Mercredi 21 septembre 2016 Ã 11h

LATMOS site Guyancourt

Salle de réunion 2202

Studying gravity waves and turbulence in the stratosphere using satellite observations of stellar scintillation

Viktoria Sofieva

Finnish Meteorological Institute, Helsinki

Stellar scintillations observed through the Earth atmosphere are caused by air density irregularities generated mainly by internal gravity waves (GW) and turbulence. The strength of scintillation measurements is that they cover the transition between the saturated part of the gravity wave spectrum and isotropic turbulence. This allows visualization of gravity wave breaking and of resulting turbulence. We analyzed the scintillation measurements by GOMOS fast photometers on board the Envisat satellite in order to quantify GW and turbulence activity in the stratosphere.

The analysis is based on reconstruction of GW and turbulence spectra parameters by fitting the modeled scintillation spectra to the measured ones. For data interpretation, we use a two-component spectral model of air density irregularities: the first component corresponds to the gravity wave spectrum, while the second one describes locally isotropic turbulence resulting from GW breaking and other instabilities.

In this presentation, we show global distributions, seasonal and interannual variations of the GW and turbulence spectra parameters retrieved from GOMOS data. Since other measurements at such small scales are very scarce in this altitude range, the obtained global distributions provide unique and complementary information about small-scale air density irregularities in the stratosphere.