Spatial patterns and trends of extreme rainfall over the southern coastal belt of West Africa
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ORIGINAL PAPER
Spatial patterns and trends of extreme rainfall over the southern coastal belt of West Africa Marc Kpanou 1,2
&
Patrick Laux 4 & Télesphore Brou 3 & Expédit Vissin 2 & Pierre Camberlin 1 & Pascal Roucou 1
Received: 22 November 2018 / Accepted: 15 October 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract The southern coastal belt of West Africa (SCWA) with its high population density and many major cities, combined to the low elevation and poor urban planning, is very vulnerable to floods resulting from extreme rainfall events. The aim of this paper is to analyze the characteristics of extreme rainfall in the SCWA during the 1981–2015 period, in terms of frequency, intensity, seasonality, and trends. Therefore, daily rainfall of 31 stations located in the southern part of Côte d’Ivoire, Ghana, Togo, and Benin and rainfall estimation products combining in situ observations and satellites rainfall estimation data have been used. For each station and pixel, the local 95th percentile (P95) computed on all rain days of at least 1 mm was used to define extreme rainfall events. Rainfall on the coastal belt is heavier than further inland, with P95 values reaching 82 and 52 mm/day for coastal and continental stations, respectively. Extreme rainfall along the coast occurs predominantly between May and July. Interannual variations of different indicators of extreme rainfall show a broad agreement between rain gauge data and rainfall estimates from CHIRPS (Climate Hazards Group InfraRed Precipitation with Station) data. In the southern part of Côte d’Ivoire and Togo/Benin, increase of number of extreme rainfall event (NP95) and stability number of days with rainfall less than P95 (NL95) are recorded, which induces an increase of total rainfall. But, in the southern part of Ghana, there is a stable total rainfall due to an increase in NP95 compensated by a decrease in NL95. Keywords Extreme rainfall . Trend . West Africa . Coastal belt
1 Introduction Extreme rainfall events in the southern coastal part of West Africa (SCWA) constitute a major hazard. The low elevation combined to poor urban planning and high population densities participate to flood damages. As much as 30.1% of the total population of the coastal states of Côte d’Ivoire, Ghana, Togo, and Benin is concentrated in a 40-km-wide corridor
bordering the Atlantic Ocean (GPW data, CIESIN 2015). All the major cities in the region are recurrently hit by flooding. The flood that hit Accra in June 2015 affected around 53,000 people in the city and caused an estimated US$100 million in damages (Erman et al. 2018). During the night of June 30 to July 1, 2014, between 5 am and 6 am, 85 mm of rain was recorded at the Abidjan station. On June 2, 3, 4, and 5, 2015, 210 mm and 257 mm of rain were recorded
* Marc Kpanou [email protected]
Pascal Roucou [email protected] 1
Centre de Recherche de Climatologie, Biogéosciences, Université Bourgogne Franche – Comté, 6 Bd Gabriel, 21000 Dijon, France
2
Laboratoire Pierre PAGN
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