One of the most important parameters forcing the middle and upper atmosphere dynamics are stratospheric gravity waves (GWs), which propagate to mesospheric and lower thermospheric heights and strongly influence mean dynamics there. Careful parameterization of GWs is thus crucial for a successful modelling of middle atmosphere dynamics, and for understanding of dynamical processes such as wave-mean flow and wave-wave interaction in the mesosphere and lower thermosphere. However, little is known so far about the global distribution of stratospheric GWs .

The new GPS occultation method now can be used for deriving global distributions of GW activity in the stratosphere and ionosphere/lower thermosphere. Using satellite-borne GPS measurements in combination with ground-based radar, Lidar, and ionosonde data, a global climatology of gravity waves in the stratosphere and travelling ionospheric disturbances (TIDs) in the thermosphere will be constructed and validated using ground-based measurements in the middle and upper atmosphere (ionosonde, radar, Lidar).

Such global maps of GW activity will be used for estimating the GW drag of the mean flow and thus dynamical coupling between middle and upper atmosphere from comparison of stratospheric GW and ionospheric TID activity. In addition, this will also help improving parameterizations of GW dynamical and heating effects according to measurements. These parameterizations will be used, in connection with realistic GW global distributions, for forcing of a numerical model of the middle atmosphere general circulation (GCM). The numerical results will be validated using mean wind measurements in the middle and upper atmosphere (Collm wind radar, empirical models, PSMOS network).

The project will thus result in

1. A climatology of GWs in the stratosphere and TIDs in the ionosphere derived from GPS LEO satellites
2. Newly developed computer codes for analysing GW and TID from GPS measurements
3. Improved GW parameterization schemes taking into account realistic GW distribution

The partnership consists of 4 partners from Germany, UK, Russia, and Kazakhstan, who regularly carry out ground-based upper atmosphere measurements and theoretical investigations concerning the middle and upper atmosphere as well as the ionosphere. The partners are involved in international projects, which guarantees access to many additional upper atmosphere datasets.
 

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last modification: 14.8.2000