The impacts of spatial variability on the development of convection

A cloud-resolving model is used to investigate the impact of spatial variability in moisture and temperature on the timing of deep convection over land. Using a simulation of a diurnal cycle of convection, horizontal variations in moisture and temperature are shown to have a significant impact on the development of convection. The onset of deep convection can change by several hours and total rainfall amounts can change by up to 70%. Further sensitivity studies are carried out to investigate the impacts of vertical location, horizontal scale and magnitude of the variability. It is shown that variability of relative humidity in the boundary layer has the most significant impact and this is linked to its strong influence on local convective inhibition. Horizontal scales larger than 10 km are shown to have the strongest influence on the timing of convection, and the strongest amplitude of convectively generated fluctuations is shown to be on these larger scales.