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Katharine Vincent, Suzanne Carter, Anna Steynor, Emma Visman & Katinka Lund Wågsæther

Co-production is an increasingly popular approach to knowledge generation encouraged by donors and research funders. However, power dynamics between institutions in the Global North and South can, if not adequately managed, impede the effectiveness of co-production and pose risks for long-term sustainability.

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Robel Geressu; Christian Siderius; Julien J. Harou; Japhet Kashaigili; Laetitia Pettinotti; Declan Conway

Abstract

Many river basins in the Global South are undergoing rapid development with major implications for the interdependent water‐energy‐food‐environmental (WEFE) “nexus” sectors. A range of views on the extent to which such natural‐human systems should be developed typically exists. The perceived best investments in river basins depend on how one frames the planning problem. Therefore, we propose an approach where the best possible (optimized) implementations of different river basin development scenarios are assessed by comparing their WEFE sector trade‐offs. We apply the approach to Tanzania’s Rufiji river basin, an area with multiple WEFE interdependencies and high development potential (irrigation and hydropower) and ecosystem services. Performance indicators are identified through stakeholder consultation and describe WEFE sector response under scenarios of river basin development. Results show considerable potential exists for energy and irrigation expansion. Designs that prioritize energy production adversely affect environmental performance; however, part of the negative impacts can be minimized through release rules designed to replicate the natural variability of flow. The reliability of monthly energy generation is more sensitive to environmental‐oriented management than the cumulative annual energy production. Overall results highlight how sectoral trade‐offs change depending on the extent of development, something that may be difficult to regulate in the future, and that there are important basin‐scale interdependencies. Benefits and limitations of the approach and its application are discussed.

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Rebecka Henriksson; Katharine Vincent; Emmar Archer; Graham Jewitt

Smallholder farmers in the sub-Saharan Africa are vulnerable to climate variability and change, and are thus in need of adaptation. Access to climate information, such as weather forecasts, has been identified as a potential enabler for improved adaptation, but such access tends to be strongly gendered. This study uses qualitative and quantitative data to assess the availability, accessibility and use of climate information among smallholder sugarcane farmers in southern Malawi, disaggregating data according to gender, age, education level and landholding size. We found that radio is the most common, and preferred, means of accessing forecasts for men and women, but that women farmers also prefer to access forecasts through a knowledge broker. Those farmers with higher levels of education (mostly men) prefer to also obtain forecasts via internet and cell phone. Most farmers consider the forecasts reliable, timely and understandable – more so in the case of men than women. Understanding gendered preferences and barriers to climate information access is crucial for benefits of adaptation to be accessed equitably.

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Cornelia Klein and Christopher M. Taylor

Soil moisture can feed back on rainfall through the impact of surface fluxes on the environment in which convection develops. The vast majority of previous research has focused on the initiation of convection, but in many regions of the world, the majority of rain comes from remotely triggered mesoscale convective systems (MCSs). Here we conduct a systematic observational analysis of soil moisture feedbacks on propagating MCSs anywhere in the world and show a strong positive impact of drier soils on convection within mature MCSs. From thousands of storms captured in satellite imagery over the Sahel, we find that convective cores within MCSs are favored on the downstream side of dry patches ≥200 km across. The effect is particularly strong during the afternoon–evening transition when convection reaches its diurnal peak in intensity and frequency, with dry soils accounting for an additional one in five convective cores. Dry soil patterns intensify MCSs through a combination of convergence, increased instability, and wind shear, all factors that strengthen organized convection. These favorable conditions tend to occur in the vicinity of a surface-induced anomalous displacement of the Sahelian dry line/intertropical discontinuity, suggesting a strong link between dry line dynamics and soil moisture state. Our results have important implications for nowcasting of severe weather in the Sahel and potentially in other MCS hotspot regions of the world.

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Caroline M. Wainwright; Declan L. Finney; Mary Kilavi; Emily Black; John H. Marsham

Abstract

The 2019 October–December rains over East Africa were one of the wettest seasons on record, with many locations receiving more than double the climatological rainfall, leading to floods and landslides. The wet conditions were associated with the positive Indian Ocean Dipole event, with warm sea surface temperatures in the western Indian Ocean. Seasonal forecasts correctly predicted above average rainfall during the season. Climate model projections suggest that such events may become more frequent under future climate change.

East Africa’s 2019 short rains (October–December [OND]) were one of the wettest in recent decades. Floods and landslides occurred across the region, with initial estimates suggesting over 2.8 million people were adversely affected. Here we highlight some of the factors associated with this anomalously wet season and discuss the season in relation to the expected climate change signals over the region.

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Rachel James; Neil Hart; Callum Munday; Chris Reason; Richard Washington

Abstract

There are increasing efforts to use climate model output for adaptation planning, meanwhile there is often limited understanding of how models represent regional climate. Here we analyse the simulation in global coupled climate models of a key rainfall-generating mechanism over southern Africa: Tropical-Temperate Troughs (TTTs). An image-processing algorithm is applied to outgoing longwave radiation data from satellites and models to create TTT event sets. All models investigated produce TTTs with similar circulation features to observed. However, there are large differences among models in the number, intensity, and preferred longitude of events. Five groups of models are identified. The first group generates too few TTTs, and relatively dry conditions over southern Africa compared to other models. A second group generates more TTTs and wet biases. The contrast between these two groups suggests that the number of TTTs could explain inter-model variations in climatological rainfall. However, there is a third group of models which simulate up to 92% more TTTs than observed, but do not have large rainfall biases, as each TTT event is relatively weak. Finally, there are a further two groups which concentrate TTTs over the subcontinent or the ocean respectively. These distinctions between models are associated with the amount of convective activity in the Congo Basin, the magnitude of moisture fluxes into southern Africa, and the degree of zonal asymmetry in upper-level westerly flow. Model development focused on tropical convection and the representation of orography is needed for improved simulation of TTTs, and therefore southern African rainfall.

