Zonal circulations over the Indian and Pacific Oceans and the level of lakes Victoria and Tanganyika

Level records of two East African Great Lakes, Lake Victoria and Lake Tanganyika, which are considered as hydroclimatic proxies, are analysed. Comparisons between the two lake signals show synchronisms, which can only be accounted for by large-scale mechanisms. Lake-level variations associated with the short rains season (October–January) appear to have a prominent effect on the annual lake levels. The relations between lake-level variations and atmospheric circulation indexes are then investigated. Over the period 1946–2000, four indexes are selected to characterize the October–December zonal circulation over the Pacific and Indian Oceans. Over the Indian Ocean two surface zonal wind index…