National Physical Laboratory

Where can I get similar barometric pressure data for other parts of the UK? (FAQ - Pressure)

To the best of our knowledge, the NPL on-line barograph is unique inasmuch as it provides a fully traceable pressure measurement, with a properly calculated uncertainty. If you know of any other websites providing such data or run such a site and would like us to add a link, please contact us by email.

There are, of course, many sites showing general weather-related data including some pressure information.

Whenever using such values of atmospheric pressure, if accuracy is important, users should take their own steps to establish the relevant measurement uncertainty associated with them (notwithstanding the fact that differences in altitude and distance from the sensor, and weather conditions, may seriously limit the validity of using them to set a barometer - see final paragraph of on-line barograph notes). Atmospheric pressure data is rarely ascribed a clear measurement uncertainty and, where a figure is given, it can relate rather optimistically to the sensor manufacturers' specification sheet rather than a realistic in-service uncertainty determined from a long-term calibration history of the sensor.

As mentioned above, even state-of-the-art sensors, such as those used in the NPL on-line barograph, can change characteristics substantially more than suggested by the 'headline' numbers on their specification sheets. Despite being calibrated periodically against the UK's National Standard Barometer (a primary instrument that is capable of providing an uncertainty in the measurement better than ±0.004 hPa) the sensors in the barograph are ascribed an uncertainty in the measurement of ±0.3 hPa - considerably greater (worse). It is interesting to note that some sources of atmospheric pressure imply better accuracies than this with less capable sensors and with significantly less effort put into calibrating them and correcting their readings; in practise it would be wise to be particularly wary of accuracy claims for this type of data that are better than about ±0.5 hPa. It is not uncommon for uncalibrated or infrequently calibrated barometers (whether mercury or electronic, new or old) to be in error by several hectopascals (millibar).

Last Updated: 14 Jun 2018
Created: 9 Aug 2007


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