The Climate-system Historical Forecast Project: Do stratosphere-resolving models make better seasonal climate predictions in boreal winter?

• Published in: Quarterly Journal of the Royal Meteorological Society
• Main Authors: Butler, Amy H., Arribas, Alberto, Athanassiadou, Maria, Baehr, Johanna, Calvo, Natalia, Charlton-Perez, Andrew, Deque, Michel, Domeisen, Daniela I.V., Fröhlich, Kristina, Hendon, Harry, Imada, Yukiko, Ishii, Masayoshi, Iza, Maddalen, Karpechko, Alexey Yu., Kumar, Arun, MacLachlan, Craig, Merryfield, William J., Müller, Wolfgang A., O'Neill, Alan, Scaife, Adam A., Scinocca, John, Sigmond, Michael, Stockdale, Timothy N., Yasuda, Tamaki
• Format: Article in Journal/Newspaper
• Language: English
• Published: Royal Meteorological Society 2016
• Subjects: North Atlantic; North Atlantic oscillation
• Online Access: https://oceanrep.geomar.de/id/eprint/31254/; https://oceanrep.geomar.de/id/eprint/31254/1/qj2743.pdf; https://oceanrep.geomar.de/id/eprint/31254/2/qj2743-sup-0001-AppendixS1.doc; https://oceanrep.geomar.de/id/eprint/31254/8/Butler.pdf; https://doi.org/10.1002/qj.2743

Using an international, multi-model suite of historical forecasts from the World Climate Research Programme (WCRP) Climate-system Historical Forecast Project (CHFP), we compare the seasonal prediction skill in boreal wintertime between models that resolve the stratosphere and its dynamics (“high-top”) and models that do not (“low-top”). We evaluate hindcasts that are initialized in November, and examine the model biases in the stratosphere and how they relate to boreal wintertime (Dec-Mar) seasonal forecast skill. We are unable to detect more skill in the high-top ensemble-mean than the low-top ensemble-mean in forecasting the wintertime North Atlantic Oscillation, but model performance varies widely. Increasing the ensemble size clearly increases the skill for a given model. We then examine two major processes involving stratosphere-troposphere interactions (the El Niño-Southern Oscillation/ENSO and the Quasi-biennial Oscillation/QBO) and how they relate to predictive skill on intra-seasonal to seasonal timescales, particularly over the North Atlantic and Eurasia regions. High-top models tend to have a more realistic stratospheric response to El Niño and the QBO compared to low-top models. Enhanced conditional wintertime skill over high-latitudes and the North Atlantic region during winters with El Niño conditions suggests a possible role for a stratospheric pathway.