Investigating convective boundary layer heights over mountain ridges

The convective boundary layer (CBL) in valleys has been extensively studied in field experiments, and high-resolution atmospheric models have played an important role in understanding the processes underlying the observed behavior. The CBL over mountain ridges has been much less studied and is not well understood, yet its role in the initiation of convection and in the exchange of air pollutants with the free atmosphere is recognized. In this presentation, we will review current knowledge on the CBL over mountain ridges and focus on recent results from the MATERHORN field experiment. Observations and output from idealized mesoscale and large eddy simulations address the role of ambient stability, advection, topographic characteristics, and surface heating on CBL height over mountain ridges. We also compare simulated CBL heights from an operational forecasting model run at 1.1-km grid spacing, and from model runs (realistic and idealized) at higher resolution, with observations from several case studies during the MATERHORN field campaign. This study demonstrates how the MATERHORN field campaign has enhanced our understanding of CBLs over mountain ridges.