Characteristics of roll and cellular convection in a deep and wide semiarid valley: A large-eddy simulation study

The nature of organized motions within the convective boundary layer (CBL) depends on the surface heating and vertical wind shear. Moderate surface heating and strong shear favor horizontal convective rolls, while strong surface heating and weak shear favor open cellular convection. The transition between rolls and cells over land, particularly complex terrain, is still poorly understood. Due to lack of adequate measurements, variability of structural properties of rolls and cells (such as aspect ratio, wavelength and orientation relative to the mean surface winds) over complex terrain remains unclear. At present resolutions used in operational numerical weather prediction, rolls and cells are now becoming partly resolved, but the reliability of their forecasting in complex terrain remains elusive. The main objective of this research is the investigation of the characteristics of rolls and cells in a mountain valley compared to flat terrain.