A comparison of roll and nonroll convection and the subsequent deepening moist convection: An LEM case study based on SCMS data

For the case modeled, rolls persisted for surface buoyancy fluxes less than 110 W m⁻³, and formed for boundary layer wind shears greater than 5 × 10 greater than s⁻¹, which is consistent with previous studies. The simulated roll convection was compared with a nonroll simulation, which was identical except for the wind and the wind shear used. In both the roll and nonroll cases the variability in convective inhibition (CIN) was dominated by the variability in the source air, rather than the lifting of the top of the boundary layer by the convection.

Stronger moist updrafts existed in the nonroll convection, whereas roll convection gave a more symmetrical distribution of up and downdrafts, with stronger downdrafts than the nonroll case. The nonroll convection simulations have lower minimum values of CIN and clouds develop 15 min earlier in this case.