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The maximum reading was taken at Aberdeen Observatory and they still have a barometer which was in use during the period the reading was taken (the inscriptions dates it to 1888 and after 1922 it was still in use). It's not a mercury one - mercury is relevant as the article states records go back to 1692, before aneroid barometers were invented, though does ...


17

Mark's answer about mercury barometers is correct - but it is not the complete story. Barometers were initially constructed using water, not mercury, on the manometer principle. Water is lighter than mercury, so a water barometer requires a 10.3m tube. 1mbar is therefore roughly 1cm, and 0.1mbar measurement is clearly trivial using a ruler with 1mm ...


3

How are barometric pressure measurements traceable over centuries to 100 parts per million accuracy? To compare records of barometric temperature, this standard doesn't necessarily have to be met. Recording barometric pressure to 100 parts per million precision has been possible for centuries because it's reasonably trivial to observe movement of the level ...


9

A mercury barometer is a simple, easy-to-build barometer that turns the problem of calibrating a pressure standard into one of calibrating a length standard. Accuracy of length standards has long been a concern of merchants and those regulating them; in 1692, the standard would probably have been a brass prototype yard in the possession of the Royal Society....


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I don't think they are using that level of accuracy for the old readings. Reporting pressure, in hPa, to one decimal place is being done for recent measurements. There are no values given for very old readings. As for the record reading of 1053.6 hPa for 1902, I suspect that is a mathematical conversion of a reading that was most likely recorded in inches ...


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