I have mentioned my mercury barometer in a previous post, but it is not the only instrument in town. The Fisherman’s Monument at the old (Cromwell) harbour was built to provide a public barometer for the benefit of the local fishing fleet. (For more details see here and here.)
The monument has undergone at least one renovation; the barometer currently in it is not the original. (The original instrument was recorded as missing in 1996 ; the monument was renovated in that year and I suspect the current barometer dates to that renovation.)
A nearby information board claims that the barometer does not work; this statement has bothered me for a while because you can see the top of the mercury column in its glass tube at a credible point on the scale.
If the mercury column is visible it is hard to see how the instrument could fail to be working, but to be certain I needed some data. I therefore collected a few pairs of measurements from the Fisherman’s Monument barometer and my own instrument, separated in time only by the few minutes that it takes me to walk to the harbour from my house. Getting a good spread of values was made easier by the arrival of Storm Éowyn, even though the very centre of the storm did not pass over Dunbar. The highest pressure was recorded during a period of unusually settled weather late in 2024.
It is clear from a quick plot of the raw data that the two barometers are both responding to changes in pressure in the same way, and that there is a bias between them of about 0.3 inHg (inches of mercury). However, I knew that my own barometer was not exactly correct (as per my earlier post). I therefore converted all the readings from inHg to hPa and corrected the readings from my own instrument to match the values that I eyeballed from the Met Office pressure charts.
The corrected points (blue) are a bit closer to the readings from the Fisherman’s Monument barometer, the average difference is about 6 hPa, or almost 0.2 inHg. So if you are visiting the harbour you can go and read the pressure from the barometer; you just need to add 0.2 inHg if you want an unbiased reading.