Investigation of the 2016 March to May extreme rainfall over Rwanda

Umutoni, Marie Adolatha; Japheth, Lovina Peter; Lipiki, Elias Julius; Kebacho, Laban Lameck; Limbu, Paul Tilwebwa Shelleph; Makula, Exavery Kisesa

doi:10.1007/s11069-021-04697-7

Cited by 10 publications

(11 citation statements)

References 21 publications

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“…The spatial resolution of these datasets is 2.5° × 2.5°. Previous researchers have used similar datasets to explain atmospheric circulation over the region (Vigaud et al ., 2018; Makula and Zhou, 2021; Massawe and Xiao, 2021; Mbigi and Xiao, 2021; Umutoni et al ., 2021). The monthly mean anomaly was determined by calculating a deviation from the 30‐year climatological mean (1981–2010) for all the variables.…”

Section: Methodsmentioning

confidence: 99%

The dominant modes of the long rains interannual variability over Tanzania and their oceanic drivers

Kebacho

Chen

2022

Intl Journal of Climatology

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Mitigating the impacts of droughts and floods over East Africa (EA) may largely be possible through accurate predictions of the long rains (March–May). Though the close interannual variability between the long rains, Indian and Pacific Oceans has been widely studied, Tanzania's long rain variability remains unclear. This paper examines the Tanzanian long rains dominant modes through an empirical orthogonal function (EOF) analysis, and their relationship with winter sea surface temperature (SST) for the period 1951–2018. Correlation and composite analyses were applied to explore the associated mechanisms. The first EOF (EOF1) mode is characterized by negative anomalies over Tanzania. The second EOF (EOF2) mode depicts positive (negative) anomalies over northern (southern) Tanzania. The third EOF (EOF3) mode reveals positive (negative) anomalies over eastern (western) Tanzania. EOF1 is closely related to the SST anomalies (SSTAs) in the southeastern Indian Ocean (SEIO). When the SSTAs are positive, they subsequently linked to upper (lower) level convergence (southeasterly winds) over Tanzania. Associated with this convergence entails a sinking motion, leading to a negative rainfall anomaly. The southeasterly winds indicate an early onset of the southeast monsoon, leading to normal rainfall been recorded. EOF2 is linked to the SSTAs in the central Pacific (CP). Positive SSTAs are related to reversed Walker circulation (WC) over northern Tanzania, while the upper‐level convergence was observed around southern Tanzania. This meridional dipole vertical motion pattern enhances (suppresses) rainfall anomalies. EOF3 is associated with mega El Niño–Southern Oscillation (ENSO)‐like SSTAs. The SSTAs are related to eastward shift of WC over the Indian Ocean, and zonal cell over the western Indian Ocean with rising limb is located east of Tanzania. The ascending motion enhances rainfall over eastern Tanzania. Predictions based on the SEIO, CP, and mega ENSO index may significantly support long rains prediction efforts and provide early warning.

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Section: Methodsmentioning

confidence: 99%

The dominant modes of the long rains interannual variability over Tanzania and their oceanic drivers

Kebacho

Chen

2022

Intl Journal of Climatology

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“…The local climate is regulated by the complex topographical features of the country. The country experiences a bimodal rainfall pattern, with "long rains" observed from March to May (MAM), while "short rains" occur from September to December (SOND) [44,49,54]. Information on general atmospheric circulations linked to seasonal rainfall climatology can be obtained from past studies [49,[55][56][57][58][59][60].…”

Section: Study Areamentioning

confidence: 99%

“…At a local scale like Rwanda, a few previous climate-related studies conducted have generally paid attention to assessing spatiotemporal variations in different climatic variables such as rainfall and temperature [44,[48][49][50], with no studies at present emphasizing the historical behavior of the characteristics of meteorological drought over Rwanda. Furthermore, the sustainability of water resources and the environment in EA is likely to be affected by an anticipated rise in temperature, more frequent and intense precipitation, and drought events.…”

Section: Introductionmentioning

confidence: 99%

Observed Changes in Meteorological Drought Events during 1981–2020 over Rwanda, East Africa

Uwimbabazi

Jing²,

Iyakaremye

et al. 2022

Sustainability

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Drought is one of the most complex natural phenomena affecting the life and livelihood of people, especially in the current time of human-induced climate change. This research employs ground-based observations to assess the recent spatiotemporal characteristics of meteorological drought events over Rwanda. The drought is examined based on the Standardized Precipitation Evapotranspiration Index (SPEI) and Standardized Precipitation Index (SPI) at seasonal and annual time scales from 1981 to 2020. The Man–Kendal test was used to evaluate the trends in rainfall, temperature, and SPEI values at the annual scale and during the March to May (MAM) and October to December (OND) seasons. The analysis revealed nonsignificant trends in annual (8.4 mm/decade), MAM (−3.4 mm/decade), and OND (4.5 mm/decade) rainfall, while an apparent significant increasing trend in surface air temperature was obtained during the MAM (0.19 °C/decade), OND (0.2 °C/decade), and annual (0.23 °C/decade) time slices. Overall, the SPEI characteristics indicated that the country is more prone to moderate drought events than severe and extreme drought events during MAM and OND seasons. However, the intensity, duration, and frequency differ spatially among seasons. The findings of this study inform policy and decision-makers on the past experienced drought behavior, which can serve as a baseline for future drought mitigation and adaptation plans.

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“…In recent decades, East Africa has witnessed a surge in extreme climate events, notably droughts and floods, with profound socio-economic ramifications (Anande & Luhunga, 2019;Kimambo et al, 2019;Lukali et al, 2021). Specifically, studies in Tanzania have highlighted an increased frequency of floods during the October-November-December (OND) rainy season (Mbigi & Xiao, 2021), in contrast to a decadal decrease in flood events during March-April-May (MAM) rainy season in the late 1990s (Makula & Zhou, 2022;Umutoni et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Assessing the Relationship between October-November-December Rainfall and Indian Ocean Dipole in Recent Decades over Tanzania Following the 2011 Abrupt Change

Ntigwaza,

Wang

2024

GEP

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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 abovenormal 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.

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Investigation of the 2016 March to May extreme rainfall over Rwanda

Cited by 10 publications

References 21 publications

The dominant modes of the long rains interannual variability over Tanzania and their oceanic drivers

The dominant modes of the long rains interannual variability over Tanzania and their oceanic drivers

Observed Changes in Meteorological Drought Events during 1981–2020 over Rwanda, East Africa

Assessing the Relationship between October-November-December Rainfall and Indian Ocean Dipole in Recent Decades over Tanzania Following the 2011 Abrupt Change

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