Measuring Weather: Humidity Flashcards
What is humidity?
It’s the amount of water vapour or moisture in the air
What instrument is used to measure humidity?
Hygrometer
What is a hygrometer combination of?
A wet and dry bulb
What does the dry bulb thermometer do?
It measures the temperature of the air
What is the wet bulb like?
It’s covered by a muslin sleeve dipped in water, which keeps it moist. This cools the bulb and the temperature drops.
What is relative humidity?
The difference between temperatures of 2 thermometers used to find the amount of moisture in the air. The greater the difference in the reading, the drier the air and the lower the relative humidity.
How is relative humidity measured?
It’s measured as a percentage of the maximum moisture that could be in the air at a certain temperature.
When is relative humidity 50%?
If the air has half the amount of moisture it could hold
When is relative humidity 100%?
When it’s raining or snowing and the maximum amount of moisture evaporated into the air.
What happens during the day to the relative humidity?
It decreases as the temperature rises
How is humidity shown on a weather map?
Percentage
What is the Stevenson screen?
The instruments used to measure temperature, atmospheric pressure and humidity
What is the Stevenson screen like?
It’s a box that’s painted white to reflect the heat of the sun. It has slanted sides to allow it to pass through the screen. This ensures accurate readings as the instruments are not in direct sunlight.
