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Map of the East Africa. The study area with latitude (0°–12°S) and longitude (29°–41°E) boundary is represented by green colour in map. The blue colour represents water bodies surrounding study area
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Although long rains (March–May) over Tanzania exhibit significant spatiotemporal variability and the existing literature has studied extensively on a seasonal scale, relatively less research has been geared toward analyzing it at monthly. In this study, the interannual variation in Tanzanian long rains was investigated on a monthly time scale. The...
Citations
... The MAM season rainfall is also subject to interannual variability and long-term trends, which can have significant impacts on the food availability dimension of food security, water resources, hydropower generation, and disaster risk management in Ethiopia (Kebacho, 2022;Palmer et al., 2023). Some years' experience above-normal or belownormal rainfall during the MAM season, which can cause floods or droughts respectively. ...
The variability of MAM (March to May) rainfall in Ethiopia is among the most important agrometeorological parameters for the success of agriculture and water management practices. This study therefore set out to analyze the anomalous increase of MAM season rainfall in 2023 using high-resolution Tropical Applications of Meteorology using Satellite data and ground-based observations (TAMSAT) rainfall estimate. A combination of multiple statistical methods was used to analyze and compare the 2023 MAM season rainfall with baseline mean across Ethiopia using the 40 years (1983-2022) dataset. Results showed
that MAM rainfall in 2023 (412.81mm) was 79% above average for the baseline period, with extremely wet conditions in the March and April months. Similarly, the 2023 MAM season rainfall anomaly exceeded historical short rainy seasons by 80-130mm and was spatially concentrated in the southwestern and central parts of Ethiopia. Statistical analyses (t-test) also confirmed significant differences between the MAM season rainfall of 2023 and the 1983-2022 averages at p<0.001 for all months solely and at the seasonal scale. Comparisons with previous high rainfall years indicated that the 2023 MAM season was an extreme and anomalous event. The study highlights the importance of understanding seasonal rainfall variability and extremes in Ethiopia, as they have direct implications for food availability, water resource management, and climate change adaptation strategies. Further research using other datasets is needed to demonstrate the utility of high-resolution satellite rainfall estimates for monitoring anomalies and improving early warning systems in the country.
... Numerous factors, such as the East African Monsoon, the El Nino Southern Oscillation (ENSO), the westerlies from the Congo, tropical cyclones, and the Inter-Tropical Convergence Zone (ITCZ), influence the distribution and variability of precipitation. One of the primary factors influencing the distribution and unpredictability of precipitation in Tanzania and Journal of Geoscience and Environment Protection throughout East Africa is the ITCZ's passage north and south over the equator (Kebacho, 2022; Statement on the Status of Tanzania Climate, 2020). The ITCZ migrates to southern regions of Tanzania from October to December, reaching the southern part of the country in January-February and reverses northwards in March, April and May. ...
Like other countries in East Africa, Tanzania has been affected by extreme precipitation incidences both socially and economically. Determining the trend and variability features of extreme precipitation in the country is crucial. This study used data from 28 meteorological stations for 1981-2020 period to give an annual and seasonal analysis of the patterns of 10 ETCCDI's extreme precipitation indices over the regions. At annual scale, the results showed that increasing trends had high frequency percentage than the decreasing ones, collecting about 76% in total. The decreasing trend was approximately 24%, and most of the stations with increasing percentage in trend are concentrated in Northern coast, Central, West, Northeastern highlands and Lake Victoria Basin. Most of the stations depicted negative trend are concentrated over Southern region. This highlights that extreme precipitation events have increased over the country for the period 1981-2020. At seasonal scale, during October to December (OND); the patterns of extreme precipitation climatic indices except R99p, showed positive significant increasing trend over Lake Victoria Basin and some Western parts of the country. In general, spatial patterns indicate decrease of precipitation over most parts of the country during OND. The seasonal average time series depicted non-significant positive trend during March to April (MAM) season, except for Consecutive Wet Days (CWD) which showed non-significant decreasing trend. Over the highest mountain in Africa, Kilimanjaro; the study has revealed significant decrease in Annual total-wet Precipitation (PRCPTOT), the number of heavy (very heavy) days of precipitation R10 mm (R20 mm) and How to cite this paper: Ndabagenga Consecutive Wet Days (CWD) during MAM season. While the maximum one-day precipitation amount (RX1 day) was observed to decrease significantly over the Mountain during OND season. The result is very important in risk assessment and preparedness perspective in planning climate change mi-tigation and adaptations for different sectors like Tourism, Agriculture, Water and Energy.
