Week 5 Flashcards
describe the energy balance on Earth (and the sun)
equilibrium between incoming radiation and outgoing radiation
earth intercepts only a small portion of the sun’s total radiation
^^this energy from the sun drives the hydrologic cycle and all the weather phenomena on Earth
what portion of sun’s radiation does the earth absorb at its surface?
45% absorbed by Earth at the surface
25% absorbed in the atmosphere
and 30% reflected to space
describe the composition of the atmosphere
nitrogen = 78%
oxygen = 21%
the remaining 1% consists of water vapour, carbon dioxide, and other ‘trace’ of gases
what causes cloud development and formation of precipitation in the atmosphere?
water vapour in the atmosphere can lead to cloud development and the formation of precipitation
where does water vapour come from?
it is the result of evaporation from large bodies of water
what are the different levels of the atmosphere? (from surface to the outer layer)
troposphere
stratosphere
mesosphere
thermosphere
which layer/level of the atmosphere are most clouds confined to?
troposphere, the innermost layer
how does the atmosphere protect us from the sun’s harmful UV rays?
the ozone layer, found in the stratosphere, protects us from the UV rays
note that only 5% of the sun’s rays are UV rays
in which layer/level of the atmosphere is the ozone layer found?
stratosphere (2nd innermost layer)
for cloud naming, what are the prefixes for a high cloud, mid-level cloud, and a low cloud?
high: cirro-
mid: alto-
low: strato-
for cloud naming, what are the suffixes for a puffy cloud and a flat cloud?
puffy = -cumulus
flat = -stratus
what is a high puffy cloud called?
cirro - cumulus
high - puffy
what is a high flat cloud called?
cirro - stratus
high - flat
what is a mid-level puffy called?
alto - cumulus
mid - puffy
what is a mid-level flat cloud called?
alto - stratus
mid - flat
what is a low puffy cloud called?
strato - cumulus
low - puffy
what is a low flat cloud called?
strato - stratus
low - flat
what are clouds that produce precipitation called?
they contain “nimb” in their name
e.g. cumulonimbus (heavy rain/lightning/thunder) OR
nimbostratus (prolonged light to moderate precipitation)
what is a cumulonimbus?
a cloud that produces lightning, thunder, and heavy rain
puffy - precipitation
it has vertical development (it is veryyy tall!)
—— clouds such as cumulus develop in size, becoming a cumulonimbus
what is a nimbostratus?
a cloud that produces prolonged light to moderate precipitation
precipitation - flat
what is a front?
a front is a boundary between 2 air masses
the name of the front describes the air behind it
e.g.
a cold front is when dense cold air undercuts (follows behind) warm air, pushing the warm air up and forward, encouraging vertical development
a warm front which is when the less dense warm air rides on top of the cold air - but still following behind… this raises the clouds but doesn’t encourage vertical development`
how does the vertical development of clouds occur?
via a cold front
which is when dense cold air undercuts (follows behind) warm air
which type of front is the fastest?
a cold front is faster because the cold air is denser
– as a result, cold fronts have less warning time
what is needed for thunderstorm development?
water vapour
a large different in temperature between air at the ground and air aloft
rising air (or a lifting mechanism, e.g. a front)
what are the 3 stages of thunderstorm development?
cumulus, mature, dissipative
most clouds pass thru all 3 stages within one hour
cumulus
— air is pushing up, encouraging vertical development
mature
— there is a strong updraft as well as a gust front (down), both of which are going in opposite directions
dissipating
— there is an anvil head at the top - bc it’s dissipating
— weak downdrafts (going down, duh)
which clouds can have precipitation in the form of hail?
only cumulonimbus clouds
how does hail form?
in the cumulonimbus cloud, half the cloud is below 0 degrees - we need a warm sector and a cold sector
gravity pulls the hail embryo down, updraft pushes it back up - process of melting and refreezing
the droplets develop a ring of ice around it each time it enters the cold part of the cloud - causing a frozen ring structure
the ball of ice eventually becomes heavy enough to fall to the ground
describe the hail that descended in china in 2002
hail the size of basketballs (but not hollow) caused 25 deaths
what is lightning? how does it cause thunder?
a spark of electricity occurring in a cloud
most lightning strikes are from cloud to cloud rather than cloud to ground
lightning heats the air causing the air expand, thus creating a shockwave (thunder)
sometimes the atmosphere refracts thunder, making it inaudible
what is the main requirement for lightning?
a cumulonimbus cloud containing a region of opposite charges
the interaction of ice crystals, hailstones, and water droplets result in a separate distribution of charges in the cloud
what is a tornado? what is a funnel cloud?
a rotating column of low-pressure air touching the ground that forms within a supercell thunderstorm
a rotating column not touching the ground is referred to as a funnel cloud – not all funnel clouds become a tornado
what does the width of a tornado tend to be?
most range between 100 and 200 meters wide
what’s the general duration of tornadoes?
they tend to exist for less than 20 minutes with a defined life cycle
in what direction do tornadoes generally travel?
travel from the southwest towards the northeast
what’s a tornado’s average speed?
average speed of 50km/h
when are tornadoes more common in Canada? in the US?
