Multiscale modeling of a diurnal cycle during the CWEX-13 field campaign

Realistic modeling of atmospheric boundary layers requires representation of a broad range of scales ranging from synoptic and mesoscale two-dimensional eddies down to three-dimensional boundary-layer turbulence. However, existing challenges associated with disparate-scale atmospheric modeling have precluded systematic and robust use of multiscale methodologies. In this talk, we present novel multiscale simulations of an entire diurnal cycle during the CWEX-13 field campaign in central Iowa (Lundquist et al. 2014, 2016) using the Weather Research and Forecasting model in a multiple nest configuration with grid resolutions progressively refined from 9 km to 8 m. Critical aspects associated with multiscale simulation frameworks are discussed, namely issues of modeling at 'terra incognita' resolutions and proper turbulent forcing at LES-resolved scales. For the latter, we use the generalized cell perturbation method from Muñoz-Esparza et al. (2014, 2015), based upon the use of stochastic potential temperature perturbations near the inflow boundaries of the first LES domain. We demonstrate the great potential of multiscale modeling in the context of atmospheric boundary layer flows. Our multiscale simulations exhibit very good agreement with in situ lidar wind profiler and sonic anemometer measurements at the CWEX-13 site throughout the diurnal cycle. Finally, remaining challenges and areas for improvement in multiscale modeling methodologies are emphasized.