A new excitation mechanism of mixed Rossby–gravity waves

7 May 2024

Photo: S.Maho

Energy spectra of the mixed Rossby–gravity waves in simulations with realistic background zonal wind and (a) symmetric and (b) asymmetric forcing. The averaging period is the first 3 days of simulation time. Thin and thick curves denote the individual simulations and the means over June–August (JJA) and March–May (MAM) cases respectively.

Synoptic-scale motions in the tropical upper troposphere with significant cross-equatorial flow component are associated with mixed Rossby-gravity (MRG) waves.
The MRG waves have been shown to contribute significantly to tropical subseasonal variability, therefore understanding their generation is crucial for the predictability of tropical weather. However, existing theories of the MRG excitation could not explain the scale selection. A paper by Sándor Istvan Mahó and colleagues in the Atmospheric Dynamics and Predictability Group of MI introduces a new theory of the MRG wave excitation that leads to the MRG waves with horizontal scales that correspond to the synoptic scales observed in the tropical upper troposphere. The key aspect of the new theory is the interaction between waves emanating from tropical heat sources and an asymmetric subtropical zonal jet. Details and further results: https://doi.org/10.1002/qj.4742

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More information

Publication
Mahó, S. I., S. Vasylkevych, and N. Žagar, 2024: Excitation of mixed Rossby-gravity waves by wave - mean flow interactions on the sphere. Quart. J. Roy. Met. Soc., 1-17. https://doi.org/10.1002/qj.4742

DFG-funded project TRR181

Contact
Sándor Mahó
Universität Hamburg
CEN – Center for Earth System Research and Sustainability
Telefon: +49 40 42838-9203
Email: sandor.maho@uni-hamburg.de