EGU2020-6394
https://doi.org/10.5194/egusphere-egu2020-6394
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Diversity of the Madden-Julian Oscillation

Guosen Chen1, Bin Wang1,2, and Fei Liu1
Guosen Chen et al.
  • 1Nanjing University of Information science and Technology, school of atmospheric sciences, China (guosen@nuist.edu.cn; liuf@nuist.edu.cn)
  • 2University of Hawaii at Manoa, USA (wangbin@hawaii.edu)

Madden-Julian Oscillation (MJO) is the dominant mode of atmospheric intraseasonal variability and the cornerstone for subseasonal prediction of extreme weather events. Climate modeling and prediction of MJO remain a big challenge, partially due to lack of understanding the MJO diversity. Here, we delineate observed MJO diversity by cluster analysis of propagation patterns of MJO events, which reveals four archetypes: standing, jumping, slow eastward propagation, and fast eastward propagation. Each type of MJO exhibits distinctive east-west asymmetric circulation and thermodynamic structures. Tight coupling between the Kelvin wave response and major convection is unique for the propagating events (slow and fast propagations), while the strength and length of Kelvin wave response distinguish slow and fast propagations. The Pacific sea surface temperature anomalies can affect MJO diversity by modifying the Kelvin wave response and its coupling to MJO convection. An El Niño state tends to increase the zonal scale of Kelvin wave response, to amplify it, and to enhance its coupling to the convection, while a La Niña state tends to decrease the zonal scale of Kelvin wave response, to suppress it, and to weaken its coupling to the major convection. This effect of background sea surface temperature on the MJO diversity has been verified by using a theoretical model. The results shed light on the mechanisms responsible for MJO diversity and provide potential precursors for foreseeing MJO propagation.

How to cite: Chen, G., Wang, B., and Liu, F.: Diversity of the Madden-Julian Oscillation, EGU General Assembly 2020, Online, 4–8 May 2020, https://doi.org/10.5194/egusphere-egu2020-6394, 2020

Comments on the presentation

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Presentation version 1 – uploaded on 04 May 2020
  • CC1: Comment on EGU2020-6394, Paul Pukite, 06 May 2020

    Why do the SOI and MJO track each other so closely but with lag of 21 days separating them?

    • AC1: Reply to CC1, Guosen Chen, 06 May 2020

      This figure does not come from my presentation.

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

        You are correct that it isn't part of your presentation, but the question still stands.

        I retrieved the MJO times series from the NOAA site here

        and compared it against a high-resolution version of the Southern Oscillation Index from here

        They appear to be essentially the same measure apart from the 21-day shift between them. Is the MJO nothing more than the higher-frequency standing-wave modes that are spun off of ENSO?

         

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

          What kind of MJO time series do you use? Is it RMM index or something like that?

          As the MJO convection propagates from equatorial Indian Ocean to equatorial Pacific, it may cause SLP variations that resemble the SO. Therefore, the correlation between MJO and SOI could be a reflection of the influence of SLP variation by the MJO. The time lag between them is probably due to the time lag between the positve phase describe by the MJO time series you used and the MJO phase that cause SO-like SLP pattern.

          I don't think MJO is a slave to ENSO. 

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

            I am using this one, the "pentad" series from NOAA :