8-1: Water in the Atmosphere
6th Grade Earth Science
8-1: Water in the Atmosphere
• The water cycle is the continuous movement of water between the Earth’s surface and the atmosphere.
Water Cycle
8-1: Water in the Atmosphere
• Evaporation is the process by which water molecules in liquid absorb the sun’s energy and escape into the air as water vapor.
Evaporation
8-1: Water in the Atmosphere
• Humidity is the amount of water vapor in the air.
• Air’s ability to hold water depends on its temperature.
• Hot air holds more.
• Cold air holds less.
Humidity
8-1: Water in the Atmosphere
• Relative Humidity is how humidity is usually reported on weather reports.
• It is the percent of water in the air compared to the maximum it can hold at a given temperature.
Relative Humidity
8-1: Water in the Atmosphere
• A sling psychrometer is used to measure relative humidity.
• A wet bulb and a dry bulb thermometer measures two temperatures.
Measuring Relative Humidity
8-1: Water in the Atmosphere
• The dryer the air, the bigger the difference between the two temperatures.
• Wet bulb is colder since evaporation cools the thermometer.
8-1: Water in the Atmosphere
• DON’T COPY
• Sample table to figure relative humidity based on sling psychrometer.
8-1: Water in the Atmosphere
• DON’T COPY
• Easier way to find out relative humidity – not as accurate though - HYGROMETER
8-1: Water in the Atmosphere
• Clouds form when water vapor in the air condenses into millions of water droplets or ice crystals.
How Clouds Form
8-1: Water in the Atmosphere
• Condensation happens when the temperature cools down.
• AND … there is a small particle of dust, salt, or something to condense on.
8-1: Water in the Atmosphere
• If condensation happens on an object, we call it dew.
8-1: Water in the Atmosphere
• If it is frozen condensation, we call it frost.
8-1: Water in the Atmosphere
• We call the temperature that condensation occurs the dew point.
• The dew point is always changing.
What temperature will dew or frost form?
8-1: Water in the Atmosphere
• Graphs from Luiseno’s Weather Station.
• Live data
8-1: Water in the Atmosphere
• Graphs from Luiseno’s Weather Station.
• Live data
8-1: Water in the Atmosphere
• Clouds form when the temperature drops to the dew point – at the base of the cloud.
Condensation in Clouds
8-1: Water in the Atmosphere
• Timelapse Clouds
• Canary Islands
• Supercell
Time Lapse of Clouds
8-1: Water in the Atmosphere
• Clouds are classified by shape and altitude.
• Shape: Cirrus - wispy Cumulus - fluffy Stratus - flat layer
• Altitude: Alto - high
Types of Clouds
8-1: Water in the Atmosphere
8-1: Water in the Atmosphere
• Cirrus – High level clouds of ice crystals.
• Cumulus – Low level puffy clouds
• Stratus – Low level flat layer of clouds covering the sky
8-1: Water in the Atmosphere
• Altocumulus – High level puffy clouds
• Altostratus – High level flat layer of clouds covering the sky
• Fog - Ground level clouds.
8-1: Water in the Atmosphere Summary
• Water vapor in the atmosphere turns into liquid when too much is in the air – called condensation.
• Cooling the air causes condensation to form on tiny particles of dust or salt.
• Condensation causes the different kinds of clouds to form.
• Some wispy, puffy, or flat. • Some high, low, or on the ground.