Download 2015_LECTURE_3

Geography 2015N
•OUTGASSING
•TORRENTIAL RAINS
•LAKES AND OCEANS
•DISSOLVED AND UNDISSOLVED
ELEMENTS
•PRESENT VOLUME 1,360,000,000 km3
•VOLUME IS STABLE
Oceans
Ice caps, glaciers
Percent of
total water
97.24%
2.14%
Ground water
Fresh-water lakes
Inland seas
0.61%
0.009%
0.008%
Water source
Soil moisture
Atmosphere
Rivers
0.005%
<0.001%
<0.0001%
Source: U.S. Geological Survey
Some fast-moving
molecules escape
from the liquid
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
A ratio that compares the amount of
water vapour in the air to the
maximum water vapour capacity at
that temperature
The relative humidity of saturated
air is 100%
RH = [H20 vapour content/H20 capacity] x 100
The portion of atmospheric pressure that is
made up of water vapour molecules
(mb or kPa)
SATURATION VAPOUR PRESSURE:
The pressure that water vapour molecules
would exert if the air were saturated
(at a given temperature)
RELATIVE
HUMIDITY
SPECIFIC
HUMIDITY
http://www.csgnetwork.com/canhumidexcalc.html
Geography 2015N
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  cm-3
(more in lower troposphere and over land)
•Hygroscopic or hydrophobic
Source: Dust, volcanoes, factory smoke,
forest fires, ocean spray salt, sulphate
particles from phytoplankton
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
Pages 142-155
Laboratory 1 Notes
Absolute stability
Environmental lapse rate <
moist adiabatic lapse rate
Environmental lapse rate >
Dry adiabatic lapse rate
Solar heating of Earth’s surface
Warm air advection at surface
Air moving over a warm surface
Cold advection
Radiational cooling of clouds
LIFTING
OF ENTIRE
AIRMASS
Rainshadow