Stevenson screen / weather shelter

A small wooden hut, also called a meteorological shelter, intended to house part of an observatory's meteorological instruments, in order to protect them from exposure to direct sunlight, thus preventing them from being left outdoors and thereby ensuring reliable records. The screen approved by the World Meteorological Organization is the Stevenson type, of which several models exist. Painted white, its walls and doors are not smooth but of double-louvered construction, which allows ventilation inside, thus avoiding undesired artificial overheating or cooling of the air. The instruments it usually contains are maximum and minimum thermometers, the psychrometer, a thermohygrograph, and a Piche evaporimeter. All that instrumentation must be located at a height of one and a half meters above the ground, for which the base of the shelter rests on four legs of appropriate length. The access door (in the larger models there are two) is placed on the wall of the hut facing north or south, depending on the terrestrial hemisphere it is located in, to prevent sunlight from striking the instruments directly when it is opened.