The Nocturnal Low-Level Jet in Tropical West Africa: Generation and Representation in Various Data Archives

Like many regions, tropical West Africa often experiences a low-level jet stream after sunset. In general, such jets are believed to be produced as a response to the sudden decrease in turbulence in the boundary layer when daytime heating ceases. However, the nocturnal low-level jet (NLLJ) in West Africa exists in a complex environment in which (a) the boundary layer rarely gets especially stable at night, (b) the Coriolis force is extremely weak, and (c) the pressure gradient force has a particularly large diurnal cycle (due to the formation of a heat low to the north of the region). In this study, the nocturnal low-level jet is examined using radiosonde and ultra high frequency (UHF) wind profile data gathered during the African Monsoon Multidisciplinary Analysis (AMMA) field campaign in 2006. These data, as well as output from a Weather Research and Forecasting (WRF) simulation of the region, are used to quantify the forces at work at different levels of the atmosphere to explain the formation, maintenance, and dissipation of this feature of the monsoon circulation. It is shown that the NLLJ is formed due to a combination of a release of friction after sunset and advection of momentum.

Grantor dc:publisher

Creighton University

Year dc:date.issued

2012

Author dc:creator

• Rife, Adam

Advisor dc:contributor.advisor

• Schrage, Jon M.

Statement dc:rights

• Copyright is retained by the Author. A non-exclusive distribution right is granted to Creighton University and to ProQuest following the publishing model selected above.

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10504/35546

OAI identifier oai:identifier

oai:cdr.creighton.edu:10504/35546