TITLE:
The Influence of Climate Change and Variability on Spatio-Temporal Rainfall and Temperature Distribution in Zanzibar
AUTHORS:
Abdalla Hassan Abdalla, Kombo Hamad Kai, Sara Abdalla Khamis, Afredy Lawrence Kondowe, Sarah E. Osima, Philemon Henry King’uza, Asya Omar Hamad
KEYWORDS:
Climate Change, Climate Variability, Spatial and Temporal Distribution, Temperature, Rainfall, CORDEX
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.13 No.2,
April
28,
2023
ABSTRACT: Climate change has resulted in serious
social-economic ramifications and extremely catastrophic weather events in the
world, Tanzania and Zanzibar in particular, with adaptation being the only
option to reduce impacts. The study focuses on the influence of climate change
and variability on spatio-temporal rainfall and temperature variability and
distribution in Zanzibar. The station observation datasets of rainfall, Tmax and Tmin acquired from Tanzania Meteorological Authority (TMA) and
the Coordinated Regional Climate Downscaling Experiment program (CORDEX)
projected datasets from the Regional climate model HIRHAM5 under driving model
ICHEC-EC-EARH, for the three periods of 1991-2020 used as baseline (HS), 2021-2050
as near future (NF) and 2051-2080 far future (FF), under two representative
concentration pathways (RCP) of 4.5 and 8.5, were used. The long-term observed
Tmax and Tmin were used to produce time series for
observing the nature and trends, while the observed rainfall data was used for
understanding wet and dry periods, trends and slope (at p ≤ 0.05) using the
Standardized Precipitation Index (SPI) and the Mann Kendall test (MK).
Moreover, the Quantum Geographic Information System (QGIS) under the Inverse
Distance Weighting (IDW) interpolation techniques were used for mapping the three decades of 1991-2000 (hereafter D1), 2001-2010
(hereafter D2) and 2011-2020 (hereafter D3) to analyze periodical spatial
rainfall distribution in Zanzibar. As for the projected datasets the Climate
Data Operator Commands (CDO), python scripts and Grid analysis and Display
System (GrADS) soft-wares were used to process and display the results of the
projected datasets of rainfall, Tmax and Tmin for the HS,
NF and FF, respectively. The results show that the observed Tmax increased by the rates of 0.035℃ yr-1 and 0.0169℃ yr-1, while the Tmin was increased by a rate
of 0.064℃ yr-1 and 0.104℃ yr-1 for Unguja and Pemba, respectively. The temporal
distribution of wetness and dryness indices showed a climate shift from near
normal to moderate wet during 2005 at Zanzibar Airport, while normal to
moderately dry conditions, were observed in Pemba at Matangatuani. The decadal
rainfall variability and distributions revealed higher rainfall intensity with
an increasing trend and good spatial distribution in D3 from March to May (MAM) and October to December (OND). The projected results
for Tmax during MAM and OND depicted higher values ranging from 1.7℃
- 1.8℃ to 1.9℃ - 2.0℃ and 1.5℃ to
2.0℃ in FF compared to NF under both RCPs. Also, higher Tmin values of 1.12℃ - 1.16℃ was projected in FF for MAM and OND
under both RCPs. Besides, the rainfall projection generally revealed increased
rainfall intensity in the range of 0 - 25 mm for Pemba and declined rainfall in
the range of 25 - 50 mm in Unguja under both RCPs in perspectives of both NF and FF.
Conclusively the study has shown that the undergoing climate change has posed a
significant impact on both rainfall and temperature spatial and temporal
distributions in Zanzibar (Unguja and Pemba), with Unguja being projected to
have higher rainfall deficits while increasing rainfall strengths in Pemba.
Thus, the study calls for more studies and formulation of effective adaptation,
strategies and resilience mechanisms to combat the projected climate change
impacts especially in the agricultural sector, water and food security.