Hectometric-scale modelling of the mixed layer in an urban region evaluated with a dense LiDAR-ceilometer network

Glazer, R. H., Grimmond, S. ORCID: https://orcid.org/0000-0002-3166-9415, Blunn, L., Fenner, D., Lean, H., Christen, A., Morrison, W. and Looschelders, D. (2025) Hectometric-scale modelling of the mixed layer in an urban region evaluated with a dense LiDAR-ceilometer network. Weather and Climate Dynamics. ISSN 2698-4016 (In Press)

Abstract/Summary

With development in recent years of hectometric (O(100 m); hm) scale numerical weather prediction (NWP) models, there is a need for their evaluation with high spatio-temporal scale observations. Here we assess UK Met Office Unified Model (UM) simulations with grid-spacing down to 100 m using a dense network of observations obtained during the urbisphere-Berlin campaign. A network of 25 automatic lidars-ceilometers (ALCs) provide aerosol attenuated backscatter observations from which mixed-layer height (MLH) is determined. UM simulated aerosol on two days (18 April and 4 August 2022) is used to determine model MLH with a novel algorithm (MMLH). MMLH is consistently able to reproduce the vertical extent of the mixed layer during late afternoon despite the two case-study days having different maxima. MMLH performance is better in the 100 m model domain compared to a 300 m configuration, which may be explained by the higher vertical resolution in the 100 m configuration. During the August case in which an extreme heat event occurred, a delayed MLH growth is seen in the morning and afternoon over the city compared to the rural surroundings in both the model and ALCs. Both days show a distinct influence of the city through the mixed layer, including a plume extending downwind of the city that is detectable in both the observations and model. The modelled urban plume has a deeper mixed layer compared to the rural surroundings (4 August: ~500 m; 18 April: ~200 m) for up to 15 km downwind of the city.

Item Type	Article
URI	https://centaur.reading.ac.uk/id/eprint/125395
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	European Geosciences Union
Download/View statistics	View download statistics for this item