ch. 6 and 7 weather, climate and biomes mr. lesley apes
TRANSCRIPT
Ch. 6 and 7Weather, Climate and BiomesMr. Lesley APES
Weather– The short-term day-to-
day changes in temperature, air pressure, humidity, precipitation, sunshine, cloud cover and wind direction and speed.
– Most weather is predicted using:
weather balloons, aircraft, radar, and satellites
Weather Changes– Air Masses: large lump of air that
similar temperature and moisture level throughout.
– Air Masses that effect the US are
When air masses meet it causes changes in weather
• Cold front: when a cold air mass collides with a stationary warm air mass. The result is: thunderstorms, short bursts of heavy rain
Warm Front:
• when a warm air mass collides with a stationary cold air mass. The result is: warm steady rain
Weather is also affected by changes in atmospheric pressure
• High pressure has descending air that moves outward from the center of the high-pressure system. Descending air is warm and dry. The result is: nice dry weather
Low pressure• has ascending air that flows
towards the center of the low-pressure area. Ascending air-cools and condenses as it rises. The result is: clouds, rain
Weather Extremes– Hurricanes:
• What is it? Tropical storm with winds greater than 75 mph
• The bad: loss of life and property
• The good: flushes out coastline
Tornadoes:• Form when cold dry air collides
with warm moist air, which causes the warm air to rise quickly making a funnel cloud
Risk of Tornadoes
Highest
High
Medium
Low
Hurricane Frequency
High
Moderately high
Gulf of Alaska
Prince Williams Sound
CANADA
UNITED STATES
Grand Banks
Atlantic OceanMEXICO
Fig. 6.2, p. 122
Climate
– Climate is the long term average precipitation and temperature of an area
– Climate is determined by global wind patterns, latitude, altitude and ocean currents
Climate
the average weather patterns for an area overa long period of time (30 - 1,000,000 years).
is
It is determined by
Average Precipitation Average Temperatureand
which are influenced by
latitude altitude ocean currents
and affects
where people live how people livewhat they
grow and eat
Fig. 6.3, p. 123
Polar (ice)
Subarctic (snow)
Cool temperate
Warm temperate
Dry
Tropical
Highland
Major upwelling zones
Warm ocean current
Cold ocean current
River Fig. 6.4, p. 124
Global Air currents affect regional climates
• Uneven heating of the Earth’s surface causes the equator to receive more sunlight making it hotter; the poles receive less light making them cooler. This causes: global circulation
Fig. 6.6b, p. 125Initial pattern of air circulation
Deflections in the paths of air flownear the earth’s surface
30°S
Easterlies
Westerlies
Southeasttradewinds
(Doldrums)
Northeasttradewinds
Westerlies(from the west)
Easterlies(from the east)
60°S
equator
30°N
60°N
Climate type
Cold
Cool Temperate
Warm Temperate
Tropical
(equator)
Tropical
Warm Temperate
Cool Temperate
Cold
Fig. 6.6a, p. 125
Seasons
• Seasonal changes in temp and precipitation affect climate because the earth is tilted on its axis. It is colder in the winter and warmer in the summer because:
Fall(sun aims directly at equator)
Summer(northern hemisphere
tilts toward sun)
Spring(sun aims directly
at equator)
23.5 °Winter(northern hemispheretilts away from sun)
Solarradiation
Fig. 6.5, p. 124
Coriolis Effect
• Rotation of the Earth on its axis prevents air currents from moving directly north or south causing the winds to curve in what is called:
Ocean Currents
• Long term variations in the amount of incoming solar radiation
• Heat from the sun evaporates water and transfers energy from the ocean to the atmosphere. This creates convection cells that transport heat to different latitudes. This leads to: ocean currents and weather
Polar (ice)
Subarctic (snow)
Cool temperate
Warm temperate
Dry
Tropical
Highland
Major upwelling zones
Warm ocean current
Cold ocean current
River Fig. 6.4, p. 124
– Ocean Currents Affect climate• Differences in water temp, winds and
the rotation of the earth create currents.
• Currents redistribute heat. For example the gulf stream brings heat to Europe
• Upwelling is created when the trade winds blow offshore pushing surface water away from land. The outgoing surface water is replaced by nutrient bottom water. Upwelling support:
Wind
Movement ofsurface water
Diving birds
Nutrients
Upwelling
Fish
Zooplankton
Phytoplankton
Fig. 6.9, p. 126
The El Nino Southern Oscillation occurs every few years in the Pacific Ocean
– In an ENSO, prevailing westerly winds weaken or stop
– Surface waters along the coast of North America and South America (west) become warmer
– Normal upwelling stops– This reduces the population of some fish
species– Also causes severe weather, storms in
the US especially CA, and drought in southeast Asia
Normal Conditions
Cold water
Warm water
Thermocline
SOUTHAMERICA
Warm waterspushed westward
AUSTRALIA
EQUATOR
Surface windsblow westward
Fig. 6.10a, p. 127
1982–83 1997–98
Year
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
El Nino conditions
La Nina conditions
+3
+2
+1
0
-1
-2
Tem
per
atur
e/C
han
ge (
°F)
Fig. 6.12, p. 128
El Niño Conditions
Cold water
Thermocline
Warm waterWarm water deepens offSouth America
SOUTHAMERICA
Warm waterflow stoppedor reversed
AUSTRALIA
EQUATOR
Drought inAustralia andSoutheast Asia
Winds weaken,causing updraftsand storms
Fig. 6.10b, p. 127
El Niño
Unusually warm periods
Unusually high rainfall
Drought
Fig. 6.11, p. 127
La Nina
• La Ninas follow an El Nino and are characterized by cooling trends. La Nina brings more Atlantic hurricanes, colder winters in the north and warmer winters in the south, and an increase in tornadoes.
