Thursday, March 5, 2009 The generation of giant dunes explained
Ever climbed up a 200+ ft dune (I know some of you have from
your memes ...) and wondered how it formed? Well, a new paper in
Nature explains the controls on giant dune size. Andreotti et
al. (2009) use a combination of field measurements and
aerodynamic calculations to provide evidence that giant dunes
are built of smaller dunes and their terminal height is
controlled by an atmospheric boundary layer. They show that
large dunes grow by the amalgamation of superimposed dunes. Dune
growth stops (assuming it's not the result of climatic change)
by interaction with an inversion layer. Once the dune has grown
large enough, it begins interacting with the inversion layer
which confines airflow to move around the dunes rather than over
them. The height of this inversion layer correlates to the
variation in annual temperature. The greater the variation in
annual temperature the higher the altitude of the inversion
layer and the taller the giant dunes can