Empirical orthogonal function analyses of tropical Atlantic sea surface temperature and wind stress: 1964–1979

Scalar and vector empirical orthogonal function (EOF) analyses have been performed on monthly sea surface temperature (SST) and wind stress within the tropical Atlantic region for the years 1964-1979. The long-term average was subtracted from the 16-year SST and wind stress monthly fields to focus on the seasonal variability and its interannual modulations. A smaller cumulative percent of variance accounted for by the first eigenvectors of wind stress reflects the greater variability of the wind than that of SST. Analysis of regional seasonal SST events requires a combination of the first three EOFs, whereas the dominant events of the seasonal cycle of the wind stress are adequately represented by EI and E2. As in the Pacific, an increase of the trade wind system is observed between the 1960s and the 1970s. Our analyses provide diagnostic insight into two types of large spacetime scale episodes. The first type is exemplified by the following sets of observations: during the spring of 1968 (spring 1976), an abnormal relaxation (intensification) of the wind stress occurred in both the northeasterlies and the southeasterlies. Subsequently, equatonally trapped anomalous warming (cooling) occurred inside the Gulf of Guinea. The second type is exemplified by the following: during 1972 to 1975, the northeasterlies (stronger) and the southeasterlies (weaker) acted out of phase, leading to a more global response of the ocean. The oceanic response was different in the northern (colder) and southern (warmer) basins.

[1]  S. Hastenrath,et al.  Dynamics of climatic hazards in northeast Brazil , 1977 .

[2]  G. Meehl,et al.  The seesaw in winter temperatures between Greenland and Northern Europe. Part III: Teleconnections with lower Latitudes , 1979 .

[3]  J. O'Brien,et al.  The Seasonal Upwelling in the Gulf of Guinea Due to Remote Forcing , 1978 .

[4]  K. Wyrtki,et al.  El Niño—The Dynamic Response of the Equatorial Pacific Oceanto Atmospheric Forcing , 1975 .

[5]  Interannual variability versus seasonal variability in the Tropical Atlantic , 1984 .

[6]  J. O'Brien,et al.  Equatorial adjustment in the eastern Atlantic , 1978 .

[7]  J. Picaut,et al.  Seasonal Variability from a Model of the Tropical Atlantic Ocean , 1983 .

[8]  J. Merle.  Seasonal Heat Budget in the Equatorial Atlantic Ocean , 1980 .

[9]  S. Hellerman.  CHARTS OF THE VARIABILITY OF THE WIND STRESS OVER THE TROPICAL ATLANTIC , 1980 .

[10]  P. Lamb,et al.  Climatic Atlas of the Tropical Atlantic and Eastern Pacific Oceans , 1977 .

[11]  J. Servain,et al.  Evidence of Remote Forcing in the Equatorial Atlantic Ocean , 1982 .

[12]  T. Tang,et al.  Equatorial Ocean Response to Growing and Moving Wind Systems with Application to the Atlantic , 1983 .

[13]  S. Hastenrath.  On Modes of Tropical Circulation and Climate Anomalies , 1978 .

[14]  David M. Legler,et al.  Empirical Orthogonal Function Analysis of Wind Vectors over the Tropical Pacific Region , 1983 .

[15]  J. Willebrand.  Temporal and Spatial Scales of the Wind Field over the North Pacific and North Atlantic , 1978 .

[16]  J. Servain,et al.  Chapter 16 Interannual and Seasonal Variability of the Tropical Atlantic ocean depicted by Sixteen years of Sea-Surface Temperature and wind stress , 1985 .

[17]  J. Shukla,et al.  On the Dynamics of Droughts in Northeast Brazil: Observations, Theory and Numerical Experiments with a General Circulation Model , 1981 .

[18]  P. Rowntree.  Response of the atmosphere to a tropical Atlantic ocean temperature anomaly , 1976 .

[19]  M. Fieux,et al.  ANNUAL SIGNAL AND INTERANNUAL ANOMALIES OF SEA SURFACE TEMPERATURE IN THE EASTERN EQUATORIAL ATLANTIC OCEAN , 1979 .

[20]  J. Servain,et al.  Climatic atlas of the tropical Atlantic wind stress and sea surface temperature: 1980-1984 , 1987 .

[21]  P. Lamb.  Case Studies of Tropical Atlantic Surface Circulation Patterns During Recent Sub-Saharan Weather Anomalies: 1967 and 1968 , 1978 .

[22]  S. Philander.  Variability of the tropical oceans , 1979 .

[23]  R. Preisendorfer,et al.  A Significance Test for Principal Components Applied to a Cyclone Climatology , 1982 .

[24]  Charles G. Markham,et al.  Sea surface temperature related to rain in Ceará, north-eastern Brazil , 1977, Nature.

[25]  P. Hisard.  Observation de réponses de types El Niño dans l'Atlantique tropical oriental Golfe de Guinée , 1980 .

[26]  J. Merle.  Variabilité thermique annuelle et interannuelle de l'océan Atlantique équatorial Est. L'hypothèse d'un El Niño atlantique , 1980 .

[27]  J. O'Brien,et al.  Interannual variability of the equatorial Pacific in the 1960's , 1981 .

[28]  Robert F. Cahalan,et al.  Sampling Errors in the Estimation of Empirical Orthogonal Functions , 1982 .

[29]  P. K. Kundu,et al.  Some Three-Dimensional Characteristics of Low-Frequency Current Fluctuations near the Oregon Coast , 1976 .

[30]  B. Weare,et al.  Empirical orthogonal analysis of atlantic ocean surface temperatures , 1977 .