Satellites & Bleaching

50-km SST Anomaly Product

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50-km SST Anomaly Product  |  What is an anomaly?
satellite sst

Shown here is an example 50-km Sea Surface Temperature (SST) Anomaly product map. Click the image for more information and a larger view of the latest near-real-time 50-km SST Anomaly data.

To calculate a sea surface temperature (SST) anomaly, we first needed to know the long-term mean SSTs globally. We took almost 10 years of NOAA polar-orbiting satellite SST measurements and calculated the mean SSTs in each month for every ocean pixel around the world. These monthly means are called the SST "climatology" and are available on our website. We use the SST climatology to calculate the twice-weekly 50-km SST Anomaly product, which identifies where the SST is different from the normal conditions for that day of the year. An example of our 50-km SST Anomaly product is shown at the top-right of this page.

Areas in purple to blue mean a negative anomaly; that is, the water temperature is cooler than the mean. Orange to red means a positive anomaly: the temperature is warmer than the mean. The values range from -5 to 5°C. Just like the 50-km SST product, this 50-km SST Anomaly has a half-degree spatial resolution (~50km) and is updated in near-real-time twice each week. We also produce animations of the 50-km SST Anomaly product for the past 2 to 6 months of data.

The time series graphs for our 50-km Virtual Stations also give an indication of whether the SST is above or below the mean, as you will see in this example from the Seychelles:

time series graph

Remembering that the current 50-km SST is shown as a dark blue solid line, you can see that each month's mean temperature for that location is also on the graph as light blue crosses. The months are shown along the bottom of the graph. At this reef location in the Seychelles, the mean 50-km SST observed by satellite is highest in April (about 29.5°C) and lowest in July (about 25°C). Between April and July 2006, you can see that the 50-km SSTs in the Seychelles were very close to the long-term monthly means.
satellite sst

Let's look at what happened in 2005 for that same coral reef location (graph on right). Look at the 50-km satellite SST in dark blue from mid-April until the end of July and compare to the long-term monthly means in light blue. You can see that the 50-km SSTs were consistently above the monthly mean temperatures (positive anomalies) for the entire period.

Try our hands-on 50-km SST Anomaly exercises to learn more about this product.

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