Enhanced nighttime heatwaves over African urban clusters

Abstract

Despite the threat that nighttime heatwave poses to public health and the environment in the developing world, it remains relatively understudied in Africa, especially in its rapidly expanding urban areas with large populations. Using meteorological observations, climate reanalysis, remote sensing datasets, and integrated methodology, we found that during 1981-2020, nighttime heatwaves dramatically increased with early onset dates over Africa. Large scale circulation induced dry conditions over land which explains the major heatwaves across all climate zones. Meanwhile, the increasing trend of nighttime heatwaves in urban areas than rural areas in both tropical and temperate climates is largely due to urbanization, which amplifies heatwaves with urban heat island effects. The strongest contribution of urbanization to nighttime heatwaves was observed in temperate climate, leading to a 46% increase in the heatwave duration. In arid climate, urban expansion has a negative impact on nighttime heatwaves, due to the cool island effect of urban greens and weak urbanization. The major contribution of urbanization to the urban-rural contrast of nighttime heatwave trends in temperate climate can be attributed to stronger urban heat island intensity resulting from lower windspeed and less evapotranspiration. Without appropriate adaptation efforts to reduce heatwave exposure, the risks posed in Africa’s urban areas will continue to increase under future warming.

Leveraging data science and machine learning for urban climate adaptation in two major African cities: a HE2AT Center study protocol

“…[5][6][7] Enhanced night-time heatwaves over African urban clusters, as investigated by Igun et al, underline the growing threat of heatwaves exacerbated by UHI effects. 8 Furthermore, an assessment of the health-related impacts of UHIs in Douala metropolis, Cameroon, by Enete et al provides insight into the localised health burdens of urban heat. 9 Building on this foundation, our study seeks to contribute to this burgeoning field by creating an effective, data-driven urban heat health early warning system (EWS) tailored to the unique sociodemographic makeup of African metropolises.…”

“…Enhanced night-time heatwaves over African urban clusters, as investigated by Igun et al , underline the growing threat of heatwaves exacerbated by UHI effects. 8 Furthermore, an assessment of the health-related impacts of UHIs in Douala metropolis, Cameroon, by Enete et al provides insight into the localised health burdens of urban heat. 9…”