Characterization of observed sea surface temperature in the tropical atlantic: impact of spatial resolution

Sea surface temperature (SST) is a key oceanic variable controlling energy fluxes, as well as several atmospheric parameters such as wind speed, air temperature, humidity and cloudiness. During the last decades, mesoscale has received much attention and the new frontier for the coming years is the understanding of sub-mesoscale dynamics and its impact on climate. In order to address this challenge, there is a need of developing high-resolution observing systems, remote sensing sensors in conjunction with in-situ observations. Some traditional climate-oriented SST observational datasets generally do not include satellite observations and are typically based on in-situ observations, prominent examples being NOAA Extended Reconstructed SST (ERSST) and Hadley Centre SST version 3 (HadSST3). Other datasets combine both, in-situ and satellites observations, like the Hadley Centre Sea Ice and Sea Surface Temperature dataset (HadISST). The main objective of this work is to characterize sea surface temperature (SST) climatology and variability in the tropical Atlantic region. For that purpose, we thoroughly compare two standard, climate-oriented datasets, HadISST (1 degrees resolution) and ERSSTv5 (2 degrees resolution), with the GHRSST product developed by the European Space Agency (ESA) Climate Change Initiative (CCI) (0.05 degrees resolution). Our results show that, at grid-point level, the three datasets behave similarly on a large scale, but they show consistent differences in all seasons, with CCI distinctly displaying more expansive and larger variability in the equatorial Atlantic and also in the subtropical North Atlantic. The differences in climatology are less apparent. In particular, over the ATL3 region, CCI is systematically colder than ERSST and HadISST, and displays higher variability.