Satellites Draw Best-Ever Mediterranean Heat Map

By Roland Piquepaille

Observations from several satellites launched by the European Space Agency (ESA) and other organizations have been gathered to produce the most detailed heat map of the Mediterranean. With a resolution of two square kilometers for an area of about 3 million square kilometers, an equivalent ground-based map would have needed almost 1.5 million thermometers put into the water. This ESA news release adds that sea surface temperature (SST) is an important variable for weather forecasting and for checking the rate of global warming. In fact, as water takes longer than air to warm up or cool down, the top layer of our oceans is basically acting as a reservoir of heat. Did you know that "the top two meters of ocean alone store all the equivalent energy contained in the atmosphere?" I didn't, so read more...

Before going further, let's look at this best-ever Mediterranean heat map.

Here is a heat map of the Mediterranean on November 3, 2004 (Credit: Medspiration and ESA). A larger version of this map is available in Macromedia Flash format and covers the November 1-25 period.

This ultra high-resolution sea surface temperature map of the Mediterranean could only have been made with satellites. Any equivalent ground-based map would need almost a million and a half thermometers placed into the water simultaneously, one for every two square kilometres of sea.

This most detailed ever heat map of all 2 965 500 square kilometres of the Mediterranean, the world's largest inland sea is being updated on a daily basis as part of ESA's Medspiration project.

With sea surface temperature (SST) an important variable for weather forecasting and increasingly seen as a key indicator of climate change, the idea behind Medspiration is to combine data from multiple satellite systems to produce a robust set of sea surface data for assimilation into ocean forecasting models of the waters around Europe and also the whole of the Atlantic Ocean.

But why is this so important to precisely measure sea surface temperatures?

The temperature of the surface of the ocean is an important physical property that strongly influences the transfer of heat energy, momentum, water vapour and gases between the ocean and the atmosphere.

And because water takes a long time to warm up or cool down the sea surface functions as an enormous reservoir of heat: the top two metres of ocean alone store all the equivalent energy contained in the atmosphere.

The whole of their waters store more than a thousand times this same value -- climatologists sometimes refer to the oceans as the 'memory' of the Earth's climate, and measuring SST on a long-term basis is the most reliable way to establish the rate of global warming.

Please read the full ESA's news release for more details and references, but for your viewing pleasure, here is another great picture from the Atlantic ocean taken with one of the instruments of ESA's Envisat.

Envisat's Advanced Along Track Scanning Radiometer (AATSR) continuously monitors sea surface temperature to an accuracy of a few tenths of a degree. This is a false-colour representation of AATSR results over the Atlantic, with blue corresponding to coldest waters and red the warmest. (Credit: ESA)

Sources: European Space Agency news release, December 15, 2004

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• ESA
  
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• Space