... Previous studies documented the physical mechanisms associated with the variability of MAM rainfall over the region, including the enhanced low-level westerly moisture flux from the Congo basin and easterly moisture flux from the Indian Ocean, that favour enhanced MAM rainfall formation over Tanzania (Mafuru and Guirong, 2018;Makula and Zhou, 2021;Kebacho, 2022). Makula and Zhou (2021) further reported that enhanced MAM rainfall over the region is related to an enhanced upper-level northwesterly and southwesterly winds residing on the south and north flanks of the equatorial Indian Ocean, respectively, signifying an upper-level divergence over the country and lower-level enhanced cyclonic circulation over the western Indian Ocean. ...
This study investigates the relationship between the Antarctic sea ice concentration (SIC) and the precipitation variability in Tanzania during March to May (MAM) season from 1978 to 2017. It is found that the MAM SIC over the Weddell (Ross) sea is negatively correlated with the MAM precipitation, particularly over northern (southern) Tanzania, signifying that the high (low) MAM SIC over the Weddell (Ross) sea is associated with suppressed (enhanced) rainfall in Tanzania. The atmospheric circulations related to the MAM SIC anomalies were further analysed. It is revealed that the positive MAM SIC anomalies in the Weddell sea and the Ross sea are associated with the upper‐level wave train patterns propagating from the high latitudes to the low latitudes of the Southern Hemisphere, which results in anomalous upper‐level cyclonic circulation over the western Indian Ocean and Tanzania. The upper‐level cyclonic circulation anomaly favours the low‐level divergence and results in the subsidence over Tanzania. Moreover, the low‐level wind outflow over Tanzania due to divergence reduces the water vapour supply to Tanzania. This background is unfavourable for the occurrence of precipitation and thus decreases the precipitation in Tanzania. The situation is reversed for the negative MAM SIC anomalies over the Weddell sea and the Ross sea, conducive to the increase of precipitation over Tanzania.
... Over this region, the tropical rain belt (TRB) remains the main system that controls rainfall distribution. Other factors responsible for rainfall variability include equatorial Kelvin waves, Madden-Julian Oscillation (MJO), El Niño Southern Oscillation (ENSO), Congo basin westerlies, Mascarene High, Indian Ocean Dipole (IOD), monsoons and the region's sea surface temperature anomalies (SSTA) Harrison et al., 2019;Kebacho, 2021bKebacho, , 2022aKreppel et al., 2019;Rohli et al., 2019). EA experienced drought in 2019 that was associated with poor rainfall performance, which delayed the onset of seasonal rainfall from March to May. ...
East Africa (EA) suffers from significant flood and drought risks. These can be alleviated with pre-emptive action; however, currently available knowledge on the influence of tropical cyclones in the south Indian Ocean on extreme rainfall over EA is limited. Extending knowledge on understanding the effects of tropical cyclones on the basis of their location could open a window for mitigating the devastating effects of flood and drought. The current study fills this knowledge gap by examining the impact of the poor rainfall performance from tropical cyclones Idai and Kenneth during March and April, which subsequently led to delayed onset of seasonal rainfall during March–May 2019. The study reveals the link between disruption of rainfall and the direction of moisture flow across EA. Findings revealed that the location of tropical cyclones Idai/Kenneth over the Mozambique Channel/northern Madagascar as a key driver of strong easterly flow over the northern region of Tanzania, Kenya and Uganda led to drier conditions. Simultaneously, the same location of the tropical cyclone was linked to Congo westerly flow over southern Tanzania that led to wet conditions. Tropical cyclone Kenneth interacted with the Mascarene High to sharpen the moisture flow across EA, which occurred unusually late in the season. Generally, these results build on the scientific evidence that the location of tropical cyclones may determine how the EA region is affected by either flood or drought. The current study provides new insights on the mechanisms that control the weather of EA, thereby leading to better forecasting accuracy.
Eastern Africa exhibits bimodal rainfall consisting of long rains (March–May) and short rains (October–December), changes in which have profound socioeconomic and environmental impacts. In this Review, we examine the drivers and corresponding impacts of Eastern African rainfall variability. Remote teleconnections, namely the El Niño–Southern Oscillation and the Indian Ocean Dipole, exert a dominant influence on interannual variability. From the mid-1980s to 2010, the long rains have tended toward a drier state (trends of −0.65 to −2.95 mm season⁻¹year⁻¹), with some recovery thereafter, while the short rains have become wetter since the mid 1980s (1.44 to 2.36 mm season⁻¹ year⁻¹). These trends, overlain by substantial year-to-year variations, affect the severity and frequency of extreme flooding and droughts, the stability of food and energy systems, the susceptibility to water-borne and vector-borne diseases, and ecosystem stability. Climate model projections of rainfall changes differ, but there is some consensus that the short rains will deliver more rainfall than the long rains by 2030–2040, with implications for sustaining agricultural yields and triggering climate-related public health emergencies. Mitigating the impacts of future Eastern African climate requires continued investments in agriculture, clean water, medical and emergency infrastructures, and development and adoption of adaptation strategies, as well as targeted early-warning systems driven by improved meteorological observations.
