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Midterm

ATS1310 Study Guide - Midterm Guide: Atmospheric Instability, Mercedes-Benz Superdome, Silt

3 pages106 viewsFall 2018

Department
Arts - ATS
Course Code
ATS1310
Professor
Megan Farrelly
Study Guide
Midterm

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KEY CONCEPTS
All severe storms are associated with strong vertical motion in the atmosphere producing heavy precipitation & strong winds
FACTORS/CAUSES
Most rainfall is produced by rising air:
- Air forced to rise (from instability…) will cool as it expands (because air that is rising is expanding doing
work heat is being released)
- If cooling continues cloud condensation (as air reaches its dew point - can no longer hold certain
amount of water in atmosphere without forming cloud) & precipitation processes begin
Most severe weather is associated with atmospheric instability
- Instability: warm air at low levels and colder above (warm wants to rise through cold
and cold wants to sink through warm)
- Produces cloud & precipitation (if other conditions are suited i.e. sufficient moisture in
air/cloud) (e.g. surface of deserts during day are instable (intense heating of ground) yet
doesn’t produce rainfall as desert air is too dry for cloud to form)
- Stable very little vertical motion, little/no precipitation
A pressure gradient force (Pgf) sets air in motion & is directed down the pressure
gradient from higher towards lower pressure
- High pressure clear skies
- Low pressure rising air & instability
- Stronger the Pgf the closer the isobars are together stronger the winds
- Pgf (hence wind speed) proportional to spacing b/w isobars (lines of equal
pressure) on a weather map
Coriolis deflection
- Without rotation of earth air would flow in a direct line from high to low pressure
with no curvature
- Because of rotation, airflow has apparent deflection (TO THE LEFT in
SOUTHERN HEM) as it moves over the surface
- No rotation: straight from A to B
- Rotation: apparent deflection to the left from A to C
Southern Hemisphere Tropical Cyclone
- Clockwise flow around low-pressure
system
- Air is flowing into this tropical cyclone
then rises up from walls of cyclone
eye & subsides away from cyclone
Criteria for development of tropical
cyclones
1. Low-level converging air (inflow) &
low surface pressure
2. Warm tropical atmosphere conducive
to moist convective processes
(maintaining instability)
3. Ocean surface temp 26+ degrees so
sufficient heat & moisture can be
supplied
4. Weak upper winds
5. At least 4-5 degrees of latitude away
from Equator (Coriolis deflection -
spiralling)
6. Upper-air divergence (outflow) allows
air to be removed at sufficient rate for
surface pressure to continue to fall
Tropical cyclones can’t form at equator
(high pressure - stable)??
EFFECTS
Costs:
- Loss of life & injuries
- Property & infrastructure damage (pressure on natural water systems)
- Disruption to power & train services insufficient transportation for those without private means of evacuation
- Unable to remove patients & elderly to safer facilities
- People choose not to return home
- Shift in ethnic mix of city
- Cost increases in rental properties
- Many houses not rebuilt
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