Bobbling along in the sky, hot air balloons look like a fun way to spend a day. Before the invention of satellites or airplanes though, hot air balloons were used by scientists to study the atmosphere. Riding in their balloons, scientists gathered information about temperatures, humidity and even cosmic rays. For more than 150 years, balloons were considered cutting-edge atmospheric observatories. What are some differences between research hot air balloons of the past and the scientific balloons we use today?

Text Reference 56-63

1. Water makes up 75% of the surface of the earth 2. Water exists in three forms or phases (yup! Write it all!) Solid - Ice Liquid - Water Gas - Vapor Melting Condensing Freezing Evaporating

3. Phase Changes of Water a. Evaporation-Water molecules heat up and gain energy. They begin to move faster and change from the liquid to gas phase Water molecules as a vapor Water molecules as a liquid A typical glass of water

3b. Condensation Water molecules slow down and lose energy changing from a gas to a liquid phase collecting on grass and objects in the form of dew. If the temperature falls below 0 o C, it becomes frost. Dew Point - the temperature at which water vapor condenses

3c. Transpiration Water transferred from plants to the atmosphere as water vapor as they take in CO 2

2. Water vapor from condenses into clouds 4. Deep ground water and runoff return water to the rivers, lakes, and oceans 3. Precipitation (rain, snow, hail) returns water to the soil 4. The Water Cycle 1. Heat energy from the sun warms surface water on the earth, causing it to evaporate and transpirate

5. Humidity A measure of the amount of water vapor in the air Warm air holds more moisture than cool air Air feels cooler when the humidity is lower, the air is more capable of evaporating water from sweat Measured with an instrument called a “Psychrometer” Saturation-the point at which evaporation and condensation are equal (warmer-higher; cold-lower) Wet Bulb Dry Bulb

6. Relative Humidity The percentage of water vapor in the air compared to the maximum amount the air could hold. For example: If the air can hold 8 grams of water, and it has 8 grams in it, the relative humidity would be 100% If the air can hold 8 grams of water, and it has 4 grams in it, the relative humidity would be 50%

7. Dew Point The temperature at which condensation begins

a.Clouds form when the temperature falls below the dew point b.Small particles of dust must be present for the water to condense c.Three Basic Types:  Cumulus  Stratus  Cirrus

C1-Cumulus (“heap”) Clouds Thick and puffy, cotton candy clouds associated with fair weather

C2-Cumulonimbus clouds are vertically developed clouds that can yield lightning, hail, and heavy rainfall.

Low level layer of clouds that often covers the entire sky. clouds are heavier stratus clouds that give long periods of steady rain or snow. C4-Nimbostratus clouds are heavier stratus clouds that give long periods of steady rain or snow. (“spread out”) Clouds C3-Stratus (“spread out”) Clouds

C5-Cirrus - Wispy, feather clouds ◦ Only form at high levels ◦ Made mostly of ice crystals ◦ Name means “curl of hair”

Fog is a low-lying cloud at or near the surface of the earth

Common Types: Rain-bigger than 0.5 mm Drizzle-less than 0.5 mm Freezing Rain- When rain strikes a cold surface and turns to ice Sleet-When rain falls throughSleet-When rain falls through freezing air and turns to ice

Snow - Ice crystals formed inside a cloud, form in the presence of little wind Hail - Pellets of ice greater than 5 mm in diameter. Form exclusively inside cumulonimbus clouds and are associated with storms

Hail forms in cumulonimbus clouds.

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