EGU22-3948, updated on 27 Mar 2022
https://doi.org/10.5194/egusphere-egu22-3948
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Seasonal Predictability of wintertime North Atlantic cyclonic activity through the NAO and the eddy-driven jet stream

Alvise Aranyossy1, Sebastian Brune1, Lara Hellmich2,3, Mikhail Dobrynin1, Daniel Krieger4,3, and Johanna Baehr1
Alvise Aranyossy et al.
  • 1Institute of Oceanography, CEN, Universität Hamburg, Hamburg, Germany
  • 2Max Planck Institute for Meteorology, Hamburg, Germany
  • 3International Max Planck Research School on Earth System Modelling, Hamburg, Germany
  • 4Helmholtz-Zentrum Hereon, Geesthacht, Germany

We investigate the potential for enhancing the seasonal prediction skill of mid-latitude cyclonic activity, represented by eddy kinetic energy (EKE) at 250 hPa over the North Atlantic and Europe, in hindcast simulations with the Max Planck Institute Earth System Model (MPI-ESM) against the ECMWF ERA5 reanalysis. Our analysis focuses on wintertime months (December-March) from 1982 to 2019, with a 30-member seasonal hindcast ensemble initialized every November 1st. Based on the initial confirmation that in both ERA5 reanalysis and MPI-ESM hindcasts, the eddy-driven jet stream and the wintertime North Atlantic Oscillation (NAO) play a significant role in wintertime's spatial and temporal distribution of mid-latitude cyclonic activity, we perform ensemble subsampling.

Specifically, we sample each winter so that a northern position of the jet stream is consistent with a positive phase of the NAO and represents poleward enhanced EKE activity. In contrast, a southern position of the jet stream is consistent with a negative phase of the NAO and represents equatorward enhanced EKE activity. Preliminary analysis of the predictive skill of MPI-ESM hindcasts with respect to ERA5 shows that such subsampling with respect to a consistent representation of the jet stream position and the NAO phase leads to improvements over the skill from the 30-member ensemble mean, with significant correlations concentrated over areas of major frequency of storm tracks. Our results put into practical use that an enhanced representation of the large-scale climate variability plays a crucial role in the long-term prediction of high-frequency events such as mid-latitude cyclones.

How to cite: Aranyossy, A., Brune, S., Hellmich, L., Dobrynin, M., Krieger, D., and Baehr, J.: Seasonal Predictability of wintertime North Atlantic cyclonic activity through the NAO and the eddy-driven jet stream, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3948, https://doi.org/10.5194/egusphere-egu22-3948, 2022.

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