JoC article on a comparison between gravity wave momentum fluxes in observations and climate models

In their Journal of Climate article, SPARC Data Centre scientist Marv Geller and co-authors conduct for the first time, a formal comparison between gravity wave momentum fluxes in models and those derived from observations.

Abstract. Although gravity waves occur over a wide range of spatial and temporal scales, the authors concentrate in this paper on scales that are being parameterized in present climate models, sub-1,000 km scales. Only observational methods that permit derivation of gravity wave momentum fluxes over large geographical areas are discussed, and these are from satellite temperature measurements, constant-density long-duration balloons, and high vertical-resolution radiosonde data. The models discussed include two high-resolution models in which gravity waves are explicitly modeled, Kanto and CAM5, and three climate models containing gravity wave parameterizations, MAECHAM5, HadGEM3, and GISS. Measurements generally show similar flux magnitudes as in models, except that the fluxes derived from satellite measurements fall off more rapidly with height. This is likely due to limitations on the observable range of wavelengths, although other factors may contribute. When one accounts for this more rapid fall-off, the geographical distribution of the fluxes from observations and models compare reasonably well, except for certain features that depend on the specification of the non-orographic gravity wave source functions in the climate models. For instance, both the observed fluxes and those in the high-resolution models are very small at summer high latitudes, but this is not the case for some of the climate models. This comparison between gravity wave fluxes from climate models, high-resolution models, and fluxes derived from observations indicates that such efforts offer a promising path toward improving specifications of gravity wave sources in climate models.

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