Every day, about one thousand thunderstorms occur around the world, producing about 45 lightning flashes per second. One prominent infrasound station of the International Monitoring System infrasound network of the Comprehensive Nuclear-Test-Ban Treaty Organization for studying lightning activity is in Ivory Coast, where the lightning rate of this region is relatively high. Infrasound defines acoustic waves with frequencies below 20 Hz, the lower limit of human hearing. Statistical results are presented in this paper based on infrasound measurements from 2004 to 2019. One-to-one association between infrasound detections from 0.5 to 5 Hz and lightning flashes detected by the World Wide Lightning Location Network within 500 km from the infrasound station is systematically investigated. Most of the infrasound signals detected at IS17 in this frequency band are due to thunder, even if the thunderstorms are located up to 500 km away from the station. A decay of the thunder amplitude with the flash distance, d, is found to scale as d^−0.717 for flashes within 100 km from the station, which holds for direct propagation. Interestingly, the stratospheric detections reflect a pattern in the annual azimuth variation, which is consistent with the equatorial stratospheric semi-annual oscillation.

The contribution in terms of long-range transport of CO₂, CH₄, and CO concentrations to measurements at Lamto (5°02′ W–6°13′ N) was analyzed for the 2014–2017 period using the FLEXPART model that calculates the retro-plumes of air masses arriving at the station. The identification of the source-receptor relationships was also studied with a clustering technique applied on those retro-plumes. This clustering technique enabled us to distinguish four categories of air mass transports arriving at Lamto site described as follows: oceanic and maritime origin (≈37% of the retro-plumes), continental origin (≈21%), and two hybrid clusters (≈42%). The results show that continental emission sources contribute significantly to the increases in concentrations of CO₂, CH₄, and CO and explain ≈40% of their variance. These emission sources are predominantly from north and north-east directions of the measurement point, and where densely populated and economically developed areas are located. In addition, the transport of air masses from these directions lead to the accumulation of CO₂, CH₄, and CO. Furthermore, the ratios ΔCO/ΔCH₄ and ΔCO/ΔCO₂ observed in the groups associated with Harmattan flows clearly show an influence of combustion processes on the continent. Thus, the grouping based on FLEXPART footprints shows an advantage compared to the use of simple trajectories for analyzing source–receptor relationships.

This study analyzes the potential response of the seasonal cycle of heatwaves (HWDI) and dry (CDD) and wet (CWD) spell indices over West Africa for the near- (2031–2060) and the far-future periods (2071–2100) under RCP4.5 and RCP8.5 scenarios using Coordinated Regional Climate Downscaling Experiment (CORDEX) simulations. Despite the fact that some relative biases (an underestimation of 30% for CDD, an overestimation of about 60% for CWD, and an overestimation of about 50% for HWDI) exist, during the historical period (1976–2005) in general, the CORDEX simulations and their ensemble mean outperform the seasonal variability in the above-mentioned indices over three defined subregions of West Africa (i.e., the Gulf of Guinea and Western and Eastern Sahel). They show high correlation coefficients (0.9 in general) and less RMSE. They project an increase (about 10 and 20 days) in heatwave days for both the near- and far-future periods over the whole West African region under both RCP scenarios. In addition, projections indicate that the Sahel regions will experience a decrease (about 5 days) in wet spell days from March to November, while in the Gulf of Guinea, a decrease (about 3 days) is projected throughout the year, except in the CCCLM simulation, which indicates an increase (about 5 days) during the retreat phase of the monsoon (October to December). Our results also highlight an increase (about 80%) in dry spells over the Sahel regions that are more pronounced during the March–November period, while over the Gulf of Guinea, an increase (about 40%) is projected over the entire year. Moreover, the months of increasing dry spells and decreasing wet spells coincide, suggesting that countries in these regions could be simultaneously exposed to dry seasons associated with a high risk of drought and heatwaves under future climate conditions.

The aim of this study is to characterize the compound extremes of rainfall and temperature in Côte d’Ivoire. For this purpose, we analyzed the outputs of fourteen (14) climate models from the CORDEX-Africa project. Results show an increase (approximately 4.3 °C) in the surface temperature and a decrease (5.90%) of the mean rainfall in the near (2036–2065) and far futures (2071–2100) over Côte d’Ivoire during the January–February–March (JFM) period. The analysis of the compound extremes of the wet/warm type highlights an increase in the frequency of this climatic hazard in the northern and central parts of the country during the January–March (JFM) season in the near and far futures. The dry/warm mode will increase in the central and southern parts of the country in the near future and in the whole country in the far future. These increases in compound extremes could lead to an increase in droughts and natural disasters across the country and could have a negative impact on socio-economic activities, such as transportation and agricultural production. This work could provide decision support for political decision-makers in formulating future public policies for managing agricultural production, food security, and natural disasters.

The aim of this study is to characterize the compound extremes of rainfall and temperature in Côte d’Ivoire. For this purpose, we analyzed the outputs of fourteen (14) climate models from the CORDEX-Africa project. Results show an increase (approximately 4.3°C) of the surface temperature and a decrease (5,90 %) of the mean rainfall in the near (2036-2065) and far futures (2071-2100) over Côte d’Ivoire during January-February-March (JFM) period. The analysis of the compound extremes of wet/warm type highlights an increase in the frequency of this climatic hazard in the northern and central parts of the country during January-March (JFM) season in the near and far futures. The dry/warm mode will increase in the central and southern parts of the country during the near future and in the whole country during the far future. These increase in compound extremes could lead to an increase in droughts and natural disasters over the country and could have a negative impact on socio-economic activities, such as transportation and agricultural production. This work could provide decision support for political decision-makers in formulating future public policies for managing agricultural production, food security, and natural disasters.