TOPEX/POSEIDON Maps

Dynamic Topography
Significant Wave Height
Wind Speed Modulus
Sea Level Anomaly

Dynamic Topography

The dynamic topography is a measure of sea level relative to Earth's geoid (a surface of constant gravitational potential that would represent the sea surface if the ocean were not in motion). The mapping shows all the characteristics of the ocean general circulation (speed and direction of ocean currents).

Units are centimeters. The geoid is OSU91A and JGM3. Blue represents the lows, green the moderate features, and red the highs. The relief ranges over about 2 meters from low to high.

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The ocean gyres and associated western boundary currents (e.g. Gulf Stream, Kuroshio, Brazil/Malvinas Confluence area) appear clearly on the map. So does the Antarctic Circumpolar Current. These permanent features of the ocean general circulation may vary over time due to changes in ocean circulation forcing. This is particularly true for tropical regions.

Significant Wave Height

Significant wave height is determined from the shape of the return pulse from the radar altimeter: a calm sea with low waves returns a strong, condensed pulse whereas a rough sea with high waves returns a weak, stretched pulse (due to the large footprint radar measurements).
Units are centimeters. Blue represents the weak or moderate features, green the highs, and red over 5 meters wave heights. Effects due to the Roaring Forties (in the Antarct ic Ocean) are easily singled out.

Wind Speed Modulus

To forecoast ocean waves, we will need to simultaneously observe wave height and wind speed, which are closely correlated.
Units are meters per second. Blue represents the weak or moderate feaures, green the h ighs, and red over 15 meters per second wind speed. Some well known features of the atmosphe ric circulation can be observed, e.g. the Roaring Forties (in the Antarctic Ocean).

Sea Level Anomaly

The sea level anomalies are the measured sea levels referred to a mean. They illustrate the variability in the dynamic topography due to ocean circulation change in heat content of the upper ocean.
Units are centimeters. The mean is a 3-year mean (Cycles 4 to 113). Blue represents the lows, green the moderate features, and red the highs. The relief ranges over about 2 meters from low to high. The topographic relief ranges over about 20 centimeters from low to high.