Sea surface temperature

The surface temperature is the temperature of a body, which prevails on the surface thereof and thus, with respect to the heat radiation, the visible or measurable temperature is from the outside. It is important if the interior of the body a different temperature than the outer layers, as well as when you want to describe processes of heat transfer on the surface or between surfaces and body heart / body environment.

Thermodynamics and Heat Transfer

A temperature gradient within a body occurs when a body with an initial homogeneous temperature is thus located in a colder or warmer environment, heat to him or paid. The outer layers thereby adjust their temperature more quickly to the ambient temperature, than that, depending on the temperature conductivity, more or less thermally insulated inside. Thus, for example, a body which is heated in a water bath, a higher temperature than in the interior, wherein the same applies to the surface in the reverse shape for cooling.

Sea ​​surface

The sea surface temperature is defined as the water temperature one meter below the sea surface directly. It represents a central meteorological and climatological measurement unit, as it determines both the thermohaline circulation of the ocean, as well as its heat exchange with the atmosphere. Usually one uses for the sea surface temperature, the English abbreviation SST ( sea surface temperature ). The complete heat content of the oceans is determined, among other things with immersion probes and abbreviated in English with OHC (ocean heat content ). The heat content of the oceans has increased in recent years in climatology important.

Important parameters that are based directly or indirectly on the sea surface temperature and its spatial differences are the Southern Oscillation Index and the North Atlantic Oscillation. The SST plays an important role in El Niño and La Niña phenomena, and for monsoon and specifically the Indian monsoon.

There are different ways to measure the SST, and between these methods sometimes can result in significant differences in the measurement accuracy because they are associated with different large errors. First, we used a direct measurement by thermometer, either manually by measurement on a sample of water or automatically by ships. However, the data thus obtained material has significant inaccuracies, since, due to, for example, a different draft or a non-uniform position of the measuring instrument is not always measured in the same depth. Better and much more reliable data thus obtained from fixed installed buoys. Their data are usually transmitted via satellite where it is automatically evaluated. However, an advantage is not only always the same depth of the measurement, but also the fixed position. This gives for points defined by continuous measurement series and avoids distortion of the data set by a different spatially and in time data location, depending on whether at a particular location just a ship with measuring equipment is present or not. However, one problem is that the buoys are very limited seaworthy and therefore often only cover the coastal image.

Since the 1980s, satellite measurements are therefore increasingly used which have the advantage that they cover the whole area in the almost same time, in contrast to the above item measurements. Here, the ocean is scanned with electromagnetic radiation in the infrared wavelength range ( see Fig description of the illustration above right). The importance of satellite measurements seen in a direct comparison with their alternatives. The satellites will allow a high-resolution overview in a relatively very short period of time. How does a ship at a speed of ten knots about ten years by the same section to capture, like a satellite in just two minutes. However, the measurement of the absolute SST using satellite also has disadvantages. The radiation is reflected in the top ten centimeters of the ocean and represents therefore, due to the depth-dependent heating effect of the sun, the cooling in the night and the surface evaporation, not the real SST. A comparison of direct temperature measurements by buoys and ships with the measurement data of the satellites is therefore only given very limited, which at the relevant temperature change is often one-tenth degree leads to considerable evaluation problems. In addition, satellite measurements are disturbed by the cloud cover and therefore itself may have inconsistencies, if these faults are not balanced. However, these problems are minor compared to the advantages of a satellite-based measurement.

Stars

The surface temperature of stars is the measurable temperature of the star for us, but says little about its inner temperature of. It is higher there than at the surface, since large amounts of heat are released in the interior of nuclear fusion. This heat is then transported along the temperature gradient to the outside and there is radiated, wherein the relationship between the wavelength of the emitted light and the surface temperature of the star is given by Wien's displacement law.

Since you will not be able is the temperature of the star to be measured directly, but rather the wavelength of the radiation released by him, can be determined in this way, the surface temperature of the star indirectly. For example, the solar radiation has a spectrum with a maximum at 500 nm wavelength (blue- green light), from which we can deduce a temperature of its photosphere of about 5,800 Kelvin.

• Stellar physics
• Climatology