Mesoscale extreme rainfall events in West Africa: The cases of Niamey (Niger) and the Upper Ouémé Valley (Benin)
In West Africa, a sharp decrease in rainfall has occurred in conjunction with an increase in flood damage since 1970. The material damage and loss of life resulting from floods highlights the undeniable vulnerability of populations to this threat and illustrates the importance of addressing the evol...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Elsevier
2016-09-01
|
| Series: | Weather and Climate Extremes |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2212094716300238 |
| _version_ | 1819268176150528000 |
|---|---|
| author | Eric-Pascal Zahiri Ibrahim Bamba Adjoua Moise Famien Augustin Kadjo Koffi Abé Delfin Ochou |
| author_facet | Eric-Pascal Zahiri Ibrahim Bamba Adjoua Moise Famien Augustin Kadjo Koffi Abé Delfin Ochou |
| author_sort | Eric-Pascal Zahiri |
| collection | DOAJ |
| description | In West Africa, a sharp decrease in rainfall has occurred in conjunction with an increase in flood damage since 1970. The material damage and loss of life resulting from floods highlights the undeniable vulnerability of populations to this threat and illustrates the importance of addressing the evolution of hazardous precipitation caused by intense rainstorms. This work aims to improve our knowledge of the behaviour of extreme rainfall in West Africa by studying the sub-hourly, hourly and daily evolution of the most extreme rainfall events, a topic that is especially important to those interested in studying the links between heavy rainfall and flash flooding or inundation. This study analyses the classes of extreme rainfall events in two distinct climatic areas within West Africa using the meteorological scales relevant to rainfall processes. The study is based on two precipitation datasets recorded by dense networks of rain gauges set up within the meso-sites of Niamey (Niger, Sahelian area) and the Upper Ouémé Valley (Northern Benin, Soudanian zone) from 2000 to 2010 and 1998 to 2010, respectively. The Gumbel distribution was used to analyse the frequency of the maximum rainfall series for durations varying from 5 min to 24 h. The reliability of this model was examined, and the Intensity-Density-Frequency (IDF) curves derived from it were used to estimate the critical rainfall intensities at each site. The results returned exceeded frequencies that were useful for the isolation and classification of extreme rainfall cases using temporal characteristics. The climatological results confirm the existence of a latitudinal gradient in the mean annual rainfall and number of extreme events at the mesoscale. The classification methods illustrate clear distinctions between local, meso and synoptic scale events derived from convective systems over the Sahel. In contrast, Soudanian climate conditions lead to a nesting of the phenomena involved in the formation of cloud systems, making it difficult to classify rain events in that area. However, we were able to utilize the duration of rainfall events within this zone to discriminate between types of convective systems that cause extreme rainfall. For both areas, the proportion of precipitation in an extreme event compared to total yearly precipitation served as a suitable additional criterion used to objectively identify extreme precipitation event types. |
| first_indexed | 2024-12-23T21:28:54Z |
| format | Article |
| id | doaj.art-ad201b48a0ed4d15a00a1b2be3952a62 |
| institution | Directory Open Access Journal |
| issn | 2212-0947 |
| language | English |
| last_indexed | 2024-12-23T21:28:54Z |
| publishDate | 2016-09-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Weather and Climate Extremes |
| spelling | doaj.art-ad201b48a0ed4d15a00a1b2be3952a622022-12-21T17:30:30ZengElsevierWeather and Climate Extremes2212-09472016-09-0113C153410.1016/j.wace.2016.05.001Mesoscale extreme rainfall events in West Africa: The cases of Niamey (Niger) and the Upper Ouémé Valley (Benin)Eric-Pascal Zahiri0Ibrahim Bamba1Adjoua Moise Famien2Augustin Kadjo Koffi3Abé Delfin Ochou4Laboratoire de Physique de l’Atmosphère et de Mécanique des Fluides, Cote d’IvoireLaboratoire de Physique de l’Atmosphère et de Mécanique des Fluides, Cote d’IvoireLaboratoire de Physique de l’Atmosphère et de Mécanique des Fluides, Cote d’IvoireLaboratoire de Physique de l’Atmosphère et de Mécanique des Fluides, Cote d’IvoireLaboratoire de Physique de l’Atmosphère et de Mécanique des