scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Three-dimension numerical parametrization of the orographic gravity waves impact in
the middle and upper atmosphere.
Koval Andrey , Gavrilov Nikolaj
St-Petersburg State University
Internal atmospheric waves play an important role in the formation of variations of wind and
other parameters in the atmosphere. Interpretation of observations of atmospheric waves
requires the development of simple numerical schemes, which provide a satisfactory
description of wave oscillations with minimum computer time. One important source of
atmospheric waves is the topography of the Earth's surface. Wind interacts with the
irregularities of the relief and the result is a stationary atmospheric wave. In our study the
method developed by Scinocca and McFarlane is used as a basis. In this method a concept of
so called "subgrid" topography is used, which involves variations of the heights of the
terrestrial surface with horizontal scales smaller than a step of the horizontal grid, which is
used in atmospheric dynamical models. In the vicinity of each grid point the “subset”
orography is characterized by elliptical mountain barriers. After that, the horizontal force
acting on an elliptical mountain by the incident horizontal flow is calculated. Then, using the
polarization ratio for stationary gravity waves, one may obtain expressions for the total waveenergy
transfer, wave-amplitudes and wave acceleration in the case of stationary waves.
The main new feature of the developed method is usage of the theory of stationary waves
propagation in an inhomogeneous atmosphere for calculating orographic wave amplitudes and
other parameters at different altitudes up to the middle and upper atmosphere. Using the
dispersion equation and polarization relations for stationary waves in a rotating atmosphere
we obtained the equation of wave action (or energy) change in the inhomogeneous
atmosphere similar to that one obtained previously for nonstationary waves. This equation is
solved to obtain wave parameters for different atmospheric applications. Results we achieved
show important wave fluctuations that should be taken into account in atmospheric dynamic
models. Developed method may be useful for interpretation of for laser radar measurements
of atmospheric dynamics.