wind essa09 may 12...
TRANSCRIPT
WIND – ESSA09 May 12th, 2011
Prof: Tanzina Mohsin [email protected]
Midterm: June 23rd
Lecture #1: Wind
- Human mythology
- Destructiveness tornadoes, hurricanes
o 165 tornadoes in 24 hours, 194 dead in Alabama in April 2011
- Climatic importance wind chill, local cooling and heating, Chinooks (local climate)
- Power source wind power
- Atmospheric Primer:
o Wind mythology (history of wind):
Greeks (euro-centric)
Aeolus (greek god) designated by Zeus to look after the four winds
o Zephrus gentle, west wind
o Boreas chilly, north wind
o Notos southern rain bringer
o Eurus ill-tempered, east breeze
Chinese mythology:
Feng Po Po wind goddess, replaced by Feng Po
Japanese mythology:
Fujin was one of the earliest Gods of Shinto, the God of Wind
North American Indian:
Connect spiritual power with wind
Navajo (DinE) wind intimately connected to their spiritual life
Part of creation stories (Holy wind) links to breathing
o Thought we were created from wind and not earth
Others:
Wind mythology permeates most human societies
o Cultural winds
Culturally wind has been used as a metaphor, often representing change
Gone with the wind
Twister
The hurricane
o Denzel Washington’s character connected to the character of a hurricane
Monsoon wedding
o Shows different action of wind that have characters that match up with each
of the characters
Chocolate
The wind that shakes the barley
o Wind in religions
In the Hindu and Buddhist religions
Wind is viewed as the nature or state of a God
Referred to as “vayu”, “pavan”, and “godai”
In other religions, such as Islam, Judaism, or Christianity
Wind is viewed as one of the five great elements of power
The wind power had been used to teach lessons to the followers in the past
Each book of the religions describe the act of wind power in different ways
In Ancient Egypt, the 5 elements were used to create science and math
o ***Participation Opportunity slide 29!***
o Variations in atmospheric constituents
Geological Control volcanic
4.6 billion years
The atmosphere has not been stable composition is dynamic, not static, and is
always changing
o Balance comes not from static but because inputs equal outputs
In the beginning…
o Early earth:
Atmospheric composition largely the results of volcanic emissions
(geologic control) CO2, CH4
Lie appeared 3.8 billion years ago
o 2.3 billion years of methane, carbon dioxide atmosphere
Anaerobic conditions “age of bacteria”
o Abrupt change 2.3 billion years ago
O2 makes an appearance in the atmosphere and stabilizes at 21%
Aerobic life forms appear and flourish (biologic control)
Links to Gaia Hypothesis (James Lovelock)
Biological control aerobic revolution
James Lovelock basic premise is that LIFE modifies the environment to best suit
itself (survival of the fittest)
21% O2 is optimum for life
Mars and Venus are in a static equilibrium with high levels of carbon dioxide and
methane but no life
So why switch from anaerobic to aerobic conditions 2.3 billion years ago?
o Gaia Hypothesis:
Early sun produced 30% less energy (Achaean)
Solar output has been gradually increasing (making earth HOT)
Early earth with high levels of methane and carbon dioxide had a
strong greenhouse effect which lead to conditions warm enough for
life
After 2.3 billion years solar output increased and earth was
becoming too warm, the switch to aerobic life, reduced the
greenhouse gases (CO2 and CH4) and cooled the planet
We not have considerably lower levels of CO2 in the atmosphere
than the early earth
Gaia Hypothesis postulated that the atmospheric constituents have
been controlled by life to optimize conditions for life
Anthropogenic Control pollutants
During the carboniferous period (360-290 million years ago) during the Paleozoic
Age life arrives on land
o Sun’s energy converted to plant material (photosynthesis)
o Decaying plants are not full oxidized
o Converted to coal (and oil) under geologic pressure
o Stored for millions of years
o Many of today’s air quality problems arise from the release of this stored
energy (smog, acid rain, global warming)
Story of Coal
o First major anthropogenic modification of the atmosphere
o Britain industrial revolution – 19th century
o United States – 19th and 20th centuries
o China – 11th century, present
A modern Dumping Ground
o Fossil fuel (coal, oil + other hydrocarbons) source of emissions
Acid rain, global warming, ozone hole
- The Basics:
o Composition:
What is air made of?
What phase of matter is air?
o Gas mainly
o Liquid (cloud)
o Solid (particulate matter)
What are the gas phase constituents of air?
o Nitrogen, oxygen, argon, etc.
