Impact of convective organization on the response of tropical 1 precipitation extremes to warming

4 This study examines the response of tropical precipitation extremes to warming in organized 5 convection using a cloud-resolving model. Vertical shear is imposed to organize the convec6 tion into squall lines. Earlier studies show that in disorganized convection, the fractional 7 increase of precipitation extremes is similar to that of surface water vapor, which is substan8 tially smaller than the increase in column water vapor. It has been suggested that organized 9 convection could lead to stronger amplifications. 10 But regardless of the strength of the shear, amplifications of precipitation extremes in 11 the cloud-resolving simulations are comparable to those of surface water vapor, and are 12 substantially less than increases in column water vapor. The results without shear and 13 with critical shear, for which the squall lines are perpendicular to the shear, are surprisingly 14 similar with a fractional rate of increase of precipitation extremes slightly smaller than that of 15 surface water vapor. Interestingly, the dependence on shear is non-monotonic, and stronger 16 supercritical shear yields larger rates, close to or slightly larger than surface humidity. 17 A scaling is used to evaluate the thermodynamic and dynamic contributions to precipita18 tion extremes changes. To first order, they are dominated by the thermodynamic component 19 which has the same magnitude for all shears, close to the change in surface water vapor. The 20 dynamic contribution plays a secondary role, and tends to weaken extremes without shear 21 and with critical shear, while it strenghtens extremes with supercritical shear. These dif22 ferent dynamic contributions for different shears are due to different responses of convective 23 mass fluxes in individual updrafts to warming. 24