SLA (DUACS)
How high or low the sea surface stands against its long-term average, measured by satellite — bulges are warm eddies, dips are cold. Each day is re-published over six days, so values can shift.
Updates daily
More detail
What you see. Red is high water, blue is low water and white is in between; you can change the colors in Layer Settings. The colors are centered on the day's average for the whole basin. On the website the crosshair readout gives the height in whole inches when your depth unit is feet, and in meters otherwise.
How to use it. Use it to find the eddies. The current is strongest where the height changes quickly, so look along the rim of a patch and not over its middle.
How it relates to the other sea level layers. SSH (DUACS) is the same measurement shown as the height itself. A permanent feature such as the Loop Current can read near zero here and still stand out plainly on SSH (DUACS). Use this layer to find what has changed and SSH (DUACS) to find where the current edge sits. Currents (DUACS) is the current speed worked out from the slope of this same surface. SSH - Altimetry, from HYCOM (U.S. Navy model), is a forecast of the sea surface height with the tide still in it, measured from a different zero, so it will not match this layer. With this layer up, the Altimetry button draws contour lines traced from it, labeled in centimeters or whole inches.
Who makes it. It is a measurement, made by radar from several satellites, every one that is flying. The Copernicus Marine Service, the European Union's ocean data service, makes the map with a system called DUACS.
Where it covers. The layer covers the Gulf of America, the East Coast and Baja.
Its limits. The newest picture is about a day old, and there is one picture a day. By the provider's own figure, the smallest real feature is about 95 nautical miles across: the Loop Current and the big eddies, not a small filament. The provider publishes each day's map again three and six days later.
When it looks blank or wrong. It has no cloud gaps, and a blank spot is land.
The numbers
| How often it updates | Once a day, one frame per day |
| How fresh it usually is | About 1 day; a value settles after about 6 days |
| How detailed it is | About 8 nautical miles per cell, but the smallest real feature is about 95 nautical miles across |
| Where it covers | Gulf of America, East Coast and Baja |
| How far back you can look | 8 days back |
| Goes blank under cloud? | No. Blank means land |
| Observed or modeled | Measured along satellite tracks by radar, then mapped in between. The tide is taken out |
| What you see on screen | Height above or below the day's basin average. The default color range is about 18 inches (0.45 meters) either side |
Source: a satellite picture from DUACS satellite altimetry (Copernicus).