Lecture 14: severe weather Flashcards
1
Q
troposphere
A
- most weather activity occurs in the troposphere
- warmer air and higher pressure at the base
- colder air and lower pressure at the top
- tropopause: boundary between troposphere and stratosphere (8-18km)
2
Q
vertical movements of air
A
- vertical movement of air from regions of high pressure at earth’s surface to regions of low pressure high in the atmosphere
- rising air losses energy and becomes cooler
- sinking air gains energy and becomes warmer
3
Q
warm air
A
- expands in volume (less dense and low pressure)
- rises
- holds more humidity
- unstable molecules
4
Q
cold air
A
- contracts in volume (denser and higher pressure)
- sinks
- holds less humidity
- molecules move less and are more stable
5
Q
wind
A
- horizontal movement of air from regions of high pressure to regions of low pressure
- winds flows inward to fill low pressure regions
6
Q
Coriolis effect in the northern hemisphere
A
- paths veer right with respect to the friction of movement
- air moving south veers to the south west
- air moving north veers to the south east
- the opposite is true in the southern hemisphere
7
Q
rotating air masses in the northern hemisphere (cyclone and anticyclone)
A
- cyclone: counterclockwise surface winds, forms in low pressure zones, air rising: water vapour condenses into air, and upper level outflow of air
- anticyclone: clockwise surface winds, forms in high pressure zones, air descending: dry and windy conditions on the ground
8
Q
cumulus stage of thunderstorm
A
- warm and moist air is lifted upward
- by mechanical lifting: cold dense air undercut warm, less dense air
- thermal lifting: warm, less dense air flows up and over cold, dense air along a gentle slope
- warm and moist air continues to rise as long as it is less dense than the surrounding air
9
Q
mature stage of thunderstorm
A
- cloud reaches max cortical development
- ice crystals and water droplets become too heavy to be supported by the updrafts
- heavy precipitation
- downdrafts
- lightning and thunder
10
Q
dissipating stage of thunderstorms
A
- cloud drinks and shrinks
- light rain
11
Q
why does lightning occur
A
- electrical unbalance
- charges separate during the development of cumulus
- positive region at the top and negative region at the base
- when electrical unbalance between positive and negative regions becomes too strong
- then lightning occurs
12
Q
development of a lightning bolt
A
- initiation: charge imbalance
- stepped ladder: negative charges move downward in intermittent steps
- connection: a positive discharge leaps up from the group
- return stroke: connected path flashes bright during charge exchange between cloud and ground
13
Q
hail
A
- a lot in alberta rockies
- forms when updrafts carry water droplets high to extremely cold regions of the troposphere
- hailstones fall when they become too heavy to be supported by the updrafts
- hailstones add most of their mass during updrafts
14
Q
tornado
A
- wind speeds >100 km/h
- updrafts movement tilted by strong winds- might lead to the development of a supercell thunderstorm
- most tornadoes are associated with supercell thunderstorms
15
Q
cumulonimbus cloud
A
- larger than cumulus cloud
- abundant ice crystals in top region
- often develops an anvil shape
- most tornadoes are produced within cumulonimbus cloud during supercell thunderstorm
