SSS (SMAP)
How salty the surface is, measured once a day by SMAP, a NASA satellite that reads moisture and salt from orbit. Where it did not pass the map is blank, not guessed. Two to three days behind.
Updates daily
More detail
Lower numbers mean fresher water and higher numbers saltier water.
What to look for. Salinity marks the edge between bodies of water: river-influenced water against offshore blue water, or a current carrying water in from somewhere else.
The blanks move from day to day, so a spot that is blank today is often covered tomorrow.
Two limits. Satellite salinity is unreliable within about 50 nautical miles of land, so trust this layer offshore. And each measurement is about 16 nautical miles (30 km) across, so it shows a broad area of fresher water offshore but cannot draw the edge of a river plume. The layer covers the Gulf of America, the East Coast and Baja.
How it relates to the other salinity layers. SSS (Blended) blends satellite, float and ship measurements into a complete map with no gaps. It is older, and its filled spots are estimates. Use SSS (SMAP) for the fresher, measured picture offshore, and SSS (Blended) for a complete picture of the broad pattern. Sea Surface Salinity, from HYCOM (U.S. Navy model), is a forecast, not a measurement, and Salinity at Depth is the same forecast below the surface. The salinity layers share one color scale, 33 to 37.
The numbers
| How often it updates | Once a day, one frame per day |
| How fresh it usually is | About a day behind |
| How detailed it is | Each measurement is about 16 nautical miles (30 km) across |
| Where it covers | Gulf of America, East Coast and Baja. Unreliable within about 50 nautical miles of land |
| How far back you can look | 8 days back |
| Goes blank under cloud? | Blanks are where its track did not pass that day |
| Observed or modeled | Observed. Nothing is filled in |
| What you see on screen | PSU, the standard salinity unit. Surface only |
Source: a satellite picture from NASA's SMAP satellite.