Sea Surface Salinity
HYCOM's forecast of how salty the surface water is. Use it to find the edge where fresh river water meets blue — it is a simulation, not a measurement.
Updates daily; forecast in 3-hour steps
More detail
Salinity is shown in psu, the standard salinity unit, close to grams of salt in a kilogram of seawater. Open Gulf blue water sits near 36, and a strong river plume can drop below 30.
What to look for. The plume edge is where the color changes fast, and it often holds weed and bait that a temperature layer will not show, especially off the Mississippi and Atchafalaya in summer.
The forecast comes from HYCOM (U.S. Navy model), and RipIQ puts it on the map, with no gaps. Plume placement is the model's weak spot: trust that the plume is there, but not exactly where its edge falls. Each value covers a square about 5 nautical miles across over three hours. The layer covers the Gulf of America, the East Coast and Baja.
How fresh it is. The model starts one new run a day, and the newest run normally started between one and four days ago. There are eight frames a day, three hours apart, and the days after the run date are forecast, up to 7 days ahead.
How it relates to the other salinity layers. SSS (SMAP) and SSS (Blended) are the measured ones. SSS (SMAP) is about a day behind and has gaps where the satellite did not pass. SSS (Blended) is complete and six to seven days behind. This is the only salinity layer with enough detail to place a plume edge, and the only one that reaches ahead. Use this layer for the shape of the edge, and the measured layers for the value offshore. The salinity layers share one color scale, 33 to 37. Salinity at Depth is the same forecast below the surface. Salinity Front Intensity and Salinity Front Edges are worked out from this layer and show only its edges.
The numbers
| How often it updates | Once a day, as 8 frames, three hours apart |
| How fresh it usually is | The newest frame is from a run started between one and four days ago |
| How detailed it is | About 5 nautical miles per grid cell. Surface only |
| Where it covers | Gulf of America, East Coast and Baja. Outside the regions the map shows the chart alone; the layers stop at the region's edge. |
| How far back you can look | 8 days back |
| How far forward you can look | Up to 7 days ahead, as a forecast |
| Observed or modeled | Modeled. It never goes blank for cloud |
| What you see on screen | PSU, the standard salinity unit. Surface only |
Source: the HYCOM model.