Wind
 

Could somebody please offer a simplified arial view depiction / description of how wind works. I need to explain to somebody "where gusts go".

Can anybody simplify that? Who was it who said.."If you cannot explain it to a 12 year old then you dont know it yet" etc... That sort of vein.

Thankyou:ok:

Where do gusts go?
 

“Where do gusts go” they go to the same place a heavy bucket of water goes if you drop its contents from a height into a bathtub full of water. The air surrounding us is a complex blend of constantly changing pressures. Similarly the ocean may look calm and uniform, especially from the higher flight altitudes, yet it is full of conflicting currents, primary/secondary swells, tides and temperature/salinity gradients.

If you have a massive fast moving front moving through an area, the gusts are often the leading edge of the powerful pressure differential. Much the same way the pounding surf announces the incoming tide- there is a whole lot of more water coming in behind the waves. The gust will “hit” expend its energy differential moving out the preexisting air mass until the pressure differential ceases to exist. Just as you drop a heavy bucket of water into the tub there will be an initial surge and wave and moments later the water you just added has become indistinguishable from what was there before.

Hope it helps………….'twas an interesting question

Wind is air moving from a high pressure area to a low pressure area.
The viscosity and mass of the surrounding air dissipates gusts over time, so gusts just turn into air having the same properties of the air around it when they have equilibrium and cease to exist.

Wind is caused by trees moving around, in a similar way a fan moves air (have you ever noticed that when the trees are still, there's no wind?)

Some species of tree are more active than others, which accounts for the gusts you ask of. Palm trees go through cycles of inactivity for months at a time (almost dormancy), followed by the rapid waving of their fronds. Palm fronds are particularly good at moving air, and when enough palm trees move at once, they can produce what we call a tropical depression (or Cyclone/Hurricane).

I live in a tropical region, and keep all my palm trees neatly trimmed, thus I have not had a single Hurricane since I've been here. I wish more people would be as vigliant.

I hope I haven't been to scientific.

Wind changes direction all the time. Sometimes it changes direction quickly.

When you are on the ground, the wind only changes direction to come from left or right.

When you are up in the air, wind can also change direction to come from up and down as well.

Sometimes, if the wind is strong enough, some of the up and down wind from the sky hits the ground and goes SPLAT!

Here is a cross-section of a gust. The air on the ground is flowing from right to left.

http://www.weatherquestions.com/gust_front.jpg

Hey Wyle E Coyote, I live surrounded by fields with no trees however they do grow Wheat and Barley in them and sometimes I see the crops moving around and creating wind like you say.

Next year they will grow lettuce in these fields so hoping for a calmer Summer.

X213A,

All weather comes from heating off the earth's surface by the sun. Warm air rises, cool air falls, simply because warm air is less dense, and in the atmosphere, floats on cooler air. Think of a hot air balloon...heat the air in the balloon, it goes up. Let it cool, it comes down. Same with the atmsophere.

Storms are parcels of air with moisture, lifted high into the atmosphere, where they cool, where water or ice or snow forms, and again falls to earth.

Air is constantly circulating, rising falling, shifting. As it does, wind is created.

Some air is more dense than other air...a result of uneven heating of the earth's surface by the sun. Air takes on characteristics of the land beneath it, forming air masses, large bodies of air which have properties of moisture, temperature, and pressure. High pressure air moves into low pressure areas, constantly shifting, constantly seeking equillibrium...but never able because the heating of the earth's atmosphere by the sun is constantly changing.

The movement of high pressure air to a low pressure area is wind. The movement of air descending from a cloud and flowing outward is wind. The movement of air through city buildings or a canyon is wind, and it flows like water in a stream.

Where does it go? It goes nowhere, and it goes everywhere. Air is around us, and it simply circulates very much like the breeze one feels in a store as a fan blows over your shoulders...the air circulates, moves, but stays in the room...wind circulates and moves small parcels of air like currents from a fan or currents in a stream...but they go nowhere...slowing and dispersing back into the atmosphere. A little like a sand castle on a beach; it's there for a short time, but eventually morphs back into beach again. So does the atmsophere around us.

Even in a tall, towering storm cell, a big cumulonimbus rain cloud, air blows through the cloud, from one side to another. It's constantly forming, constantly dissipating, it's energy derived from heating of the earth's surface by the sun, and sometimes by the forced lifting of air by mountains, or even artificial heating by a forest fire. The air circulates through, around, and in the storm, then drifts away to become another part of the atmosphere...a constantly moving, turbulent fluid which invisibly surrounds us: air.

1) The earth spins, and all the "rough edges" of mountains and valleys drags the air around.

2) Heating & cooling from the sun and day/night cycles causes warm air to rise and cool air to sink. Air has to move sideways to replace the air that moves vertically.

3) Butterflies, birds, people, and airplanes move the air, as well as fans, air conditioners, factories, and boats.

4) The drag of trees, buildings, mountains, and air against itself slows down the wind, dissipating the gusts.

Multiply all that by a gazillion permutations, and you get the winds we feel!

I hardly dare ask, for I'm sure there is a simple answer but what creates high or low pressure for the air to flow one to the other?

I really like the one about trees creating the wind but alas it's not true.

Here is the real definition if you are still interested: Wind is the horizontal movement of air defined by it's speed and direction. So the simple explanation is that air flows from a high pressure area to a low pressure area(pressure gradient force), however in reality other forces exist. These are -

1. Pressure gradient force - described above
2. Coriolis force - an apparent deflection of moving objects when they are viewed from a rotating reference frame.

Therefore Pressure gradient force + Coriolis force = Geostrophic wind.

3. Centrifugal Force - which essentially is the effect of a clockwise rotation around a high pressure area and an anti-clockwise rotation around a low pressure area, therefore -

Geostrophic wind + Centrifugal force = Gradient wind (essentially the wind at altitude)

4. Friction force - the effect that the earths surface produces on a moving air mass - therefore -

Gradient wind + Friction force = Surface wind


After all this and you have lost all your friends you have plenty of time to get into local effects of wind such as valley winds, anabatic, foehn etc.

If only it were the trees - life would be so much simpler.

I'm not an aviator but I do have a significant interest in weather. The simple answer to the question of high/low pressure is to think of the atmos as a sea. It has waves and troughs, some on a very large scale - do a quick search for Rossby waves. Much of the 'turbulence' is generated by transport of associated large air masses from the poles to the equator (or vice versa) as the atmos attempts to moderate its overall temp to an average - cool itself down, effectively.

The Jetstream -broadly- defines a boundary between these polar and equatorial transports. Many low pressure systems are spawned along this boundary and propogate away from it to surrounding areas until they 'fill' with air from surrounding high pressure zones and die out. Some high pressure areas, in contrast to the dynamic LP systems, are relatively static - areas such as the Azores are known for this amongst weather watchers.

Yes. Again, unequal heating of the earth's surface by the sun.

Letting a few drops of ink fall in a glass of water is a reasonable start to explain gusts. The energy to "drive" the ink is gravity but atmospherically it is normally a temperature difference.

PM

If you look at the front end (in terms of direction of travel) of a thunderstorm of any significance you'll often see the above effect quite clearly. A curtain of air or 'gust front' often descends from the leading edge after plumetting from the top of the cloud and is visible as a semi-circular rim. Large volumes of rain/hail, as well as temp 'mechanics' can add significantly to these gusts, some of which are inherently hazardous.