TITLE:
Spatio-Temporal Assessment of the Performance of March to May 2020 Long Rains and Its Socio-Economic Implications in Northern Coast of Tanzania
AUTHORS:
Kombo Hamad Kai, Agnes Laurence Kijazi, Sarah E. Osima, Habiba Ismail Mtongori, Makame Omar Makame, Hafidh Juma Bakari, Omar Asya Hamad
KEYWORDS:
March to May 2020 Rainfall Assessment, Sea Surface Temperatures Anomalies (SSTA) Assessments, Precipitable Water (PRW) and Ocean Net Flux, Relative Humidity
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.11 No.4,
October
29,
2021
ABSTRACT: The
spatio-temporal analysis of the performance of the March to May (MAM) 2020
rainfall and its societal implications to Northern Coastal Tanzania (NCT) including Zanzibar was investigated. The uniqueness of the October to
December, 2019 (OND) rainfall and the extension of the January to February,
2020 rainfall in Zanzibar which coincided with MAM 2020 rainfall was among the
issues which prolonged MAM 2020 rainfall in NCT and Zanzibar. The National
Center for Environmental Prediction (NCEP) in collaboration with National
Center for Atmospheric Research (NCAR). Reanalysis 1 datasets of u (zonal) and v (meridional) winds, sea surface temperatures anomalies, relative humidity, amount of precipitable
water and ocean net flux were analyzed. Other datasets include the Tanzania
Meteorological Authority (TMA) observed rainfall records, maximum and minimum temperatures. Moreover, TMA
and Intergovernmental Climate Prediction and Analysis Center (ICPAC). MAM 2020 rainfall and temperature forecast reports
were interpreted. Gridded and observed datasets were calculated into monthly
and seasonal averages. As for observed data, long-term monthly and MAM percentage changes were
calculated. Besides, the correlation between rainfall anomalies with an area-averaged SSTA for defined regions and
stations in Zanzibar was performed. Lastly, the calculated monthly and seasonal
rainfall was compared to MAM periods of 2016, 2017, 2018 and 2019. Results
revealed that consecutive five MAM seasonal rainfall was among the highest ones
in records with that of 2020 being exceptional. These MAM seasons had
percentage contribution ranged from 68% - 212%, 150% - 304%, 22% - 163% and 57%
- 170% for stations in Zanzibar and 130% - 230%, 57% - 168% and 230% - 706% for
NCT station, respectively. Compared to previous MAM seasons of 2016-2019, MAM
2020 rainfall season was spatially well distributed in our study area with
rainfall ranging from 1200 to 2100 mm and up to 900 in most Zanzibar
and NCT stations. Indeed, the study revealed that the observed highest rainfall
and flooding was enhanced by wet seasons of MAM 2019, OND 2019 and DFJ
(2019-2020). Other dynamics which accelerated MAM 2020 rainfall were the higher
SSTA ranged from 0.5°C - 1.5°C
and 1.5°C - 2.5°C over Southwestern Indian Ocean (SWIO) and coastal
Tanzania and the increased trend of area-averaged SSTA on various SWIO blocks. Besides, parameters including Rhum, PWR and wind regimes
were supporting the MAM 2020 rainfall. The socio-economic implications of these
rains were strong and spatially well distributed in Zanzibar. For instance, a
death toll of about 10 people, a great number of road culverts were washed away, and about 3600 houses were fallen or damaged, leading to a significant number of homeless people. As for NCT, the catastrophes include loss of lives, increased water levels over Lake Victoria leading to flooded islands and re allocation of more than 1000 people. In Kenya, more than 116 people died and 40,000 people were
displaced. Conclusively, the study has shown the uniqueness (i.e., strength and societal
implications) of MAM 2020 compared to other seasons; hence more studies on understanding
the factors affecting extreme rainfall seasons in East Africa are required.