<P> Sea surface temperature (SST) is the water temperature close to the ocean's surface . The exact meaning of surface varies according to the measurement method used, but it is between 1 millimetre (0.04 in) and 20 metres (70 ft) below the sea surface . Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a short distance of the shore . Localized areas of heavy snow can form in bands downwind of warm water bodies within an otherwise cold air mass . Warm sea surface temperatures are known to be a cause of tropical cyclogenesis over the Earth's oceans . Tropical cyclones can also cause a cool wake, due to turbulent mixing of the upper 30 metres (100 ft) of the ocean . SST changes diurnally, like the air above it, but to a lesser degree . There is less SST variation on breezy days than on calm days . In addition, ocean currents such as the Atlantic Multidecadal Oscillation (AMO), can effect SST's on multi-decadal time scales, a major impact results from the global thermohaline circulation, which affects average SST significantly throughout most of the world's oceans . </P> <P> Coastal SSTs can cause offshore winds to generate upwelling, which can significantly cool or warm nearby landmasses, but shallower waters over a continental shelf are often warmer . Onshore winds can cause a considerable warm - up even in areas where upwelling is fairly constant, such as the northwest coast of South America . Its values are important within numerical weather prediction as the SST influences the atmosphere above, such as in the formation of sea breezes and sea fog . It is also used to calibrate measurements from weather satellites . </P> <P> There are a variety of techniques for measuring this parameter that can potentially yield different results because different things are actually being measured . Away from the immediate sea surface, general temperature measurements are accompanied by a reference to the specific depth of measurement . This is because of significant differences encountered between measurements made at different depths, especially during the daytime when low wind speed and high sunshine conditions may lead to the formation of a warm layer at the ocean's surface and strong vertical temperature gradients (a diurnal thermocline). Sea surface temperature measurements are confined to the top portion of the ocean, known as the near - surface layer . </P> <P> SST was one of the first oceanographic variables to be measured . Benjamin Franklin suspended a mercury thermometer from a ship while travelling between the United States and Europe in his survey of the Gulf stream in the late eighteenth century . SST was later measured by dipping a thermometer into a bucket of water that was manually drawn from the sea surface . The first automated technique for determining SST was accomplished by measuring the temperature of water in the intake port of large ships, which was underway by 1963 . These observations have a warm bias of around 0.6 ° C (1 ° F) due to the heat of the engine room . This bias has led to changes in the perception of global warming since 2000 . Fixed weather buoys measure the water temperature at a depth of 3 metres (9.8 ft). Measurements of SST have had inconsistencies over the last 130 years due to the way they were taken . In the nineteenth century, measurements were taken in a bucket off of a ship . However, there was a slight variation in temperature because of the differences in buckets . Samples were collected in either a wood or an uninsulated canvas bucket, but the canvas bucket cooled quicker than the wood bucket . The sudden change in temperature between 1940 and 1941 was the result of an undocumented change in procedure . The samples were taken near the engine intake because it was too dangerous to use lights to take measurements over the side of the ship at night . Many different drifting buoys exist around the world that vary in design, and the location of reliable temperature sensors varies . These measurements are beamed to satellites for automated and immediate data distribution . A large network of coastal buoys in U.S. waters is maintained by the National Data Buoy Center (NDBC). Between 1985 and 1994, an extensive array of moored and drifting buoys was deployed across the equatorial Pacific Ocean designed to help monitor and predict the El Niño phenomenon . </P>

At the equator what is the average seawater temperature