Salinity at Depth
HYCOM's forecast salinity at a depth you pick, surface down to 656 feet. Read it alongside temperature to see where different bodies of water meet.
Updates daily; forecast in 3-hour steps
More detail
Why salinity below the surface matters. A fresh cap sitting over salty water resists mixing, and salty water pushed onto the shelf means a different body of water has arrived.
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.
The forecast comes from HYCOM (U.S. Navy model), and RipIQ puts it on the map. It reaches from the surface to 656 feet (200 meters). Each value covers a square about 5 nautical miles across over three hours. Read it for the shape of the water, not for an exact value. The layer covers the Gulf of America, the East Coast and Baja.
A deep frame can look like one flat color: the default color range, 33 to 37, is a surface range. Narrow the range in Layer Settings to see structure. The crosshair readout gives the number whatever the color.
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. Sea Surface Salinity is the same forecast at the surface. SSS (SMAP) and SSS (Blended) are measurements, and both are surface only. Water Temperature at Depth is the same forecast for temperature and reaches deeper, to 1,312 feet. Switch between the two at one depth to see whether a temperature change and a salinity change sit in the same place.
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; from the surface to 656 feet (200 meters) |
| 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, at the depth you pick. The default color range is 33 to 37 |
Source: the HYCOM model.