Analysis of the 2006 floods over northern Tanzania

摘要

This study analyses the circulation features over the Indian Ocean that may be responsible for anomalous wet seasons over Tanzania, giving specific focus to the heavy floods that occurred during the short rainfall season of October-December (OND) 2006. These floods caused devastating loss of life and property over the northern part of the country. A comparison of the 2006 event with a previous severe flooding episode (OND 1997) is conducted. Our results indicate that very heavy rainfall events experienced within a short duration exacerbated the 2006 flood. The circulation features show that the heavy rainfall recorded during OND 2006 can be associated with strong warming over the Indian Ocean, coupled with a convective zone over the western Indian Ocean and East African region, with enhanced moisture flux convergence and uplift over the western Indian Ocean and Tanzania. In turn, this warming was related to the ongoing El Nino and the positive phase of the Indian Ocean dipole mode that occurred during this season, as in OND 1997. In both cases, the severe flooding in Tanzania seemed to be preceded by warming near the Somali coast and an easterly moisture flux anomaly over the eastern equatorial Indian Ocean.