Weather and the Environment
When two Englishmen meet the
first thing they talk about is the
weather
Dr Johnson
David Leadley P567
Weather and Climate
Weather / meteorology – study of atmosphere and atmospheric
processes, daily variation
Climate / climatology – seasonal average of weather at some
location
Climate change
– long term variation in climate
… and the environment
Environment – conditions for life or growth
Sustainability – ability of the environment to function indefinitely,
despite stresses imposed by human society
Non-sustainable Human behaviour
• Using non-renewable resources as if supplies
were unlimited eg. fossile fuels
• Using renewable resources faster than they
can be replenished eg. fresh water
• Polluting the environment as if its capacity
were unlimited eg. CFCs, CO2, acid rain
• Increasing population, despite Earth’s finite
ability to support us
Earth from the Space Shuttle
“For the first time in my life
I saw the horizon as a
curved line.
It was accentuated by a thin
seam of dark blue light
– our atmosphere.
I was terrified by its fragile
appearance.”
Ulf Merbold, astronaut
Composition of the Atmosphere
(1) Permanent Gases
Percent
Chemical
composition
(by volume of
dry air)
Nitrogen
N2
78
Oxygen
O2
21
Argon
Ar
0.93
Neon
Ne
0.002
Helium
He
0.0005
Hydrogen
H2
0.00005
Xenon
Xe
0.000009
Gas
Composition of the Atmosphere
(2) Variable Gases
Chemical
composition
Percent
ppm
(by volume of
dry air)
(parts per
million)
Water vapour
H2O
0 to 4
-------
Carbon dioxide
CO2
0.035
350
Methane
CH4
0.00017
1.7
Nitrous oxide
N2O
0.00003
0.3
O3
0.000004
0.04
Particulate matter
-------
0.000001
0.01
Chlorofluorocarbons (CFCs)
-------
Substance
Ozone
0.00000001 0.0001
Origin of the atmosphere
a)
Earth formed 4.6 billion years ago, without atmosphere
b)
Outgassing from volcanoes of N2, CO2, H2O, H2, Cl2, SO2, CH4 ,
but not oxygen
c)
Water condensed in oceans, H2 escaped, acid rain weathered rocks.
CO2 at 100 times present level – larger greenhouse effect kept the
atmosphere warmer and compensated for a 30% weaker Sun
d)
Emergence of life in oceans produced O2
and sequestered CO2 in rocks
e)
Once O2 was present O3 could be formed,
giving UV protection and allowing life to expand its range
Atmospheric Oxygen
Albedo from various surfaces
Surface
Albedo (%)
Surface
Albedo (%)
Snow
79-95
Dark Soil
5-15
Ice
30-40
Grassy Field
10-30
Thick Clouds
60-90
Forest
5-15
Thin Clouds
30-50
Water
10 (avg.)
Wet Sand
20-30
Venus
78
Dry Sand
35-45
Mars
17
Concrete
17-27
Moon
7
Tarmac
5-10
Earth
30
Planetary temperature profiles
Atmospheric profile of Venus
At surface
Ts=740 K
ps=92 bar
Atmospheres of Gas Giants
Titan’s Atmosphere
Nitrogen
90-97 %
Hydrocarbons
Methane
2-10 %
Acetylene
2.2 ppm
Ethylene
10.1 ppm
Ethane
13 ppm
Propane
0.7 ppm
Nitriles
Hydrogen
cyanide
160 ppb
Cyanoacetylene
1.5 ppb
Summary of Lecture 1
• Introduction to Earth’s atmosphere
– origin
– composition
– structure
– comparison with other planets
• Stefan’s law
4R T  R S 1   
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