# Tag Info

## Hot answers tagged dynamics

24

The answer is the scale. The fluid movement of a sink has a much smaller curvature radius than the grand-scale movements of a hurricane. This curvature radius plays a big role on whether your movement due to a pressure gradient will be balanced by coriolis, or centrifugal forces, as thorougly discussed here. You can read this wikipage, but the essence is ...

17

This question can be answered with a scaling argument. Let us start with the momentum equation (Navier-Stokes) in a non-intertial reference frame (e.g. on the rotating earth) and assuming inviscid flow (roughly true above the surface). \dfrac{\partial\mathbf u}{\partial t} = - \mathbf u \cdot \nabla \mathbf u -\dfrac{1}{\rho}\nabla p-2 \mathbf \Omega \...

13

You can think about it like this: It takes one day for the earth to perform a full rotation (about 86k seconds), on the other hand, it takes a few seconds for your sink to drain (lets say 10 seconds). So it takes 8600 times longer for the earth to do a full rotation than it takes the water to drain down the sink. It is not too hard to imagine that the earth'...

13

Ageostrophic winds are merely the component of the actual wind that is not geostrophic. In other words, given the actual wind ($\mathbf v$) and the geostrophic wind ($\mathbf v_g$), the ageostrophic wind ($\mathbf v_a$) is the vector difference between them. The ageostrophic wind represents friction and and other effects. This, for example, is responsible ...

6

The Rossby radius of deformation ($\lambda_{R}$) is a length scale over which adjustment will occur while a system approaches geostrophic equilibrium. In my class noted I have this defined as the distance at which buoyancy becomes as important as rotation. Some examples are given here but do not show their derivation. The distance that cold pools of air ...

5

Yes it is. In fact Rossby waves always move westward in the absence of a zonal mean flow. Before going into detail lets try to explain this qualitatively. In a barotropic fluid the absolute vorticity is conserved. The absolute vorticity is composed of the relative vorticity $\zeta$ and the planetary vorticity $f$ ($f$ is also called the Coriolis parameter). \$...

5

The polar vortex The AMS glossary defines the polar vortex as: A planetary-scale mid- to high-latitude circumpolar cyclonic circulation, extending from the middle troposphere to the stratosphere. The Northern Hemisphere vortex often features two centers—one near Baffin Island and the other over northeast Siberia—with analogous circumpolar asymmetry atypical ...

4

It depends. Take a look at this recorded presentation from the 27th Conference on Severe Local Storms by David C. Lewellen and the accompanying pre-print. This talk focuses on the effect of buildings on tornadoes though the buildings are examined as fixed blocks they are not modified or damaged, but remain a fixed obstacle to the tornado (he toward the end ...

4

Northern Hemisphere The spatial structure of the polar vortex is determined by the stationnary waves. Stationary waves in the northern hemisphere are primarily modulated by stationary (surprise!) forcings of the northern hemisphere : Topography : Rockies and Himalayan mountains Land-sea ocean heating contrast This spatial pattern is mostly locked but ...

3

It is strongest in the arctics,most radiation from this area will be long wave infra red and long wave infra red is absorbed and reflected by the climate gases in the atmosphere. A large part of the heat from the sun is reflected by snow and ice,But as the snow and ice melts more heat is absorbed by the water in the ocean the effect of this is larger in the ...

2

Your question is actually a three-part question in disguise, of which I cannot answer all parts, but let me tell you what I do know. Part 1: What causes variations in vertical position within the context of the refered sentence? If you read that section more carefully it is not so much variation of the seabed depth, but variation in the measurement of the ...

1

This one has not been answered for a long time and I am going to summarize what I wrote in the comments. If I understood OP's question correctly I believe it is asking why Potential Vorticity is not shown in weather maps in a operational sense. From this old(but still very useful reference) Isentropic Potential Vorticity presuming isentropic surface are ...

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