If you have a situation of cold high pressure air and hot low pressure air, what will determine how the air will flow, the pressure or the temperature?

I read somewhere that wind is caused by high pressure cold air from the poles flowing to low pressure hot air from the equator. But why isn't it the opposite, hot air flowing to cold air?

Cold air is denser, and high pressure flows to low pressure.

If you have a situation of cold high pressure air and hot low pressure air, what will determine how the air will flow, the pressure or the temperature?

I read somewhere that wind is caused by high pressure cold air from the poles flowing to low pressure hot air from the equator. But why isn't it the opposite, hot air flowing to cold air?

Simple - both statements are correct. The denser cold air slides under the less dense warm air. Both are in constant motion and form the very basis of our weather.

Is that enough or do you want a full description of air movements (and water as well) that create our weather?

Simple - both statements are correct. The denser cold air slides under the less dense warm air. Both are in constant motion and form the very basis of our weather.

Is that enough or do you want a full description of air movements (and water as well) that create our weather?

Thanks Read-Only. I will very much appreciate a full description of air movements that create our weather system.

Thanks Read-Only. I will very much appreciate a full description of air movements that create our weather system.

OK, it would take a whole book to cover it in depth but I'll start with the very basics and we'll move ahead as long as you have more questions.

First off, our weather is a heat-driven engine with the heat being supplied by the sun. More sunlight and heat land at the equator than at the poles. This results in the air (and water) at the equatorial regions being heated more.

If the Earth were a perfect sphere and with no surface aberrations like land masses and mountains, the flow of air and water would simply be North-to South and South-to North. The heated air from the equatorial regions would rise (it's less dense) and flow northward toward the polar regions. The colder air (more dense) would simply slide underneath the warm air and flow toward the equator.

With me so far?:) Good.;)

But the surface of the Earth is irregular - it does contain land masses and mountains. And they interfere with what would otherwise be the simple movements I just described and make them more convoluted and complex. The result is what we call local climate conditions. Probably the most well-known of these movements is the Gulf Stream. It's what makes it possible to live in the Northern latitudes of the British Isles which would otherwise be far too cold to produce food crops.

I'll allow you to digest that before proceeding. Any questions at this point?

OK, it would take a whole book to cover it in depth ...If the Earth were a perfect sphere and with no surface aberrations like land masses and mountains, the flow of air and water would simply be North-to South and South-to North. ...
But the surface of the Earth is irregular - it does contain land masses and mountains. And they interfere with what would otherwise be the simple movements I just described and make them more convoluted and complex. ... the most well-known of these movements is the Gulf Stream. ...
Any questions at this point?No questions. -just two corrections:

(1) not a whole book required. I do it in Chaper 5 of my book, Dark Visitor

(2) you missunderstand much by neglect of the dominate effect. Quoting from Chapter5:

" The “force” that causes north or south moving masses of air or water to be deflected sideways (the clockwise turning in the Northern Hemisphere just discussed)* is called the Coriolis force, after the French engineer Gaspard Coriolis who explained to Napoleon why his long-range cannon fire was always falling a little to the right of the target if the target was north or south of the gun, but was “on target” if the gun was aimed either east or west. The Coriolis force is not a true force, only the effect of a spinning spherical earth. "


*here is the "just dicussed" text it refers to:

" At the equator, both the land and the air are moving at about 1000 miles per hour, if seen from the moon (or any other point traveling through space with the earth). This is because at the equator it is approximately 24,000 miles around the earth and the air must go around in 24 hours. ...
At Lisbon's latitude the distance around the earth is only about 3/4 the circumference of the equator, so there the air is only moving at 750 miles per hour to go around with Lisbon in 24 hours. If you could instantly move a big chunk of this Lisbon air to the equator, the earth would be running under it so fast that the wind would come out of the East at 250 miles per hour. ...Thus as Lisbon's air moves south, it tends to head west also as it is not going around the earth fast enough to keep up with the land (or ocean) spinning under it. By the time this air from Lisbon gets near the equator, it is mainly moving towards the West as seen from the deck of a ship in the tropical ocean. On its trip southward, this air mass gained most of equatorial speed from friction with the surface – making steady winds towards the west, not 250 mile / hour gales!
Local weather phenomena such as warm clouds rising and cold air descending tend to keep the lower parts of the tropical atmosphere mixed and all moving towards the west, at least as the air mass moves west from Africa, but recall from the non-spinning earth model, this warmer air must also tend to go towards the poles to replace the air which is going toward the equator. Thus all year long east of the Caribbean region there is a general climatic circulation of air along the path of typical hurricanes - westward from Africa but turning northward. "

