Weather!Chapter 7 sections 1&4

• Measuring and recording!

• Meteorologists use a variety of weather instruments to more accurately forecast the weather.

• Write down the ones you know.

Measuring Relative Humidity• The amount of moisture that is in the air is a

major factor that influences our weather.

• Moisture in the air is known as humidity

• Relative humidity is the comparison of the amount of moisture present in the air at a certain temp. compared to the amount it COULD have in the air at that temp.

• This comparison is given as a percent (%)

• Do you know what tool is used to measure Relative Humidity????

Relative Humidity

•

Psychrometer measures in percentages (%)

Hygrometer measures in percentages (%)

Measuring Rain

• Meteorologists keep up with and record the amount of precipitation that falls.

• These measurements are given in inches or centimeters.

• Why would meteorologist want to keep with that?

Rainfall

• A Rain gauge is used to measure the amount of precipitation that has fallen.

Measuring Wind Speed• Wind (air) speed is also an influence in the

weather.

• It could signify a major temperature change, which results in storms or severe weather.

• Wind speed is measured in Mph (miles per hour) or kmph (kilometers per hour)

Wind Speed

• An anemometer is used to measure wind speed.

• As the wind spins the cups the turning is transmitted to dials that show how fast the wind is blowing.

Measuring Air pressure

• As different air masses move across the regions of our Earth they produce characteristic types of weather.

• These air masses are known as either Cyclones (low pressure systems) or Anticyclones (high pressure systems)

Air pressure• Barometers measure air

pressure.

• Mercury Barometers measure the amount of pressure the air exerts on a column of Mercury, the level of mercury goes up when the air pressure is high and goes down when its low.

• Barometric pressure can be measured in inches, millimeters, or millibars.

Air pressure• Aneroid Barometers contain NO liquid.

• It depends on a vacuum box to movie in and out as air pressure changes.

• As the vacuum box moves in and out the movement causes a dial to fluctuate.

• This barometer pressure

is also measured in in, mm,

millibars

Measuring Temperature

• What tool measures the temperature of the air? – Thermometer

• What is the temperature measured in?– Celsius C– Fahrenheit F