Stevenson screen

A shelter for meteorological instruments, particularly thermometers, providing protection from solar radiation. It is a white, wooden box with louvred sides to give ventilation. The thermometers within the screen should be 1·25 m/4·1 ft above the ground to avoid strong temperature gradients at ground level, and to give comparability from screen to screen. It was invented by Thomas Stevenson (1818–87), the father of Robert Louis Stevenson.

A Stevenson screen or Instrument shelter is a meteorological screen to shield instruments against precipitation and direct heat radiation from outside sources, while still allowing air to circulate freely around them. The Stevenson screen is usually designed to hold various instruments including thermometers (ordinary, maximum and minimum), a hygrometer, a dewcell, a psychrometer, a barometer and a thermograph.

The traditional Stevenson screen is a box shape, constructed of wood, in a double-louvered design.

The interior size of the screen will depend on the number of instruments that are to be used. A single screen may measure 765 mm high by 610 mm wide by 593 mm deep (30.1 in by 24.0 in by 23.3 in) and a double screen 765 mm high by 1050 mm wide x 593 mm deep (30.1 in by 41.3 in by 23.3 in).

The top of the screen was originally comprised of two asbestos boards with an air space between them.

The siting of the screen is very important to minimise the effects of buildings and trees.

The use of a standard screen allows temperatures to be compared accurately with those measured in earlier years and at different places.

In some areas the use of single unit automatic weather stations are supplanting the traditional Stevenson screen (and other stand-alone meteorological equipment).

Stevenson screens may also be known as a cotton region shelter, an instrument shelter, a thermometer shelter, a thermoscreen or a thermometer screen.

A special type of Stevenson screen with an eye on the roof is designed to be used on ship.

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