Does air pressure really affect weather?
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@vujacicm said in Does air pressure really affect weather?:
Does not mean that higher is pressure, lower will be temperature?
There is not a direct relationship between pressure and temperature at ground level.
Let’s take 2 examples:
In winter the Siberian anticyclone brings very high pressure and low temperatures. This thermal anticyclone is the consequence of accumulation of very cold air. The cold air is denser and it increases the air pressure.
At the opposite the Azores anticyclone is due to the air sinking in the north part of the Hadley cell. It is a dynamical anticyclone and the sinking air is compressing and increasing the temperature when reaching the surface. When you compress a gas you produce heat.
So, you can’t say high pressure = cold air
In addition the temperature is not the same in all areas of an anticyclone. In this example not uniform in the vicinity of the High because the temperature at surface level is depending on the Sea temperature.
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@idefix37 You are right. If high pressure = cold temperature, then isobars = isotermal. But because this is not the case, then this not right.
Maybe high pressure = low temperature + high adiabatic process.
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@idefix37 I think I found answear. Pressure in poles and subtropics is the same, but height is different. Here is reason, why same pressure, but different temperature.
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@vujacicm
The average thickness of the troposphere is greater in tropical areas because the average temperature is higher than in polar areas. Heating a gas, it expands.
The temperature difference between the intertropical zones and the polar zones is due to the angle that the sun makes to the surface of the globe, and consequently the Watts per m2. Nothing else. -
@idefix37 What about this law? If pressure is the same and temperature increase. Then volume change.
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@vujacicm
Yes, that’s right. It is what I said more simply : Heating a gas, it expands.
Your question was “ I still can not understand, how north pole and Pacific have the same pressure, but different temperature? Does not mean that higher is pressure, lower will be temperature? “
Hope it’s clear now. -
@idefix37 So we can say like this:
Polar high:
- high pressure
- low temperature
- low troposphere
Subtropical high:
- high pressure-
- high temperature
- high troposphere
So, temperature and height of troposphere is different.
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@vujacicm said in Does air pressure really affect weather?:
So, temperature and height of troposphere is different.
I would better say :
At global scale, the higher the temperature is, the higher is the troposphere. -
@idefix37 Perfect. Now I finally understand, why 2 high pressure areas have different temperature.
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@idefix37 I found something very good, that can explain easilly
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🌓 🌍 🌞 https://en.wikipedia.org/wiki/Season
The troposphere gets it´s discus-shape mainly through the centrifugal force caused by Earth´s rotation.
If the line of equatorial clouds (= the centre of Intertropical Convergence Zone (ITCZ)) would follow the seasons, it should be expected closer to the locations of Cuba, Emirates, Taiwan in N-summer and Rio de Janero, Madagaskar - Fidschi in N-winter. -
@Caefix This doesn't seem right.
The troposphere is thicker at the equator due to solar input being greater than the solar input at the poles. @vujacicm diagram shows it - as you increase temperature the air expands taking up more space. As you decrease temperature the air contracts taking up less space.The tilt of the Earth and it's orbit around the Sun are what determine where that solar input is most concentrated.
Thermodynamically, that warm air at the equator NEEDS to make it's way to the colder poles.
The Coriolis Force (Earth's rotational force) helps determine the direction that equatorial air moves as it makes it's way to the poles. -
@Wheats There´s also a vector of acceleration towards the equator balancing a centripetal vector of gravitation sucking back towards the polar vortex. Both are constants depending on latitude affecting the flow.
Equatorial radius
6378.137 km (3963.191 mi)
Polar radius
6356.752 km (3949.903 mi) https://en.wikipedia.org/wiki/EarthThe centrifugal force even flattens the massive globe, how could oceans and atmosphere not be affected?
It´s just thermo-dynamic embedded in the dynamics of the rotating system. -
@Wheats If I am right, then if temperature drops together with volume, then moisture will not increase. Is here then the answear, why all high pressure areas are dry, no matter of temperature?
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@Caefix I found another thing, which is maybe very important. Different between adiabatic and isothermic. Adiabatic change pressure, isoterhmal change volume. Maybe here we can see more clear picture.
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@Caefix Adiabatic process works in vertical way, but not in horizontal. There is isoterhmal process. The subtropics have the same pressure like polar poles, but different temperature. There process can only be isothermall. This is main difference.
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@vujacicm Sometimes vertical way is blocked...
🏭🌫 https://en.wikipedia.org/wiki/Inversion_(meteorology)
https://en.wikipedia.org/wiki/Fog
https://en.wikipedia.org/wiki/Cumulonimbus_cloud ⛈ -
@Wheats I think that now understand better subtropics then before. I though that desert is made because skies are clear and they rich a lot of sun. Now I see that this is not reason. Hadley cell is actually heat engine. It brings hot air from tropics to subtropics. When air reach higher troposphere, temperature drops, not heat. So heat is actually transformed like radiators in house. That's the reason, why desets are hot. In case of oceans, heat is taken by water and there temperatures are not high like in desets.
The similar story is in polar cell. Polar cell is also heat engine. But when air reach the ground, all the heat is absorbed by ice.
In Ferrell cell is simillar, only difference is that heat is going to north by ground, not by high troposphere.
If I am not right, please fix me.
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Global circulation cells play a big roll in climate areas on Earth.
You're forgetting about moisture though - lack of moisture is the reason Deserts exist. Technically, Antarctica is a desert. But lack of moisture in subtropical desert areas can be caused by the Hadley cell that circulates warm moist air at the equator northward and southward.As the warm moist air at the equator rises it expands, cools and condenses - forming clouds and eventually precipitation...This does a few things - causes low pressure, addition of water vapour to an airmass (from the ocean in this case) will actually make the air less dense, along with the increase in temperature, the air becomes more buoyant and rises - this air is destined to rise and rain itself out. As this air moves aloft (northward and southward) it eventually becomes cool enough and dry enough where it sinks towards the Earth's surface and that's essentially where you find your subtropical deserts on continents.
So the Hadley cell moves that warm (because of direct heating) equator air towards the poles.
The Polar cell moves that cold (because of lack of heating) polar air towards the equator.
and the Ferrel Cell is the in-between that helps get it all to where it wants to go.But this is just an overall look at Global circulation cells - there is a crazy amount going on in the Earth's atmosphere, oceans, and land, and if you are interested in learning more about it I would suggest taking a class or doing some online courses.
These are two resources I used quite a lot before I actually went to school for this madness lol:
https://www.meted.ucar.edu/index.php
http://www.theweatherprediction.com/Read up and then please, correct me if I'm wrong!