CANADA - summer
US - spring
what are the stages in a tornado’s life cycle? describe them
organizational, mature, rope
organizational
— wind shear (the change in wind speed/direction over a distance) causes rotation to develop
— a funnel cloud protrudes from above
— dust and debris rotate beneath
——– this horizontal tube causes turbulence for planes but is not a problem on ground
——– the (updraft) hot air rising up the ground causes the tube to go from horizontal to a vertical
mature
— most severe damage occurs at this stage
rope
— the tornado stretched out and weakens
what is wind shear?
a change in wind speed or wind direction over a distance
how are tornadoes classified?
via the EF scale
(Enhanced Fujita Scale)
tornadoes are classified on a scale of EF0 to EF5 based on the damage produced with EF5 being complete devastation and a wind speed over 322 km/h
what are EF5 tornadoes and what portion make up this section?
complete devastation; wind speed over 322 km/h
less than 1% of tornadoes are classified as EFS
which countries experience the most tornadoes?
US experiences the most tornadoes on Earth
Canada experiences the 2nd most
what is a tornado alley? where is it in the US and in Canada?
a loosely defined location of the central United States and Canada where tornadoes are most frequent
US = Kansas and Oklahoma
CANADA = southwestern Ontario
why do tornado alleys exist? why is there one in Canada?
they are areas where air masses commonly collide
they are areas of relatively flat land that allows for undisturbed rotation
tornadoes occur in southern Ontario when a southwesterly wind brings warm, moist air from the gulf of Mexico
the warm air may interact with cooler lake breezes
describe the super outbreak (tornadoes) in 1974
on this day, 148 tornadoes touched down between Ontario and Alabama
many deaths
when did the largest tornado outbreak occur and where?
2011, April
in the southeast US, 358 tornadoes touched down and 324 people were killed with 239 in Alabama
overall, there were more deaths from tornadoes in 2011 than any other year since 1925
describe the Joplin tornado
in May 2011
an E5 tornado caused 161 deaths in Joplin, Missouri
this tornado was the costliest in US history (2.8 billion) and the deadliest in the US since 1947
describe the Goderich Tornado
Aug 2011
a tornado in Goderich killed 1 person and destroyed much of the town core (circle like town)
it was the first EF3 tornado to touch down in Ontario in 15 years
the tornado was spotted over Lake Huron on RADAR and a warning was issued 12 minutes before it reached the town
able to tell it was a tornado because of the red curl in the thermal map
— rotation of diff temps
describe the Moore Tornado
on 2013, May
an EF4 tornado in Moore, Oklahoma caused 24 deaths
advances in weather technology have greatly improve warning time
a tornado warning was issued for the area 16 minutes in advance
what are tropical cyclones?
tropical cyclones only form over warm water, usually in certain latitudes (5-30 degrees)
—– they require a water temperature of at least 26 degrees, why it generally occurs in the summer
they contain high winds, heavy rain, and storm surges
synonymous with hurricanes and typhoons
hurricane considered western term; term typhoons used in asia; cyclone used in australia and india
what are extratropical cyclones?
these form over land or water in temperate regions at latitudes of 30-70 degrees
they contain rain, snow, freezing rain, etc.
they are associated with fronts and are also called mid-latitude cyclones
what are the stages of tropical cyclone development?
disturbance
— a large low-pressure area with unsettled weather
depression
— an unorganized area of thunderstorms
storm
— an organized area of storms with wind of 65-119km, also the stage where the hurricane gets a human name
hurricane
— a circle-shaped low-pressure area with wind of at least 120 km/h
when does a hurricane get a name?
at its storm stage
what is the minimum speed a fully formed hurricane is at?
at least 120km/h
what are the components of a hurricane?
eye
— a region in the centre with light winds and clear to partly cloud skies
eyewall
— a ring of intense thunderstorms that whirl directly around the eye
spiral rain bands
— rings of tall clouds and heavy rain that exists thru out the hurricane
why do hurricanes have spiral rain bands?
clouds can’t form when air sinks, only when it rises
which is why we see bands of cloud as there are areas of air sinking
there needs to be air sinking to maintain the structure – or else it will fall apart
describe how hurricanes are named
alternating male and female names are used in alphabetical order (5 letters are skipped)
the names are retired if the hurricane produced notable damage
names were exhausted for the first time in 2005 when 27 hurricanes occurred and for the second time in 2020
what hurricane names were retired (never used again)?
andrew and katrina
what happens when the list of hurricane names are exhausted?
