Weather Impacts: The View From Afar
Extreme weather is
a rare event!
Weather Impacts in
Perspective
Deaths per million
population annualy
Weather Impacts in Perspective
Weather-related deaths broken down by cause
Weather Impacts in Perspective
Key:
flooding (top)
lightning (middle)
tornado (bottom)
Weather-related deaths per million broken down by state
Weather Impacts in Perspective
Number of billion dollar weather events from 1980 to 2004
Weather events cause $10 billion in damage annually!
What is the atmosphere?
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“A delicate life-giving blanket of air surrounding the Earth”
What is the atmosphere?
●
●
“A delicate life-giving blanket of air surrounding the Earth”
More precisely: a relatively thin layer of gases
consisting mainly of N2 and O2
- 78% N2 and 21% O2
- Percentages roughly constant but reflect a
continual balance between sources and sinks
●
The atmosphere is thin: 99% of the atmosphere by
mass is below 30 km in height!
What is the atmosphere?
●
●
“A delicate life-giving blanket of air surrounding the Earth”
More precisely: a relatively thin layer of gases
consisting mainly of N2 and O2
- 78% N2 and 21% O2
- Percentages roughly constant but reflect a
continual balance between sources and sinks
●
The atmosphere is thin: 99% of the atmosphere by
mass is below 30 km in height!
- For comparison, radius of the earth is 6400 km
Composition of the Atmosphere by Volume
●
●
Dry atmosphere is mainly N2 and O2
Water vapor is the main variable constituent (up to 4%),
followed by CO2
Water Vapor and Carbon Dioxide
Two important atmospheric constituents are water
vapor and carbon dioxide
● Evaporation of water at the ground / ocean surface
and condensation in clouds plays an important role
in the Earth's heat budget
●
●
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Both are important greenhouse gases, meaning that
they trap heat energy radiated by the earth's surface
For both constituents, the concentration depends on a
competition between sources and sinks
- Residence timescales:
Carbon dioxide: 150 years
Water vapor: 10 days
Sources and Sinks
of CO2
●
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For most atmospheric
constituents, the
concentration depends
on a balance between
sources and sinks
The rate of creation /
destruction is measured
by the residence
timescale, or the time
needed to completely
replace the stuff
currently in the
atmosphere
Looking (Way) Ahead: CO2 Changes Over Time
●
Currently the sources of CO2 outweigh the sinks
Measurements at Mauna Loa
observatory, Hawaii
Looking (Way) Ahead: CO2 Changes Over Time
Mauna Loa measurements combined
with ice core record
Other Players
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Ozone lives a double life in the atmosphere:
– In the stratosphere, it absorbs UV radiation, shielding life
at the Earth's surface
– Near the ground, ozone acts as a pollutant
Chlorofluorocarbons catalyze ozone destruction in the
stratosphere
– Responsible for the ozone holes that form each spring
Particulate matter (aerosols) and other chemicals act as
pollutants at the ground
A Sea of Air
A few quick facts:
●
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A cube of air 1 mm on a side near the ground has roughly
1016 (or 10 million billion) molecules of air
On average, an air molecule at the ground moves less than
10-8 m (or one millionth of a cm) before colliding with
another air molecule
So even though we don't see it, we really are swimming in a
sea of air. The only reason we don't notice is that we're
adapted to this environment.