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A Systematic Comparison of Tropical Waves over Northern Africa. Part II: Dynamics and Thermodynamics

Schlüter, Andreas; Fink, Andreas H.; Knippertz, Peter

Abstract:
This study presents the first systematic comparison of the dynamics and thermodynamics associated with all
major tropical wave types causing rainfall modulation over northern tropical Africa: the Madden–Julian
oscillation (MJO), equatorial Rossby waves (ERs), tropical disturbances (TDs, including African easterly
waves), Kelvin waves, mixed Rossby–gravity waves (MRGs), and eastward inertio-gravity waves (EIGs).
Reanalysis and radiosonde data were analyzed for the period 1981–2013 based on space–time filtering of
outgoing longwave radiation. The identified circulation patterns are largely consistent with theory. The slow
modes, MJO and ER, mainly impact precipitable water, whereas the faster TDs, Kelvin waves, and MRGs
primarily modulate moisture convergence. Monsoonal inflow intensifies during wet phases of the MJO, ERs,
and MRGs, associated with a northward shift of the intertropical discontinuity for MJO and ERs. This study
reveals that MRGs over Africa have a distinct dynamical structure that differs significantly from AEWs.
During passages of vertically tilted imbalanced wave modes, such as the MJO, TDs, Kelvin waves, ... mehr

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Originalveröffentlichung
DOI: 10.1175/JCLI-D-18-0651.1
Zugehörige Institution(en) am KIT Institut für Meteorologie und Klimaforschung - Forschungsbereich Troposphäre (IMK-TRO)
Publikationstyp Zeitschriftenaufsatz
Jahr 2019
Sprache Englisch
Identifikator ISSN: 0894-8755, 1520-0442
KITopen-ID: 1000094215
HGF-Programm 12.01.02 (POF III, LK 01)
Erschienen in Journal of climate
Band 32
Heft 9
Seiten 2605–2625
Nachgewiesen in Web of Science
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