Singular vectors and their nonlinear evolution during the January 2009 stratospheric sudden warming

Coy, L.; Reynolds, C. A.

doi:10.1002/qj.2181

Cited by 4 publications

(2 citation statements)

References 45 publications

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“…The dynamical link between this unstable mode with extremely large growth rates and the prediction of the 2009 SSW can also be confirmed by the results of Coy and Reynolds (2014). They used a dry mechanistic multilayer model to compute stratospheric singular vectors (SVs) during the onset of the 2009 SSW.…”

Section: Discussionmentioning

confidence: 65%

On the Existence of the Predictability Barrier in the Wintertime Stratospheric Polar Vortex: Intercomparison of Two Stratospheric Sudden Warmings in 2009 and 2010 Winters

Mukougawa

Noguchi

Kuroda³

et al. 2022

Journal of the Meteorological Society of Japan

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To compare the predictability of two stratospheric sudden warming (SSW) events occurring in 2009 and 2010, ensemble forecast experiments are conducted using an Atmospheric General Circulation Model (AGCM). It is found that the predictable period of the vortex splitting SSW in 2009 is about 7 days which is much shorter than that of the vortex-displacement SSW in 2010. The latter event is predictable more than 13 days in advance. The ensemble spread in the upper stratosphere for medium-range forecasts is found to be enlarged just prior to the onset of the 2009 SSW event, while no such enlargement is seen for the 2010 SSW event.Stability analysis of the zonally asymmetric basic states specified by the ensemble mean forecast using a nondivergent barotropic vorticity equation reveals that the extremely distorted polar vortex in the upper stratosphere just before the onset of the 2009 SSW event is highly unstable to infinitesimal perturbations, whereas there is no such unstable mode with an extremely large growth rate during the 2010 SSW event. In addition, the most unstable mode during the onset of the 2009 SSW event has a similar horizontal structure to the 1 st EOF of the ensemble spread. Thus, it is suggested that a predictability barrier inherent in the upper stratospheric circulation, characterized by the presence of dynamically unstable modes with large growth rates limits the predictable period of the 2009 SSW event.

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Section: Discussionmentioning

confidence: 65%

On the Existence of the Predictability Barrier in the Wintertime Stratospheric Polar Vortex: Intercomparison of Two Stratospheric Sudden Warmings in 2009 and 2010 Winters

Mukougawa

Noguchi

Kuroda³

et al. 2022

Journal of the Meteorological Society of Japan

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“…Slowly-varying climate anomalies are made up of generally "nonorthogonal" dynamical modes (e.g., Farrell and Ioannou 1996, Penland and Matrosova 2006, Coy and Reynolds 2014, Henderson et al 2020, Albers and Newman 2021, which typically have similar spatial patterns yet evolve on different but overlapping timescales. This nonorthogonality is a consequence of fundamental asymmetries within the physical climate system (Farrell and Ioannou 1996).…”

Section: Dynamical Climate Modes and The Lim Dynamical Filtermentioning

confidence: 99%

The February 2021 Cold Air Outbreak in the United States: A Subseasonal Forecast of Opportunity

Albers

Newman

Hoell

et al. 2022

Bulletin of the American Meteorological Society

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The sources of predictability for the February 2021 cold air outbreak (CAO) over the central United States, which led to power grid failures and water delivery shortages in Texas, are diagnosed using a machine learning-based prediction model called a Linear Inverse Model (LIM). The flexibility and low computational cost of the LIM allows its forecasts to be used for identifying and assessing the predictability of key physical processes. The LIM may also be run as a climate model for sensitivity and risk analysis for the same reasons. The February 2021 CAO was a subseasonal forecast of opportunity, as the LIM confidently predicted the CAO’s onset and duration four weeks in advance, up to two weeks earlier than other initialized numerical forecast models. The LIM shows that the February 2021 CAO was principally caused by unpredictable internal atmospheric variability and predictable La Niña teleconnections, with nominally predictable contributions from the previous month’s sudden stratospheric warming and the Madden-Julian Oscillation. When run as a climate model, the LIM estimates that the February 2021 CAO was in the top 1% of CAO severity and suggests that similarly extreme CAOs could be expected to occur approximately every 20-30 years.

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Subseasonal predictability of the North Atlantic Oscillation

Albers

Newman

2021

Environ. Res. Lett.

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Skillfully predicting the North Atlantic Oscillation (NAO), and the closely related northern annular mode (NAM), on ‘subseasonal’ (weeks to less than a season) timescales is a high priority for operational forecasting centers, because of the NAO’s association with high-impact weather events, particularly during winter. Unfortunately, the relatively fast, weather-related processes dominating total NAO variability are unpredictable beyond about two weeks. On longer timescales, the tropical troposphere and the stratosphere provide some predictability, but they contribute relatively little to total NAO variance. Moreover, subseasonal forecasts are only sporadically skillful, suggesting the practical need to identify the fewer potentially predictable events at the time of forecast. Here we construct an observationally based linear inverse model (LIM) that predicts when, and diagnoses why, subseasonal NAO forecasts will be most skillful. We use the LIM to identify those dynamical modes that, despite capturing only a fraction of overall NAO variability, are largely responsible for extended-range NAO skill. Predictable NAO events stem from the linear superposition of these modes, which represent joint tropical sea-surface temperature-lower stratosphere variability plus a single mode capturing downward propagation from the upper stratosphere. Our method has broad applicability because both the LIM and the state-of-the-art European Centre for Medium-Range Weather Forecasts Integrated Forecast System (IFS) have higher (and comparable) skill for the same set of predicted high skill forecast events, suggesting that the low-dimensional predictable subspace identified by the LIM is relevant to real-world subseasonal NAO predictions.

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Singular vectors and their nonlinear evolution during the January 2009 stratospheric sudden warming

Cited by 4 publications

References 45 publications

On the Existence of the Predictability Barrier in the Wintertime Stratospheric Polar Vortex: Intercomparison of Two Stratospheric Sudden Warmings in 2009 and 2010 Winters

On the Existence of the Predictability Barrier in the Wintertime Stratospheric Polar Vortex: Intercomparison of Two Stratospheric Sudden Warmings in 2009 and 2010 Winters

The February 2021 Cold Air Outbreak in the United States: A Subseasonal Forecast of Opportunity

Subseasonal predictability of the North Atlantic Oscillation

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