A simulation of realistic weather conditions over the Netherlands was conducted using the newly developed open boundary and nesting features of the open-source MicroHH large-eddy simulation (LES) model.

In the outer domain, with a horizontal resolution of 900 m, MicroHH is coupled to the global ERA5 reanalysis at the lateral boundaries. Convection and turbulence are then downscaled in several steps to achieve a 33.3 m horizontal resolution in the inner domain. Yellow markers (KNMI automatic weather stations) and red markers (major observation sites) highlight the dense observation network across the Netherlands.

The lower boundary conditions, including the land-surface model and realistic land use coupling, were developed by our team at Wageningen University & Research (WUR) as part of the NWO-funded Ruisdael Observatory project. Under the NWO-funded VIDI project "Shedding Light on Cloud Shadows" (SLOCS), we implemented the open boundary conditions and nesting capabilities in MicroHH. Currently, in the SLOCS project, we are using this model setup to more accurately simulate clouds and the interactions between clouds, radiation, and the land surface, with the goal of determining whether such simulations can fill the solar irradiance mesoscale energy gap that is typically observed in doubly-periodic LESs.

Acknowledgement is made for the use of ECMWF's computing and archive facilities in this research.

Links:
MicroHH model: microhh.org/
Our group at WUR: dub.sh/9z3SN7g
Our observation sites: maq-observations.nl/
SLOCS project: chiel.cloud/Projects/SLOCS
Ruisdael project: ruisdael-observatory.nl/