Aspects of the fine-scale climatology over Lake Tanganyika as resolved by a mesoscale model

An hourly averaged climatology at 0.05 degrees horizontal resolution over t he Lake Tanganyika region was created by making simulations with a mesoscal e model (HIRLAM) using a high resolution physiography to represent the surf ace. Initial and boundary values were interpolated from ECMWF analyses. Cli matologies for a typical dry season month (July 1994) and wet season month (March 1994) were created by 7-day segmenting. Model results were validated by utilizing a special coastal observation network. A number of experiment s were made with changes to the physiography (mountains/no mountains, lake/ no lake). The results reveal local channelling and blocking effects of the near-surfa ce southeasterly trade winds by the high mountain chains in the region of t he East African rift. Furthermore, surface winds display regular diurnal cy cles in many places, due to slope winds over hills and lake-landtype breeze s near the coast. The diurnal coastal winds (defined by the observation net work) are reasonably well simulated. Precipitation patterns display the sem i-annual march of the ITCZ across the area, plus considerable topographic e ffects. There is high evaporation from lakes and wetlands during the windy dry season, while evaporation from the moist land surface dominates the rai ny season.