Evaluating MODIS sea surface temperature data and chlorophyll-a data from both MODIS and SeaWiFS in the Peruvian Coastal Upwelling System

Satellite products are widely used to understand and monitor the dynamics of the Peruvian coastal upwelling system (PCUS), one of the four major eastern boundary upwelling systems. They complement in situ observations obtained through surveys and oceanographic stations periodically operated by the Peruvian Marine Research Institute (IMARPE). Therefore, we mainly aim to assess the reliability of satellite products for sea surface temperature (SST) and surface chlorophyll-a (chl-a) using a unique in situ database from IMARPE. We evaluated SST data from MODIS (levels 2 and 3) and chl-a data from MODIS and SeaWiFS (both at level 3) due to their prior and continuous utilization. In the case of SST, our results demonstrated a strong correlation and good performance from MODIS compared with IMARPE data, although there is a tendency to slightly overestimate it, particularly during autumn. For surface chl-a, during their respective satellite periods, both sensors exhibited a favorable correlation and performance, with SeaWiFS outperforming MODIS. When analyzing matching points in terms of location and timing, both sensors tended to underestimate IMARPE data (autumn). Despite some differences between satellite and IMARPE data, the evaluated satellite products provide reliable information for understanding and monitoring the PCUS. However, for chl-a, it is important to consider the differences between sensors for retrospective studies.