edu.ucar.opensky::articles:42959 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-24T17:55:45.458749 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.net/ark:/85065/d74x5d5s A process-based evaluation of biases in extratropical stratosphere-troposphere coupling in subseasonal forecast systems 2025-02-07T00:00:00Z publication https://n2t.net/ark:/85065/d74x5d5s https://doi.org/10.5194/wcd-6-171-2025 Garfinkel, C. I. author Lawrence, Z. D. author Butler, A. H. author Dunn-Sigouin, E. author Statnaia, I. author Karpechko, A. Y. author Koren, G. author Abalos, M. author Ayarzagüena, B. author Barriopedro, D. author Calvo, N. author de la Cámara, A. author Charlton-Perez, A. author Cohen, J. author Domeisen, D. I. V. author García-Serrano, J. author Hindley, N. P. author Jucker, M. author Kim, H. author Lee, R. author Lee, S. H. author Osman, M. author Palmeiro, F. M. author Polichtchouk, I. author Rao, J. author Richter, Jadwiga H. author Schwartz, C. author Son, S. author Taguchi, M. author Tyrrell, N. L. author Wright, C. J. author Wu, R. W. author UCAR/NCAR - Library publisher <p>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 poor representation of such coupling processes; drifts in a model's circulation related to model biases, resolution, and parameterizations have the potential to feed back on the circulation and affect stratosphere–troposphere coupling. We introduce a set of diagnostics using readily available data that can be used to reveal these biases and then apply these diagnostics to 22 S2S forecast systems.&nbsp;</p><p>In the Northern Hemisphere, nearly all S2S forecast systems underestimate the strength of the observed upward coupling from the troposphere to the stratosphere, downward coupling within the stratosphere, and the persistence of lower-stratospheric temperature anomalies. While downward coupling from the lower stratosphere to the near surface is well represented in the multi-model ensemble mean, there is substantial intermodel spread likely related to how well each model represents tropospheric stationary waves.&nbsp;</p><p>In the Southern Hemisphere, the stratospheric vortex is oversensitive to upward-propagating wave flux in the forecast systems. Forecast systems generally overestimate the strength of downward coupling from the lower stratosphere to the troposphere, even as most underestimate the radiative persistence in the lower stratosphere. In both hemispheres, models with higher lids and a better representation of tropospheric quasi-stationary waves generally perform better at simulating these coupling processes.</p> UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication <span style="font-family:Arial;font-size:10pt;font-style:normal;" data-sheets-root="1">Copyright author(s). This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.</span> None eng geoscientificInformation