# Imprint of Mesoscale Eddies on Air-Sea Interaction in the Tropical Atlantic Ocean
## 2 Materials and Methods
### Sea Surface Temperature, Heat Fluxes and Precipitation Data  
In order to investigate mesoscale eddy signatures on SST, we used the v2.1 version of the optimum interpolated sea surface temperature (OISST) analysis [[https://www.ncei.noaa.gov/products/](https://www.ncei.noaa.gov/products/)]([https://www.ncei.noaa.gov/products/](https://www.ncei.noaa.gov/products/)) (accessed on 15 February 2023). The OISST product, formerly known as Reynolds SST, is a multi-platform product merging infrared satellite observations of the Advanced Very High-Resolution Radiometer and in situ measurements [37; 38]. This dataset provides daily SST data on a grid with a resolution of 0.25\({}^{\circ}\) longitude by 0.25\({}^{\circ}\) latitude, with a good accuracy (bias = 0.04 \({}^{\circ}\)C and root mean square difference = 0.24 \({}^{\circ}\)C, see Table 3 in [37]).  
To study the impact of mesoscale eddies on turbulent heat fluxes, we used the LHF and SHF products, version 4.1, provided by the Institut Francais de Recherche pour l'Exploitation de la Mer (IFREMER, [[https://www.ifremer.fr/oceanheatflux/](https://www.ifremer.fr/oceanheatflux/)]([https://www.ifremer.fr/oceanheatflux/](https://www.ifremer.fr/oceanheatflux/)), accessed on 15 February 2023). These products offer daily global heat fluxes at a spatial-resolution of 0.25\({}^{\circ}\)\(\times\) 0.25\({}^{\circ}\) in longitude and latitude. The computation of LHF and SHF is derived from atmospheric boundary layer parameters including wind-speed, air and SST and air specific humidity [39; 40; 41]. Ocean IRF is calculated based on the SST. The LHF, SHF and IRF are given by the following bulk formulae:  
\[LHF=\rho C_{E}L_{v}U(q_{s}-q_{a}) \tag{1}\]  
\[SHF=\rho C_{p}C_{h}U(\theta_{s}-\theta_{a}) \tag{2}\]  
\[IRF=\epsilon\sigma(SST)^{4} \tag{3}\]  
where \(\theta_{s}\) and \(\theta_{a}\) represent the sea surface and air (10 meters above sea level) temperature respectively, \(q_{s}\) and \(q_{a}\) denote the saturated and specific humidity in the air. The air density \(\rho\) and latent heat of vaporization (\(L_{v}\)) are also taken into account, as well as the specific heat capacity of air at constant pressure (\(C_{p}\)), turbulent exchange coefficients for latent heat (\(C_{E}\)) and sensible heat (\(C_{h}\)), wind-speed at 10 meters above the sea surface (U), sea surface emissivity (\(\epsilon\)), and the Boltzmann constant (\(\sigma\)). For IRF, SST represents the sea surface skin temperature in Kelvin degrees (\({}^{\circ}\)K).  
The analysis of PR over mesoscale eddies were performed using the 3B42 version of the Tropical Rainfall Measuring Mission Multi-satellite Precipitation Analysis (TMPA) distributed by the National Aeronautics and Space Administration (NASA, [[https://disc.gsfc.nasa.gov/](https://disc.gsfc.nasa.gov/)]([https://disc.gsfc.nasa.gov/](https://disc.gsfc.nasa.gov/)), accessed on 15 February 2023). This product is elaborated from a satellite constellation equipped with infrared and microwave sensors measuring PR between latitudes 50\({}^{\circ}\)N and 50\({}^{\circ}\)S [42; 43]. Daily PR data were obtained by accumulating the 3-hourly data over 24-h periods. The mean latitude and the northernmost and southernmost locations of the ITCZ were determined using the latitude of the maximum annual mean PR and the maximum latitude during the boreal summer (July to September) and winter (January to March).