The Stevenson Screen

 A Stevenson screen or instrument shelter is a shelter or an enclosure used to protect meteorological instruments against precipitation and direct heat radiation from outside sources, while still allowing air to circulate freely around them.

Figure 1.1 shows a Stevenson screen 

Characteristics of the Stevenson screen:

•It has a double roof to help keep out the direct rays of the sun. The roof is also slightly sloped to allow the rainwater to run off.

•The screen is made of wood and painted white to reflect the direct rays of the sun.

•It is placed away from buildings and trees so that it is not standing in the shade.

•The sides are slatted or louvered to allow a gentle flow of air , so that the temperature of moving air can be measured.

•The door must face south so that the direct rays of the sun do not fall on the instruments if the door is open.

•It is raised about 1.2 m off the ground and planted in grass to ensure accurate air temperatures are measured. Grass radiates less heat than soil.

•Inside you will find a barograph or barometer, a wet and dry bulb thermometer and a maximum and minimum thermometer.