when the list of names is exhausted, the remaining storms are named after the letters of the greek alphabet (in order);
has only happened twice
describe hurricane movement
hurricanes typically travel very slowly (less than 20km/h)
—– so we can warn people days in advance!
because wind in a hurricane rotates counter-clockwise, wind speed varies thru out the hurricane
highest winds are where the arrow of direction (of the hurricane is) is on the circle, lowest winds are opposite (blue) – when doing this note that the hurricane rotates counter-clockwise
what are storm surges?
it is the most devastating effect of hurricanes
storm surges result from powerful winds that create a rapid rise in sea level
how are hurricanes classified?
in categories (1-5) via the Saffir-Simpson scale
the classification is based on wind speed
what regions are more at risk for hurricanes?
in North America, the Atlantic coast and the Gulf of Mexico coast are at highest risk of hurricanes
many hurricanes occur in August and early September because this is when the water is warmest
what are the dates for the official hurricane season?
the official hurricane season ranges from june 1st to november 30th
why does the eye disappear as soon as it hits land?
the eye disappears as soon as it hits land as it needs water to maintain its structure
what are the known hurricanes in Canada?
fiona and hazel
fiona was category 2 when it made landfall in nova scotia
hazel was the worst hurricane in canada’s history in terms of death toll (81 people)
— no other natural disaster has caused that many deaths in Canada to this day
what is fog?
a cloud with its base at the Earth’s surface
it occurs at night when the air cools to the dew point at which point water vapour condenses into droplets
fog can also form when warm air moves over a cold body of water
describe snowstorms as hazards?
in the Great Lakes region, more deaths have been caused by snowstorms than any other hazards
the worst natural disaster in Detroit in terms of death toll was a snowstorm in 2003
the storm resulted in the deaths of 36 people from heart attacks while shovelling snow
what are blizzards? what are the requirements for it?
intense winter storms with very specific conditions
– wind of at least 40km/h
– snow falling or blowing snow occurring
– visibility less than 400 m
all of these must occur for at least 4 hours
blizzards are rare in southern Ontario because we don’t get as strong winds
why are blizzards rare in Ontario?
because we don’t get as strong winds
what are lake effect snow?
increased snow fall caused by the presence of lake
snowbelts are found downwind of the lakes
——– in winter, the wind is often from the northwest
lake effect snow is caused by cold air moving over relatively warm water
describe lake effect snow in southern Ontario
London and Kitchener frequently receive lake effect snow from Lake Huron causing high annual snowfall
Windsor occasionally receives lake effect snow from Lake Michigan
describe Lake Effect Clouds
cumulus clouds that form when cold air passes over warm lakes, picking up heat and moisture
southern Ontario frequently experiences lake effect clouds in Winter
what weakens lake effect cloud and lake effect snow?
both lake effect clouds and lake effect snow diminish when ice appears on the lakes
what is a haboob?
a sandstorm that occurs in arid and semi-arid regions
what causes a haboob to form?
downdrafts on the leading edge of a thunderstorm
in a sand-environment
what is a dust devil? what causes a dust devil to form?
a small spinning vortex of air formed over hot, dry land
unlike tornado, it starts from ground up
it is relatively harmless
as hot air rises, the wind direction may change due to an obstacle
this may result in a spinning column of air
what are ice storms?
there are mainly caused by freezing rain
the weight of the ice can pull down trees and power lines
freezing rain is rain that freezes as soon as it lands on a surface
—- caused by a warm front that gently runs over the cold air
what are droughts?
an extended period of unusually low precipitation
droughts affect more people in North America than any other hazard
what hazard affects North America the most?
droughts
they cause water shortages that can lead to crop failure. in developing countries, this may lead to malnutrition and famine
droughts are linked to global weather pattens and are a normal part of the climate systems
what is wind chill?
a correction factor to an air temperature caused by the presence of wind making the air feel cooler than the temperature suggests
why does the wind make us feel colder?
—- the wind takes the warm layer of air surrounding your body, blowing it away from you
why does the wind make us feel colder?
the wind takes the warm layer of air surrounding your body, blowing it away from you
what is the humidex?
a correction factor to a temperature reading caused by high humidity making the air feel warmer than the temperature suggests
too humid for your sweat to evaporate timely (n consequentially, unable to cool you)
nowadays, how do we minimize severe weather hazards?
forecasting has improved dramatically with better technology; 3-day forecasts are very accurate today
weather satellites detect cloud cover and aid in forecasting hurricanes and mid-latitude cyclones
RADAR detects precipitation (both the type of precipitation and intensity)
what are the 3 type of alerts?
watch, warning, advisory
watch
— conditions favour the development of hazardous weather, but none has been reported – doesn’t mean it happens, just that it’s more probable
— an alert covering a wide area
warning
— it indicates that hazardous weather is currently occurring in the area
— an alert that usually covers smaller areas
advisory
— it is issued to alert the public of less hazardous weather conditions
