Assessment of the Off-season Rainfall of January to February 2020 and Its Socio Economic Implications in Tanzania: A Case Study of the Northern Coast of Tanzania

Kombo Hamad Kai (Tanzania Meteorological Authority (TMA), Zanzibar P. O. Box 340 Zanzibar, Tanzania)
Sarah E Osima (Tanzania Meteorological Authority (TMA), Zanzibar P. O. Box 340 Zanzibar, Tanzania)
Agnes Laurence Kijazi (TMA Dar es Salaam office, P. O. Box 3056 Ubungo Plaza, Tanzania)
Mohammed Khamis Ngwali (TMA Dar es Salaam office, P. O. Box 3056 Ubungo Plaza, Tanzania)
Asya Omar Hamad (Tanzania Meteorological Authority (TMA), Zanzibar P. O. Box 340 Zanzibar, Tanzania)

Article ID: 3135



This article examines the off season rainfall in northern coast Tanzania (NCT) including Zanzibar which occurred in January and February 2020 (JF). Like the JF rainfalls of 2001, 2004, 2010, 2016 and 2018, the JF (2020) rainfall was more unique in damages including loss of lives, properties and infrastructures. The study used the NCEP/NCAR reanalysis data to examine the cause of uniqueness of JF rainfall in 2001, 2004, 2010, 2016, 2018 and 2020 over NCT and Zanzibar. These datasets include monthly mean u, v wind at 850, 700, 500, and 200 mb; SSTs, mean sea level pressure (MSLP) anomalies, Dipole Mode Index (DMI), and monthly rainfall from NCT and Zanzibar stations. Datasets were processed and calculated into long term, seasonal, and monthly averages, indeed, Precipitation Index (PI) was calculated. Correlation analysis between the rainfall (December to January), SST, DMI and 850 mb wind vectors; and long-term percentage contribution of investigated parameters was calculated. Results revealed significant positive and negative correlations between JF rainfall, SSTs and DMI. Moreover, JFs of 2004 and 2016 had higher rainfalls of 443 mm with percentage contribution of up to 406%, while January and February, 2020 had the highest of 269.1 and 101.1mm in Zanzibar and 295 and 146.1 mm over and NCT areas, with highest January long-term rainfall contribution of 356% in Zanzibar and 526% over NCT. The DJF (2019/20) had the highest rainfall record of 649.5 mm in Zanzibar contributing up to 286%, while JF 2000 rainfall had a good spatial and temporal distribution over most NCT areas. JF, 2020 rainfall had impacts of more than 20 people died in Lindi and several infrastructures including Kiyegeya Bridge in Morogoro were damaged. Conclusively, more research works on understanding the dynamics of wet and dry JF seasons should be conducted.


Indian ocean dipole; Dipole mode index (DMI); Sea surface temperatures (SSTs); Rainfall; Relative humidity; Correlations

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