P. Poli et al.: SVP-BRST: genesis, design, and initial results 
211 
www.ocean-sci.net/15/199/2019/ 
Ocean Sci., 15,199-214, 2019 
Sea level anomaly data 2018-05-29 to 2018-06-13 
0.215 
0.180 
0.145 
0.110 
0.075 
0.040 
0.005 
-0.030 
-0.065 
-0.100 
E 
Figure 10. Mean sea level anomaly map with the two SVP-BRST 
prototypes’ tracks overlaid (prototype no. 1 in red, prototype no. 2 
in blue) for the time period 29 April to 6 May 2018. 
Figure 12. Mean sea level anomaly map with the two SVP-BRST 
prototypes’ tracks overlaid (prototype no. 1 in red; prototype no. 2 
in blue) for the time period 29 May to 13 June 2018. 
Mean solar local time (MSLT) 
[K] 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 
0 6 j (a) Prototype no. 1, 
o4 29 April-5 May 
0.2 - 
0.0- 
0.6 4 (b) Prototype no. 2, 
04 29 April-5 May 
0.2 - 
o.o- 
0.6 4 (c) Prototype no. 1, 
04 29 May-11 June 
0.2 - 
o.o- 
0.6 -j (d) Prototype no. 2, 
04 _ 29 May-11 June 
0.2 - 
o.o- 
00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 
Mean solar local time (MSLT) 
Mean solar local time (MSLT) 
[K] 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 
Mean solar local time (MSLT) 
Figure 11. Average SST diurnal cycle observed by the two SVP- 
BRST prototypes’ HRSST sensors, during time periods A and B 
defined in Fig. 9. For each panel, the reference is the mean SST at 
00:00UTC. Horizontal thin dotted lines indicate zero. 
Figure 13. Diurnal cycle of differences between each 5 min per 
centile (five percentiles are reported by the SVP-BRST prototypes: 
10 %, 30 %, 50 % or median, 70 %, and 90 %), and the 5 min mean. 
Horizontal thin dotted lines indicate zero and ±0.01 K. 
surface. Figure 13 shows that the two buoys during time pe 
riod A, as well as the first buoy during time period B, present 
smaller departures from the mean throughout the day than 
the second buoy during time period B. The maps in Figs. 10 
and 12 may hold the clue to explaining this: in the first three 
cases, the buoys are the closest to eddies, while the fourth 
situation is when the buoy is traveling furthest from an eddy 
core. Overall, these remarks suggest that the ocean surface 
circulation may be of importance too, in addition to sea state, 
to properly exploit the in situ SST data for satellite cal/val, as 
this may affect the representativeness of the SST observed in 
situ. 
5 Conclusions 
Revisiting the previous HRSST drifter initiatives, it was 
found that higher-quality SST was likely to be collected by 
such drifting buoys, as compared to general drifters. The fol 
lowing points were also identified to require further consider 
ation, to improve upon HRSST-2 drifters. First, the sea-state 
dynamics, affected by the wind and wave activity, has in 
fluence on the vertical stratification, consistent with earlier 
findings (e.g., Dong et ah, 2017), so the depth of the sensors 
is an important parameter to monitor. Second, the housing of 
the HRSST sensors needs to be insulated from external influ 
ences other than exchanges of heat with the seawater, in order