EGU2020-7171
https://doi.org/10.5194/egusphere-egu2020-7171
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Troposphere-Stratosphere Coupling In S2S Models and Its Importance for a Realistic Extratropical Response to the Madden-Julian Oscillation

Chen Schwartz and Chaim Garfinkel
Chen Schwartz and Chaim Garfinkel
  • The Fredy & Nadine Herrmann Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel (chen.schwartz1@mail.huji.ac.il)

The representation of upward and downward stratosphere-troposphere coupling and its influence on the teleconnections of the Madden Julian oscillation (MJO) to the European sector is examined in five subseasonal-to-seasonal (S2S) models. We show that while the models simulate a realistic stratospheric response to transient anomalies in troposphere, they overestimate the downward coupling. The models with a better stratospheric resolution capture a more realistic stratospheric response to the MJO, particularly after the first week of the integration. However, in all models examined here the connection between the MJO and vortex variability is weaker than that observed. Finally, we focus on the MJO-SSW teleconnection in the NCEP model, and specifically initializations during the MJO phase with enhanced convection in the west/central pacific (i.e. 6 and 7) that preceded observed SSW. The integrations that simulated a SSW (as observed) can be distinguished from those that failed to simulate a SSW by the realism of the Pacific response to MJO 6/7, with only the simulations that successfully simulate a SSW capturing the North Pacific low. Furthermore, only the simulations that capture the SSW, subsequently simulate a realistic surface response over the North Atlantic and Europe.

How to cite: Schwartz, C. and Garfinkel, C.: Troposphere-Stratosphere Coupling In S2S Models and Its Importance for a Realistic Extratropical Response to the Madden-Julian Oscillation, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7171, https://doi.org/10.5194/egusphere-egu2020-7171, 2020

Comments on the presentation

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Presentation version 1 – uploaded on 03 May 2020
  • CC1: Comment on EGU2020-7171, Paul Pukite, 05 May 2020

    Very interesting presentation. In terms of teleconnections, why is it that ENSO has such a strong correlation to MJO when a 21 day lag is applied?

    This is a 6-part chart (uploaded according to image restrictions) which shows the SOI matched to MJO after a 21 day shift.

  • AC1: Comment on EGU2020-7171, Chen Schwartz, 06 May 2020

    Hi Paul,

    Thank you for your comment.

    How are the MJO and SOI indices defined here (is the SOI here the Tahiti-Darwin pressure difference?)?

    The fluctuations in the SOI index that are correlated with the MJO could be possibly, in part, related to the surface westerly anomalies induced by the MJO, but this is something I've never looked on (the ENSO signal is usually has to be separated from the MJO). 

    The connection to El-Nino events is more complex as far as I know, and it's on timescales longer than 3 weeks. 

     

    Chen

     

    • CC2: Reply to AC1, Paul Pukite, 06 May 2020

      Yes, the SOI that I compared against is the diff between Tahiti and Darwin obtained from here

      The comparison continues to the satellite peaks, i.e. not only the main ENSO cycles but the higher frequency peaks "bleed" from one index to the other. 

      The big difference is that the MJO features traveling waves as opposed to the standing waves of ENSO. Could the MJO be traveling waves that are spawned off by ENSO?

      • AC2: Reply to CC2, Chen Schwartz, 06 May 2020

        Hi Paul, 

        As far as I know, ENSO can modulate the MJO and also its extratropical response, but it does not trigger it (their timescales are not the same). Nevertheless, tropical meteorology is not my expertise, so you may want to attend the Tropical Meteorology session tomorrow, so you can get more in-depth answers. 

         

        Best, 

        Chen 

        • CC3: Reply to AC2, Paul Pukite, 06 May 2020

          Yes, their timescales are not the same but they do seem to bleed into each other from what I can gather by analyzing the time series.

        • AC3: Reply to AC2, Chen Schwartz, 06 May 2020

          Correction: the tropical meteorology is today at 2pm CET