Transcript Weather

CLIMATE AND WEATHER
WHY DO WE HAVE SEASONS?
WHAT IS THE ATMOSPHERE?
WHAT DRIVES THE WEATHER-ENGINE?
THE GAS LAWS
BOYLES LAW
For a mass of gas at constant Temperature
the product of the Volume and the Pressure
is a constant. V x P = K (as P rises, V falls)
CHARLES LAW
Under constant Pressure,
the Volume of a mass of gas
will increase proportionally with Temperature
V = KT (as temperature rises, volume rises)
IDEAL GAS LAW
P1V1
P2V2
_____ = ______
T1
T2
What happens to the volume of a gas under
constant pressure if the temperature
falls to absolute zero?
What happens to the pressure of a gas of
constant volume if the temperature
falls to absolute zero?
REFRIGERATOR
The refrigerant gas is compressed into a smaller volume,
which causes the temperature of the gas to increase. Since
there is less room for the molecules to move, this excess heat
is shed into the room via convection and radiation from the
radiator at the back of the fridge.
Then the gas is allowed to expand, which expansion requires
heat to be taken from its environment (the inside of the
fridge), to allow the molecules to move about in the larger
volume.
PRESSURE
WHAT IS PRESSURE?
THE ACTION OF GAS MOLECULES MOVING
THE HOTTER THE GAS,
THE MORE RAPID THE MOTION
THE HIGHER THE PRESSURE
THE ATMOSPHERE
HOW HIGH IS UP?
HOW THICK IS THE ATMOSPHERE?
WHAT IS THE ATMOSPHERE MADE OF?
THE HISTORY OF THE ATMOSPHERE
EARLY
-4.4-4.0 Byr
H2O, HCN,
NH3, CH4
SECONDARY -4.0 -3.3Byr H2O, CO2
N2;
at 3 B
O2 begins
LIVING
-3.3 Byr
to now
N2, O2
H, He
escape to
space
heavy clouds
bacteria start
to convert
CO2 to O2
O2 1% to 21%
levels at -500Myr
COMPOSITION OF ATMOSPHERE
NITROGEN
N2
OXYGEN
O2
WATER
H2O
ARGON
Ar
CARBON DIOXIDE CO2
NEON
Ne
HELIUM
He
METHANE
CH4
HYDROGEN
H2
NITROUS OXIDE N2O
OZONE
O3
~ variable amounts
78.08%
20.95%
~0 to 4%
0.93%
~0.036%
0.0018%
0.0005%
~0.00017%
0.00005%
~0.00003%
~0.000004%
LAYERS OF THE ATMOSPHERE
PERCENT
HEIGHT
THERMOSPHERE
90~1000 KM
MESOSPHERE
55~80 KM
STRATOSPHERE
14%
20~50 KM
TROPOSPHERE
85%
0 to 9~17 KM
1000km
Pressure (mb)
200
600thermosphere 1000
mesopause
80km
60km
Altitude
Pressure
(m)
40km
mesosphere
Temperature
stratopause
stratosphere
20km
tropopause
0
-100
-80
troposphere
-60
0
-40 o -20
Temperature ( C)
20
TROPOSPHERE
THICKNESS VARIES WITH LATITUDE
At the equator ~16 km; at the poles ~9 km
DENSITY FALLS WITH ALTITUDE
pressure decreases by half every 6 kms
ONLY PART OF ATM WITH CLOUDS
TEMPERATURE DECREASES WITH ALTITUDE
TO -50 to -70 oC
STRATOSPHERE
OZONE LAYER
TEMPERATURE RISES WITH ALTITUDE
TO ~ +7oC
WINDS MOVE ONLY HORIZONTALLY
MESOSPHERE
TEMPERATURE FALLS WITH ALTITUDE
-80 oC at 80 km up
THERMOSPHERE
Temperature rises to -40 oC at 100Km
THERMOMETERS
Fluid is mercury or alcohol
Volume expands proportional to temperature
THE BAROMETER
Atmospheric pressure is the “weight” of the air
pressing down upon everything.
This pressure is omnidirectional
Air pressure is strong enough to hold up
a column of water ~10 m high
Or a column of mercury 76 cm high
Tornicelli
SOLAR RADIATION
4%
5%
20%
100% incoming radiation
20 % absorbed by
atmosphere and
clouds
Atm
clouds
23%
4% Reflected
from surface
28%
51% absorbed
at surface
SEASONAL INSOLATION
Summer Solstice
N
Winter Solstice
Ottawa
Ottawa
sun
S
S
90o
sun
45o
N
Earth
Vernal equinox
March 20/21
Summer solstice
June 21/22
Aphelion
July 4
SUN
152,500,000 km
Autumnal
equinox Sept 22/23
147,500,000 km
Perihelion
Jan 3
Winter Solstice
Dec 21/22
MAJOR ATMOSPHERIC
CIRCULATION PATTERNS
Polar cell
Polar Jetstream
H
Ferrel cell
Polar easterlies
L L L L L L
Subtropic Jet
Westerlies
H H H H H H
Hadley cell
NE Trade winds
doldrums
L L L L L L L L
SE Trades
H H H H H H H
Westerlies
L L L L L L
H
CORIOLIS FORCES
WIND
DIRECTION
WESTERLIES
RESULT OF
CORIOLIS
EFFECT
DIRECTION OF EARTH’S ROTATION
FRONTAL SYSTEMS
CUMULONIMBUS
CLOUDS
NIMBOSTRATUS AND
STRATUS CLOUDS
COLD AIR
WARM AIR
COLD AIR
COLD FRONT
WARM FRONT
TYPES OF CLOUDS
HIGH:
6 km +
MIDDLE:
2-6 km
CIRRUS CIRROCUMULUS CIRROSTRATUS
“hair curl”
ALTOCUMULUS
LOW: CUMULUS SRATOCUMULUS
0-2 km
“heap”
RAIN
CUMULONIMBUS
CLOUDS:
2 - 12 km
ALTOSTRATUS
STRATUS
“layer”
NIMBOSTRATUS
HIGH
ANTI-CYCLONE
L
H
WINDS CLOCKWISE
LOW
CYCLONE
ANTI-CLOCKWISE WINDS
L
ICE AGES
LAST GLACIAL MAXIMUM WAS 20,000 YEARSAGO.
THE ICE WAS 3 KMS THICK OVER ALL OF CANADA.
WHEN IT MELTED THE SEAS ROSE 100-200 METRES.
THIS SEPARATED LANDMASSES, ISOLATING SPECIES
AND DISRUPTING MIGRATIONS.
IF THE GREENLAND ICE CAP MELTS, THE SEA LEVEL
WILL FALL IN THE NORTH AND RISE IN THE SOUTH.
WHY? THE MASS OF ICE HAS A GRAVITY EFFECT ON
THE OCEANS NEARBY.
ICE AGES (2)
TEMPERATURE IN THE LAST 10,000 YRS HAVE BEEN
UNUSUALLY STABLE. DURING LAST ICE AGE
100,000-10,000 BC, FLUCTUATED WILDLY +/- 20OC
AVERAGE SURFACE TEMPERATURE FELL SMOOTHLY
BETWEEN 1000AD AND 1900 A.D.
SHARP INCREASE SINCE 1960, CORRESPONDING TO A
DRAMATIC RISE IN CO2 STARTING IN 1900.