Transcript Weather and Climate

Weather and Climate
Climate vs. Weather
• Weather: Short term state of the atmosphere.
– Temperature, humidity, cloud cover, precipitation,
winds, visibility, air pressure, air pollution, etc…
• Climate: The average weather conditions in an
area over a long period of time
– Described by temperature and precipitation
Climate Graph
Measurement
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Temperature
Air Pressure
Definition
Instrument
Thermometer
How hot or cold the air is
The weight of the air
Barometer
Wind Speed
How fast the wind is blowing
Anemometer
Wind Direction
Where the wind is blowing from
Weather Vane
Humidity
Amount of water vapor in the air
Amount of rain or snow that falls
Precipitation
Hygrometer
Rain Gauge
Measuring Weather
Instruments used in measuring weather in the upper atmosphere
•
Radiosonde:
•
Radar: radio detection and ranging
•
Weather Satellites:
•
Computers
– a package of instruments that is carried aloft by balloons to measure upper atmospheric
conditions, including temperature, dew point, and wind velocity
– sends measurements as radio waves to a receiver that records the information.
– When the balloon reaches a very high altitude, the balloon expands and bursts, and the
radiosonde parachutes back to Earth.
– a system that uses reflected radio waves to determine the velocity and location of objects
– The newest Doppler radar can indicate the precise location, movement, and extent of a storm.
It can also indicate the intensity of precipitation and wind patterns within a storm.
– Satellite images provide weather information for regions where observations cannot be made
from ground.
– The direction and speed of the wind at the level of the clouds can also be measured by
examining a continuous sequence of cloud images.
– Satellite instruments can also measure marine conditions.
– Solving very difficult mathematical equations
– Store weather data
– Can provide information that is useful in forecasting weather changes
Measuring Weather Continue
Measuring Climate
Methods of Studying Past Climates
Method
What is measured
What is indicated
Length of time
measured
Ice Core
Concentrations of
gases in ice and
melt water
High levels of CO2 indicate
warmer climate; ice ages follow
decreases in CO2
Hundreds of
thousand of
years
Sea-floor
Sediment
Concentration of
18O in shells of
microorganisms
High 18O levels indicate cool
water; lower 18O levels indicate
warm water.
Hundreds of
thousand of
years
Fossils
Pollen types, leaf
shapes, and animal
body adaptations
Flower pollens and broad leaves
indicate warm climates;
evergreen pollens and small,
waxy leaves indicate cool
climates. Animal fossils show
adaptations to climate changes.
Millions of years
Thin rings indicate cool weather
and less precipitation
Hundreds to
thousands of
years
Tree Rings Ring width
Measuring Climate Continue
• Long term weather measurements
– Satellites
• Geological Evidence
– Evidence of glaciation
– Rock layers
SOLAR ENERGY AND HOW IT
EFFECTS CLIMATE AND
WEATHER
SOLAR ENERGY
Indirect and Direct Sunlight are a result of the Earth’s tilt. In the
Northern Hemisphere during winter Earth is titled away from the Sun
and in the summer the Earth is titled towards the sun.
• Cooler Temperatures = Cooler
Climates
• Higher latitudes
• Sun’s rays hit Earth at a
smaller angle
• Solar energy is spread out over
a larger area
• Higher Temperatures =
Warmer Climates
• Lower latitudes
• Sun’s rays hit Earth
around 90 degrees
• Solar energy is more direct,
smaller areas
ATMOSPHERE
Troposphere:
• the lowest layer of the atmosphere
• temperature drops at a constant rate as altitude increases
• weather conditions exist
• Tropopause: upper boundary of the troposhere.
Stratosphere:
• between the troposphere and the mesosphere
• temperature increases as altitude increases
• contains the ozone layer
• heated from above by absorption of solar radiation by ozone
Mesosphere
• the coldest layer of the atmosphere
• between the stratosphere and the thermosphere
• temperature decreases as altitude increases
• Mesopause: upper boundary of the mesosphere
• Average temp. 90°C
Thermosphere:
• the uppermost layer of the atmosphere
• temperature increase as altitude increases
• Ionosphere:
• lower region of the thermosphere, at an altitude of 80 to 400 km
• Interactions between solar radiation and the ionosphere cause auroras
ATMOSPHERE CONTINUE
ATMOSPHERIC PRESSURE(AIR PRESSURE)

Gravity holds the gases of the atmosphere near
Earth’s surface. As a result, the air molecules are
compressed together and exert force on Earth’s
surface.
atmospheric pressure:
 the force per unit area that is exerted on a surface by
the weight of the atmosphere
 decreases as altitude increases
 changes as a result of differences in temperature and
in the amount of water vapor in the air

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Temperature increase pressure decreases
Water vapor increases pressure decreases

