Abstract
Abstract. Four major sources of inertia-gravity waves are known in the Earth atmosphere: upper-tropospheric jet-streams, lower-tropospheric fronts, convection and topography. The Andes Cordillera region is an area where all of these major sources are potentially present. By combining ECMWF and NCEP-NCAR reanalysis, satellite and radiosoundings data and mesoscale WRF simulations in the Andes Cordillera region, we were able to identify the cases where, respectively, the jet-stream source, the convective source and the topography source are predominantly in action. We retrieve emitted wave parameters for each case, compare them, and analyse possible emission mechanisms. The WRF mesoscale model shows very good performance in reproducing the inertia-gravity waves identified in the data analysis, and assessing their likely sources.
Highlights
The key role of the gravity waves in the dynamical, transport and mixing properties of the atmosphere is well-known (Andrews et al, 1987; Fritts and Alexander, 2003)
We identified three events of the IGW emission by each of the three major sources in the Andes Cordillera region: jetstream, convection, and topography
The IGW emission by the jet is associated with a geostrophic adjustment happening in the regions of the jet with large Lagrangian Rossby numbers, which confirms the previous diagnostics (e.g. Plougonven et al, 2003)
Summary
Using aircraft measurements, Fritts and Nastrom (1992) and Nastrom and Fritts (1992) showed that the variances of horizontal velocity and temperature are enhanced in the vicinity of fronts and jets, as well as near mountains. Scavuzzo et al (1998), using data from the PYRenees EXPeriment (PYREX), identified IGW with low intrinsic frequency propagating upward and downward from the level where the amplitudes of initial mountain waves are large. These authors suggested that the observed IGW resulted from the geostrophic adjustment of the large-scale flow due to the high amplitude and, eventually, the breaking of the main mountain wave. We combine different technical tools in order to identify and quantify the IGW emission events corresponding to each source
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