1. The Water Cycle and Climates
© Lisa Michalek

2. The Water (Hydrologic) Cycle
Earth has a limited supply of water
This supply is constantly being recycled between the oceans, atmosphere, and land

3. The Water Cycle
During the recycling of water, water enters the atmosphere by evaporation and transpiration
Transpiration is the process where living plants release water vapor to the atmosphere
Of the precipitation that falls on Earth’s surface
50% returns to the atmosphere by evaporation
18% infiltrates (sinks into) the ground (groundwater)
32% is surface runoff that enters lakes and rivers

5. Groundwater Zone of saturation The Water Table
All spaces, cracks and other openings in soil and rock grains become completely filled with water
Water will stop sinking into the soil once it has reached a layer of solid rock that it cannot pass through
The Water Table
Boundary between the zone of aeration and the zone of saturation

6. Groundwater
The amount of water in the ground and the movement of water through the ground are controlled by the characteristics of the soil and rock found near the surface
Almost all materials on Earth’s surface are porous

7. Porosity The number of pores in a material compared with its volume
The porosity (percent of empty space) determines how much air or water a sample of rock can hold
Particle size alone does not affect the porosity of a soil

8. Permeability The ability of a soil to transmit water
The rate (how fast water can pass through a soil) depends on the size of the pores and how the pores are connected
Surface runoff occurs when rainfall exceeds the permeability of a soil, when a soil is saturated, or when the slope (gradient) of a soil’s surface is too great to allow infiltration to occur

9. Capillarity
The ability of a soil to draw water upward into tiny spaces between soil grains
Soils composed of very small particles show the most capillary uptake
This is because these soils have more surface area per unit volume for water to cling to them than do soils with large particles
Capillary water moves upward against the force of gravity because of the attraction between water molecules and the surfaces of the soil particles

10. Rainfall and Stream Flow
Streams and rivers do not respond immediately to rainfall
Most precipitation falls on the ground and then must flow over the land as runoff to reach a stream
A time lag occurs between maximum precipitation and maximum stream discharge

11. Factors Affecting Stream Flow
Slow falling precipitation
Low gradient of the land
Vegetation blocks overland flow
Large rivers respond slowly because most runoff must flow a great distance to reach the rivers
Small streams and streams in mountain areas where the land is steep and rocky respond quickly to rainfall
Runoff is very rapid and very brief in regions with buildings, paved streets, and parking lots

12. Watersheds (Drainage Basin)
The geographic area that drains into a particular stream or other body of water
Bounded by a drainage divide, usually a line of high land, across which streams do not flow

14. How Heat Energy Travels
Convection is heat flow by density currents within a fluid
Uneven heating of Earth’s surface by the sun causes winds

15. How Heat Energy Travels
Conduction is a form of heat flow that occurs when a hot substance comes in contact with a cooler substance
The vibrational energy of the warmer atoms and molecules is transferred to the cooler atoms and molecules, making them vibrate more

16. How Heat Energy Travels
Earth’s primary source of energy is the sun
Radiation is the flow of energy as electromagnetic waves, such as visible light
It is the fastest form of heat transfer
All radiation travels at the speed of light, 300,000,000 meters per second

17. Insolation Earth receives nearly all of its energy from the sun
The sun’s electromagnetic energy that reaches the earth is called insolation (INcoming SOLar radiATION)
The intensity (strength) of insolation depends on several factors
Angle
Duration
Type of surface

18. Angle of Insolation A measure of how high the sun is in the sky
As the sun rises and sets, this angle changes
This angle is measured from the horizon up to the position of the sun
The noon sun has the greatest angle of insolation
The angle also changes seasonally

19. Angle of Insolation
Because Earth is spherical, each latitude has a different angle of insolation

20. Duration of Insolation
The length of time (from sunrise to sunset), or daylight period, that the sun appears in the sky
A section of Earth’s surface receives the most heat energy when the sun is highest in the sky and when the duration of insolation is the greatest
As the angle of insolation and the duration of insolation increases, the temperature at Earth’s surface increases

21. Variations in Day Length

22. Variations of Insolation

23. Absorption of Insolation
Upon reaching the Earth’s surface, visible light waves are absorbed, scattered, or reflected
Light-colored objects reflect most of the light that falls on them
Dark-colored objects absorb most of the light that falls on them
Some of the absorbed energy is changed into infrared heat waves that reradiated back into the atmosphere at night

24. Absorption of Insolation

25. Reflection of Insolation
When light is reflected, it bounces off a surface
Clouds reflect about half of the light falling on them
The lower the angle of insolation, the greater the reflection of solar rays
More reflection also occurs when the land is light in color or covered by snow or ice

26. Reflection of Insolation

27. Terrestrial Radiation
Energy waves emitted from Earth’s surface are longer in wavelength than energy waves emitted from the sun
The longer heat waves radiated by Earth are absorbed by gases and remain trapped in the atmosphere
This process is called the greenhouse effect

28. Greenhouse Effect

29. Insolation Temperature Lag
A time lag exists between the time of greatest intensity of insolation and the time of highest air temperature
This is because insolation energy is first absorbed by Earth’s surface and then reradiated as heat energy that warms the air

30. Climate
Unlike weather, the climate for a large geographical region is based on the atmospheric conditions measured over a long period of time
The average conditions of temperature and precipitation and the annual distribution of these conditions characterize a region’s climate

31. Factors that Affect Climate
Latitude
The location is an important factor that determines the average local temperatures
Altitude
High-altitude locations have cool climates because of the cooling of air as it moves to higher elevations
Mountain Ranges
Can modify precipitation and temperature patterns

32. Factors that Affect Climate
Oceans and Large Bodies of Water
Because of its specific heat, water heats up and cools down more slowly than land areas
The climates of locations near the ocean or other large bodies of water are more moderate than inland climates
Coastal and marine climates are cooler in the summer and warmer in the winter than are inland climates

33. Factors that Affect Climate
Ocean Currents
Air above an ocean current is affected by the surface temperature of the water
Cool water will cool the air, and warm water will warm the air

34. Factors that Affect Climate
Planetary Wind Belts
Prevailing winds are important in determining the effect of ocean currents on nearby climates
There are various regions of rising (low-pressure systems) and sinking (high- pressure systems) air currents

35. Factors that Affect Climate
Monsoons producing Rainy weather
Typical Storm Tracks
US Weather systems usually move from west to east