Atmospheric eddies, waves etc: definitions

[jf22901]

Hi all.

I'm reading up on types of atmospheric motion, and when discussing the meridional transport of various properties, the motion is generally split into three components:

1. Mean meridional circulation
2. Transient eddies
3. Stationary waves

However, depending on what book, article or website I read, I come across the terms transient eddies, stationary eddies, traveling waves, stationary waves and non-travelling waves. Is this just a case of different terminology for the same thing, or are there specific differences?

Are transient eddies and traveling waves the same? Are stationary eddies, stationary waves and non-travelling waves the same?

Thanks in advance!

 

[JesseC]

It is difficult to know without reading the texts, could you link the websites and books? When I was learning about this the lecturer often talked about waves and eddies interchangeably. The latter is often caused by instabilities in the former. One thing that you could do is check the mathematics for consistency. When considering meridional transport, eddies are characterised by quantities that vary in time and stationary eddies by quantities that vary zonally but not in time.

 

[madrespek]

the definition i know about is

$$v = <\bar{v}>+<v> + v'$$ where $$<\cdot>$$ is time averaging, and $$ \bar{\cdot}$$ is zonal averaging. The terms of the RHS are, respectively, the mean meridional velocity, the stationary eddies, and the transient eddies.

When people talk about "stationary/traveling waves" I thought they were typically talking about Rossby waves/kelvin waves/etc.

 

[olivermsun]

In a general sense, waves are typically the motions which have a well-defined dispersion relation, e.g., Rossby waves. In the framework you're talking about, the "stationary" Rossby/planetary waves are important because they're associated with fixed topographic features (the big mountain ranges), so they "survive" even after time-averaging. The eddies on the other hand have some transient zonal structure which supposedly averages to zero (if you average both in time and in the zonal direction).

 

[LudusRex]

As a scientist studying atmospheric motion, I can provide some clarity on the terminology used to describe these different types of motion. While there may be some overlap in the terms used, there are specific differences between them.

Transient eddies, also known as synoptic eddies, refer to small-scale disturbances in the atmosphere that are constantly evolving and moving. They are usually associated with weather systems such as storms and cyclones, and have a short lifespan of a few days to a few weeks.

Stationary waves, on the other hand, are large-scale disturbances that remain in the same location in the atmosphere. They are caused by differences in temperature and pressure and can persist for longer periods of time. These waves are responsible for creating the jet streams and other major wind patterns in the atmosphere.

Traveling waves, also known as Rossby waves, are large-scale disturbances that move from west to east in the atmosphere. They are caused by the Earth's rotation and the Coriolis effect, and can have a significant impact on weather patterns.

Non-traveling waves, also known as standing waves, refer to disturbances in the atmosphere that do not move horizontally but instead oscillate vertically. These are often seen in the form of gravity waves and are important in redistributing energy in the atmosphere.

In summary, while there may be some overlap in the terminology used, there are specific differences between transient eddies, stationary waves, traveling waves, and non-traveling waves. It is important to understand these distinctions in order to accurately describe and study atmospheric motion.