Fluides, Cote d’IvoireIn West Africa, a sharp decrease in rainfall has occurred in conjunction with an increase in flood damage since 1970. The material damage and loss of life resulting from floods highlights the undeniable vulnerability of populations to this threat and illustrates the importance of addressing the evolution of hazardous precipitation caused by intense rainstorms. This work aims to improve our knowledge of the behaviour of extreme rainfall in West Africa by studying the sub-hourly, hourly and daily evolution of the most extreme rainfall events, a topic that is especially important to those interested in studying the links between heavy rainfall and flash flooding or inundation. This study analyses the classes of extreme rainfall events in two distinct climatic areas within West Africa using the meteorological scales relevant to rainfall processes. The study is based on two precipitation datasets recorded by dense networks of rain gauges set up within the meso-sites of Niamey (Niger, Sahelian area) and the Upper Ouémé Valley (Northern Benin, Soudanian zone) from 2000 to 2010 and 1998 to 2010, respectively. The Gumbel distribution was used to analyse the frequency of the maximum rainfall series for durations varying from 5 min to 24 h. The reliability of this model was examined, and the Intensity-Density-Frequency (IDF) curves derived from it were used to estimate the critical rainfall intensities at each site. The results returned exceeded frequencies that were useful for the isolation and classification of extreme rainfall cases using temporal characteristics. The climatological results confirm the existence of a latitudinal gradient in the mean annual rainfall and number of extreme events at the mesoscale. The classification methods illustrate clear distinctions between local, meso and synoptic scale events derived from convective systems over the Sahel. In contrast, Soudanian climate conditions lead to a nesting of the phenomena involved in the formation of cloud systems, making it difficult to classify rain events in that area. However, we were able to utilize the duration of rainfall events within this zone to discriminate between types of convective systems that cause extreme rainfall. For both areas, the proportion of precipitation in an extreme event compared to total yearly precipitation served as a suitable additional criterion used to objectively identify extreme precipitation event types.http://www.sciencedirect.com/science/article/pii/S2212094716300238Extreme rainfall eventsWest AfricaReturn periodIDF curvesDurationStorm classification |
| spellingShingle | Eric-Pascal Zahiri Ibrahim Bamba Adjoua Moise Famien Augustin Kadjo Koffi Abé Delfin Ochou Mesoscale extreme rainfall events in West Africa: The cases of Niamey (Niger) and the Upper Ouémé Valley (Benin) Weather and Climate Extremes Extreme rainfall events West Africa Return period IDF curves Duration Storm classification |
| title | Mesoscale extreme rainfall events in West Africa: The cases of Niamey (Niger) and the Upper Ouémé Valley (Benin) |
| title_full | Mesoscale extreme rainfall events in West Africa: The cases of Niamey (Niger) and the Upper Ouémé Valley (Benin) |
| title_fullStr | Mesoscale extreme rainfall events in West Africa: The cases of Niamey (Niger) and the Upper Ouémé Valley (Benin) |
| title_full_unstemmed | Mesoscale extreme rainfall events in West Africa: The cases of Niamey (Niger) and the Upper Ouémé Valley (Benin) |
| title_short | Mesoscale extreme rainfall events in West Africa: The cases of Niamey (Niger) and the Upper Ouémé Valley (Benin) |
| title_sort | mesoscale extreme rainfall events in west africa the cases of niamey niger and the upper oueme valley benin |
| topic | Extreme rainfall events West Africa Return period IDF curves Duration Storm classification |
| url | http://www.sciencedirect.com/science/article/pii/S2212094716300238 |
| work_keys_str_mv | AT ericpascalzahiri mesoscaleextremerainfalleventsinwestafricathecasesofniameynigerandtheupperouemevalleybenin AT ibrahimbamba mesoscaleextremerainfalleventsinwestafricathecasesofniameynigerandtheupperouemevalleybenin AT adjouamoisefamien mesoscaleextremerainfalleventsinwestafricathecasesofniameynigerandtheupperouemevalleybenin AT augustinkadjokoffi mesoscaleextremerainfalleventsinwestafricathecasesofniameynigerandtheupperouemevalleybenin AT abedelfinochou mesoscaleextremerainfalleventsinwestafricathecasesofniameynigerandtheupperouemevalleybenin |