LIDAR observations of lower stratospheric aerosols over South Africa linked to large scale transport across the southern subtropical barrier

Abstract : The study of the variability of stratospheric aerosols and the transfer between the diierent atmospheric regions improves our understanding of dynamical processes involved in isentropic exchanges that take place episodically in the lower stratosphere through the subtropical barrier. One useful approach consists in combining in situ ground-based and global measurements with numerical analyses. The present paper reports on a case study of a horizontal transfer evidenced ÿrst by Rayleigh–Mie LIDAR observations over Durban (29:9 • S, 31:0 • E, South Africa). Additional data from MeteoSat and SAGE-2 experiments, and from ECMWF meteorological analysis have been used in this study. Contour advection maps of potential vorticity from the MIMOSA model derived from ECMWF ÿelds, were also used. By the end of April, 1999, LIDAR observations showed that aerosol extinction, in the lower stratosphere, has increased signiÿcantly and abnormally in comparison with other LIDAR and SAGE-2 observations recorded for the period from April 20 to June 14, 1999. The dynamical context of this case study seems to exclude the possibility of a local innuence of the subtropical jet stream or tropical convection, which could inject air masses enriched with tropospheric aerosols into the stratosphere. On the contrary, a high-resolution model based on PV advection calculations and ECMWF meteorological analyses shows that air masses are isentropically advected from the equatorial zone close to Brazil. They cross the southern barrier of the tropical reservoir due to laminae stretching and reach the southern subcontinent of Africa 5–6 days later.
Type de document :
Article dans une revue
Journal of Atmospheric and Solar-Terrestrial Physics, Elsevier, 2003, 65 (6), pp.707 - 715. 〈10.1016/S1364-6826(03)00006-3〉
Liste complète des métadonnées

Littérature citée [36 références]  Voir  Masquer  Télécharger

http://hal.univ-reunion.fr/hal-01387242
Contributeur : Réunion Univ <>
Soumis le : mardi 25 octobre 2016 - 12:35:04
Dernière modification le : jeudi 11 janvier 2018 - 06:26:31

Fichier

Bencherif et al, JASTP 2003_ha...
Fichiers produits par l'(les) auteur(s)

Identifiants

Collections

Citation

Hassan Bencherif, Thierry Portafaix, Jean-Luc Baray, Béatrice Morel, Serge Baldy, et al.. LIDAR observations of lower stratospheric aerosols over South Africa linked to large scale transport across the southern subtropical barrier. Journal of Atmospheric and Solar-Terrestrial Physics, Elsevier, 2003, 65 (6), pp.707 - 715. 〈10.1016/S1364-6826(03)00006-3〉. 〈hal-01387242〉

Partager

Métriques

Consultations de la notice

88

Téléchargements de fichiers

24