What is a greenhouse gas?
o Atmospheric constituent that traps outgoing terrestrial radiation
o These include water vapour, carbon dioxide, methane, nitrous oxide, ozone,
and CFC’s
Understand the difference between natural greenhouse effect and enhanced
greenhouse effect
o Natural greenhouse effect desired, we want it
Without it the temp of the earth will be 33 degrees C lower (avg.
temp= 15degreesC) therefore will be -18 degrees
o Enhanced referred to as global warming, extreme
Heat waves, more air condition used, more electricity
o Anthropogenic emissions of greenhouse gases have increased in the past
few decades and have great impacts on the natural atmosphere
Clouds (liquid constituent) ** know the names and meanings of general cloud terms)***
Stratus, strato layer clouds
o Status, nimbostratus, altostratus, cirrostratus, stratocumulus
Cumulus, cumulo “puffy” clouds (storm clouds?)
o Cumulus, stratocumulus, cumulonimbus, altocumulus, cirrocumulus
Cirrus, cirro high clouds
o Cirrus, cirrostratus, cirrocumulus
Nimbus, nimbo rain clouds
o Nimbostratus, cumulonimbus
Alto middle clouds
o Altostratus, altocumulus
Vertical structure of the atmosphere:
Four distinct layers in the atmosphere:
o Troposphere
0 to 11 Km
Where temp decreases with high altitude
Pressure, density changes with high altitude
Whenever you have more gas in the mixture, you increase
the temp.
o In the ground level, cars and etc. creates more gas =
therefore temperature increases
Focus of the course
All the climate change occurs in this layer
o Stratosphere
Ozone is in the middle of troposphere and stratosphere
Therefore temperature is higher with high altitude
o Mesosphere
Less mixing, very stable layer
o Thermosphere
o **know all the layers and the temp. change and why**
What is wind?
Movement of air in an “ordered” fashion formal definition
Can we see it?
o Not directly, we can see the effects of wind in dust, tree movement
o We can feel the wind
o We can hear the wind
What causes air to move?
o Differences in air pressure, vertical or horizontal
o Differences in pressure forms a pressure gradient
o Air tends to flow from high pressure to low pressure pressure gradient
force
o Isobars lines of constant pressure (on diagram)
o Observing the atmosphere
What do we measure?
How do we measure?
Temperature thermometer
o Late 16th century
o Liquid in glass thermometer
Temperature changes are assessed using the expansion of a fluid
(mercury, alcohol)
Fitzroy thermometer, 19th century standardized thermometer
o Electrical thermometer
Electrical resistance a function of temperature
o Bimetallic thermometer
Two metals welded together, thermal expansion different for
different metals
Pressure barometer
o Barometer (1643, Torricelli)
o Mercury: pressure changes assessed using the movement of mercury in a
column
o Aneroid: pressure measures by changes in volume of partially evacuated box
Humidity hygrometer, psychrometer
o Hygrometer (1780)
Expansion and contraction of material due to changes in humidity
Hair was used traditionally
Hair shrinks in the winter
o Psychrometer:
Wet bulb temperature Cooling of air due to evaporation of water
until saturation occurs
Wind speed anemometer
Wind direction weather vane
Precipitation rain gauge, snow gauge, radar
Wind – Lecture 2: Global Wind Circulation
Troposphere !!
What is wind? Movement of air in an “ordered” fashion
What causes air to move?
- Differences in air pressure, vertical or horizontal
- Differences in pressure forms a pressure gradient force
o Two isobars lines of constant pressure – wind moves from high to low pressure which
creates the pressure gradient force
- Air tends to flow from high pressure to low pressure
- Called a pressure gradient force
- Differences in the two figures:
o The first figure isobars were nicely spread out 100Meters apart
o Second figure they are randomly spread apart, not equally spread apart
Different pressure gradient force
Closely spaced isobar = STRONG pressure gradient force strong wind!
Coriolis Force: “fictitious” force due to rotation of the earth
- Arises due to the rotation of Earth
o Very hard to graph because this force is applicable to any moving object on Earth
- In Northern hemisphere, causes a deflection to the right of the motion
- In Southern hemisphere, deflection to the left of the motion
o E.g., rocket launch eventually curves to the right or left depending on the hemisphere
- Related to the distance from the equator – at the equator, Coriolis force = 0
- Acts at right angle to the wind affecting the direction
- Formulated mathematically by Gaspard Gustave de Coriolis in 1835; described by George Hadley a
century before
- Thought exercise: starting at North Pole, you aim your place towards Toronto. What city are you
more likely to arrive at? Toronto, Montreal, or Winnipeg?
o ???
