Weather elements

 Humidity 

How to measure Humidity 

Humidity is the amount of water vapour in the air and is expressed as a percentage (%). The instrument that we use to measure humidity is called a wet and dry bulb thermometer, also known as a hygrometer.

Figure 1.1 A wet and dry bulb thermometer 

The wet and dry bulb thermometer consists of two normal thermometers that are exactly the same. These thermometers are mounted parallel to each other. Underneath one of the thermometers is a small bottle filled with distilled water. The bulb of this thermometer is covered with a small wick or cloth. The end of the wick hangs in the bottle with distilled water. ( see Figure 1.1).

As the water rises up the wick, it evaporates causing the wet bulb thermometer to cool down, and to measure a lower temperature. The dry bulb thermometer will indicate the real air temperature.

Watch video on how to measure humidity 

Sunshine

How to measure sunshine

Sunshine is measured with a Sunshine recorder which records the hours of sunshine received during the day. It records the hours the sun actually shines, not just when it is light. A sunshine recorder consists of a solid glass ball that acts as a lens. The lens concentrates the rays of the sun onto a piece of card which is marked off in hours. As the sun moves from sunrise to sunset, a line is burnt into the card. At the end of the day the number of hours can be counted from the card.

Figure 1.2 Sunshine recorder