Report on SEQUAL/FOCAL

Abstract

In Eos (April 6, 1982), United States plans for a program to study the dynamic response of the equatorial Atlantic to seasonally varying surface winds were described. Now, 6 years later, we report on progress toward our goal “to describe accurately, and to model correctly” the changes in the currents and density field of the upper equatorial Atlantic Ocean during a 2‐year period. A major effort toward this goal was the field phase of SEQUAL (Seasonal Response of the Equatorial Atlantic) and the closely coordinated French program FOCAL (Français Océan et Climat dans l'Atlantique Equatorial).Between February 1983 and September 1984 changes in the surface winds and in oceanic conditions in the equatorial Atlantic were monitored continuously with a variety of instruments. Figure 1 shows key deployments and sections. The resulting data include six current meter moorings, 15 inverted echo sounders and island tide gauges, 57 near‐surface drifters, and 18 French and five U.S. cruises that made 1200 hydrographic stations and 800 current profiles. All these data, as well as nearly 10,000 expendable bathythermographs (XBTs) (from the cruises, from air‐dropped expendable bathythermograph (AXBT) programs, and from repeated ship of opportunity lines run between 1980 and 1985) were combined and documented by George Heimerdinger, of the National Oceanographic Data Center, and are available from NODC on request.