The reader I was trying to reach with my book would never intentionally open a book on physic, so I disguised lots of physics in simple terms anyone could understand. I did give the name of this effect of Earth's rotation, but never called Kepler's three laws by their names. Like the text above, I only explained them in simple terms so any one could understand and used all three in numericsal examples smoothly as part of the story I was telling about the pending devastation of the Earth as a "dark visitor" (probably a small black hole) passed thru the solar system but 12 times farther away Earth than the sun.

Other parts of Chapert 5 mention that Columbus first sailed South because he knew of the steady strong winds towards the west (called the "trade winds" later as that is what the trading ships did too to reach the new world quickly.) Other parts of Chapter 5 also use the same approach but now with North moving air to help the US reader understand why his weather strongly tends to come out of the west (winds moving east). -I.e the air mass that was in the south is moving faster eastward than the land under it (opposite conditions from the Lisbon air mass heading south and turning westward.) etc. Physcs can be simple, easy to understand, even fun to learn, if taught well. BUT WHEN MAKING IT SIMPLE, PLEASE DO NOT MAKE IT WRONG.

No questions. -just two corrections:

(1) not a whole book required. I do it in Chaper 5 of my book, Dark Visitor

(2) you missunderstand much by neglect of the dominate effect. Quoting from Chapter5:

" The “force” that causes north or south moving masses of air or water to be deflected sideways (the clockwise turning in the Northern Hemisphere just discussed)* is called the Coriolis force, after the French engineer Gaspard Coriolis who explained to Napoleon why his long-range cannon fire was always falling a little to the right of the target if the target was north or south of the gun, but was “on target” if the gun was aimed either east or west. The Coriolis force is not a true force, only the effect of a spinning spherical earth. "


*here is the "just dicussed" text it refers to:

" At the equator, both the land and the air are moving at about 1000 miles per hour, if seen from the moon (or any other point traveling through space with the earth). This is because at the equator it is approximately 24,000 miles around the earth and the air must go around in 24 hours. ...
At Lisbon's latitude the distance around the earth is only about 3/4 the circumference of the equator, so there the air is only moving at 750 miles per hour to go around with Lisbon in 24 hours. If you could instantly move a big chunk of this Lisbon air to the equator, the earth would be running under it so fast that the wind would come out of the East at 250 miles per hour. ...Thus as Lisbon's air moves south, it tends to head west also as it is not going around the earth fast enough to keep up with the land (or ocean) spinning under it. By the time this air from Lisbon gets near the equator, it is mainly moving towards the West as seen from the deck of a ship in the tropical ocean. On its trip southward, this air mass gained most of equatorial speed from friction with the surface – making steady winds towards the west, not 250 mile / hour gales!
Local weather phenomena such as warm clouds rising and cold air descending tend to keep the lower parts of the tropical atmosphere mixed and all moving towards the west, at least as the air mass moves west from Africa, but recall from the non-spinning earth model, this warmer air must also tend to go towards the poles to replace the air which is going toward the equator. Thus all year long east of the Caribbean region there is a general climatic circulation of air along the path of typical hurricanes - westward from Africa but turning northward. "

The reader I was trying to reach with my book would never intentionally open a book on physic, so I disguised lots of physics in simple terms anyone could understand. I did give the name of this effect of Earth's rotation, but never called Kepler's three laws their names. like the above, I only explained them in simple terms so any one could understand and used all three smoothly as part of the story I was telling about the pending devastation of the Earth as a "dark visitor" (probably a small black hole) passed thru the solar system but 12 times farther away Earth than the sun.

Sorry, Billy, but you have some common factual errors there. And indeed, it does require more than one chapter in a book to cover it in proper detail. Not to worry, though, I have no intention of going into that much depth here - meteorology books are readily available for anyone who wants the FULL story.

