final exam Flashcards
clouds
a large aggregation of tiny moisture droplets and ice crystals suspended in air
cloud formation
warm air parcel rises and cools
once air parcel reaches dew point temp, it becomes saturated
condensation occurs around a cloud condensation nuclei
a cloud cannot form without this nuclei
a particle >10^-4mm around which condensation occurs and cloud formation begins
natural sources
meteoric dust, clay, silt, volcanic material and sea salt
anthropogenic sources
sulfur and nitrogen compounds from combustion
cloud forming processes
1.collision- coalescence
-temp in the cloud are above freezing (0 deg. C)
-water is in liquid and vapour form
heavier moisture droplets begin to fall & collide with other droplets
-the colliding droplets merge together to form large drops–> rain
2. Bergeron Ice-crystal process
-temps are below freezing
-water is in super-cooled liquid, vapour &ice forms
-air surrounding ice has lower vapour pressure than air surrounding water
-water vapour travels from high to low pressure areas (towards ice)
-water vapour freezes and ice crystal grows (accretion/riming)
cloud classification low: up to 2000m
- Stratus: uniform, featureless grey clouds (stratiform)
- Nimbostratus: grey, dark, low clouds with drizzling rain (stratiform)
- Cumulus: grow vertically, can extend into middle level, puffy, billowy flat based clouds with swelling tops, associated with fair weather (cumuliform)
- Stratocumulus: soft, grey, globular cloud masses in groups or waves (both stratiform & cumuliform)
- Cumulonimbus: dense, heavy, massive, grow vertically into higher levels, associated with thunder storms, forms anvil shape (cumuliform)
cloud classification middle: 2000m-6000m
- Altostratus: thin to think grey clouds, similar to stratus (stratiform)
- Altocumulus: globular clouds in groups or lines (cumuliform)
cloud classification high: 6000m-13000m
- Cirrus: wispy, feathery, thin, “mares’ tales” can indicated oncoming storms
Cirrostratus: (stratiform)
1. Stratiform: flat, ;layered, with horizontal development
2. Cumuliform: puffy, globular, with vertical development
Snow
precipitation falls through cold layer from cloud to ground as frozen
sleet
precipitation falls frozen though cold layer (partially) melts through warm layer
refreezes through cold layer and falls to surface as frozen precipitation
T<0 degree refreeze partially melted
T< -6 degree from >750 m, ice pellets from liquid
freezing rain
precipitation falls frozen through cold layer
T<10 deg
melts through warm layer
T>3 deg
rain falls to surface and freezes at surface
Rain
falls through frozen cold layer
melts through warm layer
precipitation falls to surface as rain
Hail
Originates in a cumulonimbus clouds
raindrops circulate between above and below freezing
Ice layer build as a result of this
ice pellets> 0.5cm fall to ground
produced during thunderstorms
largest hailstone recorded is 47cm diameter in south Dakota
goes up and down within the cloud fluctuating between warm and cold before allowing it to fall, it grows here
winter storms include combinations of
major snowfall freezing rain strong winds blowing snow extreme wind chill
types of winter storms
ice storms
snow storm Blizzards
occur in mid to high latitudes
can result in power outages, infrastructure damage, & human health impacts
ice storms
winter storm involving at least 6.4 mm accumulation of ice
occur when a layer of warm air is between 2 layers of cold air
freezing rain
snow storms
winter storms with a large accumulation of snow
blizzards
snowstorms with:
winds > 40km/h for more than 4 hours
blowing snow that reduces visibility to 400 or less
often involve large snowfall
thunderstorms
turbulent weather accompanied by: heavy precipitation lightening thunder cumulonimbus clouds can involve squall lines of: hail, strong winds, freezing ppt , tornadoes, squall line
squall line
sudden episode of high winds and thunderstorms in an area slightly ahead of an advancing cold front
occur with frequency at ITCZ (intertropical convergence zone –> low pressure band near the equator)
warms low pressure air–> air converges at surface and rises
cooling of the air resulting in condensation, hence clouds forming–> precipitation will likely occur
thunderstorm development
warm moist air rises rapidly and cools (water vapour–> water liquid= condensation)=energy is released –> local heating of the air
violent updrafts and downdraft develop
thunderstorm activity depends on
activity depends on variation of wind speed and direction (wind shear)
can produce strong winds near the ground (downbursts)
supercells
strongest type of thunderstorm
contain persistent rotating updrafts (mesocyclone)
need high wind/convection currents, warm moist air mass
lightning and thunderstorms
lightning: flashes of light caused by huge electrical discharges that superheat the air
thunder: violent expansion of heated air created by lighting which send out audible shock waves
8 million lighting strikes/day on Earth
tornadoes
violently rotating column of air in contact with ground surface
usually produces a visible vortex of spinning clouds and debris
diameter: a few m to hundreds of km
time: a few moments to tens of minutes
formation: updraft from thunderstorm
strong wind aloft
supercell development
supercell mutation
Measurement: Fujita tornado scale –> measuring wind speed
tonado distribution
NA experiences the most tornadoes worldwide
US has the most tornadoes
Canada has the 2nd most tornadoes
