Explaining the scales of mixed Rossby-gravity waves

9 December 2024

Photo: S.Maho

MRG wave in linear theory (left), reanalysis data (middle) and numerical simulations (right). Colours in different panels show the MRG wave geopotential height perturbations. The location of background wind maxima are hatched. The top and bottom rows show MRG wave typical for the upper stratosphere and the upper troposphere, respectively.

Mixed Rossby-gravity (MRG) waves are westward-propagating disturbances associated with cross-equatorial flows throughout the tropical atmosphere. Observations show that their spatial scales increase with altitude so that MRG waves in the upper stratosphere and higher up have planetary scales whereas the upper troposphere MRG waves appear at synoptic scales. An explanation of scale differences remained elusive until recently. Sandor Istvan Maho and colleagues from the Atmospheric Dynamics and Predictability group have now shown that wave-mean flow interactions generate MRG waves in such a way that the latitude location of the jet determines the peak scales of the excited MRG waves. Details can be found in just published paper in Geophysical Research Letters.

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Publication

Mahó, S.I., Žagar, N., Lunkeit, F., & Vasylkevych, S. (2024). The mechanism of scale selection for mixed Rossby-gravity waves in the upper troposphere and the upper stratosphere. Geophysical Research Letters, 51, e2024GL110811, https://doi.org/10.1029/2024GL110811

Contact

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