Potential uncertainties in using the hodograph method to retrieve gravity wave characteristics from individual soundings

Low-frequency gravity waves are an important component of the dynamics of the upper-troposphere and lower-stratosphere region. They affect processes that are sensitive to temperature fluctuations such as the formation of PSCs, and contribute, when wave-breaking occurs, to mixing and turbulence. Observational studies of low-frequency waves have largely relied on the hodograph method to retrieve characteristics (intrinsic frequency, vertical and horizontal wavelength) of individual gravity waves from profiles of the horizontal winds. The method is based on the linear theory of gravity waves on the background of a fluid at rest. In order to estimate the uncertainties of this method, we have analyzed meso-scale numerical simulations of a gravity wave event in which a quasi-monochromatic inertia-gravity wave packet is present. Single vertical profiles are extracted from the simulations, analyzed using the hodograph method, and the derived wave characteristics are compared to the reference values determined from the four-dimensional simulated fields. Although the conditions favor the use of the hodograph method, the derived wave parameters possess significant uncertainties.