An assessment of a mountain-wave parametrization scheme using satellite observations of stratospheric gravity waves

Gravity-wave-induced temperature fluctuations predicted by a mountain-wave parametrization scheme are compared with observed stratospheric temperature fluctuations from the High-Resolution Dynamics Limb Sounder (HIRDLS) instrument. The focus of the study is on the southern Andes region during the month of August 2006. The comparison reveals that while the mean amplitude of temperature fluctuations predicted by the parametrization is broadly consistent with those observed by HIRDLS, there are significant differences for individual cases. Ray-tracing calculations performed for these cases suggest that these differences are likely to be associated with horizontal propagation of mountain waves, which is not represented by current column-based parametrization schemes. The results presented in this note suggest that this is a deficiency of mountain-wave parametrization schemes that may affect models at resolutions typical of both climate and numerical weather prediction modelling. Copyright (C) 2011 Royal Meteorological Society and British Crown Copyright, the Met Office