## 4 Results
### Examples of Filtering Data of Individual Buoys  
We reprocessed \(i\)Quam data from DTM buoys for 1981-2021 with the experimental set of QC checks (EXP QC). In addition to the DRC, the EXP QC retained the five current binary \(i\)Quam checks (DR, GC, TC, SC, and IC). The Buddy Check was not included in the EXP QC because its effect was found to be insignificant. The highest QL = 5 was assigned in EXP QC to \(T_{IS}\)'s that pass all six checks. Figures 9-12 compare the results of processing selected drifters' records with the current \(i\)Quam v2.10 QC and the EXP QC. The matching \(T_{SAT}\) were selected from the MDS listed in Table 2. If matchups for the specific \(T_{IS}\) are found in more than one MDS, then the median of all matching \(T_{SAT}\) is taken as a single matchup. Figure 8: (**a**) Medians and (**b**) RSDs of \(T_{SAT}-T_{IS}\) and (**c**) fractions of \(T_{IS}\)’s, as a function of \(\gamma\) for satellites listed in Table 2.  
Figure 9 shows the results of QC'ed \(T_{IS}\) for the drifter 4201591 in the Gulf of Mexico in July 2018. Significant ADSs up to 5 K were observed over 19 days, and consistent diurnal variations are seen in \(T_{SAT}\). The current QC cuts off the peak values of daytime \(T_{IS}\)'s (cf. Figure 9b), whereas the EXP QC preserves the full DS (Figure 9c). Figure 10 shows the SST record for the drifter 1500607 in the Atlantic Ocean near Brazil in December 2018. During the second decade of the month, the \(T_{IS}\) showed ADSs from 1-5 K and consistent diurnal variations in \(T_{SAT}\). In the third decade, the ADSs increased to \(\sim\)10 K, but the \(T_{SAT}\) did not show such diurnal variations. This suggests that these large ADSs in \(T_{IS}\) were caused by extraneous factors rather than variations in the water temperature. In Figure 10b, the current iQuam RC rejects all significant deviations from \(T_{LA}\) after December 10. In Figure 10c, the EXP QC preserves the diurnal \(T_{IS}\) variations from 10-20 December, consistent with \(T_{SAT}\), but rejects the daily segments with unrealistic ADSs from 20-30 December. Note, however, that the EXP QC also preserves the DS on 29 December, when its amplitude is less than 5 K, despite its inconsistency with \(T_{SAT}\). This  
Figure 10: Same as in Figure 9 but for buoy 1500607 drifting to the Brazilian coast in December 2018. Figure 9: Filtering the \(T_{IS}\) record for the drifter 4201591 in July 2018. **(a)** Drifter’s track in the Gulf of Mexico; Results of processing with **(b)** current iQuam v2.10 QC and **(c)** EXP QC. The points show (black) \(T_{IS}\) with QL \(<\) 5, (green) \(T_{IS}\) with QL \(=\) 5, and (red) matched \(T_{SAT}\). \(T_{LA}\) is shown with a black dashed line. may suggest the need for a more conservative threshold for the ADS in the coastal zones. Such refinements will be explored in the future. Figure 11 shows \(T_{IS}\) from buoy 3300688 in the Agulhas current in February 2017. The current QC rejects a significant number of \(T_{IS}\)'s (which note are reasonably consistent with \(T_{SAT}\); Figure 11b). Significant deviations of \(T_{IS}\) from \(T_{L4}\) are due to the diurnal warming (on days 2, 3, 6, 14, 20, and 24) and inaccurate \(T_{L4}\) (typical for a dynamic zone). In contrast, the EXP QC preserves the whole record (cf. Figure 11c), thanks to the ADS-dependent thresholds for \(T_{IS}-T_{NIGHT}\) and adequately liberal thresholds for \(T_{NIGHT}-T_{L4}\). Lastly, Figure 12 shows the \(T_{IS}\) for buoy 6500599 near the Norwegian coast in June 2017. Significant diurnal variations in \(T_{IS}\), consistent with \(T_{SAT}\), occurred on 8-9 June. The possibility of large diurnal SST variations in the high latitudes was discussed in [14,15]. The current RC rejects daytime \(T_{IS}\) due to significant deviations from \(T_{L4}\) (Figure 12b), whereas the EXP QC fully preserves the DS in \(T_{IS}\) (Figure 12c). 2018 without preliminary QC. Figure 13c_d show the same statistics produced from \(T_{IS}\) of QL = 5 by the _i_Quam QC.