The GASS/EUCLIPSE model intercomparison of the stratocumulus transition as observed during ASTEX: LES results

摘要: Large-eddy simulations of a Lagrangian transition from vertically well-mixed stratocumulus-topped boundary layer to situation in which shallow cumuli penetrate an overlying thin and broken stratocumulus are compared with aircraft observations collected during the Atlantic Stratocumulus Transition Experiment. Despite complexity case long simulation period 40 h, six participating state-of-the-art models skillfully consistently represent observed gradual deepening layer, negative buoyancy flux at top subcloud development double-peaked vertical velocity variance profile. The moisture cloud by cumulus convection exhibits distinct diurnal cycle. During night base exceeds surface evaporation flux, causing net drying vice versa daytime. spread liquid water path (LWP) among is rather large first 12 h. From additional sensitivity experiments it demonstrated that this mainly attributable differences parameterized precipitation rate. LWP limited through feedback mechanism enhanced drizzle fluxes result lower entrainment rates subsequently reduced top. furthermore day as layers greater absorb more solar radiation hence evaporate more.