Sensitivity testing of WRF parameterizations on air–sea interaction and its impact on water cycle in the Gulf of Guinea

A strong ocean–atmosphere coupling exists in the eastern equatorial region of the tropical Atlantic at intraseasonal time‐scales, with a significant contribution in the functioning and partitioning of the water cycle in spring over the ocean, as well as later in the season over West Africa. Uncertainties in simulating the air–sea interaction in the Gulf of Guinea and its impact on the water cycle are studied using modelling experiments during spring–summer 2006 with the Weather Research and Forecasting model (WRF). Tested parameters include physical packages of cumulus (Cu), planetary boundary‐layer (PBL), microphysics (MP) and radiative (RAD) schemes. The simulations are compared with satellite‐based observations, ship‐based radiosonde data and state‐of‐the‐art atmospheric model reanalyses. Results show that cumulus, microphysics and radiative parametrizations exert a large influence on the simulated seasonal distribution of regional convective rainfall. Non‐local PBL schemes are determinant to simulate the correct surface wind pattern and water vapor distribution in order to get realistic precipitation from intra‐seasonal to diurnal scales, especially over the ocean where the nocturnal rainfall representation is improved.