Response of Atmospheric Convection to Vertical Wind Shear: Cloud-Radiation Interaction

A series of cloud resolving simulations with parameterized large-scale circulation is conducted to explore the effect of the environmental vertical wind shear on deep convection in the presence of cloud-radiation feedback. The mean horizontal wind is relaxed to a prescribed simple linear vertical profile. It is found that for a shear with a depth of the troposphere, transition from unsheared to small sheared flow produces a sharp transitional drop in mean precipitation to an RCE-like state in the water budget, i.e. P~E. For stronger shear, precipitation does not deviate much from evaporation (RCE-like state). This transitional feature is also apparent in large-scale vertical motion, thermodynamic variables, cloud properties, and radiative profiles and is very similar for different shear strength of the same deep depth. We show that this transition is associated with the formation of stratiform clouds and declination of convective clouds as one goes from unsheared flow to sheared on of tropospheric depth. Increasing the shear depth gradually from shallow to deep increases the radiative heating in the middle to upper troposphere associated with increasing the Stratiform clouds trailing ahead of deep clouds.