Peak months for tornadoes: May & June
Tornadoes in Canada: - 80 tornadoes/year
continental polar (cP)
form only in the northern hemisphere
most developed in the winter and cold weather
cold, dense air displaces moist and warm air in its path, producing lifting, cooling, and condensation
an area covered by cP air in winter experiences
cold, stable air
clear skies
high pressure
anti-cyclonic wind flow
Maritime Polar (mP)
occur over oceans in the Northern hemisphere
an area covered by an mP air mass experiences:
cool temps
moist air
unstable condition year round
mT gulf/Atlantic
unstable
active from late spring to early fall
mT Pacific:
stable to conditionally unstable
lower in moisture and energy than the mT Gulf/Atlantic
air mass modification
as air mass migrate from source regions, their temperature and moisture characteristics slowly take on those of the land over which they pass ex. Lake-effect snow melts of the Great Lakes
four atmospheric lighting mechanisms
- convergent lifting
- air flows from high to low pressure
- low pressure centre: air converges, ascends, cools and condensation occurs - convectional lifting
- air aboie a warm surface heats up
- warm air rises
- warmer surfaces result from local heating (ex. UHI, forest) - Orographic lifting
- air is forced to ascend upslope as it is pushed against a mountain - Frontal lifting
- front: leading edge of an advancing air mass line of conflict between 2 air masses
stationary front
a front between warm and cold air masses that is moving very slowly or not at all
clod fronts
- cold dense advancing air masses forces warm air upward
- warms air lifting abruptly and cools adiabatically
sings of cold front
- a few days before a cold front passes, high cirrus clouds are often observed along the leading edge of a cold front: - winds shift -temp decreases -low pressure develops -cumulonimbus clouds form -precipitation occurs
squall line:
sudden episode of high winds and thunderstorms in an area slightly ahead of an advancing cold front
after a cold front passes
northerly winds in N.H.
temp drops
high pressure develops
clear skies
Pineapple Express
warm air carried by the jet stream from Hawaii and the pacific to the pacific coast of N.A
jet streams
irregular concentrated bands of westerly wind
stronger in winter
300 km/hr
warm front
warming advancing air masses pushes air into a wedge shape and slides up and over it
warm air lifts gently and cools adiabatically
occluded front
a composite of two fronts formed when cold front overtakes a warm front
cyclogenesis- stationary front
initially a stationary boundary separates warm and cool air masses
cyclogenesis - disturbance/wave
a disturbance triggers a wave to form within the front
cold and warm air masses conflict
air converges at surface
air diverges aloft
open stage of cyclone
cyclones draw warm air from the south
cyclone draw cold air from the north and west
cyclone matures
occluded stage of cyclone
cold front wedges under warm front forming an occluded front
dissolving stage of cyclone
occlusion increases
lifting mechanism weakens as supply of warm moist air gets cut off
cyclonic system dissipates
tropical cyclones
cyclonic circulation originating in tropics
tropical cyclones are names according to they location
80 tropical cyclones occur annually
45 per year are powerful enough to be classified as hurricanes, typhoons, and cyclones
also classified according to wind speed
tropical cyclone terminology
hurricanes- both America
typhoons - china, Japan, philippines
cyclones/ tropical cyclones- Australia, India, Indonesia, Africa
tropical cyclone vs Midlatitude cyclone
tropical cyclones:
- homogeneous air masses
- high moisture
- warm
- leads to more powerful storms*
tropical cyclone anatomy
eyewall: dense wall of rain bands created as winds rush towards the centre and turn upward
cyclone Idai
made landfall on march 14, 2019-03-28
1.7 million people living in cyclone path in Mozambique
cyclone formed in Mozambique
local winds
land and sea breezes
mountain and valley breezes
daytime valley breeze
top: high temp (lower pressure)
bottom: low temp (high pressure)
nighttime valley breeze
top: lower temp (higher pressure)
bottom: high temp (lower pressure)
driving Oceanic forces
frictional drag of wind Coriolis force density differences land configuration astronomical forces
gyres
oceanic circulation system
equatorial currents
currents remain near the equator due to weak Coriolis force
water accumulates on eastern side of continents near the equator (western intensification)
accumulated water spills northward or southward (ex. Gulf Stream & Kuroshito)
upwelling flows
cool, nutrients - rich water is brought upward
occurs when water is swept away from a coast
downwelling flows
excess water travels downward
occurs when water has accumulated as with the equatorial current
thermohaline circulation
deep currents resulting from differences in salinity and temperature
Freshening: decrease in salt content of ocean water resulting fro freeze-thaw processes
fresh water is less dense than saltwater
climate change can threaten global ocean circulation patterns
ENSO (El Nino - southern Oscillation)
large scale ocean- atmosphere climate interaction
warmer SST in centraal and eastern Pacific affects temp & precipitation on a global scale
cirrostratus
formed from fused sheets of ice crystals
milky, veil - like appearance
cirrocumulus
while tufts with mackerel appearance
occur in lines or groups
fog
a cloud layer on the ground
