7.6 The effects of a gravity-wave stress parameterization a time-dependent mesoscale model

Thursday, 5 August 2010: 11:45 AM
Torrey's Peak I&II (Keystone Resort)
Gunilla Svensson, Stockholm University, Stockholm, Sweden; and C. J. Nappo

It is now well established that terrain of even gentle relief can generate gravity waves in the nighttime atmosphere. These waves propagate upward, and under very common conditions they will grow in amplitude until becoming convectively unstable. Because linear wave theory does not encompass wave breakdowns, this process must be parameterized. This parameterization has been used to explain the observations of turbulence in the residual layer where turbulence is not expected.

However, to date this wave-stress parameterization has been confined to kinematic models, and so it is not clear how the wave-stress divergence impacts time-dependent models. This question is explored using a single-column version of a mesoscale model. The results from some initial experiments are reported. The first experiment uses idealized terrain with an initial Ekman wind profile and constant thermal stratification, and the second experiment uses the CASES-99 terrain with initial wind and temperature profiles derived from soundings. In the later case, the models run alternatively with and without the wave stress parameterization, and the results are compared with observations made at later times.

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