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Now I am working on a Tropical Cyclone project, and want to figure out the SST status when a TC passes by. I've been searching for SST products, yet there only show up to daily SST. My question is does there exist four-times daily SST, and if no, why is that?

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  • $\begingroup$ Does SST change that much during the course of a day? (Maybe that's better as a separate question) $\endgroup$ – JeopardyTempest Nov 24 '20 at 22:13
  • $\begingroup$ Which sst do you want? Skin sst or sst$_{skin}$, foundation sst or sst$_{found}$, interface sst or sst$_{int}$, or sst at depth. Most reanalysis models produce foundation sst, sst with no diurnal variation, the temperature at the first time of the day when the heat gain from the solar radiation absorption exceeds the heat loss at the sea surface. $\endgroup$ – Gemechu Fanta Garuma Nov 24 '20 at 23:55
  • $\begingroup$ @GemechuFantaGaruma Thanks you for such a thorough explanation, I think what I'm looking for is SKIN SST, while I'm also searching for the ocean heat content product, which better represents the thermodynamic conditions in-depth for a TC overpass. $\endgroup$ – D.Zhang Nov 25 '20 at 0:47
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    $\begingroup$ @JeopardyTempest Yeah, that could be a whole new question. According to Yoshimi Kawai & Akiyoshi Wada in their paper, they indicated that "...in an extreme case the diurnal amplitude of SST exceeds 5 K...temporal mean of the increase exceeds 10 Wm−2.". I guess the SST diurnal variations matter in finer NWP models. The initial thought for me is to better quantify the conditions at a certain time like in the hurricane forecast (I'm not a model user), now I guess the hurricane model would give SST condition when TC overpassed. I would revise my research thought. $\endgroup$ – D.Zhang Nov 25 '20 at 1:07
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The issue with satellite SST is that in most cases it is captured via infrared radiometers. Those sensors can't see through clouds. Daily products are used to try to remove the cloud effects. Alternatively, passive microwave radiation can be used (e.g., TMI, AMSR2, AMSR-E). It is not affected by cloud cover, but has lower horizontal resolution (~25km, vs 1-5km from IR). You can try to get the individual passes of each satellite and deal with gaps: For instance

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  • $\begingroup$ Thanks arkaia, for pointing this out. Now I know this inherent shortage for satellite retrieval of SST, another question is that why the numerical model (e.g. ECMWF, NCEP, ...) output don't involve four-times daily SST, while other factors, like relative humidity, they have hourly output. I searched for ERA-5 SST, which has same hourly data, but no diurnal variations. $\endgroup$ – D.Zhang Nov 24 '20 at 0:48

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