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Interactions between convection and a moist vortex associated with an extreme rainfall event over southern West Africa

Maranan, Marlon; Fink, Andreas H.; Knippertz, Peter; Francis, Sabastine D.; Akpo, Aristide B.; Jegede, Gbenga; Yorke, Charles

Abstract:
An intense mesoscale convective system (MCS) in the Guinea Coast region caused one of the highest ever recorded daily rainfall amounts at the Nigerian station Abakaliki on 12 June 2016 (223.5 mm). This paper provides a detailed analysis of the meso- and synoptic-scale factors leading to this event, including some so far undocumented dynamical aspects for southern West Africa. The MCS formed over the Darfur Mountains due to diurnal heating, then moved southwestward along a mid- to lower-tropospheric trough, and developed into a classical West African squall line in a highly sheared environment with pronounced midlevel dryness. Strong moisture flux convergence over Nigeria prior to the MCS passage led to extreme values in precipitable water and was caused by the formation of a local, short-lived heat low. According to the pressure tendency equation, the latter resulted from tropospheric warming due to MCS-forced subsidence as well as surface insolation in the resulting almost cloud-free atmosphere. In this extremely moist environment, the MCS strongly intensified and initiated the formation of a lower-tropospheric vortex, which resulted in a deceleration of the MCS and high rainfall accumulation at Abakaliki. ... mehr



Originalveröffentlichung
DOI: 10.1175/MWR-D-18-0396.1
Zugehörige Institution(en) am KIT Institut für Meteorologie und Klimaforschung - Forschungsbereich Troposphäre (IMK-TRO)
Publikationstyp Zeitschriftenaufsatz
Jahr 2019
Sprache Englisch
Identifikator ISSN: 0027-0644, 1520-0493
KITopen-ID: 1000094124
HGF-Programm 12.01.02 (POF III, LK 01)
Erschienen in Monthly weather review
Band 147
Seiten 2309–2328
Vorab online veröffentlicht am 17.04.2019
Schlagworte Atmosphere; Africa; Convective storms/systems; Mesoscale processes; Rainfall
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