However, the mistakes you just made are the same/similar that Fraggle made in another thread. Here is a copy/paste of my reply about those misunderstandings:

Fraggle, I cannot tell for sure but I think you've fallen in the trap of a very common misconception. For instance, your first paragraph about water and air moving in the opposite direction of the Earth's rotation is a fallacy. The jet streams move from West to East in BOTH hemispheres. And the warm water in the Gulf Stream moves from Southwest to Northeast - you will note that all of that is moving in exactly the same direction that the Earth is rotating - West to East.

If the world was a perfectly smooth sphere and nothing impeded the flow, warm air and water would flow directly North. And cold air and water would flow directly South. But the surface is irregular so that those currents cannot just follow their "natural" heat-driven path.

Now... the Coriolis effect does come into play in the case of the jet streams. And there are boundaries that keep them more or less in place. The primary factors that determine their location are called "hydrostatic" and "geostropic." The latter is the one in which the Coriolis force is a factor. They also meander North and South by what is called a Rossby wave.

I won't fault you for it because few people study such things in college (I did mine years ago) and it's all covered in Meteorology-102.

Sorry, Billy, but you have some common factual errors there. ...Fraggle, I cannot tell for sure but I think you've fallen in the trap of a very common misconception. For instance, your first paragraph about water and air moving in the opposite direction of the Earth's rotation is a fallacy. The jet streams move from West to East in BOTH hemispheres....No. I have no such error. You are falsely assuming that I think the circulation is different in the southern hemisphere. I agree and say same in the book that the near polar latitiudes have jet streams are flowing from West to East. They are driven by the Coriolis loops at more moderate latitudes. To give the same sort of example as my Lisbon air mass. Consider some air mass initially south of the equator that is also moving with the surface of the earth at about 1000 mph. When it get down to Sao Paulo, where the distance around the Earth is about 75% of that at the equator it is going too fast Eastward so to a ground based observer, it is a wind coming out of the west SAME AS IN THE USA. In both hemispheres, these winds out of the west at higher latitudes drag the lower level circulation westward all the way around the poles. The full story is more complicated than I care to go into here as at higher altitudes the speed are much higher, but the directions of jets streams is the same out of the west towards the east for the Coriolis reason I have explained and you completely fail to even mention this true cause, falsely saying it is due the the mountains etc.

On all planets which rotate on an axis roughly perpendicular to the ecliptic plane (I think., by memory, that Neptune is the only one that does not) with or without mountains, near their equator the wind blows in the opposite direction to the rotation because seen from outside the planet, it is not moving as fast as the land under it rotates. Likewise without any mountains or surface irregularities at about 60 degrees north and south the warmer air that is trying to go towards the poles is moving too fast (still, due to inertia, has the speed corresponding to a more equatorial location) and to the land based observer appears to be going in the same direction as the rotation as a wind.

You simply have the cause WRONG. This universals fact of planet's atmospheres is caused by the Coriolis Effect, not the surface roughness/ mountains as you falsely state. Make sure you understand before you falsely inform others.

PS I have not read Fraggle's post, but bet you simply did not understand him also. That is often the case when one uses terms like clockwise rotation in different hemisphere because the very same rotation can be called clockwise one hemisphere and counter clockwise in the other. To see this clearly look at the sweep second hand of your wrist watch (or a wall clock if yours is only digital) it is clockwise. Now flip the watch over / upside down so a person in the other hemisphere could see it if the Earth were transparent. He would say the sweep second hand is going around clockwise but now you label that rotation as counter clockwise. This explains why people sometimes say the water drained form the tub clock wise in one hemisphere and counter clock wise in the other but in fact view from the moon both are turning the same way as are the Coriolis wind circulations. I bet Fraggle used terms like clock wise and you simple did not understand correctly that the same circulation does have the names switched as you move from one hemisphere to the other.

