Does air pressure really affect weather?
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It's often said: "Low pressure brings cloudy weather, high pressure brings clear weather."
But when I see weather maps, this is not true. What do you think about that?
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@vujacicm Here is also interesting thing, where cyclon has 1031hPa value.
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@vujacicm
At location shown, pressure (although seems high) is relatively lower than the surrounding.
Imagine a pond on a mountain! -
So, this mean, that when I use air pressure to track the weather, the most important is air pressure compare to surrouding, not the value?
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š Yes.
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@Caefix Here is something, there is very difficult to understand.
Here is pressure area for Pacific
Temperature over Pacific
Humidity over Pacific
Why here is difference in pressure, but not in temperature and humidity?
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@Caefix 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?
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@vujacicm Pressure modifies the conditions of the climate-zones. ItĀ“s not converting arctic to tropic or vice versa.
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@vujacicm
It is more complicated than you think.
Donāt forget to take the Sun into account, which plays a very significant role. It rises only a few degrees above horizon.
Hence different temperatures. -
@dariusmil Probablly here is are air density in game. Troposphere is higher near the equator then near the poles. Pressure is the same, but volume is different.
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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.
Letās 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 canāt 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, thatās right. It is what I said more simply : Heating a gas, it expands.
Your question was ā 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? ā
Hope itās 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.
