This site provides useful practical information related to global and national weather observing practices and instruments, including independent equipment reviews.
You will find much of the background in my book The Weather Observer’s Handbook (published by Cambridge University Press), details of which can also be found on this site, together with useful links and downloads.
Author, The Weather Observer’s Handbook
A nation obsessed with the weather? Yes, certainly, but which nation?
Tip of The Day
The traditional method of measuring humidity is by using a pair of matched mercury-in-glass thermometers, known individually as dry-bulb and wet-bulb thermometers and in combination as a dry- and wet-bulb psychrometer. The wet-bulb is a thermometer whose bulb is kept permanently wet using a thin close-fitting cotton cap or sleeve. The wet-bulb is cooled by evaporation, and the difference in temperature between dry-bulb and wet-bulb thermometers is a measure of the humidity of the air. Using tables, an online calculator or formulae, the relative humidity (or any of the other humidity measures) can be quickly and easily determined from simultaneous readings of the two thermometers.
Earth temperatures are most frequently measured at depths of 5, 10, 20, 30, 50 and 100 cm below ground level. Measurements at 30 cm or deeper are normally made under a grass surface, while the shallower depths are measured under a bare soil plot. Both should remain fully exposed to sunshine, wind and rainfall.
Recording raingauges can be easily and accurately calibrated by passing a known volume of water through the gauge, and comparing with the indicated measurement. ‘Out of the box’ errors for some AWS tipping-bucket raingauges of this type can exceed 20 per cent, so this is a vital test for all new instruments at first installation. Recording raingauges should not be adjusted merely to attempt exact agreement, or near-agreement, with a standard raingauge, because instrumental and exposure differences inevitably lead to slight variations in the amount of rainfall recorded.
Most national weather services welcome and encourage the contribution of weather observations made by private individuals or organizations, as these provide a richer network of observing points to supplement the wider spacing of professional observing networks. For more than 120 years in the United States, the Cooperative Observer Program has proven itself as a cost-effective method in weather data collection, and currently administers about 11,000 observing sites. The Australian Bureau of Meteorology oversees in excess of 6,000 rainfall stations across the continent.
Most manual raingauges are read once daily, usually at a standard morning observation time, typically between 7 A.M. and 9 A.M. local time. The morning reading should be ‘thrown back’ to the previous day’s date.