While it's a common misconception, there's no official requirement for a Stevenson screen to face north. The primary purpose of a Stevenson screen is to provide a shaded, ventilated, and protected environment for weather instruments.
Here's why the north facing is often seen:
* Sunlight: The screen's louvered design allows for air circulation while blocking direct sunlight. Placing the screen facing north in the Northern Hemisphere minimizes direct sunlight during the hottest hours of the day.
* Wind: Facing north often provides some protection from prevailing winds, which can affect temperature readings.
* Tradition: Historically, Stevenson screens were often placed facing north, and this practice has become a bit of a convention.
However, optimal placement depends on the local environment and the prevailing weather conditions. In some cases, facing east, south, or even west might be more beneficial. Ultimately, the most important factor is ensuring the screen provides a consistent and accurate measurement environment.