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Katharine Vincent; Declan Conway; Andrew J. Dougill; Joanna Pardoe; Emma Archer; Ajay Gajanan Bhave; Rebecka Henriksson; Neha Mittal; David Mkwambisi; Estelle Rouhaud; Dorothy Tembo-Nhlema

Abstract

Making climate-resilient planning and adaptation decisions is, in part, contingent on the use of climate information. Growing attention has been paid to the “usability gap” and the need to make information both useful and useable to decision-makers. Less attention has, however, been paid to the factors that determine whether, once created, useful and useable information is then actually used. In this Perspectives piece, we outline a framework that puts together the pieces necessary to close the “usability gap” – highlighting not only what is required to make information useful and useable, but also what is required to ensure that useful and useable information is actually used. Creating useful information is subject to understanding and being able to deliver metrics that address identified needs in a range of decision-making contexts. Creating useable information requires legitimate and credible information that is visualised and communicated in ways that are accessible and understandable. The framework highlights traditionally under-recognized enablers necessary to promote effective use of the growing availability of useful and useable climate information in decision-making; supportive institutions, appropriate policy frameworks, capacity of individuals and agency to make decisions. Whilst this is not enough in itself to effect information use, we argue that greater focus on these enablers can re-balance the activities promoted through climate services and increase the likelihood of successful use. We illustrate the framework with case examples of co-producing climate information for the tea and water sectors in sub-Saharan Africa.

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Salomon Obahoundje et al

Abstract

The Bui hydropower plant plays a vital role in the socio-economic development of Ghana. This paper attempt to explore the combined effects of climate-land use land cover change on power production using the (WEAP) model: Water Evaluation and Planning system. The historical analysis of rainfall and stream flow variability showed that the annual coefficient of variation of rainfall and stream flow are, respectively, 8.6% and 60.85%. The stream flow varied greatly than the rainfall, due to land use land cover changes (LULC). In fact, the LULC analysis revealed important changes in vegetative areas and water bodies. The WEAP model evaluation showed that combined effects of LULC and climate change reduce water availability for all of demand sectors, including hydropower generation at the Bui hydropower plant. However, it was projected that Bui power production will increase by 40.7% and 24.93%, respectively, under wet and adaptation conditions, and decrease by 46% and 2.5%, respectively, under dry and current conditions. The wet condition is defined as an increase in rainfall by 14%, the dry condition as the decrease in rainfall by 15%; current account is business as usual, and the adaptation is as the efficient use of water for the period 2012–2040.

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Largeron, Y., Guichard, F., Roehrig, R. et al

Abstract

North Africa experienced a severe heatwave in April 2010 with daily maximum temperatures () frequently exceeding 40C and daily minimum temperatures () over 27C for more than five consecutive days in extended Saharan and Sahelian areas. Observations show that areas and periods affected by the heatwave correspond to strong positive anomalies of surface incoming longwave fluxes () and negative anomalies of incoming shortwave fluxes (). The latter are explained by clouds in the Sahara, and by both clouds and dust loadings in the Sahel. However, the strong positive anomalies of  are hardly related to cloud or aerosol radiative effects. An analysis based on climate-model simulations (CNRM-AM) complemented by a specially-designed conceptual soil-atmospheric surface layer model (SARAWI) shows that this positive anomaly of  is mainly due to a water vapor greenhouse effect. SARAWI, which represents the two processes driving temperatures, namely turbulence and longwave radiative transfer between the soil and the atmospheric surface layer, points to the crucial impact of synoptic low-level advection of water vapor on . By increasing the atmospheric infrared emissivity, the advected water vapor dramatically increases the nocturnal radiative warming of the soil surface, then in turn reducing the nocturnal cooling of the atmospheric surface layer, which remains warm throughout the night. Over Western Sahel, this advection is related to an early northward incursion of the monsoon flow. Over Sahara, the anomalously high precipitable water is due to a tropical plume event. Both observations and simulations support this major influence of the low-level water vapor radiative effect on during this spring heatwave.

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Sacré Regis M., D.; Mouhamed, L.; Kouakou, K.; Adeline, B.; Arona, D.; Houebagnon Saint. J., C.; Koffi Claude A., K.; Talnan Jean H., C.; Obahoundje, S.; Issiaka, S

This study aims to provide improved knowledge and evidence on current (1986–2015) climate variation based on six rainfall indices over five West African countries (Senegal, Niger, Burkina Faso, Ivory Coast, and Benin) using the Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) dataset. On average, precipitation has increased over the central Sahel and the western Sahel. This increase is associated with increase in the number of rainy days, longer wet spells and shorter dry spells. Over the Guinea Coast, the slight increase in precipitation is associated with an increase in the intensity of rainfall with a shorter duration of wet spells. However, these mean changes in precipitation are not all statistically significant and uniform within a country. While previous studies are focused on regional and sub-regional scales, this study contributes to deliver a climate information at a country level that is more relevant for decision making and for policy makers, and to document climate-related risks within a country to feed impact studies in key sectors of the development, such as agriculture and water resources.

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