Hi, I'm Waveguyde
I'm a postdoctoral researcher at the German Aerospace Center (DLR) in Oberpfaffenhofen, Germany. My field of research is the dynamics of the middle atmosphere which is about the altitude range from 10km to 90km. In particular, I'm investigating the lifecycle of internal gravity waves.
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What is an internal gravity wave?
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When the air’s density decreases monotonically with greater altitudes, the atmosphere is termed stably stratified. If air masses are displaced vertically in this stratification, an oscillation about the position of equilibrium arises due to the interplay of gravity and buoyancy force. This oscillation, which can propagate horizontally and vertically under suitable propagation conditions, is called a gravity wave.
In the atmosphere, most of these gravity waves are generated in the troposphere, e.g. when strong winds blow over mountains or when they are excited by convection in the tropics. As they propagate to greater altitudes their amplitudes increase enforced by the conservation of energy until they finally shuffle denser air over lighter air. The point of convective instability is reached and the wave breaks. At its death, the wave deposits its momentum into the ambient flow resulting in an acceleration of the same. This mechanism is one of the main drivers of the global circulation in the middle atmosphere.
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How are gravity waves detected in the middle atmosphere?
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There are many different ways, one more sophisticated than the other. During my PhD I had the opportunity to analyze lidar temperature measurements. Lidar stands for "light detection and ranging" and is a remote sensing technique where short laser pulses are shot vertically into the sky. The photons are scattered at air molecules and return to the telescope on the ground. Counting the time between emission and reception of the photons allows one to measure the density profile of the atmosphere. Assuming hydrostatic equilibrium, i.e. gravity counteracts the vertical pressure gradient, and an aerosol-free atmosphere one can conclude from density profiles on temperature profiles. Now, gravity waves lift and lower air masses and due to adiabatic cooling and heating the gravity waves can be detected in those lidar temperature profiles.
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If you are curious, check out the CORAL calender. It shows all measurements of the CORAL lidar system that is operating in Río Grande, Argentina, since 2017.
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Feel also free to check out my dissertation.
