Download Solar Radiation Incidence

Solar Radiation Incidence
Solar Radiation Incidence
Average surface temperatures
Radiative equilibrium temperature = -18o C
Actual Average temperature = 15o C
Average surface temperatures
Solar Insolation (W/m2)
Temporal variations:
S
Seasonal
l changes
h
i average daily
in
d il solar
l insolation
i
l ti (W/m
(W/ 2)
Haverford, PA Dec 1st, 2001 - June 30th 2002
500
21-Jun
400
21-Mar
Average
Daily
Insolation
(W/m2)
300
21-Dec
200
100
0
0
50
100
Day
150
200
Average surface temperatures
Temporal variations:
Daily Δ Temp. due to day/night cycle.
Why do we have seasons?
Haverford, PA Dec 1st, 2001 - June 30th 2002
500
21-Jun
400
21-Mar
Average
Daily
Insolation
(W/m2)
300
21-Dec
200
100
0
0
50
100
Day
150
200
Changes of state
Changes of state
Water Phase Diagram
Humidity – amount of water vapor in the air
The higher the temp the more water vapor
can be held
When humidity reaches 100%,
100% excess
water vapor condenses and forms liquid
water
The temp at which an air reaches 100%
humidity is its Dew Point Temperature
satturation concenttration o
of waterr vapor ((g/m3)
Quantity of water vapor that air
can hold depends strongly on
air temperature.
temperature
How does moisture content
( t vapor)) vary iin atmosphere
(water
t
h
1. Moisture is derived from surface,
1
surface by
evaporation and evapotranspiration.
2. Air temp. strongly affects air’s ability to
hold moisture.
moisture
3. At constant temp
3
temp., moist air is less
dense than dry air.
Humidity
Absolute Humidity
= mass of WV/volume of air
( t vapor d
(water
density)
it )
Specific Humidity
= mass of WV/total mass of air
(not influenced by volume)
Relative Humidity
= % of WV capacity
=WV content/WV capacity
p
y * 100%
(a function of temperature)
Humidity
How do you change
relative
l ti humidity?
h idit ?
•Change WV content
•Change the temperature
Dew Point
Dew Point
January
July
Dew Point – and regional Humidity
Atmospheric heat transfer and temperature
Latent heat of vaporization:
600 cal/g or 2.501
2 501 x 106 J/kg
So, to convert liquid
q
water into water vapor
p
requires addition of 2.501 x 106 Joules of heat
energy for every kilogram of water evaporated:
Latent heat of condensation:
2.501 x 106 J/kg
When H2O vapor condenses into liquid H2O cloud
droplets 2.501 x 106 Joules of heat energy is
released to the surrounding air for every kg of
water condensed:
Heat vs. Temperature
Thermal energy – energy that a substance possesses due to
the motion of its molecules – kinetic energy
Temperature – average kinetic energy of a substance’s
molecules
Heat – transfer of thermal energy from a hotter to a colder
object
Atmospheric heat
transfer and temperature
Specific Heat:
Liquid water (15°C):
Dry
y air (constant
(
p
pressure):
)
Sandy clay:
Quartz sand or Granite:
4186 J kg-1 K-1
1005 J kg
g-1 K-1
1381 J kg-1 K-1
795 J kg-1 K-1
Increasing the temperature of a kilogram of liquid water by
1 K requires the addition of 4186 J of heat energy.
g
of water cools by
y 1 K,, it likewise must release
If a kilogram
4186 J of heat.
Adiabatic Cooling
Decrease in Temp without loss of heat
latent heat released by
condensation reduces the
rate of cooling
Dew Point (100% humidity) and cloud formation
Cool air – less ability to hold moisture relative humidity
increases
Cools at adiabatic
rate of 10OC/1000m
At
Atmospheric
h i Circulation
Ci
l ti
Convection:
Density differences due to
1 uneven solar
1.
l insolation
i
l ti
2. distribution of land / water on planet
3 temperature
3.
t
t
/ humidity
h idit patterns
tt
different densities = different atmos. pressure
Average surface temperatures
General Air Motion
0 km/sec
464 km/sec
15o per hour
Clockwise Rotation
Counterclockwise
Rotation
What controls the magnitude of Coriolis Force?
Coriolis
Effect
60oN
30oN
0o
30oS
Coriolis Effect Cross Section
Generally
y warmer
Generally cooler
200-400 km/hr
Polar Front – Jet Stream
Ocean circulation
Clockwise
Counterclockwise
Gulf Stream Current
Ekman effect
Enriched in nutrients
Upwelling Zone
Intertropical Convergence ZONE
Density Driven Currents
Th
Thermohaline
h li circulation
i
l ti
1000 Year Cycle
y
Global Ocean Circulation
Weather Fronts
Fronts are air mass boundaries
L
H
front
Cold, dry air
Warm, moist air
ground surface
1.
2.
3
3.
4.
Sharp temperature changes
Changes in moisture content
Pressure changes
Clouds and precipitation patterns
Warm Front - produced as warm air glides
p over a cold air mass. Precipitation
p
is
up
moderate and occurs within a few hundred
kilometers of the surface front.
In general, warm fronts create a stable atmosphere
Cold Front - produced as a cold air mass
moves under a warm air mass. Clouds and
thunderstorms form above front.
Cold Front
Occluded Front - produced at the collision
g cold front that overtakes a
of a fast-moving
warm front and lifts the base of the warm
g
front off the ground
Occluded Front - produced at the collision of a fast-moving
cold front that overtakes a warm front and lifts the base of
the warm front off the ground
Cloud Formation
Condensation - Nucleation
Hygroscopic
yg
p
vs.
H d
Hydrophobic
h bi
Radiation Fog
g
vs.
Advection Fog
Air Stability
Air Stability
Air Stability
Cloud Formation
Frontal Uplift
Precipitation – Rain development
The collision-coalescence process
Sl t – rain
Sleet
i falls
f ll th
through
h ffreezing
i air
i
Precipitation – Rain development
Warm Moist Tropical Cloud
Warm,
Precipitation – Rain development
3000 m
1500 m
Precipitation – snow development
Precipitation – snow development
Bergeron Process
Precipitation – snow development
Bergeron Process
Precipitation – snow development
Bergeron Process
How much precipitation depends on ratio of droplets to ice.