[A-CG30] Extratropical oceans and atmosphere

[ACG30-14] Diurnal cycle of precipitation over the Gulf Stream simulated by a regional atmospheric model

*Givo Alsepan¹, Shoshiro Minobe¹ (1.Hokkaido University)

Although the diurnal cycle of precipitation is not prominent over most mid-latitude oceans, recent studies show that an exceptionally strong diurnal cycle occurs over the Gulf Stream during summer. Diurnal peaks tend to occur in the early to late morning, with an oceanward phase propagation like what is commonly found in the tropics. A striking difference between the Gulf Stream and the tropical ocean is that strong amplitude enhancement is observed over the Gulf Stream, indicating the active role of the Gulf Stream in modulating the diurnal cycle. In this study, we conduct a numerical simulation for the first time on the diurnal cycle of precipitation over the Gulf Stream using the Weather Research Forecasting (WRF) model. We focus our simulation on July during which the diurnal cycle is most profound in the summertime. In general, the main features of the diurnal cycle are well simulated, including the oceanward phase propagations and strong diurnal amplitudes along the Gulf Stream with a clear gap in small amplitudes between the Gulf Stream and the continent. The reproducibility of the simulation indicates that the model can be used further for understanding the mechanisms of diurnal precipitation, especially to understand why oceanward phase propagation occurs over the Gulf Stream.