EGU24-13684, updated on 09 Mar 2024
https://doi.org/10.5194/egusphere-egu24-13684
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Development of the signal-to-noise paradox in subseasonal forecasting models: After how long? Where? Why?

Chen Schwartz1,4, Chaim I. Garfinkel1, Jeff Knight2, Masakazu Taguchi3, Judah Cohen5,6, Wen Chen7,8, Amy H. Butler9, Daniela I.V. Domeisen10,11, and Zachary Lawrence9,12
Chen Schwartz et al.
  • 1Hebrew University of Jerusalem, Fredy and Nadine Herrmann Institute of Earth Sciences, Hebrew University, Jerusalem, Israel, Earth Sciences, Jerusalem, Israel (chen.schwartz1@mail.huji.ac.il)
  • 2Met Office Hadley Centre, Exeter, Devon, UK
  • 3Aichi University of Education, Japan
  • 4Centre for Climate Research Singapore, Singapore
  • 5Atmospheric and Environmental Research Inc., Lexington, MA, USA.
  • 6Massachusetts Institute of Technology, Cambridge, MA, USA
  • 7Yunnan Key Laboratory of Meteorological Disasters and Climate Resources in the Greater Mekong Subregion, Yunnan University, Kunming, China
  • 8Department of Atmospheric Sciences, Yunnan University, Kunming, China
  • 9Cooperative Institute for Research in Environmental Sciences, Boulder, CO, USA
  • 10Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
  • 11University of Lausanne, Lausanne, Switzerland
  • 12NOAA Physical Sciences Laboratory, University of Colorado, Boulder, CO, USA

Subseasonal forecast models are shown to suffer from the same  inconsistency found in climate models between the low strength of predictable signals and the relatively high level of agreement they exhibit with observed variability of the atmospheric circulation. That is, subseasonal forecast models show higher correlation with observed variability than with their own simulations, i.e., the signal-to-noise paradox. Also similar to climate models, this paradox is particularly evident in the North Atlantic sector.  The paradox is not evident in week 1 or week 2 forecasts, and hence is limited to subseasonal timescales. The paradox appears to be related to overly fast decay of Northern Annular  Mode regimes. Three possible causes of this overly fast decay and for the paradox in the Northern Hemisphere are identified:  a too-fast decay of polar stratospheric signals, overly weak downward coupling from the stratosphere to the surface (in some models),  and overly weak transient synoptic eddy feedbacks. While the paradox is clearly evident in the North Atlantic, things are qualitatively different in the Southern Hemisphere:  Southern Annular  Mode regimes persist realistically, the stratospheric signal is well maintained, and eddy feedback is, if anything, too strong and zonal.  

How to cite: Schwartz, C., Garfinkel, C. I., Knight, J., Taguchi, M., Cohen, J., Chen, W., Butler, A. H., Domeisen, D. I. V., and Lawrence, Z.: Development of the signal-to-noise paradox in subseasonal forecasting models: After how long? Where? Why?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13684, https://doi.org/10.5194/egusphere-egu24-13684, 2024.

Supplementary materials

Supplementary material file

Comments on the supplementary material

AC: Author Comment | CC: Community Comment | Report abuse

supplementary materials version 1 – uploaded on 14 Apr 2024, no comments