Units: atmospheres (atm), millimeters or inches of
mercury, and millibars (mb).
Measures with a barometer
ATMOSPHERIC PRESSURE CONTINUE
ATMOSPHERIC PRESSURE CONTINUE
CORIOLIS EFFECT
• The circulation of the atmosphere and of the ocean
is affected by the rotation of Earth on its axis. Winds
that blow from high pressure areas to lower-pressure
areas curve as a result of the Coriolis effect.
Coriolis effect the curving of the path of a moving
object from an otherwise straight path due to Earth’s
rotation
CORIOLIS EFFECT CONTINUE
HOW AIR MOVES
• Air moves from areas of high pressure to areas of
low pressure. Therefore, there is a general,
worldwide movement of surface air from the poles
toward the equator.
• Temperature and pressure differences on Earth’s
surface create three wind belts in the Northern
Hemisphere and three wind belts in the Southern
Hemisphere.
• The Coriolis effect, which occurs when winds are
deflected by Earth’s rotation, also influences wind
patterns.
Global Wind Patterns
 Because Earth receives different amounts of solar energy at
different latitudes, belts of cool, dense air form at latitudes
near the poles, while belts of warm, less dense air form
near the equator.
 Winds affect many weather conditions, such as
precipitation, temperature, and cloud cover.
 Regions that have different global wind belts often have
different climates.
 As seasons change, the global wind belts shift in a north or
south direction.
 As the wind and pressure belts shift, the belts of
precipitation associated with them also shift.
Global Wind Patterns
trade wind:
• prevailing winds that blow from
east to west from 30º latitude to
the equator in both hemispheres
Westerlies:
• prevailing winds that blow from
west to east between 30º and
60º latitude in both hemispheres
• descending air moving toward
the poles is deflected by the
Coriolis effect
Polar easterlies:
• prevailing winds that blow from
east to west between 60 and 90
latitude in both hemispheres
• Surface winds created by the
polar high pressure are deflected
by the Coriolis effect
Jet Stream
 a narrow band of strong winds that blow in the upper
troposphere
 These wind exist in the Northern and Southern
Hemisphere.
 Polar jet streams:
 reach speeds of 500 km/h
 can affect airline routes and the paths of storms.
 Subtropical jet stream.
How Topography, ocean currents,
and air currents effect weather
patterns
HOW TOPOGRAPHY EFFECTS WEATHER
Mountain and Valley Breezes
• A valley breeze forms when warm air from the
valleys moves upslope.
• At night, the mountains cool more quickly than the
valleys do. At that time, cool air descends from the
mountain peaks to create a mountain breeze.
• Areas near mountains may experience a warm
afternoon that turns to a cold evening soon after
sunset.
HOW TOPOGRAPHY EFFECTS CLIMATE
•
Land heats faster than water and thus can reach
higher temperatures in the same amount of time.
•
Waves, currents, and other movements
continuously replace warm surface water with
cooler water from the ocean depths.
•
In turn, the temperature of the land or ocean
influences the amount of heat that the air above
the land or ocean absorbs or releases.
•
The temperature of the air then affects the climate
of the area.
OCEAN EFFECT CLIMATE AND
WEATHER
Ocean Currents
• The temperature of ocean currents that come in
contact with the air influences the amount of heat
absorbed or released by the air.
• If winds consistently blow toward shore, ocean
currents have a strong effect on air masses over
land.
• For example, the combination of a warm Atlantic
current and steady westerly winds gives
northwestern Europe a high average temperature
for its latitude.
AIR MASS MOVEMENT
OCEAN EFFECT CLIMATE AND
WEATHER
Seasonal Winds
monsoon a seasonal wind that blows toward the land
in the summer, bringing heavy rains, and that blows
away from the land in the winter, bringing dry
weather
•
Temperature differences between the land and
the oceans sometimes cause winds to shift
seasonally in some regions.
•
Monsoon climates, such as that in southern Asia,
are caused by heating and cooling of the northern
Indian peninsula.
EL NINO
El Niño Southern–Oscillation
El Niño the warm-water phase of the El Niño Southern
Oscillation; a periodic occurrence in the eastern
Pacific Ocean in which the surface-water
temperature becomes unusually warm (ENSO)
• The event changes the interaction of the ocean
and the atmosphere, which can change global
weather patterns.
• The ENSO also has a cool-water phase called La
Niña, which also affects weather patterns.
OCEAN EFFECT WEATHER
hurricane a severe storm that develops over tropical oceans
and whose strong winds of more than 120 km/h spiral in
toward the intensely low-pressure storm center
• A hurricane begins when warm, moist air over the ocean rises
rapidly.
• When moisture in the rising warm air condenses, a large
amount of energy in the from of latent heat is released. This
heat increase the force of the rising air.
• A fully developed hurricane consists of a series of thick
cumulonimbus cloud bands that spiral upward around the
center of the storm.
• The most dangerous aspect of a hurricane is a rising sea level
and large waves, called a storm surge.
• Every hurricane is categorized on the Safir-Simpson scale by
using several factors. These factors include central pressure,
wind speed, and storm surge.
HOW ELEVATION EFFECTS CLIMATE
Elevation
• The surface features of the land, or topography,
also influences climate.
• The elevation, or height of landforms above sea
level, produces distinct temperature changes.
• Temperature generally decreases as elevation
increases.
HOW MOUNTAINS EFFECT WEATHER
Rain Shadows
• When a moving air mass encounters a mountain
range, the air mass rises, cools, and loses most of its
moisture through precipitation.
• As a result, the air that flows down the other side of
the range is usually warm and dry. This effect is
called a rain shadow.
• One type of warm, dry wind that forms in this way is
a the foehn (FAYN), a dry wind that flows down the
slopes of the Alps.
HOW VOLCANIC ACTIVITY EFFECTS
CLIMATE AND WEATHER PATTERNS
Volcanic Activity
• Large volcanic eruptions can influence climates
around the world.
• Sulfur and ash from eruptions can decrease
temperatures by reflecting sunlight back into space.
• These changes last from a few weeks to several
years and depend on the strength and duration of
the eruption.