air temp and DPT @ ground level are nearly equal
near ground, air is saturated
for affects visibility
types of fog
radiation rime ice- crystal advection evaporation
radiation fog
a surface cools --> air above the surface cools air above surface reaches DPT occurs: over moist ground on clear nights does not occur over water
rime fog
similar process to radiation fog super-cooled water droplets often turn into frost occurs: cold weather air temp @ surface is below freezing air is moist clear skies
ice-crystal fog
air becomes full of ice crystals that forms by sublimation
reduces visibility substantially
occurs: low temp
advection fog
occurs when: warm moist air moves over cool oceans–> air cools to DPT –> advection fog
warm moist air moves to higher elevations –> adiabatic cooling to DPT –> upslope fog
cool dense air moves down into a valley –>valley fog
evaporation fog
involves advection and evaporation
cold air over warm water boy
water evaporates from water body
moisture content of overlying air increases
weather vs climate
WEATHER: SHORT-TERM, DAY TO DAY CONDITION OF THE ATMOSPHERE
CLIMATE: LONG TERM AVERAGE (E.G. OVER decades) of weather conditions and extremes in a region
elements contributing to weather
temp air pressure relative humidity wind speed and direction seasonal factors such as insolation
air masses
distinctive bodies of air with homogenous temp, humidity, and stability
air masses initially reflects the characteristics of their source region
interaction of air masses produce weather patterns
classification of air Masses
moisture
temp of their sources regions
moisture
- '’m’’ for maritime (wet)
- ‘‘c’’ for continental (dry)
temp
''A'' for arctic ''p'' for polar ''t'' for tropical ''E'' for equatorial ''AA'' for Antarctic
polar highs
frigid & dry
descend and diverge clockwise or counter clockwise
antarctic high is stronger than Arctic high
subpolar lows
cool and moist
weaker in summer, stronger in winter
subtropical highs
dry and hot
westerlies and trade winds
stronger in summer, weaker in winter
what direction does low pressure system air moves?
moves up
ITCZ Band
intertropical convergence zone
energy surplus
warm, low-density, low pressure air
converging and rising air creating clouds
westerlies
prevailing surface winds flowing from subtropics to higher latitude
stronger in the winter
jet stream
higher altitude
irregular concentrated bands of westerly winds
stronger in winter
300 km/ hour
dew point temperature
temperature at which a given mass of air becomes saturated and net condensation begins to form water droplets
maximum specific humidity
maximum amount of moisture possible at that specific temperature
explain how cyclones and anticyclones develop
Winds in an anticyclone blow just the opposite. Vertical air movements are associated with both cyclones and anticyclones. In cyclones, air close to the ground is forced inward toward the center of the cyclone, where pressure is lowest. It then begins to rise upward, expanding and cooling in the process.
describe regional wind patterns
At the ground level, however, the movement of the air toward the equator in the lower troposphere deviates toward the west, producing a wind from the east. The winds that flow to the west (from the east, easterly wind) at the ground level in the Hadley cell are called the Trade Winds.
driving forces within the atmosphere
gravitational force
pressure gradient force
Coriolis force
friction force
gravitational force
Exerts virtually uniform pressure on atmosphere at Earth’s surface
•Responsible for atmospheric pressure
pressure gradient force
- The pressure gradient results in a net force that is directed from high to low pressure and this force is called the pressure gradient force.
- The pressure gradient force is responsible for triggering the initial movement of air
Coriolis Force
- Coriolis Force is an effect of Earth’s rotation
- Deflects a moving object to the right of its moving direction in the Northern Hemisphere
- Deflects a moving object to the left of its moving direction the Southern Hemisphere
friction force
- Friction force drags on wind at surface
- Decreases with height above surface
- Friction effects extend to ~ 500 m
2 types of local winds
land and sea breezes
mountain and valley breezes
evapotranspiration
the process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants.
transpiration
is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere.
Potential Evapotranspiration (POTET)
Amount of water that could evaporate and transpire given unlimited soil moisture
Actual Evapotranspiration (ACTET)
Evapotranspiration that occurs given a limited amount of soil water
trade winds
- Winds that converge at the equatorial low
- Can arise form Northeast (in N.H.) or Southeast (in S.H.)
- Most consistent winds on Earth
Hadley cells
is a global scale tropical atmospheric circulation that features air rising near the Equator, flowing poleward at a height of 10 to 15 kilometers above the earth’s surface, descending in the subtropics, and then returning equatorward near the surface.
high level clouds include:
Cirrus, Cirruscumulus and cirrusstratus
In the Southern Hemisphere, the air associated with an anticyclone primarily moves:
towards the centre, counterclockwise
climate change
change in statistical property of the atmosphere ex. temperature
Hugging the ground, air mass 1 quickly approaches air mass 2. When they meet, air mass 2 to is expected to quickly lift. This can best be described as a:
occluded front
