Four-hour SST is a 4-hour composite SST produced every 4 hours at 2km resolution, using all available satellite SST:
Method: Step 1: 4-hour composites of Him8 SST (with 2-4km resolution) are made, taking the median SST at every pixel. Step 2: the final composite is made using the Him8 composite and all other available AVHRR and VIIRS SST. The composite is made in two steps so that if the BoM Him8 SST is unavailable we can replace it with NOAA hourly Him8 composites. All SST is adjusted by the SSES bias before compositing and an offset of 0.17C is added to obtain the bulk SST.