TITLE:
Assessing the Relationship between October-November-December Rainfall and Indian Ocean Dipole in Recent Decades over Tanzania Following the 2011 Abrupt Change
AUTHORS:
Charles Yusuph Ntigwaza, Wen Wang
KEYWORDS:
Sea Surface Temperature (SST), Percentage Departure of Rainfall, Atmos-pheric Circulations, Walker Circulation, Hadley Circulation
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.12 No.3,
March
25,
2024
ABSTRACT: The present study explored how the Indian Ocean Dipole (IOD) influences
October-November-December (OND) rainfall
over Tanzania in recent decade following the 2011 abrupt change. The study
spans 50 years, from 1973 to 2022. Notable abrupt changes were observed in 1976
and 2011, leading us to divide our study into two periods:
1976-2010 and 2011-2022,
allowing for a close investigation into the existing relationship between OND
IOD and OND rainfall and their associated large-scale atmospheric circulations.
It was found that the relationship between OND IOD and OND rainfall
strengthened, with the correlation changed from +0.73 during 1976-2010 to +0.81
during 2011-2022. Further investigation revealed
that, during 1976-2010, areas that received above- normal rainfall during positive IOD experienced
below-normal during 2011- 2022 and vice versa. The same pattern relationship
was observed for negative IOD. Spatial analysis demonstrates
that the percentage departure of rainfall across the region mirrors the
standardized rainfall anomalies. The study highlights that the changing
relationship between OND IOD and OND rainfall corresponds to the east-west shift of Walker circulation, as
well as the north-south shift of Hadley circulation. Analysis of sea surface
temperature (SST) indicates that both positive and negative IOD events
strengthened during 2011-2022 compared to 1976-2010. Close monitoring of this
relationship across different timescales could be useful for updating OND
rainfall seasonal forecasts in Tanzania, serving as a tool for
reducing socio-economic impacts.