Desmond Manatsa （Bindura University of Science, Zimbabwe)によるセミナーを2月29日15：30より行います。Manatsaさんは、現在JSPS-Ronpaku研究員として、海洋技術環境学専攻のベヘラJAMSTEC連携講座教授の指導で、博士研究を行っています。インド洋における気候変動について、東アフリカの降雨とインド洋ダイポールとの関連に着目した研究成果を発表されます。学生、教職員、ご関心のある方は、是非来てください。
Location: Environmental Studies Building, lecture room 3rd floor 環境棟3階講義室
Speaker: Desmond Manatsa (Bindura University of Science, Zimbabwe)
Title: Shifts in IOD Association with East Africa Rainfall
Desmond Manatsa1,2, Barnabas Chipindu4and Swadhin K. Behera2,3
1Department of Geography, Bindura University of Science, Zimbabwe;
2University of Tokyo Department of Ocean Technology, Policy, and Environment;
3Research Institute for Global Change/JAMSTEC, Japan;
4Department of Physics, University of Zimbabwe.
The decadal shift in the relationship between the Indian Ocean Dipole (IOD) and the East African Rainfall is investigated using historical observational data. The climate system for equatorial East Africa (EEA) during the October to December (OND) ‘short rains’ season is characterized by spatiotemporal variations of the equatorial East African rainfall (EEAR). Therefore, the EEAR index is derived from the first principal component of the empirical orthogonal function analysis (EOF) of the EEA’s rainfall domain. The IOD, which has been linked with the EEAR in the previous studies, is the main climate mode controlling the tropical Indian Ocean during the OND period. It is usually represented by a Dipole Mode index (DMI) based on the zonal gradient of SST anomalies in the tropical Indian Ocean. Therefore the climate modes, IOD and EEAR are assumed to form a two-node network of subsystems which primarily control the climate of equatorial East Africa during the OND period. The collective behavior of these climate modes is investigated through the examination of their representative indices for the period 1901 to 2009 using simple statistical techniques. The results suggest that the interaction between these two climate modes, which comprise the network, is not predominantly linear as previously assumed, but is characterized by shifts which are determined by the coupling and synchronization processes of the tropical systems. In cases where synchronization is preceded by an abrupt increase in coupling strength between the two sub systems, the established synchronous state is destroyed and a new climate state emerges such as in the years 1961 and 1997. This alteration in the regional climate is accompanied by notable changes in the regional rainfall and IOD variations. But in those events where synchronization is followed by a sudden loss in coupling strength, the climate state is not disturbed and no shift in the climate of equatorial East Africa is noticed as in 1917. This climate shift mechanism appears to be consistent with the theory of synchronized chaos and is useful for long range predictions of the East African short rains.