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Surface observations provide ground evidence of climate change to support the scientific guidance paving the way to better adaptation and mitigation actions. The West African Science Service Centre on Climate Change and Adapted Land Use (WASCAL) has designed a multistakeholder initiative to rescue the deteriorated near-surface weather, climate and hydrological equipment of West African countries. The main goal for this multi-stakeholder framework was to monitor the climate and collect long term and high-quality records of essential climate variables in support of research, education, capacity building, and climate services provision. Proactive and inclusive partnership initiatives were developed to jointly (re)design and (re)implement near surface observatiories with the national meteorological and hydrological services or agencies (NMHS/As) in West Africa. The co-production scheme used by this framework succeeded in evaluating the existing observations networks, to modernizing sensors and field equipment, and densifying the sites in order to improve the quality of data collection, transmission, archiving, processing and sharing policies. After more than four years of community-of-practice, the existing regional basic hydroclimatic was increased/upgraded by 45% with automatic weather observing systems while fifty automatic water level, ten water quality sensors, three mesoscale research catchments, and several pilot sites to benefit countries' services provision, research infrastructure, education, and capacity building. Country-specific data sharing policies were harmonized and signed to support data services delivery. This practice paper exposes the concepts, outcomes, challenges, lessons learned and the ways forward in setting-up the framework and keeping it on working to leverage the co-production of data & information services for better-informed decision-making in the field of sustainable development in West Africa.

The “Great Green Wall” of trees (GGW) is an emblematic Pan‐African initiative of re‐greening the Sahel through afforestation and assisted natural regeneration of trees in order to tackle desertification, soil degradation and to mitigate greenhouse gases. This study investigates (i.e., The Sahel Greenbelt) the potential impacts of the GGW and other assisted natural regeneration of trees on the frequency and intensity of extreme climate events over the Sahel and West Africa using the regional climate model (RegCM version 4.3). Our investigation shows that the Sahel greenbelt would increase significantly the number of rainy days (+9%) and the intensity of heavy rain events over the Sahel while extreme dry spells decrease (−4%). Important shifts appear in the modes of variability of all precipitation indices. These probability distribution shapes reveal tremendous intra‐seasonal variability as the new land use land cover (LULC) changes affect the regional climate. Changes in atmospheric circulation including increase of the moisture convergence and evapotranspiration appeared to be the main drivers of heavy rainfall changes. For temperature extremes, the maximum temperature shows significant decrease around the GGW area during summer and an increase in other seasons while the diurnal temperature range increases significantly without an evident change in temperature trends. Intra‐seasonal distributions of temperature extremes show less obvious changes compared to precipitation extremes. This investigation highlights the role of the planned and implemented re‐greening policies (i.e., afforestation by the GGW project and policies of assisted natural regeneration of trees) in affecting the frequency and the amplitude of some climatic extreme events (e.g., heavy rain events, maximum temperatures, etc.). These planned LULC policies need to be accounted for in the diagnostics and future projections of climate extremes over the region.

The data described in this article are sets of daily rainfall values derived from observed station records. The data was recorded by 72 in-situ rain gauges spread over the West African Sahel. The daily rainfall time series from synoptic, climate, agro-meteorological, and rainfall stations are assessed for quality and consistency before extreme values are extracted based on 90th, 95th, and 99th percentile thresholds. This data is free for use as part of the study "Scales for rating heavy rainfall events in West African Sahel" [1] (Salack et al., 2018). Complementary and up to date time series can be taken from WASCAL data infrastructure (WADI) geoportal https://wascal-dataportal.org/wascal_searchportal2/. This is a derived product (DP), made public in line with WASCAL׳s “3rd party data sharing policy” signed by the WASCAL member countries.

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