- Summary Facts:
o PGF (pressure gradient force) is always directed from high pressure towards the lower
pressure
o Steep PG (closely spaced isobars) indicate strong PGF and high winds
o When the wind starts to blow, the Coriolis force causes it to bend to the right of its
intended path in the Northern Hemisphere and to the left of its intended path in the
Southern Hemisphere
Geostrophic wind: balance between PGF and Coriolis results in geostrophic wind
- Geostrophic wind is typically 1km or so above the Earth’s surface blowing freely above 1km from
the surface
- One characteristic is that the wind is blowing parallel to the isobars
- Therefore, PGF and Coriolis force comes to a balance at approx. 1km above the surface
o So what is happening between 0-1km?
Surface winds: Below 1km – the wind is influenced by friction
Friction disrupts the balance between PGF and Coriolis Force
Wind is not blowing parallel to the isobars, they are blowing at an angle, 3
things are acting together now
Characteristic at a lower pressure system, wind is blowing anti-clockwise
at a high pressure system, wind is blowing at clockwise rotation in
NORTHERN HEMISPHERE
o OPPOSITE FOR SOUTHERN HEMISPHERE
At high – wind clockwise
At low – wind anti-clockwise
Divergence at low, convergence at high pressure system
Global Circulation:
- Three broad categories of atmospheric circulation:
o Global 10,000’s of km
o Synoptic 100’s to 1000’s of km
o Small scales less than 100 km
- Observation of global circulation: there is more energy released in the polar regions than is
received from the sun – the reverse is true for the equatorial region
o How can we account for this? atmospheric circulation – poleward transport by wind
One Cell Theory: one large overturning atmospheric cell
- Air rises at the equator, moves poleward and then sinks at the pole – one large Hadley cell
o Named after George Hadley – British Lawyer and amateur meteorologist
- Atmospheric hear transport:
o Sensible heat heat you can “feel”
o Latent Heat stored as water vapour, heat is absorbed when water evaporates, heat is
released when water condenses “hidden heat”
- Energy transportation:
o Energy is transported as sensible and latent heat
o Latent heat transport occurs when moist equatorial air moves poleward, cools, condenses,
and releases latent heat
o Is this theory reasonable??? it would be ok if the Earth did not rotate however the tilt
and land/water contrast also play a role
3 main causes that One Cell Theory cannot explain:
Rotation introduces the Coriolis Effect
Tilt causes seasonality
Continentality causes land/sea variation due to varying thermal inertia (e.g.,
Monsoons)
One cell theory with a rotating Earth:
Prevailing wind from the east
Clearly not observed prevailing wind in the midaltitudes is from the west
Therefore, NEED A BETTER THEORY
Three Cell Theory:
- 3 cells Hadley Cell, Ferrel Cell, and Polar Cell
- Hadley cell near the equator Air rises at the equator, moves poleward and sinks at 30deg
North and 30deg South
- Surface flow is equatorward and produces winds from the east
- Ferrel cell exists roughly between 30deg (arises) and 60deg (sinks) in each hemisphere - thermally
indirect
- Surface winds travel north and under the influence of Coriolis force veers to the east
- Named after William Ferrel – American Meteorologist and mathematician
- Polar cell rising at 60deg, and sinking at both North and South Poles
o Polar easterlies produced
Definitions:
- Intertropical Convergence Zone (ITCZ): area of rising air at or near the equator, heavy precipitation
(0-5deg North and South)
- Trade Winds: winds that blow to the south west, surface component of Hadley Cell, among from
northeast (0-30deg N and S)
- Subtropical High: subsiding air at 30deg North and 30deg South – little precipitation or descending
air, referred to as the horse latitudes
- Westerlies: winds blowing to the east and north in the midaltitudes – surface component of the
Ferrel Cell
- Polar Front: division of polar air and midaltitudes air, plays a huge role in Toronto’s zone
(midlatitude)
- Polar Easterlies: winds that blow south west from the North Pole (southwest from South Pole)
Continentality and Seasonality:
- Seasonality summers and winters and two other seasons
- Continentality land masses heat and cool faster than water, land also has more friction than
water
Upper Level Flow: global circulation
- High pressure system sinking air
- Low pressure system rising air
- Why does this differ from the surface flow?
