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Open AccessArticle

Classification of Intense Rainfall Days in Southern West Africa and Associated Atmospheric Circulation

1
Centre de Recherches de Climatologie/Biogéosciences, Université Bourgogne Franche-Comté, 25000 Dijon, France
2
Laboratoire Pierre Pagney: Climat, Eau, Ecosystèmes et Développement, Université d’Abomey-Calavi, 01 B.P. 526 Cotonou, Benin
*
Author to whom correspondence should be addressed.
Atmosphere 2020, 11(2), 188; https://doi.org/10.3390/atmos11020188
Received: 18 December 2019 / Revised: 3 February 2020 / Accepted: 8 February 2020 / Published: 11 February 2020
(This article belongs to the Special Issue Trends in Hydrological and Climate Extremes in Africa)
Daily rainfall in southern West Africa (4–8° N, 7° W–3° E) is analyzed with the aim of documenting the intense rainfall events which occur in coastal Ivory Coast, Ghana, Togo, and Benin. The daily 99th percentile (P99) shows that the coastline experiences higher intensity rainfall than inland areas. Using Tropical Rainfall Measuring Mission (TRMM) rainfall data for 1998–2014, a novel way of classifying the intense events is proposed. We consider their space-time structure over a window of 8° latitude-longitude and five days centered on the event. A total 39,680 events (62 at each location) are classified into three major types, mainly found over the oceanic regions south of 5° N, the Bight of Benin, and the inland regions respectively. These types display quite distinct rainfall patterns, propagation features, and seasonal occurrence. Three inland subtypes are also defined. The atmospheric circulation anomalies associated with each type are examined from ERA-interim reanalysis data. Intense rainfall events over the continent are mainly a result of westward propagating disturbances. Over the Gulf of Guinea, many intense events occur as a combination of atmospheric disturbances propagating westward (mid-tropospheric easterly waves or cyclonic vortices) and eastward (lower tropospheric zonal wind and moisture anomalies hypothesized to reflect Kelvin waves). Along the coast, there is a mixture of different types of rainfall events, often associated with interacting eastward- and westward-moving disturbances, which complicates the monitoring of heavy precipitation.
Keywords: intense rainfall; equatorial waves; coastal climates; West Africa; Gulf of Guinea intense rainfall; equatorial waves; coastal climates; West Africa; Gulf of Guinea
MDPI and ACS Style

Camberlin, P.; Kpanou, M.; Roucou, P. Classification of Intense Rainfall Days in Southern West Africa and Associated Atmospheric Circulation. Atmosphere 2020, 11, 188.

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