MEASURING THE WEATHER Teacher: Mariana Lavenás

WEATHER Weather refers to the state of the atmosphere: Pressure Temperature Precipitation Wind Sun Instruments are used to measure each of these. Weather refers to the state of the atmosphere: Pressure Temperature Precipitation Wind Sun Instruments are used to measure each of these.

AIR PRESSURE Air has weight and exerts a force or pressure on the earth’s surface. The instrument used for measuring this is The BAROMETER.

IMPORTANCE OF AIR PRESSURE LOW PRESSURE Air rises from the surface Moisture in the air cools as it rises Condensation and precipitation can result LOW PRESSURE Air rises from the surface Moisture in the air cools as it rises Condensation and precipitation can result HIGH PRESSURE Air sinks towards the surface Air warms up and becomes drier Dry, sunny weather often results HIGH PRESSURE Air sinks towards the surface Air warms up and becomes drier Dry, sunny weather often results

MERCURY BAROMETER

ANEROID BAROMETER

TEMPERATURE Air temperatures are recorded by thermometers in the shade. THE MAXIMUM THERMOMETER A glass tube containing mercury Metal index Temperature rises, the mercury expands and pushes the index up the tube. The temperature falls,the mercury contracts and leaves the index behind.The reading of t· is taken from the bottom of the index. THE MINIMUM TERMOMETER Identical glass tube containig alcohol Metal index Temperature falls, the alcohol contracts and its MENISCUS pulls the index down. Temperature rises, alcohol expands flows past the index. The reading for minimum T· is taken from the top of the index.

MINIMUM THERMOMETER

PRECIPITATION Precipitation is measured by the RAIN GAUGE Rain falling into the FUNNEL placed on top of the outer METAL CONTAINER. Two thirds of the container is buried underground to prevent evaporation

WIND Direction and speed of wind are measured WIND VANE ANEMOMETER