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Questions tagged [vorticity]

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3 votes
1 answer

Why does relative vorticity in spherical coordinates have an extra term as compared to the usual cartesian derivation?

With $u, v$ denoting the components of wind velocity along zonal (x) and meridional (y) direction, atmospheric (relative) vorticity is usually defined by $$\zeta_z = \frac{\partial v}{\partial x} -\...
4 votes
0 answers

Why positive PV Anomaly moves westwards?

In Jonathan Martin's Book "Mid-Latitude Atmospheric Dynamics" there is a chapter about PV anomalies. As an example, a positive PV anomaly is discussed. What is the reason, that high PV is ...
2 votes
1 answer

Why are there different Notations of Vorticity Equation?

I'm a student of meteorology in first year. This time my question is not about a particular problem I have, but rather about teaching and learning: In a recent lecture on atmospheric dynamics we ...
1 vote
0 answers

Rossby waves in the atmosphere

I have trouble understanding the Rossby waves in the atmosphere. Sometimes they are said to be caused by the jets moving from west to east. But the phase velocity of the waves is in the west direction ...
4 votes
1 answer

Why is potential vorticity so emphasized in technical work, but often neglected in maps on weather websites?

When I was first introduced to potential vorticity, I was told that it is a very important tool for meteorologists to learn. Sure, it solved a simple problem in dynamics, but it wasn't apparent to me ...
10 votes
1 answer

Unstable North Polar Vortex?

What would cause a polar vortex to become unstable a split into 3 smaller ones? How rare is this and what long term effects could this cause if the vortex stays unstable?
7 votes
1 answer

Computing Isentropic Potential Vorticity from Hybrid Sigma Pressure levels

My task is to compute isentropic potential vorticity on a grid. All data (ECMWF ens) are given on a hybrid sigma pressure grid. Since I really cannot find reference, I assume (!) that relative ...
4 votes
1 answer

Why is the zonal component of flow in the ocean much larger than the meridional component

I am reading an Oceanography Textbook which explains that in the ocean, planetary vorticity tends to be much larger than relative vorticity therefore, the potential vorticity can be simplified to be f/...
7 votes
1 answer

Vortices in the Atmosphere Sustained only by PGF

In a cyclone, the pressure gradient force (PGF) and the Coriolis force sustain the spinning motion and causes the direction of spin (counterclockwise in the Northern Hemisphere and clockwise in the ...
21 votes
2 answers

How do tropopause folds form and do they have any impact on synoptic scale weather?

What is the process that creates a tropopause fold? Do these features have any significant impact(s) on weather patterns or the atmosphere?
18 votes
1 answer

Why do tropical cyclones not tear themselves apart?

A tropical cyclone is the generic term for a hurricane, typhoon, or tropical storm. Tropical cyclones derive their energy from evaporation of water at the ocean surface which ultimately recondenses ...