Climatology: Seasonal Changes of Rainfall Around Mount Kenya and Its Relation to Atmospheric Circulation

The regions surrounding Mount Kenya have both long and short rainy seasons, and the corresponding peak rainfalls occur during April and November, respectively. Rainfall in these two seasons reach their maximum potential in areas centered on the southeastern part of the foothills of Mount Kenya and in the Aberdare Range. The relationships between the onset of these rainy seasons and the inland penetrations of the easterly winds at 700 hPa demonstrated that during the long rainy season, wind penetration from the Indian Ocean occurs along the ridge, extending northwards from the southern hemisphere along the eastern coast. During the short rainy season, wind penetration occurs with the strengthening of easterly winds associated with deepening low pressure in the Congo Basin. The relationship between the location of the convergence and divergence of wind field at 700 hPa and the seasonal march of rainfall around Mount Kenya suggest that the seasonal changes in rainfall are not only a result of north–south movement of the convergence zone with the meridional component of wind, but also a result of east–west movement of the divergence zone with the zonal component of wind.