It's probably not a co-incidence that our latest sea barge heading rocket launch is carrying something that will measure the heights of the ocean surface from space!
Jason-3 is the 4th member in a long series of ocean altitude measuring satellites co-developed by NASA and the French CNES since TOPEX/Poseidon flying in 1992, followed by Jason-1 in 2001 and Jason-2 in 2008. These satellites use a radar altimeter to measure the time delay in the reflected radar beep from the ocean surface. This, combined with precise measurements of the satellite's position (by GPS receivers, laser reflectors and a radio transmitter), means that the heights of the ocean (which can vary by up to 2 meters around the world!) can be measured to the nearest inch or so (2-3 cm).
So what is the use of such measurements? Besides obvious ones such as monitoring the sea level rise from global warming and providing tide changes info to commercial entities, there's the fact that higher ocean level areas tend to be warming and lower ones being colder, so it also provides a measurement of the heat capacity in that ocean region. This temperature difference is the crux of how strong hurricanes become, as well as being the key parameter of causing El Nino (happening right now as I am writing this)/La Nina effects.
[ame="http://www.youtube.com/watch?v=qjf5uL31n-Y"]Getting To Know Jason-3 - YouTube[/ame]
[ame="http://www.youtube.com/watch?v=D0AgqhS6B-U"]The Science of Jason-3 - YouTube[/ame]