Tuesday, January 17, 2012

Intensive -> Extended

The "Intensive Observing Period" of DYNAMO has ended, but the experiment is not over.  We are now in the "Extended Observing Period".  What this means is that a lot of the instruments and people are being (or have already been) packed up and shipped home, but some are still out there in the Indian ocean for a few more months.  In particular, we are down to one radiosonde and surface observation site, Gan (in the Indian ocean;  one more, Manus, in the Pacific);  one radar (SMART-R, also at Gan);  no airplanes;  and no ships, if I'm not mistaken.  There are still many more measurements being taken in this spot every day than there would be if DYNAMO weren't still happening, but many fewer than there were for the first couple of months.

Why do we do drag it out like this?  Why are there multiple phases of an experiment?  If we know what we want to measure, why don't we just measure it as long as we need to and then stop when the job is done - or when we can't afford it any more?

Field experiments exist to address several different types of gaps in the regular observational network.  The different phases of the experiment exist because those different needs require different balances between (for lack of a better phrase) the intensity of the observational effort - the frequency, redundancy, density of spatial coverage, and range of different types of observations being taken - and the length of time over which those observations are taken.  In our dreams, we would like all the observations we can imagine to be taken continuously forever, but in reality we have to make compromises.  The different periods reflect an attempt to make different kinds of compromises so as to satisfy different sorts of needs within a single experiment.  To understand this more deeply, it is useful to know a bit about where our more routine observations of the atmosphere - the ones that are used every day for weather prediction and climate monitoring - come from.  I'll write more about this in the next post.

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