Abstract
Abstract. Large-eddy simulations (LESs) of a multi-week period during the HD(CP)2 (High-Definition Clouds and Precipitation for advancing Climate Prediction) Observational Prototype Experiment (HOPE) conducted in Germany are evaluated with respect to mean boundary layer quantities and turbulence statistics. Two LES models are used in a semi-idealized setup through forcing with mesoscale model output to account for the synoptic-scale conditions. Evaluation is performed based on the HOPE observations. The mean boundary layer characteristics like the boundary layer depth are in a principal agreement with observations. Simulating shallow-cumulus layers in agreement with the measurements poses a challenge for both LES models. Variance profiles agree satisfactorily with lidar measurements. The results depend on how the forcing data stemming from mesoscale model output are constructed. The mean boundary layer characteristics become less sensitive if the averaging domain for the forcing is large enough to filter out mesoscale fluctuations.
Highlights
Large-eddy simulation (LES) studies have usually focused on a specific atmospheric boundary layer type, often with the purpose of addressing a specific theoretical question
PALM, UCLA-LES and COSMO are able to reproduce the development of the boundary layer as the models lie inside the spread of the measurements resulting from surface heterogeneity and spatial variability of the boundary layer depth between the three sites
In this study long-term LESs with PALM and UCLA-LES are evaluated to assess the ability of LES in a semi-idealized setup to simulate observed characteristics of boundary layer turbulence
Summary
Large-eddy simulation (LES) studies have usually focused on a specific atmospheric boundary layer type, often with the purpose of addressing a specific theoretical question. For idealized LES case studies focusing on a specific boundary layer type, the larger-scale forcing is usually constructed based on observations from measurement campaigns (e.g., Siebesma et al, 2003; Stevens et al, 2005). Regarding long-term simulations in the semi-idealized setup, relaxation towards a reference state given by a larger-scale model or observations can be used in combination with advective forcing to prevent model drift in time (Neggers et al, 2012). As the long-term LES approach relies on prescribing larger-scale forcing it is important to know how sensitive the LES results are with respect to details of the forcing like the calculation of the larger-scale advective tendencies from the mesoscale model or the relaxation (nudging) to the mesoscale model This gives us the opportunity to assess the extent to which mesoscale variability plays a role in determining boundary layer characteristics.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
