Large-eddy simulations of a diurnal cycle driven by mesoscale and observational profile assimilation*

The coupling of microscale large-eddy simulations (LES) to mesoscale models enables a more realistic representation of turbulent atmospheric boundary layers and may allow for accurate prediction of wind-turbine performance and loading under a wide variety of inflow conditions. One of the challenges associated with meso-micro coupling is the specification of driving conditions for the microscale simulation. One approach is to use spatially and temporally averaged budget terms or tendencies from the mesoscale simulation, but the choice of averaging parameters affects the microscale solution. In this study, we investigate an alternative approach to drive LES based on data-assimilation techniques. The assimilation approach employs Newtonian relaxation to nudge the mean profiles in the microscale simulation towards a desired velocity and temperature profile. We simulate a diurnal cycle observed at the Scaled Wind Farm Technology (SWiFT) facility in Texas, and we compare LES driven by mesoscale profile assimilation, mesoscale tendencies, and observational profile assimilation.