...Now... the Coriolis effect does come into play in the case of the jet streams. And there are boundaries that keep them more or less in place. ...You have this ENTIRELY WRONG ALSO !! To the extent that the jet stream stays at the same latitude there is ZERO Coriolis force on it! Read my explanation of the Coriolis effect until you understand what you are talking about. It arises only when something is changing latitude. For example it did not bend the trajectory of Napoleon's cannon fire if it was a shot to the East or to the West (like the jets stream) - only when the target was North or South of the gun. That was what puzzled Napoleon and, again quoting from my book it was: "French engineer Gaspard Coriolis who explained to Napoleon why his long-range cannon fire was always falling a little to the right of the target if the target was north or south of the gun, but was “on target” if the gun was aimed either east or west."

No. I have no such error. You are falsely assuming that I think the circulation is different in the southern hemisphere. I agree and say same in the book that the near polar latitiudes have jet streams are flowing from West to East. They are driven by the Coriolis loops at more moderate latitudes. To give the same sort of example as my Lisbon air mass. Consider some air mass initially south of the equator that is also moving with the surface of the earth at about 1000 mph. When it get down to Sao Paulo, where the distance around the Earth is about 75% of that at the equator it is going too fast Eastward so to a ground based observer, it is a wind coming out of the west SAME AS IN THE USA. In both hemispheres, these winds out of the west at higher latitudes drag the lower level circulation westward all the way around the poles. The full story is more complicated than I care to go into here as at higher altitudes the speed are much higher, but the directions of jets streams is the same out of the west towards the east for the Coriolis reason I have explained and you completely fail to even mention this true cause, falsely saying it is due the the mountains etc.

On all planets which rotate on an axis roughly perpendicular to the ecliptic plane (I think., by memory, that Neptune is the only one that does not) with or without mountains, near their equator the wind blows in the opposite direction to the rotation because seen from outside the planet, it is not moving as fast as the land under it rotates. Likewise without any mountains or surface irregularities at about 60 degrees north and south the warmer air that is trying to go towards the poles is moving too fast (still, due to inertia, has the speed corresponding to a more equatorial location) and to the land based observer appears to be going in the same direction as the rotation as a wind.

You simply have the cause WRONG. This universals fact of planet's atmospheres is caused by the Coriolis Effect, not the surface roughness/ mountains as you falsely state. Make sure you understand before you falsely inform others.

PS I have not read Fraggle's post, but bet you simply did not understand him also. That is often the case when one uses terms like clockwise rotation in different hemisphere because the very same rotation can be called clockwise one hemisphere and counter clockwise in the other. To see this clearly look at the sweep second hand of your wrist watch (or a wall clock if yours is only digital) it is clockwise. Now flip the watch over / upside down so a person in the other hemisphere could see it if the Earth were transparent. He would say the sweep second hand is going around clockwise but now you label that rotation as counter clockwise. This explains why people sometimes say the water drained form the tub clock wise in one hemisphere and counter clock wise in the other but in fact view from the moon both are turning the same way as are the Coriolis wind circulations. I bet Fraggle used terms like clock wise and you simple did not understand correctly that the same circulation does have the names switched as you move from one hemisphere to the other.

You have this ENTIRELY WRONG ALSO !! To the extent that the jet stream stays at the same latitude there is ZERO Coriolis force on it! Read my explanation of the Coriolis effect until you understand what you are talking about. It arises only when something is changing latitude. For example it did not bend the trajectory of Napoleon's cannon fire if it was a shot to the East or to the West (like the jets stream) - only when the target was North or South of the gun. That was what puzzled Napoleon and, again quoting from my book it was: "French engineer Gaspard Coriolis who explained to Napoleon why his long-range cannon fire was always falling a little to the right of the target if the target was north or south of the gun, but was “on target” if the gun was aimed either east or west."

Billy, you have gotten yourself both confused AND highly emotional. Some of what you say is absolutely correct but you have also made errors.

But, just as I have in the past for the same reason, once you become this emotionally charged (!!!!) I have no desire to speak with you further. I'll also allow you to have the last word but offer one caution: while you are gnashing your teeth, be careful you don't injure them or yourself in the process. At your age (and mine) it's not fun to get replacements.

Billy, ... Some of what you say is absolutely correct but you have also made errors. ...Please tell me specifically what error I have posted. I was very specific in pointing out your errors. Please do the same for me. I.e. quote my erroneous text, as I did yours, and then explain why it is wrong, as I did for you.