Stevenson screen is a rectangular box made up of wood, colored white, and has a standard height of 4 ft above the ground. Meteorological thermometers are placed inside it to get standard temperatures according to WMO standards. Stevenson screen is used to measure the air temperature at the height of 4 ft above the ground and it is usually located in a weather observatory. It is a simple and inexpensive way to measure the air temperature in a given area. Stevenson screen is also used to measure the humidity of the air.
As we know Stevenson screen is one of the important weather station equipment. These are being used for a long time. Nowadays modern methods of measurement of weather parameters are also being used but these primitive methods have their own significance and reliability. Stevenson screen has many characteristics. Here are the 5 most important characteristics of a Stevenson screen:
Standard White Colour of Stevenson Screen:
Stevenson screen is painted white as a standard color. It is painted white so that it reflects sunshine to provide thermometers with standard environmental conditions. This white color screen is the best color for all weather and climate conditions. White color has its own unique features and properties. As we know that sunlight is a combination of different colors. Any object that is white reflects the sunlight. The white color of the stevenson screen is doing the same function. Suppose it is painted black then it absorbs all the light energy and hence there would be many possibilities of error in meteorological parameters that are to be measured inside the Stevenson screen.
Height and Size of Stevenson Screen:
The standard size of the Stevenson screen is a single screen 76.5 by 61 by 59.3 cm (30.1 by 24.0 by 23.3 in) and a double screen 76.5 by 105 by 59.3 cm (30.1 by 41.3 by 23.3 in). The standard height is set as a standard because there would be variations of different weather patterns at different height levels.
Double-louvered design of Stevenson Screen:
The double louvered design of Stevenson Screen is unique and enhances airflow and ventilation. The louvers also help to prevent insects and other pests from entering the screen. The louvers help to keep the screen clean and free of dust and dirt. The louvers are designed to provide a smooth flow of air. The structure of Stevenson screen is designed to get accurate temperatures from thermometers placed inside it. The structure and other characteristics are proposed after considering all the environmental impacts that have to take into account all around the world.
Double Roof of Stevenson Screen:
Stevenson screen has a double-layered roof. It is double-layered to reflect sunlight hitting directly on the screen. Both layers are attached to each other. This type of roof is very durable. This type of roof is a bit expensive. Aesthetically, the double-layered roof looks beautiful. As we know that double room provides insulation from the surroundings. The roof of stevenson screen has insulting characteristics from the direct sunlight.
Legs of Metal or Treated Wood
Stevenson screen legs are made up of metal or treated wood to prevent damage. The legs are made from a durable and attractive material that will last for years. The legs have a heavy base and are built to be sturdy. The lowest part i.e the legs are in direct contact with the ground. They are more prone to external environmental factors. It is necessary to protect the legs of the Stevenson screen from external environmental factors for its durability and longer life.
WMO Standards For Stevenson Screen.
Besides the construction standards of Stevenson screen, there are other environmental factors that must be kept in mind. The area where the Stevenson screen is being installed should have proper ground clearance and no tall buildings or hurdles in front of it. Stevenson screen is always mounted in the open air. It is not placed indoors.
In conclusion, a Stevenson screen is a very useful tool to use in the weather observation process. It is a great way to quickly get a feel for the current weather situation in a region. These play a vital role in weather observatories. weather observers need to record the standard temperature. Standard temperature can only be obtained in standard conditions. Probably if a thermometer measure temperature inside a building it will be different when it is placed on the ground. It is inevitable to have such standards and necessary conditions which are to be kept in mind while taking accurate measurements of temperature. Stevenson screen solves this problem and provides worldwide accepted WMO standards for accurate standard temperature measurements. WMO is an international organization. It issues special guidelines for all weather-related protocols.
If you are a meteorology aspirant or interested in met equipment and other weather phenomena then a local weather observatory is must visit place for you. In the weather observatory, you can find stevenson screen and all other met instruments. If you visit a met observatory and practically observe stevenson screen you will better get an understanding of the facts and characteristics of stevenson screen.