Sustained Water Storage in Horn of Africa Drylands Dominated by Seasonal Rainfall Extremes

Adloff, Markus; Singer, Michael Bliss; MacLeod, David; Michaelides, Katerina; Mehrnegar, Nooshin; Hansford, Eleanor; Funk, Chris; Mitchell, Dann

doi:10.1029/2022gl099299

Cited by 14 publications

(14 citation statements)

References 72 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similarly, no significant change in the overall frequency and amplitude of the IOD is projected by coupled models 176,177 , although the frequency of extreme positive IOD events is thought to increase 173,178 . Assuming that present-day relationships between Eastern African rainfall and ENSO and IOD remain the same in the future, the short rains would then become wetter, with an increasing chance of torrential rains and associated higher risk of flooding, but also the potential for groundwater recharge 6 .…”

Section: Enso and Iodmentioning

confidence: 99%

“…Moreover, rainfall is pivotal to energy production, particularly given that hydropower represents a large fraction of electricity generation in Eastern Africa 4 . Aquifer recharge from rainfall 5,6 also provides a sustainable reservoir of groundwater for potable water (and irrigation) during periods of drought 5 , demonstrating the importance of rainfall for water security, especially when looking to the future 7 .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Drivers and impacts of Eastern African rainfall variability

Palmer

Wainwright

Dong

et al. 2023

Nat Rev Earth Environ

107

View full text Add to dashboard Cite

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 −1 year −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 vectorborne 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 climaterelated 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. Sections 2015 coincided with a weaker IOD, producing anomalies ~50% above the climatological mean 18 . However, these relationships are nonlinear, as demonstrated by extreme 2019/2020 rainfall that occurred during an anomalously positive phase of the IOD but neutral ENSO conditions 20 .The IOD and ENSO physically influence Eastern African short rains by modifying regional atmospheric circulation features (Fig. 2a,b).Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author selfarchiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

show abstract

Section: Enso and Iodmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Drivers and impacts of Eastern African rainfall variability

Palmer

Wainwright

Dong

et al. 2023

Nat Rev Earth Environ

107

View full text Add to dashboard Cite

show abstract

“…Similarly, the anomalies in short rains are driven by uniform increases and decreases in rainfall during all its constituent months, with few exceptions. We clearly see the impact of the unprecedented El Niño event in 1997 (McPhaden, 1999) on all 3 months of the short rains, and to a lesser extent in 2006 and 2015 (which have been documented as years of high groundwater recharge (Adloff et al., 2022)), and during the exceptional drought of 2010.…”

Section: Resultsmentioning

confidence: 90%

A Lagrangian Analysis of the Sources of Rainfall Over the Horn of Africa Drylands

et al. 2023

Self Cite

View full text Add to dashboard Cite

The Horn of Africa drylands (HAD) are among the most vulnerable regions to hydroclimatic extremes. The two rainfall seasons—long and short rains—exhibit high intraseasonal and interannual variability. Accurately simulating the long and short rains has proven to be a significant challenge for the current generation of weather and climate models, revealing key gaps in our understanding of the drivers of rainfall in the region. In contrast to existing climate modeling and observation‐based studies, here we analyze the HAD rainfall from an observationally‐constrained Lagrangian perspective. We quantify and map the region's major oceanic and terrestrial sources of moisture. Specifically, our results show that the Arabian Sea (through its influence on the northeast monsoon circulation) and the southern Indian Ocean (via the Somali low‐level jet) contribute ∼80% of the HAD rainfall. We see that moisture contributions from land sources are very low at the beginning of each season, but supply up to ∼20% from the second month onwards, that is, when the oceanic‐origin rainfall has already increased water availability over land. Further, our findings suggest that the interannual variability in the long and short rains is driven by changes in circulation patterns and regional thermodynamic processes rather than changes in ocean evaporation. Our results can be used to better evaluate, and potentially improve, numerical weather prediction and climate models, and have important implications for (sub‐)seasonal forecasts and long‐term projections of the HAD rainfall.

show abstract

“…However, despite no inclusion of initial hydrological conditions prior to each forecast season, we still find high skill in the forecasts. This may arise due to the highly modal nature of the dry and wet seasons in the region: the start of the wet season forecast follows a persistent lack of rainfall during the dry season, reducing water stores to the same low level by the start of most rainfall seasons [33]. Start-of-season variability in surface water may offer limited predictability compared to the subsequent seasonal rainfall total which will end up dominating hydrological predictability.…”

Section: Plos Climatementioning

confidence: 99%

Translating seasonal climate forecasts into water balance forecasts for decision making

et al. 2023

View full text Add to dashboard Cite

Seasonal rainfall forecasts support early preparedness. These forecasts are typically disseminated at Regional Climate Outlook Forums (RCOFs), in the form of seasonal tercile probability categories—above normal, normal, below normal. However, these categories cannot be related directly to impacts on terrestrial water stores within catchments, since they are mediated by non-linear hydrological processes occurring on fine spatiotemporal scales, including rainfall partitioning into infiltration, evapotranspiration, runoff and groundwater recharge. Hydrological models are increasingly capable of capturing these processes, but there is no simple way to drive such models with a specific RCOF seasonal tercile rainfall forecast. Here we demonstrate a new method, “Quantile Bin Resampling” (QBR), for producing seasonal water forecasts for a drainage basin by integrating a tercile seasonal rainfall forecast with a hydrological model. QBR is based on mapping historical quantiles of basin-average rainfall to historical simulations of the water balance, and circumvents challenges associated with using climate model output to drive impact models directly. We evaluate QBR by generating 35 years of seasonal reforecasts for various water balance stores and fluxes for the Upper Ewaso Ng’iro basin in Kenya. Hindcasts indicate that when input tercile rainfall forecasts have skill, QBR provides accurate water forecasts at kilometre-scale resolution, which is relevant for anticipatory action down to village level. Pilot operational experimental water forecasts were produced for this basin using QBR for the 2022 March-May rainfall season, then disseminated to regional stakeholders at the Greater Horn of Africa Climate Outlook Forum (GHACOF). We discuss this initiative, along with limitations, plans and future potential of the method. Beyond the demonstrated application to water-related forecasts, QBR can be easily adapted to work with any rainfall-driven impact model. It can translate objective tercile climate probabilities into impact-relevant water balance forecasts at high spatial resolution in an efficient, transparent and flexible way.

show abstract

Sustained Water Storage in Horn of Africa Drylands Dominated by Seasonal Rainfall Extremes

Cited by 14 publications

References 72 publications

Drivers and impacts of Eastern African rainfall variability

Drivers and impacts of Eastern African rainfall variability

A Lagrangian Analysis of the Sources of Rainfall Over the Horn of Africa Drylands

Translating seasonal climate forecasts into water balance forecasts for decision making

Contact Info

Product

Resources

About