Stevenson Screen

The Stevenson Screen or thermometer screen is a standard shelter (from rain, snow and high winds, but also leaves and animals) for meteorological instruments, particularly wet and dry bulb thermometers used to record humidity and air temperature.

It is kept 1.25m/4.1ft (UK standard) above the ground by legs to avoid strong temperature gradients at ground level, has louvred sides to encourage the free passage of air, and is painted white to reflect heat radiation, since what is measured is the temperature of the air in the shade, not of the sunshine.

To allow comparability from screen to screen every aspect of construction and exposure is specified by the World Meteorological Organization. For example, its doors opens towards the pole to minimize disturbance when reading in daylight. Double roof, walls and floor of white-painted wood provide screening, and extensive louvres maintain adequate ventilation on all but the stillest days.

It was invented by the British engineer and meteorologist Sir Thomas Stevenson (1818-1887), the father of Robert Louis Stevenson.

Lessico del tempo