Non-Monotonic Convective Response to Vertical Wind Shear: A Closer Look From Cloud Resolving Model Simulations

Using a three-dimensional cloud-resolving model, a systematic exploration is undertaken of the response of a radiative-convective equilibrium state to imposed vertical wind shear of varying magnitude. Domain-averaged surface precipitation exhibits a non-monotonic sensitivity to increasing shear magnitude, characterized by a decrease with increasing shear for weakly sheared conditions (<1.5 × 10⁻³ s⁻¹) and an increase under stronger shear (>1.5 × 10⁻³ s⁻¹), with a similar trend in surface heat fluxes. During the first 30–40 min after wind shear is imposed, convective activity and rainfall are suppressed, which is attributed to increased surface drag and reduced boundary layer eddy kinetic energy. As the shear persists over time, it eventually fosters the development of deep convection. An analysis of the condensed water budget shows that the overall response of the domain-mean surface precipitation rate to increasing shear magnitude is mainly explained by changes in condensation rate, which in turn is primarily controlled by the cloudy updraft mass flux. In the lower to middle troposphere where most condensation occurs, cloudy updraft fraction steadily increases with increasing shear magnitude, whereas mean updraft vertical velocity exhibits a general decreasing trend as the shear magnitude increases. The compensating responses of updraft fraction and mean vertical velocity explain the non-monotonic surface precipitation response to vertical wind shear. Vertical shear does not significantly impact the evaporation or precipitation efficiencies.