why? Open
Subseasonal forecast models are shown to suffer from the same inconsistency found in climate models between the low strength of predictable signals and the relatively high level of agreement they exhibit with observed variability of …
View article: Anomalous Arctic Warming Linked with Severe Winter Weather in Northern Hemisphere Continents
Anomalous Arctic Warming Linked with Severe Winter Weather in Northern Hemisphere Continents Open
We have extended a recently developed index of accumulated winter season severity index (AWSSI), originally based on temperature and snowfall observations from weather stations in the United States only, to the entire Northern Hemisphere u…
View article: No detectable trend in mid-latitude cold extremes during the recent period of Arctic amplification
No detectable trend in mid-latitude cold extremes during the recent period of Arctic amplification Open
It is widely accepted that Arctic amplification—accelerated Arctic warming—will increasingly moderate cold air outbreaks to the mid-latitudes. Yet, an increasing number of recent studies also argue that Arctic amplification can contribute …
View article: The Arctic
The Arctic Open
Rapid warming due to human-caused climate change is reshaping the Arctic, enhanced by physical processes that cause the Arctic to warm more quickly than the global average, collectively called Arctic amplification. Observations over the pa…
View article: Introduction
Introduction Open
—J. BLUNDEN, T. BOYER, AND E. BARTOW-GILLIES Earth’s global climate system is vast, complex, and intricately interrelated. Many areas are influenced by global-scale phenomena, including the “triple dip” La Niña conditions that prevailed in…
View article: Summer atmospheric circulation over Greenland in response to Arctic amplification and diminished spring snow cover
Summer atmospheric circulation over Greenland in response to Arctic amplification and diminished spring snow cover Open
View article: Adaptive bias correction for improved subseasonal forecasting
Adaptive bias correction for improved subseasonal forecasting Open
View article: Response to Limited surface impacts of the January 2021 sudden stratospheric warming
Response to Limited surface impacts of the January 2021 sudden stratospheric warming Open
View article: CESM2 Idealized Experiment Output: Summer atmospheric response to zero May North American snow cover
CESM2 Idealized Experiment Output: Summer atmospheric response to zero May North American snow cover Open
The National Center for Atmospheric Research’s Community Earth System Model version 2.2 (CESM2) (Danabasoglu et al., 2020) was run in the Atmospheric Model Intercomparison Project (AMIP) configuration. SSTs and sea-ice were prescribed as m…
View article: CESM2 Idealized Experiment Output: Summer atmospheric response to zero May North American snow cover
CESM2 Idealized Experiment Output: Summer atmospheric response to zero May North American snow cover Open
The National Center for Atmospheric Research’s Community Earth System Model version 2.2 (CESM2) (Danabasoglu et al., 2020) was run in the Atmospheric Model Intercomparison Project (AMIP) configuration. SSTs and sea-ice were prescribed as m…
View article: Subseasonal Prediction of Central European Summer Heatwaves with Linear and Random Forest Machine Learning Models
Subseasonal Prediction of Central European Summer Heatwaves with Linear and Random Forest Machine Learning Models Open
Heatwaves are extreme near-surface temperature events that can have substantial impacts on ecosystems and society. Early warning systems help to reduce these impacts by helping communities prepare for hazardous climate-related events. Howe…
View article: Adaptive Bias Correction for Improved Subseasonal Forecasting
Adaptive Bias Correction for Improved Subseasonal Forecasting Open
Subseasonal forecasting -- predicting temperature and precipitation 2 to 6 weeks ahead -- is critical for effective water allocation, wildfire management, and drought and flood mitigation. Recent international research efforts have advance…
View article: Measuring “Weather Whiplash” Events in North America: A New Large‐Scale Regime Approach
Measuring “Weather Whiplash” Events in North America: A New Large‐Scale Regime Approach Open
The term “weather whiplash” was recently coined to describe abrupt swings in weather conditions from one extreme to another, such as from a prolonged, frigid cold spell to anomalous warmth or from drought to heavy precipitation. These even…
View article: The “Polar Vortex” Winter of 2013/2014
The “Polar Vortex” Winter of 2013/2014 Open
The term “polar vortex” remained largely a technical term until early January 2014 when the United States (US) media used it to describe an historical cold air outbreak in eastern North America. Since then, “polar vortex” has been used mor…
View article: Influence and prediction value of Arctic sea ice for spring Eurasian extreme heat events
Influence and prediction value of Arctic sea ice for spring Eurasian extreme heat events Open