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# Tag Info

18

Wind is caused by pressure differences. Think of a balloon full of air; poke a hole in it and the air comes out. Why? Because the pressure in the balloon is higher than outside, and so to regain equal pressure, mass moves and that is the wind. There is a bit more to this in the atmosphere as the Earth rotates and near the surface friction also plays a ...

18

The subtropical jetstream The subtropical jetstream can be explained with angular momentum arguments. In an idealized circulation model of the atmosphere, there is a hadley cell that circulates upward at the equator, poleward along the tropical tropopause, downward around 30 N/S and equatorward at the surface. Parcels rising at the equator have a fair bit ...

10

As your diagram shows, the jet stream actually has two circulating components: one is "around the earth" (which is why the transatlantic crossing is so much faster going East than going West), while the second is more like a vortex, with a circulating flow "around" the main direction. This circulating flow is vertical in two places: North of the jet stream ...

8

The way I understand it is the height above the surface at which buoyant (heat) production of turbulence first equals the mechanical (shear) production of turbulence. A more useful definition is given by the American Meteorological Society: A parameter with dimension of length that gives a relation between parameters characterizing dynamic, thermal, and ...

8

This has been tried to some extent; Strata in London was a skyscraper that was built with three wind turbines at the top, with a deliberate design to funnel wind into them. There are other examples. Siting renewable energy generation in cities is very attractive, partly because many people feel that the "industrial" feel fits better there, but also because ...

7

Yes, but it may not be valid. The extrapolation will be valid for about 0.1 * PBL Height using the Log-Wind Profile You will need: PBL Height. A second Wind speed (within 0.1*PBL Height) Surface Sensible Heat Flux Surface Latent Heat Flux Potential Temperature You can use the last three variables to calculate the Monin-Obukhov Length (MOL). Then use the ...

6

The Obukhov length ($L$) measures the relative importance of mechanical shear-generated turbulence and density-driven (buoyancy) fluxes (1) $L$ can be used to determine the eddy structure of the flow and it provides a measure for the hydrodynamic stability of the boundary layer - it effectively imposes an upper limit on the vertical excursion of fluid ...

5

A few thoughts - assuming like you say that the aqua-planet is the same size as earth, and all else being equal, it's best to consider the two major classes of waves: Nondispersive wind generated waves: Here the maximum wave height is a function of wind speed (fetch). However, wind speed in general is not a function of wave height (unless you invoke ...

5

There's just not that much kinetic energy in the air within the urban canopy layer; much of what there is, is in the form of turbulence, rather than the laminar flow that turbines harness. Furthermore, air is very low density, which means that to get a decent amount of energy out of it, we need lots of effective rotor area, and even with the funnelling ...

4

You are correct that air generally moves along the surface from high pressure towards low pressure (not directly, but deflected due to the coriolis effect). However, this does not imply that it is moving from a colder area to a warmer area. And, there is nothing contradictory in a cool air mass moving horizontally to displace a warm air mass. Extratropical ...

4

Jet streams are caused by a combination of a planet's rotation on its axis and atmospheric heating. These form air masses near each other of different temperatures, which cause jet streams. Also, a links that might help you: What causes the jet stream?

4

Keep in mind that your jetstream map is only a schematic description. In reality you will experience shear (strong wind along jet axis, decreasing outwards). Assuming that the airship would drift with the wind, the shear would throw you off the jetstream and you would sooner or later been taken to convergent areas in the upper troposphere (poles, or ...

3

They would come to equilibrium, or rather steady state, at which energy input ultimately from the Sun matches energy dissipation by friction. The wind speeds would be somewhat higher because water presents less friction than land, but not higher by a huge factor. This state of affairs exists to a good approximation in the prevailing westerlies of the ...

3

Because you specifically asked about winds and pressure, there is a fairly applicable rule of thumb. It's called Buys Ballot's Law. Basically, if the wind is to your back (coming behind you), and you're in the Northern Hemisphere, generally low pressure is to your left and high pressure is to your right. This graphic from http://www.maiamarinelli.com/ ...

3

In theory, maybe you could do it, but some of the jet stream loops are even tighter than in Aabaakawad's examples. The wind shear and associated turbulence in and around the jet stream's are so severe that no 'light plane' could survive. Any glider-like aircraft would break up almost immediately.

2

The characteristic funnel of a tornado is caused by condensed water. A tornado is a swirling mass of air with very high vertical vorticity and a corresponding drop in pressure. Large tornados can have pressure deficits on the order of 100 hPa, which is significant compared to synoptic horizontal pressure gradients. The drop in pressure causes air to ...

2

It is not clear that the Obukhov length has an exact physical interpretation. The length L is certainly a length that dimensional argument shows to follow from the set of basis parameters that Monin and Obukhov proposed was sufficient to describe turbulence in the bottom 10% or so of atmospheric boundary layers. We may ask several questions: is the MO basis ...

2

The atmosphere has various layers. Going upwards they are - troposphere, stratosphere, mesosphere, thermosphere, exosphere. (There are "pause" layers between, like tropopause, stratopause etc.) The density gets less and less and the exact height to the top of the exosphere is difficult to determine because the gas is so thin. However, we normally talk about ...

1

The atmosphere, as a whole, is approximately in hydrostatic equilibrium. This means that the gravity of the earth holds the atmosphere to the earth, preventing its escape, though few molecules may escape every so often. Mathematically, this can be described by $$\frac{dP}{dr}=-\rho g$$ where P is the pressure, $\rho$ is the density, and $g$ is gravity. ...

1

It takes about 2 weeks for a mass of air to circle the globe along its latitude from West to east. I used to work for a French climate research lab in the 70s, and was based on Crozet island (South Indian Ocean) . At the time I was carrying atmospheric radioactivity measurements, and the French army was carrying nuclear test above ground in the pacific, I ...

1

Quick answer is its too vague to give a firm estimate. The geostrophic wind - what the wind would be in theory with no complicating variables, is a function of height, temperature and latitude. There is a calculator for this on http://www.shodor.org/os411/courses/_master/tools/calculators/geostrophic/ The wind speed for New York could be anything from 1 ...

1

The shape of a tornado is due to the movement of air and not dust. The shape of a tornado is called a vortex. A vortex can occur in any fluid (air or liquid) where the fluid rotates about an axis line. Vortices are examples of turbulent fluid flow (air or liquid). When vortices occur in liquids they are sometimes called whirlpools. Tornados are high energy ...

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