# Tag Info

67

Improbable. It is well known that the Coriolis force is needed to form a hurricane, and the figure of 5oN/S as the minimum for formation is widely publicized. You can also find record of tropical storm formation near India as far south as 1.4oN. The problem of crossing the Equator isn't one of hurricane formation though, it is one of hurricane motion. ...

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 ...

23

You can use the Foucault pendulum to determine the hemisphere: Its plane of movement rotates: anti-clockwise in the southern hemisphere; clockwise in the northern hemisphere. The rotation of the plane can be explained by the Coriolis force.

19

Don't think of the Coriolis force as deflecting motion clockwise/counter clockwise, but to the right (NH) or left (SH), when looking in the direction of the motion. So this is sort of 'by definition'. A cyclone is a low pressure system, and air will move from a location with high pressure towards a location with low pressure. The Coriolis force will deflect ...

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

It's my understanding that the famous "sink swirl" example doesn't work simply because the Coriolis effect is too weak at that scale: it's insignificant compared to the motion of the water from residual momentum from when it entered the sink, and from vibration, air motion, and so on. For long-range artillery, the Coriolis effect can become noticeable: it ...

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 ...

12

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'...

12

To correct your phrasing slightly: The Coriolis force acts to turn flows in the northern hemisphere to the right. This is not quite the same as "in a clockwise pattern", as will become evident in a moment. Cyclones have a low pressure core and higher pressure outside. Therefore, the wind is flowing from the outside in. When we think of a cyclone, we think ...

10

Here are your choices with regard to modeling the atmosphere. There aren't many, and only one of them makes sense. Model the atmosphere from the perspective of an inertial frame of reference. Good luck with that! As an advisor told me decades ago, "Name one!" It's certainly not an Earth-centered frame; the Earth is orbiting the Sun. It's certainly not Sun-...

10

The Coriolis force does not impart any difference in the draining of your sink or toilet, that has much more to do with the construction and design of the basin. In fact, for Coriolis to do anything it needs hours to take effect. The Coriolis effect requires large spatial and time scales. You can, however, look for its influence to determine which ...

8

Coastal trapped Kelvin waves are important processes contributing to variability in the sea surface height and temperature near the coast. Field studies have measured large temperature fluctuations mainly made up of low-frequency internal Kelvin waves mostly of semi-diurnal tidal period at the continental shelf on the great barrier reef (Wolanski, 1983). ...

7

That means from the perspective of the equator to the north pole, it is rotating clockwise That's the part you got wrong. As seen from the Equator (as any other point on the Earth), the North pole is not rotating. The rotation only shows up in an external frame of reference. And is actually using an internal frame of reference (like an observer on the ...

7

The Coriolis acceleration is only present in a rotating reference frame as is the case with Earth. The Coriolis effect is caused by Earth's rotation and the inertia of the mass experiencing the effect. If you are in an inertial frame of reference, thus non-accelerating, there will be no Coriolis effect. Let's assume that you are capable of modeling the ...

6

Ocean currents can be described as flow oscillations that are forced at different frequencies. In the absence of any external forces (wind, friction), the resulting flow is the inertial motion, which is the response to the balance between Coriolis and inertia. The Coriolis parameter, $f$, can be described as a frequency: the effective planetary rotation ...

6

The Coriolis effect is necessary for FORMATION but NOT for MAINTENANCE of a tropical cyclone. Once formed, in a full-fledged tropical cyclone of hurricane intensity the wind balance is cyclostrophic, between the pressure-gradient and centrifugal force, with the Coriolis effect negligible by comparison. This is especially true if the tropical cyclone is ...

6

If your question is: I have an equation with force term $F(x,t)$, and suppose that $F(x,t)$ is caused by effect A, then will the solution of the equation be the same as if the force $F(x,t)$ had been caused by effect B, then the answer is of course "yes". Same force (i.e., same magnitude, same direction) will always cause the same reaction of the system, ...

5

The Coriolis Effect occurs in all directions equally, even straight zonal (east-west) winds. Many indeed struggle with this idea - this Physics SE question has a fair explanation as to why. As arkaia commented, the total deflection magnitude is $f=2{\omega}\cdot{\sin(latitude)}$, which is an orthogonal vector change (and as such shows up as terms in both ...

5

The effects of Coriolis in rivers and estuaries are more subtle than in the open ocean. Coriolis tends to be a second or third order process in fast-moving and relatively small systems like rivers. On the other hand, when the residual flow in an estuary is considered, then that process tends to be slow and persistent and the effects of Earth's rotation (...

4

The Beta effect describes how the Coriolis force affects fluid motion depending on spatial changes due to the curvature of the Earth. In other words, it describes the variation of the Coriolis parameter with latitude. One can model this change exactly or approximate it via Taylor series expansion at a given latitude. The latter option is typically used to ...

4

There have been a number of answers here that answer slightly different questions. As I understand it the question is "Why does the Coriolis force apply to objects (or air parcels) moving east and west, as well as those with a north/south component?" It's a good question. The common intuitive explanation of the Coriolis effect, which you describe, considers ...

3

Another way of telling the hemisphere is with the phases of the moon. In the northern hemisphere, the illuminated part of the moon "moves" from right to left, the opposite from the southern hemisphere, in which it moves from left to right. For more details, check wikipedia: Lunar Phase

3

My answer will only relate to the question in the title: Why is pressure on the poles higher in summer and lower in winter? Due to the axis tilt of the earth the winter hemisphere gets less heated by solar radiation. This leads to a high temperature gradient from equator to the winter hemisphere pole (strong baroclinicity). In contrast we have a low ...

3

First forget about the cardinal directions and accept the next notions about the directions of forces relative to the air flow. The air parcel is affected by the pressure force towards the low pressure. The Coriolis force pulls air 90 degrees to the right relative to the current wind direction. The friction force that affects the flow is always directed to ...

3

The full answer is that you're moving through the Ekman layer. In the upper atmosphere, away from the ground, the wind direction is such that the Coriolis force and the pressure gradient balance each other, for the most part. Near the surface, you also have turbulent friction/drag and all three components of the force have to balance. If you follow the math ...

2

It's been a while since I've thought about this... and every time it still does take some careful thinking through it all. But hopefully this can really help you get it put together! First: Yes the Earth rotates counterclockwise around the Pole... The thing is, when you shoot an object "due north" towards the North Pole... you really aren't shooting it ...

2

No, the mountains would still need to be west of tornado alley. It all starts with temperatures. You often hear the colloquial "warm\cold airmass battle" image. But more specifically, the vital requirement for tornadoes is warm air advection. Why? Because warm advection fundamentally means the proper wind shear (cyclonic turning with height) for sustained ...

2

In an idealised scenario (ie where the plane is flying due north or south at a and there are no other perturbations to its course apart from the Coriolis effect), yes. And I guess it would be the most efficient course too!

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