Afternoon precipitation peak simulated in an aqua-planet global non-hydrostatic model (aqua-planet-NICAM)

An aqua-planet simulation using the Nonhydrostatic ICosahedral Atmospheric Model (NICAM) shows a diurnal precipitation cycle with a minor maximum in the afternoon, even though sea-surface temperature is constant during the simulation. The present study explores the factors that control the afternoon precipitation peak, making use of the simulation results. The temperature in the lower troposphere shows a minor minimum in the afternoon, coinciding with the precipitation peak. It is suggested that the "squeezing through temperature reduction" (whereby condensation is enhanced and more water vapor is squeezed within a cloud due to reduced temperature) is the most important factor in explaining the afternoon precipitation peak. The temperature minimum is associated with a dynamical process (not a diabatic process), and its relationship with the atmospheric tide is discussed.