if you have ever bought a new or antique barometer and needed some information on how toset it up, adjust, or just ensure it works accurately, so that you can create you own weather forecasts then why not follow these simple steps?
What do they do?
It doesn’t matter whether you own a pocket barometer, desk barometer, or a barometer that is fixed to your wall, essentially they simply measure air pressure – expressed in millibars or inches. If you have an aneroid barometer this will display the reading by means of dial and a needle, as opposed to a mercury barometer which uses the height of liquid mercury within a glass tube. Since changes in air pressure accompany changing weather, these instruments can be used to help forecast local weather some 24-48 hours in advance.
Set up for altitude
Additionally changes that are associated with weather patterns means barometric pressure also changes with altitude –decreasing the higher you are situated. Aneroid barometer movements are generally set at from production in order to give the correct reading at sea level (the standard measurement point). This may not be the case as far as antique barometers are concerned however. In addition if the barometer is to be mounted above sea level – i.e. for most domestic use – it is required to adjust your barometer as a result of this.
Obtain an accurate pressure reading from the nearest weather or meteorological station. In theUKthis can be achieved by dialling 0870 900 0100 (local call rate), or+44 1392 885 680from overseas. This is a point of contact for the main Met Office Headquarters in Exeter, which has a very obliging customer care centre. Alternatively you can pay a visit to their website atwww.metoffice.gov.uk.
Once you have established the accurate pressure for your location you should use a small screwdriver, to adjust the screw on the back of the movement turning until the adjusted needle indicates fittingly.
Creating a weather forecast
The notes on the barometer face (RAIN, CHANGE etc) are broad indications and less important than the actual pressure change. Regular observation will quickly lead to a greaterunderstanding of weather patterns.Generally:
–Increasing Pressure(movement of the needle in a clockwise direction) suggests improving weather, associated with a HIGH or “anti-cyclonic” pressure system.
– Decreasing Pressure(movement of the needle in an anti-clockwise direction) suggests deteriorating weather, associated with a LOW or “cyclonic” pressure system.
–Steady Pressure, typical of extended fine weather periods, suggests more of the same.
To observe the trend, the movable pointer is turned so that it sits directly above the barometer needle. Later (perhaps 6 hours for an easily-identifiable change), the barometer glass is tapped gently and the direction of movement of the needle noted.