Variabilidade espaço-temporal da concentração de clorofila-a no Oceano Atlântico Equatorial baseados nos dados do sensor MODIS-AQUA

Abstract

This study aims to describe the spatial and temporal variability of chlorophyll of Western Equatorial Atlantic Ocean (WEA) based on the analysis of 11 years (2002-2012) of sea surface color (SSC) data collected by the sensor Moderate Resolution Imaging Spectroradiometer (MODIS). The annual and semi-annual variability of the SSC were estimated based on a harmonic analysis using least squares fit. A low pass filter with 365 days was used to quantify the inter-annual variability of the data. Finally, the annual, semi-annual and interannual signals were removed from the data, and the standard deviation of this residue was used to estimate the intra-annual variability. The annual cycle explained most of the variability of chlorophyll-a on the North Brazil Current (R²> 60%) and the South Equatorial Current (SEC). The amplitudes of the annual cycle in this region varied from 0.02 to 0.05 mg/m3 . The annual phase of maximum values occurred earlier on the oceanic region and later on the region under influence of the South Equatorial Current (SEC). The semi-annual cycle do not significantly explain the temporal variability of the SSC in the WEA region. The amplitude of the intra-annual was greater than the inter-annual variability, but its influence was smaller than the annual cycle.