UNIT 8 Natural Science 1 Weather and climate The thermometer The thermometer is used to measure the temperature of the atmosphere. Since the temperature varies throughout the day, it is convenient to record the highest and lowest temperatures during each day. This temperature data is generally expressed in degrees centigrade ºC, although in other countries the Fahrenheit scale is more frequently used.

UNIT 8 Natural Science 1 Weather and climate The pluviometer The pluviometer is used to measure the volume of precipitation. Each day it is necessary to record the amount of rain water that has fallen. This water is collected in a container, and the rainfall is measured in millimetres. This means that each millimetre corresponds to a precipitation of 1 litre per square metre. When the precipitation has been recorded, the container is emptied, in order to have it ready for the following day.

UNIT 8 Natural Science 1 Weather and climate The hygrometer The hygrometer is used to measure atmospheric humidity. Atmospheric humidity is the amount of water vapour contained in the air we breathe at a certain temperature, in relation to the humidity it could contain (without condensing). Atmospheric humidity is expressed as a percentage. For instance, if it is 25% at a temperature of 25 ºC, it means that the air contains, at that moment, a quarter of the quantity of water vapour it could have in total at that temperature.

UNIT 8 Natural Science 1 Weather and climate The anemometer The anemometer is a device which is used to measure the speed of the wind. This is a device which spins on an axis at a speed which corresponds to the pressure exerted by the wind on its metallic pans. The speed of the wind is expressed in kilometres per hour (km/h). The weather vane The weather vane is a meteorological instrument we use to measure the speed of wind. It consists of a needle which turns round until the arrow is pointing in the direction of the wind. It is often placed on a disc on which the four cardinal points of the compass are indicated.

UNIT 8 Natural Science 1 Weather and climate The barometer A barometer is an instrument used to measure atmospheric pressure, that is, the pressure exerted by the air. The records of atmospheric pressure in a certain area allow us to establish which are the high pressure areas (anticyclones) and which are the low pressure areas. Looking at the chart you can see, can you explain how a barometer works? Activity