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Abstract
The stratosphere can be a source of predictability for surface weather on timescales of several weeks to months. However, the potential predictive skill gained from stratospheric variability can be limited by biases in the representation of stratospheric processes and the coupling of the stratosphere with surface climate in forecast systems. This study provides a first systematic identification of model biases in the stratosphere across a wide range of subseasonal forecast systems. It is found that many of the forecast systems considered exhibit warm global-mean temperature biases from the lower to middle stratosphere, too strong/cold wintertime polar vortices, and too cold extratropical upper-troposphere/lower-stratosphere regions. Furthermore, tropical stratospheric anomalies associated with the Quasi-Biennial Oscillation tend to decay toward each system’s climatology with lead time. In the Northern Hemisphere (NH), most systems do not capture the seasonal cycle of extreme-vortex-event probabilities, with an underestimation of sudden stratospheric warming events and an overestimation of strong vortex events in January. In the Southern Hemisphere (SH), springtime interannual variability in the polar vortex is generally underestimated, but the timing of the final breakdown of the polar vortex often happens too early in many of the prediction systems. These stratospheric biases tend to be considerably worse in systems with lower model lid heights. In both hemispheres, most systems with low-top atmospheric models also consistently underestimate the upward wave driving that affects the strength of the stratospheric polar vortex. We expect that the biases identified here will help guide model development for subseasonal-to-seasonal forecast systems and further our understanding of the role of the stratosphere in predictive skill in the troposphere.
Original language | English |
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Pages (from-to) | 977-1001 |
Number of pages | 25 |
Journal | Weather and Climate Dynamics |
Volume | 3 |
Issue number | 3 |
DOIs | |
Publication status | Published - 19 Aug 2022 |
Bibliographical note
Funding Information:This research has been supported by the Eidgenössische Technische Hochschule Zürich (grant no. ETH-05 19-1); the Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (grant nos. PP00P2_170523 and PP00P2_198896); the Israel Science Foundation (grant no. 3259/19); the Universidad de Buenos Aires (grant no. UBACyT20020170100428BA); the Agencia Nacional de Promoción Científica y Tecnológica (grant no. PICT-2018-03046); the Ministerio de Ciencia e Innovación (grant nos. PID2019-109107GB-I00, RTI2018-096402-B-I00, and PID2019-110234RBC21); the Ministerio de Economía y Competitividad (grant no. RYC-2016-21181); the Natural Environment Research Council (grant no. NE/S00985X/1); the Royal Society (grant no. UF160545); the National Research Foundation of Korea (grant no. 2017R1E1A1A01074889); the Department of Energy, Labor and Economic Growth (grant no. DE-SC0022070); the Division of Atmospheric and Geospace Sciences (grant no. IA 1947282); and the National Oceanic and Atmospheric Administration (grant nos. NA18OAR4320123 and NA20NWS4680051).
ASJC Scopus subject areas
- Atmospheric Science
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Dive into the research topics of 'Quantifying stratospheric biases and identifying their potential sources in subseasonal forecast systems'. Together they form a unique fingerprint.Projects
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Planetary and Gravity Waves as Drivers of Sudden Stratospheric Warmings
Wright, C. (PI) & Mitchell, N. (CoI)
Natural Environment Research Council
1/07/19 → 31/03/23
Project: Research council