The predictability of the extratropical stratosphere on monthly time-scales and its impact on the skill of tropospheric forecasts

• Published in: Quarterly Journal of the Royal Meteorological Society
• Main Authors: Tripathi, Om P., Baldwin, Mark, Charlton-Perez, Andrew, Charron, Martin, Eckermann, Stephen D., Gerber, Edwin, Harrison, R. Giles, Jackson, David R., Kim, Baek-Min, Kuroda, Yuhji, Lang, Andrea, Mahmood, Sana, Mizuta, Ryo, Roff, Greg, Sigmond, Michael, Son, Seok-Woo
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Royal Meteorological Society 2018
• Subjects: QUASI-BIENNIAL OSCILLATION; POLAR-NIGHT VORTEX; NORTHERN-HEMISPHERE; SUDDEN WARMINGS; PLANETARY-WAVES; ANNULAR MODE; WINTER STRATOSPHERE; ARCTIC OSCILLATION; CLIMATE RESPONSE; NUMERICAL-MODEL; stratospheric predictability; tropospheric forecast; seasonal predictability; polar night
• Online Access: https://hdl.handle.net/10371/207237; https://doi.org/10.1002/qj.2432

Extreme variability of the winter- and spring-time stratospheric polar vortex has been shown to affect extratropical tropospheric weather. Therefore, reducing stratospheric forecast error may be one way to improve the skill of tropospheric weather forecasts. In this review, the basis for this idea is examined. A range of studies of different stratospheric extreme vortex events shows that they can be skilfully forecasted beyond 5 days and into the sub-seasonal range (0-30 days) in some cases. Separate studies show that typical errors in forecasting a stratospheric extreme vortex event can alter tropospheric forecast skill by 5-7% in the extratropics on sub-seasonal time-scales. Thus understanding what limits stratospheric predictability is of significant interest to operational forecasting centres. Both limitations in forecasting tropospheric planetary waves and stratospheric model biases have been shown to be important in this context. Y 1