Effects of time step size on the simulation of tropical climate in NCAR-CAM3

A set of multi-year integrations are carried out in a real-planet framework using actual land-ocean distribution and observed sea surface temperature. Over the tropics there is an increase in total rainfall with a decrease in time step size.

Using a lower time step, there is a decrease in the convective component of rainfall, however, the stratiform component increases, and more than compensates the decrease in the former, thus leading to a higher total rainfall. A decrease in time step leads to an increase in the frequencies of moderate, and heavy rainfall categories, which is responsible for the increase in time mean total rainfall over the tropics. Also, the spatial distribution of rainfall becomes more realistic during both summer and winter seasons.