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

• Type: Article in International Scientific Journal
• Date: 2025

Authors

Houtman, HG (Author) Other; Teixeira, MAC (Author) FEUP; Gray, SL (Author) Other; Sheridan, P (Author) Other; Vosper, S (Author) Other

Journal

The Journal is awaiting validation by the Administrative Services.

Title: QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY

ISSN: 0035-9009

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Other information

Authenticus ID: P-017-TD0

DOI: 10.1002/qj.4921

Abstract (EN): 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 (similar to$$ \sim $$ 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.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 15