Transcript The Water Cycle and Climates

The Water (Hydrologic) Cycle
• Earth has a limited supply of water.
• This supply is constantly being recycled
between the oceans, atmosphere, and land.
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.
Groundwater
• Zone of saturation
– 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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
Angle of Insolation
• Because Earth is spherical, each latitude has
a different angle of insolation.
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.
Variations in Day Length
Variations of Insolation
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.
Absorption of Insolation
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.
Reflection of Insolation
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.
Greenhouse Effect
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.
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.
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.
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.
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
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 (highpressure systems)
air currents.
Factors that Affect Climate
• Monsoons producing Rainy weather.
• Typical Storm Tracks
– US Weather systems
usually move from
west to east.