The Vasco-Cirene program explores how strong air-sea interactions promoted by the shallow thermocline and high sea surface temperature in the Seychelles-Chagos thermocline ridge results in marked variability at synoptic, intraseasonal, and interannual time scales. The Cirene oceanographic cruise collected oceanic, atmospheric, and air-sea flux observations in this region in January–February 2007. The contemporaneous Vasco field experiment complemented these measurements with balloon deployments from the Seychelles. Cirene also contributed to the development of the Indian Ocean observing system via deployment of a mooring and 12 Argo profilers.

Unusual conditions prevailed in the Indian Ocean during January and February 2007, following the Indian Ocean dipole climate anomaly of late 2006. Cirene measurements show that the Seychelles-Chagos thermocline ridge had higher-than-usual heat content with subsurface anomalies up to 7°C. The ocean surface was warmer and fresher than average, and unusual eastward currents prevailed down to 800 m. These anomalous conditions had a major impact on tuna fishing in early 2007. Our dataset also sampled the genesis and maturation of Tropical Cyclone Dora, including high surface temperatures and a strong diurnal cycle before the cyclone, followed by a 1.5°C cooling over 10 days. Balloonborne instruments sampled the surface and boundary layer dynamics of Dora. We observed small-scale structures like dry-air layers in the atmosphere and diurnal warm layers in the near-surface ocean. The Cirene data will quantify the impact of these finescale features on the upper-ocean heat budget and atmospheric deep convection.

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Laboratoire d'Océanographie Expérimentation et Approches Numériques, CNRS, UPMC, IRD, Paris, France

Laboratoire de Météorologie Dynamique, CNRS, UPMC, ENS, Ecole Polytechnique, Paris, France

NOAA/Pacific Marine Environmental Laboratory, Seattle, Washington

Old Dominion University, Norfolk, Virginia

Centre d'Etudes des Environnements Terrestres et Planétaires, Vélizy, France

Woods Hole Oceanographic Institution, Woods Hole, Massachusetts

University of Miami, Miami, Florida

Centre Européen de Formation Avancée en Calcul Scientifique, Toulouse, France

Swedish Defence Research Agency, Stockholm, Sweden

Frontier Research Center for Global Change, Yokohama, Japan

IRD, Centre de Recherche Halieutique, Séte, France

NIWA, Wellington, New Zealand

A supplement to this article is available online (DOI: 10.1175/2008BAMS2499.2)

*CURRENT AFFILIATIONS: VIALARD— National Institute of Oceanography, Goa, India

+CURRENT AFFILIATIONS: WARD— National University of Ireland, Galway, Ireland

*Pacific Marine Environment Laboratory Publication Number 3179