[PDF Notes] Brief notes on the Variations in Air Pressure and Weather

The air pressure recorded at different weather stations shows a marked variation – a fact that is of great significance in the analysis of weather conditions. As noted earlier, the standard sea level pressure is 1013.25 mb.

But the pressure changes from day to day and from time to time, and is never static. If we consider the sea level pressure observed over the entire earth, it will be seen that it varies from about 982 mb to 1033 mb.

The highest sea level pressure ever recorded was at Irkutsk in Siberia on 14 January, 1893, where the observed pressure was 1075.2 mb. The lowest sea-level pressure ever recorded was observed in the eye of a very destructive typhoon that visited Mariana Islands. The pressure was abnormally low (877 mb) there.

All the weather changes are closely related to pressure variations. It is customary to believe that high values of air pressure produce clear and stable weather, while low atmospheric pressure brings in bad weather.

However, it would be more logical to generalize that a continually rising air pressure is an indication of fine and settled weather, and a steadily falling tendency in the barometer foretells the advent of unsettled and cloudy weather.

In other words, despite the fact that air pressure is closely tied to various weather phenomena it is true that the weather at a particular station is largely controlled more by the pressure in adjoining areas, rather than the actual pressure recorded over there.

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