1. Unit: Weather Pt. 3 – Water in the Atmosphere 4c. Examine weather forecasting and describe how meteorologists use atmospheric features and technology to predict the weather. (DOK 2)

2. Introduction Key Concept: Water is always moving between the atmosphere and Earth’s surface.

3. The water cycle is the movement of water between the atmosphere and Earth’s surface.

4. Water vapor enters the air through evaporation. Evaporation is when a liquid becomes a gas. Liquid water evaporates to become water vapor.

5. The water cycle includes all forms of precipitation, including rain and snow. Water moves from the atmosphere to Earth’s surface by precipitation.

6. Is the following sentence true or false? 1.Water moves between the atmosphere and Earth’s surface through the water cycle. 2. Circle the letter of the way that water enters the atmosphere. a. evaporation b. precipitation c. condensation

7. Humidity Key Concept: Relative humidity can be measured with an instrument called a psychrometer.

8. Humidity is a measure of how much water vapor is in the air. Warm air can hold more water vapor than cold air. Relative humidity is a percentage measurement. Relative humidity is the percentage of water vapor in the air compared to how much humidity the air can hold.

9. A psychrometer (sy KRAHM uh tur) is an instrument that measures relative humidity. A psychrometer has two thermometers. One thermometer has a wet cloth covering it. You can tell the relative humidity of the air by comparing the temperatures on the two thermometers.

10. Read each word in the box. In each sentence below, fill in the correct word or words. a. An instrument that measures relative humidity is a(an) ___________________. b. The percentage of water vapor in the air compared to how much humidity the air can hold is called ________________. c. A measure of how much water vapor is in the air is called _____________________.

11. Circle the letter of each sentence that is true about a psychrometer. a. A psychrometer has two thermometers. b. One thermometer has a wet cloth covering it. c. You compare the two thermometers to find out the relative humidity.

12. - Water in the Atmosphere How Clouds Form Clouds form when warm, moist air rises and cools. Water vapor condenses on tiny particles to form liquid water or ice crystals.

13. Condensation is when a gas becomes a liquid. For example, water vapor condenses to form liquid water. This happens in the atmosphere when clouds form.

14. There are two things needed for condensation to occur in the atmosphere: 1. There must be cooling of the air. 2. There must be particles—tiny solids—in the air.

15. Cold air holds less water vapor than warm air. When air cools, water vapor condenses into little drops of water or ice crystals. The temperature at which this happens is called the dew point.

16. Tiny particles must be in the air for condensation of water to take place. Water needs something to condense onto.

17. The process in which a gas becomes a liquid is called ________________. condensation evaporation precipitation sublimation

18. Circle the letter of each thing needed for condensation to occur in the atmosphere. a. There must be particles in the air. b. There must be cooling of the air. c. There must be precipitation in the air.

19. Is the following sentence true or false? The temperature at which water vapor condenses into little drops of water is called the dew point.

20. - Water in the Atmosphere Types of Clouds Scientists classify clouds into three main types based on their shape: cirrus, cumulus, and stratus. Clouds are further classified by their altitude.

21. Cirrus (SEER us) clouds are the wispy clouds that look like feathers in the sky. Cirrus clouds only form high in the sky. Cumulus (KYOO myuh lus) clouds look like fluffy, rounded piles of cotton. Cumulus clouds can produce thunderstorms. Thunderstorm clouds are called cumulonimbus clouds.

22. Stratus (STRAT us) clouds are flat layers of clouds. Stratus clouds usually cover most of the sky. Stratus clouds that produce rain are called nimbostratus clouds. Clouds that form near the ground are called fog. Fog often forms when the ground cools at night. Fog is common near bodies of water, such as a lake.

23. Draw a line from each type of cloud to its description. Type of Cloud cirrus clouds cumulus clouds stratus clouds fog Description a. flat layers of clouds b. clouds that form at or near the ground c. clouds that look like fluffy, rounded piles of cotton d. wispy clouds that look like feathers in the sky

24. Water Cycle Activity - Water in the Atmosphere The water cycle is the movement of water between the atmosphere and Earth’s surface.

25. Determining Relative Humidity Relative humidity is affected by temperature. Use the data table to answer the following questions. First, find the dry- bulb temperature in the left column of the table. Then find the difference between the wet- and dry-bulb temperatures across the top of the table. The number in the table where these two readings intersect indicates the relative humidity in percent. - Water in the Atmosphere

26. Determining Relative Humidity – 64% Interpreting Data: – At noon, the reading on a sling psychrometer are 18ºC for the dry-bulb thermometer and 14ºC for the wet-bulb thermometer. What is the relative humidity? - Water in the Atmosphere

27. Determining Relative Humidity – 88% Interpreting Data: – At 5 p.m., the psychrometer is used again. The reading on the dry-bulb thermometer is 12ºC and the reading on the wet-bulb thermometer is 11ºC. Determine the new relative humidity. - Water in the Atmosphere

28. Determining Relative Humidity – It decreased from 18 degrees to 12 degrees. Interpreting Data: – How did the temperature change between noon and 5 P.M. ? - Water in the Atmosphere

29. Determining Relative Humidity – It increased. Interpreting Data: – How did the relative humidity change during the course of the day? - Water in the Atmosphere

30. Determining Relative Humidity – For the same amount of water in the air, as the temperature decreases, the relative humidity increases. Warm air can hold more moisture than cool air can. Drawing Conclusions: – How was the relative humidity affected by air temperature? Explain your answer. - Water in the Atmosphere

31. QuestionAnswer Asking Questions How does the water cycle work?Water evaporates from the surface, condenses to form clouds, and falls to Earth as rain or snow. What is relative humidity?The percentage of water vapor in the air compared to the maximum amount air can hold at that temperature How do clouds form? Water in the air condenses on tiny particles in the air to form liquid water or crystals. Can you determine weather conditions by looking at clouds? Yes; each type of cloud is associated with a particular type of weather. - Water in the Atmosphere