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Stevenson Screen

Stevenson screen is a shelter specially designed for protecting weather instruments from sun rays and other natural heat radiations while allowing free flow of air. It is also known as Instrument Shelter. Stevenson screen comprise of a wooden box fitted into a steel frame. The wooden frame is usually painted white and is buried 1-2 m above ground. A British civil engineer Thomas Stevenson designed the first Stevenson screen in 1818.

The interior size of the Stevenson screen increases and decreases depending on the number of instruments that is to be installed inside. A single screen measures approximately 30.1in x 24in x 23.3in, and a double screen 30.1in x 41.3in x 23.3in.

Stevenson Screen Structure:

It is a wooden box painted in white. White is a natural reflector, so it does not allow heat to penetrate inside the box.
To ensure free air flow inside, the four sides of the box has doubled louver.
There is an opening between the roof and the sides that allow free air circulation.
The slightly tilted roof allows rain water to flow down.
The Stevenson screen in the Southern hemisphere is always faced to the south to avoid direct sunlight.
It is placed 1-2 m above the ground. This is the standard level for surface temperature observations.

The Stevenson screen is designed in such a way that it can hold various kinds of weather instruments. Thermometers, hygrometers, psychrometers, barometers, dewcells, etc. are some of the instruments that can be fitted into a Stevenson screen.