Numerical simulation of the seasonal and interannual variability of the tropical Atlantic Ocean circulation during the 1980s

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7297750

Huang, Bohua

A nine-year (1980-88) surface wind stress data set over the tropical Atlantic ocean is constructed based on the European Centre for Medium Range Weather Forecasts (ECMWF) twice-daily wind analysis. Its quality is checked against an independent data set by Servain et al. (1985) based on ship observations. A comprehensive analysis of these two data sets shows a strong seasonal cycle of the wind stress over the equatorial Atlantic ocean. Interannually, the stress field is dominated by a seesaw between the northeast and southeast trade winds, with anomalously strong (weak) southeast (northeast) trade winds during 1980-83 and a reversed pattern during 1984-88. Two nine-year simulations of the tropical Atlantic ocean circulation are performed with a general circulation model, one forced by the twice-daily, and the second by monthly averaged ECMWF surface wind stresses. Comparisons with available observations show that the seasonal ocean circulation and interannual signals of the sea surface temperature (SST), i.e., the dipole oscillation and abnormal warmings, are that the seasonal cycle of the subtropical and tropical Atlantic has an in-phase relationship with the seasonal change of the surface wind stress and the interannual SST dipole oscillation is generally in balance with the seesaw pattern of the trade wind systems although wave processes are important during the transition of phase. In 1984, the transition of the SST dipole from north-warm/south-cold to its opposite occurred during an equatorial warming event. This warming event was initiated by the relaxation of equatorial easterly wind, which stimulated heat transfer first eastward along the equator, then to the southern ocean and caused a deepening of the thermocline in the Gulf of Guinea and the southern ocean. Another warming event occurred in 1987-88, which restored the disappearing north cold/warm dipole.

• Research Organization: Maryland Univ., College Park, MD (United States)
• OSTI ID: 7297750
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540110*
ANNUAL VARIATIONS
ATLANTIC OCEAN
ATMOSPHERIC CIRCULATION
COMPUTERIZED SIMULATION
SEAS
SEASONAL VARIATIONS
SIMULATION
SURFACE WATERS
VARIATIONS