Potential Vorticity Generation by West African Squall Lines release_mgg4rjimrjhwjcm3uydvwtgdsy

by Richard H. Johnson, Paul E. Ciesielski

Published in Monthly Weather Review by American Meteorological Society.

2020  

Abstract

TheWest African summer monsoon features multiple, complex interactions between African Easterly Waves (AEWs), moist convection, variable land surface properties, dust aerosols, and the diurnal cycle. One aspect of these interactions, the coupling between convection and AEWs, is explored using observations obtained during the 2006 African Monsoon Multidisciplinary Analyses (AMMA) field campaign. During AMMA, research weather radar operated at Niamey, Niger, where it surveilled 28 squall line systems characterized by leading convective lines and trailing stratiform regions. Nieto Ferreira et al. found that the squall lines were linked with the passage of AEWs and classified them into two tracks, northerly and southerly, based on the position of the African Easterly Jet (AEJ). Using AMMA sounding data, we create a composite of northerly squall lines that tracked on the cyclonic shear side of the African Easterly Jet (AEJ). Latent heating within the trailing stratiform regions produced a mid-tropospheric positive potential vorticity (PV) anomaly centered at the melting level, as commonly observed in such systems. However, a unique aspect of these PV anomalies is that they combined with a 400-500 hPa positive PV anomaly extending southward from the Sahara. The latter feature is a consequence of the deep convective boundary layer over the hot Saharan desert. Results provide evidence of a coupling and merging of two PV sources – one associated with the Saharan heat low and another with latent heating – that ends up creating a prominent mid-tropospheric positive PV maximum to the rear of West African squall lines.
In application/xml+jats format

Archived Files and Locations

application/pdf  6.0 MB
file_ttnn74rh7nbilefede7qj2ekeu
journals.ametsoc.org (web)
web.archive.org (webarchive)
Read Archived PDF
Preserved and Accessible
Type  article-journal
Stage   published
Date   2020-02-13
Language   en ?
Container Metadata
Open Access Publication
Not in DOAJ
In Keepers Registry
ISSN-L:  0027-0644
Work Entity
access all versions, variants, and formats of this works (eg, pre-prints)
Catalog Record
Revision: 2705dcec-47d4-416c-aa37-e7d45dcd232b
API URL: JSON