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Lesson 01: Water and Weather

P. 212-213

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Water Cycle

The movement of water from the land to the rivers and oceans, to the atmosphere, and back to the land again.

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Water Cycle

The major force behind the water cycle is the sun (Solar energy)

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Water Cycle: Water into air.

Processes involved in getting water into the air are:

1. Evaporation

2. Sublimation

3. Transpiration

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Water Cycle: Water into air.

1. EvaporationEvaporation is when the sun heats up liquid water in rivers or lakes or the ocean and turns it into vapor or steam. The water vapor or steam leaves the river, lake or ocean and goes into the air.

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Water Cycle: Water into air.

2. Sublimation

Sublimation occurs when the sun heats up snow and ice.  This energy changes the ice directly into vapor.  It skips the liquid phase and goes directly to a gas.

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Water Cycle: Water into air.

3. Transpiration

Transpiration is the process by which plants lose water out of their leaves.

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Water Cycle: Removing water from air.

Two main processes:

1. Condensation

2. Precipitation

a. Rain b. Hail

c. Sleet d. Snow

e. Freezing Rain

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Water Cycle: Removing water from air.

1. CondensationThe water vapor rises with the warmed air.  As the air begins to cool the water vapor in the air gets cold and changes back into liquid, forming clouds. This is called condensation.

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Water Cycle: Removing water from air.

1. CondensationWhen this condensation occurs on a cold surface close to the ground we call it dew. 

If the surface is below zero the water vapor re-sublimes to form solid frost.

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Water Cycle: Removing water from air.

2. PrecipitationPrecipitation occurs when so much water has condensed that the air cannot hold it up anymore.  The clouds get heavy and water falls back to the earth in the form of rain, hail, sleet or snow.

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Water Cycle: Removing water from air.

2. PrecipitationType of precipitation we get depends on the

a. Air temperature

b. In some cases the ground temperature.

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Types of Precipitation: Rain

As the water vapor condenses small droplets form.  These small droplets collide with other droplets forming bigger droplets which fall from the atmosphere. 

Drizzle is rain that is made up of drops smaller than 1/2 mm. 

Rain is made up of drops between 1/2 mm and 5.0 mm. 

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Types of Precipitation: Snow

Snow forms when water vapor crystallizes (turns into a solid) on  the surface of tiny dust particles. 

Wet snow occurs when snow flakes pass through some warm air, melting the snow flake slightly. 

Dry snow occurs when the snow flakes stay in cold air.

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Types of Precipitation: Hail

Hail is formed as water droplets ride the updrafts inside thunderclouds.  Each time the hail stone rises a new layer of ice forms on its surface.  After about 20 trips up the hail stone is too heavy to rise again and then crashes down to earth!

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Types of Precipitation: Sleet

Sleet is formed by snow that passes through a layer of warm air, melts slightly, and then passes through a cold layer of air re-freezing as a little ball of ice.

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Types of Precipitation: Snow

Snow forms when water vapor crystallizes (turns into a solid) on  the surface of tiny dust particles. 

Wet snow occurs when snow flakes pass through some warm air, melting the snow flake slightly. 

Dry snow occurs when the snow flakes stay in cold air.

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Types of Precipitation: Freezing Rain

Freezing rain forms when a super cooled rain drop (the drop is still liquid below 0oC) hits an object on the ground.  The rain drop freezes on contact. 

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Water Cycle: Collection

When water falls back to earth as precipitation, it may fall back in the oceans, lakes or rivers or it may end up on land.  When it ends up on land, it will either soak into the earth and become part of the “ground water” that plants and animals use to drink or it may run over the soil and collect in the oceans, lakes or rivers where the cycle starts all over again.