What does a Stevenson screen measure?
Stevenson screens may also be known as a cotton region shelter, an instrument shelter, a thermometer shelter, a thermoscreen, or a thermometer screen. Its purpose is to provide a standardised environment in which to measure temperature, humidity, dewpoint, and atmospheric pressure.
What are the three features of a Stevenson screen?
The Stevenson screen holds instruments that may include thermometers (ordinary, maximum/minimum), a hygrometer, a psychrometer, a dewcell, a barometer and a thermograph. Its purpose is to provide a standardised environment in which to measure temperature, humidity, dewpoint and atmospheric pressure.
What are the characteristics of a Stevenson screen?
Important Features of a Stevenson Screen: The sides and floor are made of louvers or slats to allow free circulation of air and to keep off direct sun rays. It has an insulated roof to create a bad conductor of heat. This is done by creating an air space between the layers of the roof.
How does BOM measure temperature?
The most commonly used thermometer in the Bureau has been the liquid-in-glass thermometer, consisting of a reservoir of liquid (the bulb) and a slim capillary tube through which the liquid rises when warming and descends when cooling.
How are temperature readings taken?
Air temperature is measured with thermometers. Common thermometers consist of a glass rod with a very thin tube in it. The tube contains a liquid that is supplied from a reservoir, or “bulb,” at the base of the thermometer. Sometimes the liquid is mercury, and sometimes it is red-colored alcohol.
Why is the Stevenson screen 1.2 m above the ground?
It is kept 1.25m/4.1ft (UK standard) above the ground by legs to avoid strong temperature gradients at ground level, has louvred sides to encourage the free passage of air, and is painted white to reflect heat radiation, since what is measured is the temperature of the air in the shade, not of the sunshine.
How does a rain gauge measure precipitation?
These gauges work by catching the falling rain in a funnel-shaped collector that is attached to a measuring tube. The area of the collector is 10 times that of the tube; thus, the rain gauge works by magnifying the liquid by a factor of 10.
What is humidity measured in?
Absolute humidity is expressed as either mass of water vapor per volume of moist air (in grams per cubic metre) or as mass of water vapor per mass of dry air (usually in grams per kilogram).