Spatial Analysis of the Sea Surface Temperature in the Southwestern Atlantic

LAURA RUIZ ETCHEVERRY AND MARTÍN SARACENO

Foz do Iguassu

Encuentro; The Meeting of the Americas- AGU; 2010

With the purpose of explain the difference observed between temporal series of current data in the edge of the shelf and velocities derived from gridded data of satellite altimetry, in this present work we studying the spatial and temporal variability in Sea Surface Temperature (SST) images obtained by the radiometer AVHRR. In the initial stage, we use two years of 4 km resolution 5 days composite data. We characterize the spatial patterns based on the autocorrelation ellipses of each SST image, defined as a length scale of maximum correlation to the major axis of those ellipses. The spatial pattern of mean over two year of axis major data is consistent with the surface temperature distribution (Figure 1). The higher values of the amplitude of the mayor axis are located over Malvinas Current indicating that, for the two years mean analyzed, this is the domain region with minor variability. Also, in the recirculation region of Brazil Current the major axes have lower values and are less organized. The distribution of the standard deviation, on the right of the 300 meters isobath, is dominated by higher values that are associated with the temporal variability of the surface temperature structure. Instead, on the left of the 300 meters isobath, the values are lower, being more stable in time. The spatial analysis of the seasonal variation indicate that in summer and spring the mean mayor axis of the correlation ellipse values have a similar distribution to the mean of the period 1985 – 1986. Although during these season, there is a minor spatial variability eastward of the edge of the shelf. In autumn and winter the all region is dominated by higher values of standard deviation of major axis. We conclude that the presence of the edge of the shelf separates the region in two zones: 1) west side, where the length scale of major axis of the correlation ellipse is higher and the temporal variability is lower; 2) east side, where the spatial and temporal variability is higher. Figure 1: Mean values of SST in grades Celsius for the period January 1985 – December 1986. The mean major axis of the correlation ellipse values are superimposed on the temperature for the same period.