CFM 2019

Structure and Dynamics of the Ras Al Hadd dipole in the Arabian Sea
Adam Ayouche * , Charly De Marez, Mathieu Morvan, Xavier Carton  1@  , Pierre L'hegaret, Alex Stegner  2@  , Briac Le-Vu  3@  
1 : Laboratoire dÓcéanographie Physique et Spatiale  (LOPS)  -  Site web
Université de Brest
Rue Dumont DÚrville, 29280 Plouzané -  France
2 : Laboratoire de Météorologie Dynamique  (LMD)  -  Site web
CNRS
Ecole Polytechnique, Route de Saclay Palaiseau -  France
3 : Laboratoire de Météorologie Dynamique  (LMD)  -  Site web
Centre National de la Recherche Scientifique : UMR8539, Polytechnique - X, Institut national des sciences de l\'Univers, Université Pierre et Marie Curie - Paris 6, École normale supérieure - Paris, Ecole des Ponts ParisTech, Institut national des sciences de l\'Univers, Institut national des sciences de l\'Univers, Institut national des sciences de l\'Univers, Institut national des sciences de l\'Univers, Institut national des sciences de l\'Univers, Institut national des sciences de l\'Univers, Institut national des sciences de l\'Univers
Palaiseau -  France
* : Auteur correspondant

The Arabian Sea and Marginal Seas (AMS), the northern part of the Indian Ocean, show a strong eddy activity as revealed by satellite observations and by high resolution HYCOM (primitive equation) model simulations. The East Arabian Current (EAC) propagating to the north along the Omanian coast during the Summer Monsoon season (from May to September) has a prominent feature, the Ras Al Hadd (RAH) jet a large meander that demarcates an eddy dipole (RAH dipole) with a cyclone to the north and anticyclone to the south. Using a vortex identification and tracking algorithm, AMEDA, based on angular momentum and using also Okubo Weiss calculations, applied to 15 years (from 2000 to 2015) high resolution altimetric data (1/8th degree resolution), we identify the RAH dipole, a cyclone and an anticyclone, in the vicinity of the Gulf of Oman near Ras Al Hadd Coast, which lives longer than a month. We compute its characteristics (amplitude, radius) and compare them with historical data. Moreover, we identify its formation region and propose a mechanism for this formation. Then, we analyze its evolution, strengthening or dissipation by (i) its interaction with the wind curl or (ii) the vortex-vortex interactions. Finally, we study the vertical structure of the Ras Al Hadd dipole using Argo profiles.


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