Water: An Earth History
OUTGASSING
TORRENTIAL RAINS PRODUCED
LAKES AND OCEANS
DISSOLVED AND UNDISSOLVED
ELEMENTS
PRESENT VOLUME 1,360,000,000 km3
VOLUME IS STABLE
Water Reservoir
Oceans
97.24%
Ice caps, glaciers
2.14%
Ground water
0.61%
Fresh-water lakes
0.009%
Inland seas
0.008%
Soil moisture
0.005%
Atmosphere
<0.001%
Rivers
<0.0001%
Source: U.S. Geological Survey
Some fast-moving
molecules escape
from the liquid
Evaporation, condensation and saturation
balanced
In cool air, H2O molecules
are more likely to join
nuclei
CHANGES
DOES NOT
CHANGE
MASS / VOLUME
g H2O / m3 air
Specific humidity:
the mass of water vapour (g) per mass
of air (kg)
Maximum specific humidity is the
maximum mass of water vapour that
can be held by 1kg of air at a given
temperature
MASS OF WATER VAPOUR
TOTAL MASS OF DRY AIR
g H2O / kg air
The ratio of the amount of water vapour
in the air to the maximum amount of
water vapour that could be present at the
same temperature
The relative humidity of saturated air is
100%
RH = [H20 vapour content/H20 capacity] x 100
Influence of temperature
on relative humidity
The portion of atmospheric pressure that is
made up of water vapour molecules (mb or
kPa)
SATURATED VAPOUR PRESSURE:
The pressure that water vapour molecules
would exert if the air were saturated (at a
given temperature)
RELATIVE
HUMIDITY
SPECIFIC
HUMIDITY
Sling psychrometer
http://www.csgnetwork.com/canhumidexcalc.html
Heat Index
Why do surfaces facing
the wind have more frost?
BLACK FROST
•A surface is required for condensation
•Condensation nuclei >0.1 m best
•About 10-1000 large nuclei per cm3
(more in lower troposphere and over land)
•Hygroscopic or hydrophobic
Source: Dust, volcanoes, factory smoke,
forest fires, ocean spray salt, sulphate
particles from phytoplankton
Dry adiabatic cooling
Fog forms
if Td is reached
Cold water advection fog
WHY DOES FOG
FORM HERE?
Warm water advection fog
CAN ADVECTION
FOG FORM OVER
LAND MASSES?
YES
Base camp
2º30´25´´N, 77º00´02´´W, 1450 m
Field Station
Tambito al
Cocal River
Definition:
The difference in
atmospheric
pressure per unit
distance
PGF acts at right
angles to isobars
of equal pressure
H
L
102.2
99.8
101.4
100.6
600 km
Pressure Gradient Force = 2.4 kPa / 600 km
= 0.4 kPa / 100 km
Where are winds strongest ?
Oct 18, 2004 Solution: HUDSON BAY
Check the spacing of the isobars of equal surface pressure
Source: NASA
Surface roughness decreases wind speed
Reduces impact of Inertial Coriolis Force
Winds cross isobars, spiralling out of
ANTICYCLONES (H), and into CYCLONES (L)
H
L
weather.unisys.com
H
L
Air tends to be unstable in low pressure (tendency to rise)
Air tends to be stable in high pressure (tendency to fall)
1. Equatorial Low Pressure Trough
2. Subtropical High Pressure Cells
3. Subpolar Low Pressure Cells
4. Weak Polar High Pressure Cells
ICE CAP
TUNDRA
BOREAL
MIXED TEMPERATE
BROADLEAF
DESERT
SAVANNA
RAIN FOREST
SAVANNA
DESERT
MIXED TEMPERATE
TUNDRA
ICE CAP
How does this relate to the “jet stream”?
Geostrophic wind
(above strong influence of friction)
CHAPTER 10
ULTRASONIC SOUND
WAVES DETERMINE
WIND SPEED,
DIRECTION &
TEMPERATURE
Sonic
http://www.wrds.uwyo.edu/wrds/rmfres/fendrift.htm
Also SW Ontario
Cooling
At MALR
6°C/km
Cooling
At MALR
6°C/km
Warming
At DALR
10 °C/km
Warming
At DALR
10 °C/km
Cooling
At DALR
10 °C/km
X
VANCOUVER
8°C
X
LETHBRIDGE
12°C
More sensible heat
“Don’t try this at home
Santa
Ana
Winds
Entrained Particle
Exposed section
Buried Portion