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.
Stephen Burt
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.
By convention, weather measurements throughout the world are made to a common time standard – Coordinated Universal Time (UTC). For all practical purposes, UTC is identical to Greenwich Mean Time (GMT).
Snowfall is difficult to measure accurately with most types of raingauge, and without some form of wind shield most raingauges will lose 50 per cent or more of the ‘true’ catch through wind errors introduced by the presence of the gauge, which interferes with the flow of the wind over it, causing a loss of some of the catch.
Terminal hours based around ‘day maximum’ and ‘night minimum’ temperatures (where the extremes span only 12 hour periods) will generally give results which are incompatible with ‘24 hour’ sites, particularly in temperate latitudes in the winter months.
The most common measurements made are of sunshine duration, using a sunshine recorder, and global solar radiation on a horizontal surface, using a pyranometer. ‘Sunshine’ is defined in terms of the intensity of a perpendicular beam of solar radiation from the solar disk. The intensity of solar radiation is measured in Watts per square metre (W/m2), and daily totals in Megajoules per square metre (MJ/m2). Sunshine durations are measured in hours, or quoted as a percentage of the maximum possible duration.
