Atmospheric Gravity Waves: What Are They and How Do They Affect Our Planet?

[Dragrath]

Hi I am Peter Clark currently a student at George Mason University (GMU). I have a BS in physics with a minor in astronomy and math from James Madison University (JMU) I have started to work with Dr. Yigit on the subject of atmospheric gravity waves interacting through multiple levels of planetary atmospheres. Mostly as the stage where have to read more and more papers to try and find those that are useful references which can be a daunting task. In particular it can be quite disparaging to see how poor some fits or even badly parameterized models lacking substance on a theoretical basis. Atmospheric gravity waves arise from the Navier Stokes equations which are quite hard as like all multivariate partial differential equations they lack a general solution and are highly dependent on initial conditions not to mention chaotic.

I have a wide interest in the natural sciences particularly interested in multidisciplinary connections as an area where I think my skill set is best able to apply at recognizing possible connections that are often overlooked. I have a more or less hobby of going off on research binges on various areas of science in particular always looking to correct my ignorance where possible typically through the lense of physics. I am inclined towards the many worlds interpretation of quantum mechanics as it avoids the special treatment of an observer at the cost of accepting we can't be nonobjective observers conceptually as the observer can become intertwined with a particular wave function. The possibility that we might be able to predict and respond before a quantum jump occurs as potentually game changing if true. I find the amount of information we have been able to learn about our planet's history fascinating and really enlightening on the role of evolution and extinctions.

I worry that there is a tendency in the public perception of the sciences to apply Occam's razor too broadly even after evidence strongly suggests that the simple solution in dogma isn't robust or allow biases to infiltrate. While it is important to science that hypothesis be constantly challenged I noticed this hasn't been conveyed to the general public very well especially in the current horrific state of political dysfunction. For instance the public still thinks in the binary sense that the asteroid or the volcanoes did the dinosaurs in rather than recignizing the compelling link between these phenomenon playing a causal role in the extinction. Or the whole misinformation campaign done to obscure the scientific consensus on the extent of the current climate crisis and biodiversity crisis. With the current attacks on science I have become a bit unsure of what is the best approach to contribute to society. I regularly read Scientific American, Physics Today, when I have time and admittedly when I don't as well. I help take care of the birdies by providing food and water for them in exchange for getting to see them and wish other people could better respect life I'm not sure what else to mention... Basically I live to learn and expand my horizons and perspective

 

[berkeman]

Welcome to the PF, Peter.

I hadn't heard of gravity waves in atmospheres before, but it sounds interesting. Kind of like gravity waves on water, but more 3-dimensional? What are typical propagation speeds?

 

[Dragrath]

Welcome to the PF, Peter.

I hadn't heard of gravity waves in atmospheres before, but it sounds interesting. Kind of like gravity waves on water, but more 3-dimensional? What are typical propagation speeds?

Hmm it depends largely on what wavelengths you are interested in and particularly the density of the atmosphere at a given altitude as the amplitude and thus momentum transfer is variable with height. The exact details of wavelength and period are determined by the dispersion relation for a given system and as such there is no specific value but rather a continuum of wavelengths scaled from individual particles to the height of a fluid layer capable of wave propagation with periods ranging from seconds to days typically driven by the particular waves source, i.e. tides, orography, weather even spontaneous propagation due to flow instability. As such gravity waves are defined primarily by their direction of propagation namely as atmospheric waves that propagate vertically with waves limited to those of interest for an investigation. These waves break as their amplitudes become too large thus transferring their kinetic energy into heat.

They can occur in any fluid system as they emerge as a consequence of the Navier Stokes equation so they are indeed the same phenomenon that occurs in water, which is also three dimensional we just tend to be only interested on their effect on the surface due to impacts towards seafaring. In the air it is similar with probably the most direct impact being turbulence. Waves are also deeply coupled with other atmospheric phenomenon such as convection, Coriolis effects, geography, jet streams, even internal effects such as sudden stratospheric warming events(SSW) Quasibiennual Oscillations, Semiannual Oscillations, etc.

In research so far the focus has been mainly on waves with a wavelengths around tens of kilometers as they can propagate up into the thermosphere depositing momentum and inducing a net downward heat flux. These waves tend to be formed in the troposphere and propagate upward but you can also get gravity waves from the ionosphere during solar activity propagated by the coupling between the ionized ionosphere and the neutral thermosphere. Note that the waves of interest vary depending on what planet you are looking at since they depend largely on the state variables of the fluid. You get these waves in the Sun, on Venus, Earth Mars, Jupiter, Titan Saturn Uranus Neptune and Pluto ect. and probably in subterranean oceans elsewhere in the solar system as well as elsewhere in the universe beyond the solar system we just lack the ability to detect them.