*4.2. South Madagascar*

Based again on clear sky maps and tidal currents maps, we selected a second region South of Madagascar (latitude between 30◦S and 24◦S , longitude between 42◦E and 48◦E). The number of L2 granules available between 1 January 2014 and 31 December 2016 are summarized in Table 2. For this region, the number of days with more than one granule is 267 (24 % of the period considered). As shown by the METOP SST observation of 5 June 2014 (Figure 4), this region is characterized by strong SST gradients (0.3-0.4 ◦C km<sup>−</sup>1) see Figure 4b).

Both baroclinic and barotropic tidal currents are weaker in this area with values of the order of 0.07 m s−<sup>1</sup> and 0.3 m s−1, respectively. Barotropic currents extend to deep areas, which is different than the Northwest Australia case, shown in Figure 3c.

Figure 4 illustrates the procedure to quantify the signature of the semidiurnal M2 baroclinic motion on SST for the South of Madagascar case study region from a SST image captured by METOP on the 5 June 2014. M2 barotropic currents (see Figure 4c) induce SST fluctuations that are up to 0.2 ◦C which is less than for the Northwest Australia case. The maximum amplitude of M2 baroclinic tidal SST fluctuations reaches 0.08 ◦C for this particular case (Figure 4e), i.e., about twice than for the Northwest Australia region. These two opposite trends emphasizes that SST tidal fluctuations result from the product between SST gradients and tidal currents.

**Table 2.** Number of L2 granules available from 1 January 2014 to 31 December 2016 in the Madagascar case study region.

