Mesoscale gravity waves (GW) are important enough for atmospheric (and oceanic) flow that nowadays neither numerical weather-forecast (NWF) models nor general-circulation models (GCM) can do without a parameterization of their effects. Nonetheless they are still insufficiently understood so that corresponding parameterizations considerably differ among each other even in fundamental concepts about the essentials of their dynamics (e.g. Lindzen 1981, Hines 1997). Much of this is made up by tuning, within general-circulation models, in comparison with the present circulation. How reliable this is under climate variations is not clear at all. An additional need to revisit the problem of GW parameterization is posed by the new situation that at least in present NWF models and increasingly also in GCMs part of the GW spectrum is resolved, while another part still remains to be parameterized. Parameterized GWs propagate on a background with considerable transience and horizontal gradients, two factors not taken into account by present schemes. Another key issue is wave breaking: When and how does it happen (Achatz 2007)? Finally, even GW emission by tropospheric flow is only insufficiently understood. The talk will address these issues and report some contributions to progress on the long road to their solution. Achatz, U., 2007: Gravity-wave breaking: Linear and primary nonlinear dynamics. Adv. Space Res., 40, 719-733 Hines, C.O., 1997: Doppler-spread parameterization of gravity-wave momentum deposition in the middle atmosphere. Part 2: Broad and quasi monochromatic spectra, and implementation. J. Atmosph. Sol.-Terr. Phys., 59, 387-400 Lindzen, R. S., 1981: Turbulence and stress owing to gravity wave and tidal breakdown. J. Geophys. Res., 86, 9707–9714

Diese Veranstaltung ist Teil der Reihe Karlsruher Meteorologisches Kolloquium

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Referent/in
Prof. Dr. Ulrich Achatz

Johann Wolfgang Goethe-Universität Frankfurt/Main
Institut für Atmosphäre und Umwelt

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Institut für Meteorologie und Klimaforschung
Karlsruher Institut für Technologie
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