Transcript Weather,Climate and Biodiversity

Weather, Climate
and
Mrs. Sandefur
Weather
– The short-term day-today 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 lowpressure area. Ascending aircools 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
Prince Williams
Sound
Gulf of Alaska
Risk of Tornadoes
Highest
High
Medium
Low
CANADA
UNITED STATES
Grand Banks
Hurricane Frequency
High
Moderately
high
MEXICO
Atlantic
Ocean
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
is
the average weather patterns for an area over
a long period of time (30 - 1,000,000 years).
It is determined by
Average Precipitation
and
Average Temperature
which are influenced by
latitude
altitude
ocean currents
and affects
where people live
how people live
what they
grow and eat
Fig. 6.3, p. 123
Polar (ice)
Warm temperate
Highland
Warm ocean current
Subarctic (snow)
Dry
Major upwelling zones
Cold ocean current
Cool temperate
Tropical
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
Easterlies
(from the east)
60°N
Westerlies
(from the west)
Northeast
tradewinds
30°N
(Doldrums)
equator
30°S
60°S
Initial pattern of
air circulation
Southeast
tradewinds
Westerlies
Easterlies
Deflections in the
paths of air flow
near the earth’s surface
Fig. 6.6b, p. 125
Cold
Cool Temperate
Warm Temperate
Tropical
(equator)
Tropical
Warm Temperate
Cool Temperate
Cold
Fig. 6.6a, p. 125
Climate type
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:
Spring
(sun aims directly
at equator)
Winter
(northern hemisphere
tilts away from sun)
23.5
°
Solar
radiation
Summer
(northern hemisphere
tilts toward sun)
Fall
(sun aims directly at equator)
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)
Warm temperate
Highland
Warm ocean current
Subarctic (snow)
Dry
Major upwelling zones
Cold ocean current
Cool temperate
Tropical
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 of
surface water
Diving birds
Fish
Upwelling
Zooplankton
Phytoplankton
Nutrients
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
Surface winds
blow westward
EQUATOR
AUSTRALIA
Warm waters
pushed westward
SOUTH
AMERICA
Warm water
Thermocline
Cold water
Normal Conditions
Fig. 6.10a, p. 127
Temperature/Change (°F)
+3
+2
1982–83
El Nino conditions
La Nina conditions
1997–98
+1
0
-1
-2
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
Year
Fig. 6.12, p. 128
Winds weaken,
causing updrafts
and storms
Drought in
Australia and
Southeast Asia
EQUATOR
AUSTRALIA
Warm water
flow stopped
or reversed
SOUTH
AMERICA
Warm water deepens off
South America
Warm water
Thermocline
Cold water
El Niño Conditions
Fig. 6.10b, p. 127
El Niño
Drought
Unusually high rainfall
Unusually warm periods
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
(a) Rays of sunlight penetrate
the lower atmosphere and
warm the earth's surface.
(b) The earth's surface absorbs much of (c) As concentrations of greenhouse
the incoming solar radiation and
gases rise, their molecules absorb
degrades it to longer-wavelength
and emit more infrared radiation,
infrared radiation (heat), which rises
which adds more heat to the
into the lower atmosphere. Some of
lower atmosphere.
this heat escapes into space and some
is absorbed by molecules of
greenhouse gases and emitted as
infrared radiation, which warms the
lower atmosphere.
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
Water also changes climate by causing land
breezes and sea breezes
Cool air
descends
Warm air ascends
Land warmer than
sea; breeze flows
onshore
Fig. 6.15a, p. 130
Cool air
descends
Warm air
ascends
Land cooler than
sea; breeze flows
offshore
Fig. 6.15b, p. 130
a Winds carry
moisture inland
from Pacific Ocean
b Clouds, rain on
windward side of
mountain range
Moist habitats
c Rain shadow on
leeward side of
mountain range
4,000/75
3,000/85 2,000/25
1,800/125
1,000/25
1,000/85
15/25
The rain shadow effect changes climate
Fig. 6.14, p. 129
Tropic of
Cancer
Equator
Tropic of
Capricorn
Arctic tundra (polar grasslands)
Desert
Boreal forest (taiga), evergreen coniferous
forest (e.g., montane coniferous forest)
Tropical rain forest,
tropical evergreen forest
Semidesert,
arid grassland
Mountains
(complex zonation)
Temperate deciduous forest
Tropical deciduous forest
Ice
Temperate grassland
Tropical scrub forest
Dry woodlands and
shrublands (chaparral)
Tropical savanna,
thorn forest
Fig. 6.16, p. 131
Polar
Tundra
Subpolar
Temperate
Coniferous forest
Desert
Deciduous
forest
Grassland
Tropical
Chaparral
Desert
Savanna
Rain forest
Tropical
seasonal
forest
Scrubland
Fig. 6.17, p. 132
Low
Alpine
Tundra
Elevation
Montane
Coniferous
Forest
Deciduous
Forest
High
Tropical
Forest
Tropical Forest
High
Temperate Deciduous
Forest
Northern Coniferous
Forest
Moisture Availability
Arctic Tundra
Low
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