Evaluating trapped lee‐wave characteristics over the UK and Ireland in convection‐permitting model forecasts using satellite imagery

Houtman, H. G. ORCID: https://orcid.org/0009-0007-5957-5756, Teixeira, M. A. C. ORCID: https://orcid.org/0000-0003-1205-3233, Gray, S. L. ORCID: https://orcid.org/0000-0001-8658-362X, Sheridan, P. ORCID: https://orcid.org/0000-0002-0408-1501 and Vosper, S. ORCID: https://orcid.org/0000-0002-1117-4351 (2025) Evaluating trapped lee‐wave characteristics over the UK and Ireland in convection‐permitting model forecasts using satellite imagery. Quarterly Journal of the Royal Meteorological Society. ISSN 1477-870X doi: 10.1002/qj.4921

Abstract/Summary

Trapped lee waves exert frictional forces on the atmosphere which, due to the small scale of the orography that causes the waves, must be parametrised in coarser-resolution weather and climate models. Because of the scarcity of in situ observations, numerical model data have been used in previous climatological studies of trapped lee waves, which necessitates model evaluation. While the occurrence of trapped lee waves in models has been evaluated in a systematic manner before, their characteristics have not. To this end, the wavelength and orientation of trapped lee waves in the (UK) Met Office's convective-scale variable-resolution model (UKV) are validated against geostationary satellite imagery for the year 2023. The validation is performed using a newly developed wavelet transform technique for the objective estimation of wavelengths and orientations from pre-selected satellite images and corresponding model-derived vertical velocity fields. The model is shown to be skilful in reproducing trapped lee-wave wavelengths, but consistently overestimates them, especially when these wavelengths are below 9 km ( six times the model grid spacing). Anisotropy in the satellite's resolution complicates the analysis of wave orientations between the model and the satellite imagery, but they are nonetheless found to be correlated. There is no evidence for a decline in trapped lee-wave production in short-range forecasts and most of the model's skill in wavelength and orientation prediction is retained at a two-day lead time. Overall, the wavelength and orientation of trapped lee waves are generally found to be well-reproduced, which, due to the high sensitivity of trapped lee-wave characteristics to flow parameters, suggests that the UKV provides an accurate representation of the conditions relevant to trapped lee-wave formation. The model may therefore be considered a suitable substitute for observations in climatological studies of trapped lee waves and in the future development of a trapped lee-wave drag parametrisation.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/120368
Identification Number/DOI	10.1002/qj.4921
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	Royal Meteorological Society
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