85th AMS Annual Meeting

Tuesday, 11 January 2005: 4:30 PM
Global forecasts of thermospheric gravity wave activity as generated from tropospheric sources: an overview of the FOREGRATS model with application to the prediction of equatorial spread-F
Timothy J. Kane, Penn State University, University Park, PA; and A. J. Gerrard and A. Hassiotis
Poster PDF (306.2 kB)
Atmospheric gravity waves, generated primarily from tropospheric mesoscale convective complexes and frontal systems, propagate into the middle atmosphere and subsequently impact the entire global circulation. Furthermore, the short-period/long vertical wavelength portion of the gravity wave spectrum can propagate into the thermosphere, where such waves can, amongst other space weather related impacts, potentially “seed” equatorial spread-F (ESF), an instability phenomena which causes scintillation in the radio portion of the electromagnetic spectrum. Recently, the desire to acquire 4-6 hour forecasts of ESF has come to the forefront of upper atmospheric research because of the impacts on radio communications and GPS signals. However, to extend these forecasts beyond the 6 hour limit, the modeling of the synoptic gravity waves associated with ESF needs to be addressed. As such, in this paper we present a global gravity wave forecasting model called FORGRATS (FORcasting of Gravity waves via Ray-tracing algorithms with prescribed Tropospheric Sources), which uses a myriad of data resources to identify dominant tropospheric gravity wave sources, prescribe a relevant source spectrum, and then propagate the resultant gravity waves through the middle and upper atmosphere via a linear ray-tracing theory. An example of the entire data assimilation and forecasting processes is presented, outlining each of the major components of the model.

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