Gone with the Wind
Once it has been swirled up into the air, fine desert dusk is often transported long distances by wind currents. This effect can be exploited to reveal complex wind currents in the lower atmosphere, which is especially useful when studying small gravity waves in the atmosphere. The direction of propagation and horizontal wavelengths can almost be read off with the eye.
The Terra-MODIS image gives a good indication of how desert dust makes visible the characteristic riblike structure of a gravity wave field over the Red Sea. This field was mainly induced by orography and the transition from land to ocean.
Information about the structure function of atmospheric gravity waves is required to improve the forecast quality of atmospheric and climate models. Such information is needed continuously and globally over a wide range of spatial and temporal scales, especially for the whole atmosphere from the ground up to the lower thermosphere. This allows quantification of the amount of energy and momentum being redistributed by these waves in the atmosphere. Figure 2 is a simulation of the vertical wind field generated by the U.S. Weather Research Forecast Model. It reveals a pattern similar to that in the MODIS image.
DFD investigates this topic using both satellite-based measurements and its own ground-based measurements of mesopheric airglow using the GRIPS system, and models the identified structures.
