Analysis of convectively-generated gravity waves in mesoscale model simulations and wind-profiler observations

The characteristics of convectively-generated gravity waves during an episode of deep convection near the coast of Wales are examined, in high-resolution mesoscale simulations with the Met Office Unified Model and in observations from a mesosphere-stratosphere-troposphere wind-profiling Doppler radar. In this episode, deep convection reached the tropopause and generated vertically-propagating high-frequency waves in the lower stratosphere that produced vertical-velocity perturbations of order of 1 ms(-1). Wavelet analysis is applied in order to determine the characteristic periods and wavelengths of the waves. Both in the simulations and in the observations, the wavelet spectra contain several distinct preferred scales, indicated by multiple spectral peaks. The peaks are most pronounced in the horizontal spectra at several wavelengths less than 50 km. Although these peaks are most clear, and of largest amplitude, in the highest-resolution simulations (with 1 km horizontal grid length), they are also evident in coarser simulations (with 4 km horizontal grid length). Peaks also exist in the vertical and temporal spectra (at approximately 2.5-4.5 km and 10-30 min respectively), with good agreement between simulation and observation. Two-dimensional (wave-number-frequency) spectra demonstrate that each of the selected horizontal scales contains peaks at each of the preferred temporal scales revealed by the onedimensional spectra alone. Copyright (C) 2008 Royal Meteorological Society.