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November 1, 2001 — The satellite image shown here represents recent global sea surface temperature anomalies. The data used to construct this image were obtained with an AVHRR sensor (Advanced Very High Resolution Radiometer) carried on a NOAA satellite operated by National Environmental Satellite, Data, and Information Service. This sensor measures the amount of thermal infrared radiation given off by the surface of the ocean. SSTs are measured globally by NOAA satellites twice-daily and usually range between -1 and 32 degrees Celsius.

The key to getting the most out of SST observations is realizing that the raw water temperatures are less important than relative offset in water temperature above or below what is "normal." Thus, the values you see represented in the image above are not "actual" temperatures, but are instead current deviations from what are considered to be normal ocean surface temperatures (for that location at that time).

The wide range of colors in the color bar (shown below the image) is used to emphasize these subtle, but often important, temperature variations. For example, purple and blue indicate areas where the water is colder than normal, while yellow, orange and red areas signify where the water temperature is higher than normal. Lightest yellow and lightest blue areas have a temperature that is nearly the same as in past years. This and other NOAA/NASA Pathfinder AVHRR SST images are available in a variety of spatial and temporal resolutions, map projections, and formats, even animations, to accommodate both the public and researchers with varying processing capabilities and scientific interests. The basic product consists of a "daily," global SST fields at a mapped spatial resolution of 50-km, representing only descending (nighttime) orbits (found to be slightly more accurate for assessing bulk water temperatures).

Daily SSTs, and their anomalies, are useful for a large range of users of the marine community, including fishermen, beach-goers and environment specialists. These data are most popular with oceanographers, however, because SSTs serve as important environmental indicators—providing information about ocean current flow, probable distribution of sea life, global energy budget, and weather and climatological trends. For example, obvious indications of an El Niño—an abnormal warming of the ocean temperatures across the eastern tropical Pacific that affects weather around the globe—are changes in sea surface temperature associated with the eastward displacement of the Pacific warm pool and the disappearance of the equatorial and coastal upwellings of cold, nutrient rich waters. Thus, analyzing the large-scale changes in sea surface temperature patterns provided by satellites allows scientists to study the onset, intensity, and duration of specific El Niño events. In fact, NOAA researchers and scientists are now using this SST Anomaly image (above) to catch the first glimpse of the formation of a possible weak El Niño in the near future. Based on this and other recent SST images, researchers are predicting that the United States could experience very weak-to-marginal El Niño events late this winter to early next spring 2002. However, the researchers caution that at this early stage there is a great deal of uncertainty about the timing and intensity of the next El Niño. Before NOAA could officially announce the formation of the next El Niño, a number of conditions must persist over several consecutive months, including persistent weakening of the trade winds, precipitation over the warmer than normal waters and sustained sea surface temperatures of-at least-a degree above normal. Make sure you revisit the SST site periodically over the next few months to stay updated as NOAA monitors the situation and issues monthly updates in NOAA's Climate Prediction Center's ENSO Diagnostic Discussion.

Relevant Web Sites
Sea Surface Temperature Product Overview

NOAA's SST Web Site at the Ocean Research & Applications Division (animations, etc.)

Media Contact:
Patricia Viets, NOAA Satellite Service, (301) 457-5005