SMuK 2021 – scientific programme

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UP: Fachverband Umweltphysik

UP 4: Measurement Techniques & Miscellaneous

UP 4.6: Talk

Friday, September 3, 2021, 12:15–12:30, H7

Does the solar 27-day variability influence the Madden-Julian oscillation in the tropical troposphere? — •Christoph G. Hoffmann and Christian von Savigny — Institut für Physik, Uni Greifswald, Deutschland

The solar irradiance is subject to variations on different time scales including the 27-day cycle. These variations are known to introduce variability in the upper and middle atmosphere. Implications for the troposphere are currently under discussion.

The Madden-Julian oscillation (MJO) is a major source of intraseasonal variability in the troposphere. We analyze whether the temporal evolution of the MJO phases could be linked to the solar 27-day cycle. We basically count the occurrences of particular MJO phases as a function of time lag after the solar 27-day extrema in about 38 years of MJO data.

We find indications for a synchronization between the MJO phase evolution and the solar 27-day cycle, which are most notable under certain conditions: MJO events with a strength greater than 0.5, during the easterly phase of the Quasi-biennial oscillation, and during boreal winter. The MJO appears to cycle through its 8 phases within 2 solar 27-day cycles. However, these results strongly depend on the used MJO index.

We point out that we do not claim to unambiguously prove this relationship; neither in a statistical, nor in a causal sense. Instead, we challenge these unexpected initial findings ourselves in detail by varying underlying datasets and methods.