Sci-ber Text - 4th Grade

Weather Observations - Meteorologist Tools

If you had to measure and predict the weather, what tools would you use?

A rake or shovel?

A hammer? Hammer

Here you will learn the basic tools of a meteorologist.

Pop goes the ear!
It is time to pack the car and visit more of our great state of Utah. Your trip will begin in St. George. After a day of hiking in the sun, you will travel north on Interstate 15 to Provo . Once there you will head up Provo Canyon to your final destination in the Uintah Mountains. Suddenly, you feel pressure in your ear and you are unable to hear what your little sister said. Something has happened to your hearing. You might yawn, take a drink of soda, and chew some gum to try to get your ears. Not long after your ears crunched, your mother starts complaining about her ears. What is happening and what does it have to do with the air pressure?

Highlight the box below to see if your answer is correct.

Your ears "popped" because of the weight of the surrounding air. As you travel up the canyon to the higher elevation of the mountains, there is less air pressing on your eardrums. This causes the eardrums to adjust, which causes the uncomfortable sensation we call "popping."

"Weigh" to go!
Compared to a rock or even a feather, air does not weight very much. But air is a gas made up of tiny molecules of matter. Air has weight. It is pressing all around us. Air pressure is the weight of air in our atmosphere pressing down upon Earth.

YOU'RE THE SCIENTIST!
You can prove that air has weight by performing the following activity.

Materials:

Meter stick
String
Two balloons

Procedure:

Tie a 24-inch piece of string in the middle of the meter stick.
Tie a 6-inch piece of string on each balloon.
Attach the string with the balloons to each end of the meter stick.
Make sure the balloons balance.
Remove one balloon and blow it up.
Attach it to the end of the meter stick again.
Does it balance?

What has happened?

Explain how this activity demonstrates that air has weight.

Can you create and perform a different experiment that demonstrates that air has weight?

"Pressing" into the future
Meteorologists, the scientists who study the weather, call air pressure "Barometric (bear-o-met-ric) Pressure." A barometer (ba-ro-meter) is a weather instrument used to measure the air pressure. Changes in air pressure usually mean a change in the weather. Stormy weather often occurs after the barometer falls, or the air pressure decreases. Good or fair weather usually can be predicted by a rising barometer. Meteorologists learn to use a barometer to predict the weather.

A sticky Situation
Have you ever walked into a bathroom right after someone has taken a hot shower? How does the air feel? Does your skin feel kind of sticky? What you are feeling is water in the air. The water is in the form of a gas. Scientists call this gas "water vapor."

Desert areas do not get a lot of rain or snow during the year. There is usually much less water vapor in the air in St. George. Areas located near oceans almost always have more moisture in the air.

Weather forecasters often mention the term "relative humidity." This term refers to the amount of water vapor in the air compared to the amount of water the air could hold at that temperature. The relative humidity is always given as a percentage.

Measuring Relative Humidity
Scientists have a way to measure the relative humidity. They use a tool called a hygrometer (hi-grom-eter). There are different kinds of hygrometers. You can make a simple hygrometer by doing the following:

Materials:

Two thermometers
One paper towel
Paper

Procedure

Place the two thermometers side by side on your desk or on a table.
Compare and record the temperatures of both thermometers. They should display the same temperature.
On one thermometer, place the paper towel around only the bulb of the thermometer.
Wet the paper towel.
Using the paper, fan some air across the thermometers for a minute or two.
Record the temperatures in Fahrenheit of both thermometers.
You will probably notice that the thermometer with the paper towel on the bulb shows a lower temperature than the dry bulb thermometer.
Explain why the temperature changed on one of the thermometers.

Cool it!
Have you ever gotten out of a swimming pool and felt cold, even on a hot day? The water evaporating from your skin cools your body.

In addition to the tools that you learned about on this page remember the wind vane that you learned to make earlier on the Windward Ho! Web page.