Weather Instuments Thermometer Thermometers measure air temperatures Thermometers

Weather Instuments

Thermometer

Thermometers measure air temperatures. Thermometers work because matter expands when heated. Most thermometers are closed glass tubes containing liquids such as alcohol.

Barometer

A barometer measures air pressure. n There are two types of Barometers: Mercury Barometer and Aneroid Barometer. n

Aneroid Barometer Mercury Barometer

n A Mercury Barometer consists of a glass tube inserted into a dish of mercury or colored denatured alcohol.

n The surrounding air presses down on the mercury in the dish and forces some of the mercury up into the tube. The height to which the mercury rises in the tube is directly proportional to the atmospheric pressure.

Hygrometer

A hygrometer n measures the humidity of the air. One of the two thermometers has a wick (cloth cover) which is dipped in distilled water. n

Evaporation of water from the wick on the wet bulb thermometer leads to cooling. n Using a Relative Humidity Table, the temperature difference between the two thermometers gives the relative humidity of the air (in percent). n

n This is an example of the type of table you would use. Your book might also have an example.

Anemometer

An Anemometer measures the wind speed. The cups catch the winds, turning a dial attached to the instrument. n Think you could build one of these? n

WIND VANE Shows the wind direction

Rain Gauge

Time for a little review!

1. 2. If I wanted to find out if the pressure was rising, I’d use which of the following? Used to determine the relative humidity. A) B) C) D) E) F) Thermometer Barometer Psychrometer Wind Vane Rain Gauge Anemometer

3. Can help you find out the wind speed. 4. If I wanted to know the difference between the temperature inside and outside of the classroom. A) B) C) D) E) F) Thermometer Barometer Psychrometer Wind Vane Rain Gauge Anemometer

How did you do? Here are the correct answers 1. Barometer 2. Psychrometer 3. Anemometer 4. Thermometer