The chemical makeup of the atmosphere affects the weather.
Small amounts of water vapor, carbon dioxide, ozone, methane, nitrous oxide and chlorofluorocarbons trap heat in the atmosphere warming the planet. These gases are called: greenhouse gases
• The greenhouse effect is when greenhouse gases allow light, infrared radiation and UV radiation through to the surface of the earth where it is reflected back into space. The greenhouse gases trap some reflected infrared radiation
Rays of sunlight penetrate the lower atmosphere and warm the earth's surface.
The earth's surface absorbs much of the incoming solar radiation and degrades it to longer-wavelength infrared radiation (heat), which rises into the lower atmosphere. Some of this heat escapes into space and some is absorbed by molecules of greenhouse gases and emitted as infrared radiation, which warms the lower atmosphere.
As concentrations of greenhouse gases rise, their molecules absorb and emit more infrared radiation, which adds more heat to the lower atmosphere.
(a) (b) (c)
Fig. 6.13, p. 128
Ozone Layer• The ozone layer is located in the
stratosphere. It is created when ultraviolet light turns oxygen into ozone. The chemical reactions is:– Ozone blocks all short wavelength UV-C radiation,
50% of the UV-B radiation and almost no long wavelength UV-A radiation.
– Ozone also forms a thermal cap which: traps heat
Topography of the earth also creates microclimates
A microclimate is small area that has a different climate than the general climate of an area.– Vegetation in an area influences climate:
forests stay warmer in the winter and cooler in the summer because of the trees
– Cities create heat islands that trap heat and decrease wind
speeds
Cool airdescends
Land warmer thansea; breeze flowsonshore
Warm air ascends
Fig. 6.15a, p. 130
Water also changes climate by causing land breezes and sea breezes
Warm air ascends Land cooler than
sea; breeze flowsoffshore
Cool airdescends
Fig. 6.15b, p. 130
a Winds carrymoisture inland
from Pacific Ocean
b Clouds, rain onwindward side ofmountain range
c Rain shadow onleeward side ofmountain range
Moist habitats 15/25
1,000/85 1,800/125
3,000/854,000/75
1,000/252,000/25
Fig. 6.14, p. 129
The rain shadow effect changes climate
Dry woodlands and shrublands (chaparral)
Temperate grassland
Temperate deciduous forest
Boreal forest (taiga), evergreen coniferousforest (e.g., montane coniferous forest)
Arctic tundra (polar grasslands)
Tropical savanna,thorn forest
Tropical scrub forest
Tropical deciduous forest
Tropical rain forest,tropical evergreen forest
Desert
Ice
Mountains(complex zonation)
Semidesert,arid grassland
Tropic ofCapricorn
Equator
Tropic ofCancer
Fig. 6.16, p. 131
Polar
Subpolar
Temperate
Tropical
Desert
Desert
Deciduousforest
Deciduousforest
Coniferous forestConiferous forest
ChaparralChaparral
GrasslandGrassland
SavannaSavanna
ScrublandScrublandTropical
seasonalforest
Tropicalseasonal
forest
Rain forestRain forest
TundraTundra
Fig. 6.17, p. 132
AlpineTundra
MontaneConiferous
Forest
DeciduousForest
TropicalForest
Tropical Forest Temperate Deciduous Forest
Northern Coniferous Forest
Arctic Tundra
LowHigh Moisture Availability
High
LowE
levation
Fig. 6.18, p. 133
Plant and animal adaptations to climate
– For plants precipitation is generally the limiting factor in determining whether a climate is a desert, forest or grassland, but biomes are not uniform. They have the same general characteristics but there are microclimates that determine the actual plants you will find in any given area.
Plants exposed to cold year around or in the winter have:
• Traits that keep them from losing too much heat or water
• They stay small
Desert plants must be able to lose heat and conserve water. They do this by:
• Lose heat and store water
• Fleshy tissue, vertical, no leaves, store water
In wet tropical climates the plants have
• Broadleaf evergreen, maximize sunlight
In climates that are hot in summer and cold in winter, plants have:• Deciduous leaves that fall off in
winter
In areas with cool short summers, the trees have:
• Coniferous evergreen
• Needle shaped leaves