| Context |
| WHERE DOES ALL THE WATER GO ? |
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When rain or snow
reaches the ground or the vegetation cover, it either evaporates
(thus immediately returning to the atmosphere) or it infiltrates
into the soil and either flows to join a river or the sea or gets
drawn into vegetation. One way or another, however, it will eventually
return to the atmosphere. So-called “evapotranspiration”
is the sum of evaporation from land and water surfaces plus the
transpiration from vegetation. This is a very important phenomenon
for “hydrometeorology”, the study of the water cycle in
its relationship to meteorological conditions. |
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Evapotranspiration assessment isn’t easy: direct measurements are impossible, so indirect approaches have to be used which are based on measuring various atmospheric parameters. This requires very expensive instruments which are only available in a few meteorological reference stations, thus making it difficult to get a good estimation of evapotranspiration over large areas. Fortunately, data from meteorological satellites can complement the available ground-level data. These satellites can be useful in detecting clouds and deducing characteristics of the earth’s surface. Moreover, the meteorological geostationary satellites provide ample data to monitor the daily evapotranspiration cycle. |
