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Changes in Atmospheric Pressure

  • 07-08-2023 9:34am
    Registered Users Posts: 678 ✭✭✭

    I have observed two different events, both very different in values yet causing similar effects.

    I do understand the chart with a severe low of 981 Pa causing "tight isobars" however the other attach indicates a similar effect with a modest low of 1001 Pa. Can you explain this in a manner I can follow please.


  • Registered Users Posts: 10,843 ✭✭✭✭Furze99

    If you referring to the spacing/ tightness of isobars, then it's all relative to the air pressure in the surrounding region. In both cases here there is a substantial gradient.

    Think of a steep hill - you can have a very steep slope at sea level. You can also have a very steep slope near the top of say Mount Everest. It doesn't matter that one is near sea level and the other at 8000 metres.

  • Moderators, Home & Garden Moderators, Science, Health & Environment Moderators Posts: 17,858 Mod ✭✭✭✭DOCARCH

    It's not really the actual pressure values themselves that cause it to be windy or not, it's the difference in pressure over distance that causes it. What's called the gradient. Very similar to contours on a map.

    So, an area of higher pressure closer to an area of lower pressure will cause it to be winder than an area of higher pressure further away from an area of lower pressure.

    Quite often the actual pressure value is irrelevant as you it can be windy with high pressure (if there is higher pressure nearby) and it can be calm with low pressure (if there is higher pressure further away).

  • Registered Users Posts: 678 ✭✭✭mrtom

    Ah, clarity, so a wider map would reveal the proximity of another system that influences the gradient rather than the Pa.

     On a separate point are there any subtle changes we can sense when experiencing a high or low?