Observing the tropical Atlantic Ocean in 1986–1987 from altimetry


  • Sabine Arnault,

  • Yves Menard,

  • Jacques Merle


Geosat altimeter data from November 1986 through November 1987 are analyzed over the tropical Atlantic Ocean, between 20°N to 20°S and 60°W to 20°E, using the colinear profile method. The altimetric sea level anomalies are consistent with the large-scale signal of the tropical Atlantic as observed by historical dynamic height. The agreement in the North Equatorial Countercurrent region (around 5°N) is particularly good. Comparison of altimetric anomalies with 1986–1987 in situ data points out the part of interannual events in the explanation of the differences encountered between altimetry and climatology. Altimetric data are also compared with the results of a simple model forced with monthly 1986–1987 wind stresses. This comparison confirms and emphasizes the hypothesis of a weak and early 1987 summer up welling in the Gulf of Guinea.