Drought Continuum in Africa: A Multidimensional Assessment of Meteorological, Hydrological, Agricultural, and Socioeconomic Drought

Africa’s climate is shaped by a complex interplay between atmospheric and oceanic systems that affect each part of the region rather differently with distinct seasonality. The northernmost and southernmost areas of the continent have a Mediterranean-type climate, with dry-hot summers and moist-moderate winters, which results in distinct seasonality in the hydrological cycle and semi-aridity [1, 2]. The Sahara, a large desert in northern Africa, is located in the subtropics and has an arid climate characterised by highly variable precipitation patterns and water scarcity. A large part of sub-Saharan Africa, however, is under the influence of monsoonal systems, whose dynamics and seasonality are heavily influenced by large-scale meridional temperature gradients that lead to cross-equatorial energy imbalance and shifts of the intertropical convergence zone [3], that is, a narrow low-pressure band where moist air ascends and results in heavy precipitation.

Monsoonal systems are highly crucial for the tropical African countries' socio-economic development, particularly their agriculture, ecosystem, and energy systems. The interaction between monsoonal systems and the large-scale modes of variability, such as the El Niño-Southern Oscillation and the Indian Ocean Dipole [4], gives rise to strong spatial precipitation gradients and pronounced year-to-year variability.

As a result of human-induced warming, the atmospheric and oceanic circulation patterns are expected to change, which can lead to changes in precipitation patterns and distribution, increased evapotranspiration, and increased extreme events such as floods and droughts. In this work, we monitor and project extreme events over Africa, with a particular focus on droughts, to understand how drought propagates from one system to another. We consider drought not as a single event but as a continuous, evolving process [5] with interconnected impacts on the hydrological, agricultural, socio-economic, and overall African energy systems across different timescales.

To address this, we use observational records, reanalysis, climate model historical simulations and projections of different scenarios, and examine different meteorological and impact-based indices to 1) understand the climatology of Africa in the historical/present-day period, 2) analyse the spatiotemporal changes in its hydroclimate within the historical records and in the coming decades, and 3) identify drought events in the past and in the coming decades to check if, and to what extent, Africa's infrastructure can buffer the impacts of extreme events.

 

References:

[1] Giorgi, F. (2006). Climate change hot-spots. Geophys. Res. Lett, 33, 8707. https://doi.org/10.1029/2006GL025734
[2] Seager, R., et al. (2019). Climate Variability and Change of Mediterranean-Type Climates. Journal of Climate, 32(10), 2887–2915. https://doi.org/10.1175/jcli-d-18-0472.1
[3] Nicholson, S. E. (2018). The ITCZ and the Seasonal Cycle over Equatorial Africa. Bulletin of the American Meteorological Society, 99(2), 337–348. https://doi.org/10.1175/BAMS-D-16-0287.1
[4] Hoell, A., & Funk, C. (2013). The ENSO-Related West Pacific Sea Surface Temperature Gradient. Journal of Climate, 26(23), 9545–9562. https://doi.org/10.1175/JCLI-D-12-00344.1
[5] Van Loon, A. F., et al. (2024). Review article: Drought as a continuum – memory effects in interlinked hydrological, ecological, and social systems, Nat. Hazards Earth Syst. Sci., 24, 3173–3205, https://doi.org/10.5194/nhess-24-3173-2024