A model study of regional air-sea interaction in the austral summer precipitation over southern Africa

The importance of air-sea interactions in the simulation of southern Africa precipitation is brought out using a fully coupled regional model and by forcing the atmospheric component of the coupled model with the coupled model-simulated sea surface temperature (SST). The coupled model has the Advanced Research Weather Research and Forecasting model as the atmospheric component and the Regional Ocean Modeling System as the oceanic component. The spatial and temporal distribution of the coupled model-simulated SST shows good agreement with observations. The coupled model shows a bias of about 0.25 degrees C near the east coast of southern Africa. Comparison of the precipitation between the coupled and uncoupled model shows that the air-sea interactions play an important role in the simulation of the precipitation during the peak precipitation season January to March, when the precipitation is mostly due to tropical processes. It is found that the two-way specification of SST to the atmospheric model results in significant larger (smaller) precipitation depending on the spatial distribution of SST, due to the increase (decrease) of moisture from the surrounding oceans into the landmass. The results also show that the air-sea interactions are not so important during the initial phases of the precipitation from October to December.