WAVE DRAG EFFECTS IN A MESOSCALE MODEL WITH A HIGHER-ORDER CLOSURE TURBULENCE SCHEME

An incompressible, mesoscale model is used to estimate wave drag (WD) profiles over inhomogeneous 2D terrain. The goal is twofold: to evalua te the WD based on the model's fields and to analyze the atmospheric b oundary layer(ABL) response to wave breaking. The model employs a simp lified higher-order closure scheme for turbulent fluxes. A sponge laye r mimics a radiative upper boundary condition (BC). Due to the no-slip lower BC for dissipative flows, the Eliassen-Palm theorem is not fulf illed and WD is generally not constant with height. Within the lower t roposphere, the model's mean WD values compare to those from theory an d other simulations. Above the ABL, where no physical processes dissip ate waves, WD attenuates with height to roughly one-third of its theor etical value. This is mainly due to numerical dissipation of the used first-order advection scheme. However, the acceleration identified wit h the wave pattern reduction is small compared to governing accelerati ons. Two simulation sets are presented: one is a linear and another is a nonlinear airflow. The latter exhibits wave overturning and alters the ABL from above. The ABL becomes horizontally inhomogeneous over a distance equal to several times the characteristic width of the ridge.