Lecture 9 + 10: fire and climate change Flashcards
1
Q
difference between climate and weather
A
- climate - long term variations (30 years or more)
- weather - short term variations (a few days to a few years)
2
Q
Global energy budget
A
- powered by the sun
- energy received by the sun is 4000 times greater than the energy that is within the earth’s interior
3
Q
greenhouse effect
A
- where gases in the lower atmosphere absorb and reradiate the energy to the earth
- water vapor = the most abundant gas
- CO2
- methane
4
Q
Hydrologic cycle
A
- 24% of solar energy is used to evaporate water in the hydrologic cycle
- water is uniquely qualified to be a medium for energy transfer
5
Q
Coriolis effect
A
- forces imposed on the earth by the earth’s rotation
- sets cold and warm air into motion
- influences ocean surface water motion which in turn influences the motion of deep ocean water
- the force responsible for transporting the energy stored in water around the world
6
Q
ice age
A
- icehouse: an ice age where glaciers are created
- requirements (1) large continental masses near the poles to collect snowfall and build ice sheets and (2) ocean circulation that favors north-south directions
7
Q
mitigation strategies for climate change
A
- reduce greenhouse gas
- Paris agreement
- who pays for it? it’s hard to get all countries to agree
8
Q
benefits of fire
A
- the boreal frosts is a fire-dependent ecosystem
- certain plants need smoke and or fire to germinate their seeds
- control parasite
- percent overaccumulation of organic debris
9
Q
lightning caused fires
A
- occur in remote locations
- burn undetected longer
- tend to merge into large fires
10
Q
duff
A
- mat or organic debris on the ground
- lightning on moist duff does not start fires
- lighting on dry duff starts fired
11
Q
pyrolysis
A
- receding combustion is pyrolysis
- chemical decomposition by the action of heat
- input: wood material heated above initiation temperature
- output: flammable hydrocarbon vapors; water vapor; tar; mineral residue
12
Q
combustion
A
- the act of burning
13
Q
three stages of combustion of wood
A
- preheating: resting T degrees expels water from wood
- flaming combustion: stage if greatest energy release; if heat and oxygen are present, hydrocarbon vapors from pyrolysis ignite. moves slowly into wood through cracks
- smoldering and glowing combustion: flames gradually die off; slowing combustion: heat slowly reaches the interior of the log
14
Q
heat transfer mechanisms
A
- conduction: transfer through a material or between materials in contact
- convection: transfer through fluid
- radiation: heat transfer via radiation (like warming coffee in microwave)
15
Q
heat transfer in a log-tree
A
- heat moves inward (conduction: particles in pyrolyzed gases in cracks)
- heat moves outward (conduction from collisions of particles from hot to cold areas)
