The Diurnal Cycle of Precipitation over the Globe: Observations vs. Model Simulations

Precipitation exhibits considerable diurnal variations over most of the globe, especially over continents during the warm season. There have been a large number of studies to document these diurnal variations and to investigate their underlying physical processes, although these efforts have often been hampered by insufficient observations. Because of its coherent phase, large amplitude and short time scales, the diurnal cycle of precipitation provides an excellent test bed for evaluating cumulus and other parameterizations in numerical weather and climate models. In this presentation, I will provide an overview of the diurnal variations of various types of precipitation based on surface and satellite observations, and then examine the precipitation diurnal cycle in several climate models. Some underlying mechanisms will be discussed, and results from model diagnostic analyses will be presented.