o Think in terms of what do you have at the surface
January:
Isobars are now straight lines and is indicating that winds are now moving
freely in both Northern and Southern Hemispheres (geostrophic wind)
Ferrel cell is not so obvious, Hadley cell we can explain somehow the
High’s and Low’s are not so obvious but we can still explain energy of
transportation through the cells
July:
Anti-cyclonic conditions or clear skies in the summer
Can explain both upper level and surface low
o What you don’t have above 1km from the surface
- Low pressure system near the equator (rising) and high pressure systems near the poles (sinking)
- For northern hemisphere Winter season (January surface) at 30deg = sinking air, therefore look
for H pressure system
o Wind is moving according to the cell in this case, the Hadley Cell
o Continentality can effect wind movement because in N hemisphere there is more land and S
hemisphere there is more water
o For winter more distinguished L pressure system so wind movement and cell features
better in Northern Hemisphere than the S hemisphere
Jet Streams: swift flowing current of air/wind
- Thousands of km long, a few hundred km wide, a few km thick (10-15 km above the surface)
- Speed ranged from 150 to 300 km/h
- Jets occur at the divisions of the three cells
- Polar Jet: we experience this in North America
o For midaltitudes regions, the polar jet is more important
o Typically, if we are experiencing very cold weather, the polar jet stream is to the south of
us, and vice versa during the winter thaw
If we have mild winter, the jet stream stays in the North of us (summer of 2009)
Jets can affect the seasonality
o Surface features, such as low pressure systems (storms) tend to follow the direction of the
upper level jet stream
**Air Masses: large body of air whose properties of temperature and moisture are fairly uniform in any
horizontal direction at any given altitude (DEFINITION ON MIDTERM OR FINAL!!!)
- Typically air masses cover many thousands of km’s
- Source region: the area where an air mass originates
o Typical sources includes the Oceans, the Northwest Territories, Nunavut, Northern Mexico
- Classification: understand and memorize!!!
o P polar latitudes
o T Tropical latitudes (0-35deg N and S, otherwise Polar)
o C land (continental)
o M water (moisture), maritime
Land (c) + Polar (P) = cold, dry, stable
Water (m) + Polar (P) = cool, moist, unstable
Land (c) + Tropical (T) = hot, dry, stable aloft, unstable surface
Water (m) + Tropical (T) = warm, moist, usually unstable
- Modifying Air Masses
o E.g., mP if going over the mountains – ultimately it will turn lose all precipitation and air
mass turns into something else – cool air mass turns to dry and most of the time turns
warmer than the original air mass
Stratospheric Winds:
- Dobson-Brewer Circulation:
o It has one cell, air rises at the equator, raises at the stratosphere zone
o Thermally driven, provides equator to pole transport, some exchange between the layers
o 20-40mm above the surface
o Causes QBO!!!
- QBO: Quasi-Biennial Oscillation
o Cause of Dobson-Brewer Circulation
o 2 to 3 year oscillation (west <- -> east) in the upper troposphere and stratosphere
equatorial winds
o Shifting of upper level tropospheric winds/lower level stratospheric winds from east to west
Opposite in the tropical zone (more intense hurricanes in the east) than our zone
o Linked to ozone hole, hurricane frequency
Air Mass Classification System (Sheridan) improved identification scheme (applicable to North America)
- SIX air mass types: DP, DM, DT, MP, MM, MT
- First Letter: D (dry), M (moist)
- Second Letter: P (polar), M (moderate), T (tropical)
o DP very similar to cP
Cool, dry, little cloud
Source – northern Canada/Alaska
o DM mild, dry
No traditional source – modified air of mixtures of other air masses
o DT similar to cT
Hot, dry
Source – SW USA deserts, Mexico
o MP similar to mP (modified air mass)
Cool, cloudy , humid
Source – North Atlantic, North Pacific, Great Lakes
o MM cloudy, but warmer, more humid than MP
Source – usually modified mP
o MT similar to mT
Warm, humid
Source – Gulf of Mexico, tropical Atlantic
MT+ subcategory of MT hot, very humid
o In Toronto, during July and August, this kind of air mass created
SMOG
o TR transitional air mass
When any area mass does not fit in the above 7 categories, then that air mass is put
under the TR category
- Links to Air Quality:
o DM and MT are strongly associated with poor air quality in Toronto
Advection of pollutants from the southwest (USA)
Stable air masses (no clouds or rain), clear skies
Pollutants collect
Wind – Lecture 3: HURRICANES
Terms for Tropical Cyclones:
- Hurricane: North American term (Atlantic hurricanes, Eastern pacific hurricanes)
o Taino language of Caribbean meaning “god of evil”
- Typhoon: term used in Western Pacific
o “Taifung” – Chinese word for “big wind”
- Cyclone: term used in Australia and in the Indian Ocean (southeast Asian storms)
- *** Define in terms of hurricane ORIGIN (hurricane, typhoon, cyclone)
Definitions:
- Tropical storm: storm (tropical region) with sustained wind of 18 to 33 ms^-1
- Hurricane: tropical storm with sustained winds ranging from 33 to 50 ms^-1
- Major Hurricane: tropical storm with sustained winds exceeding 50 ms^-1
- **defined by the wind speed**
- Saffir-Simpson Scale: Herbert Saffir (consulting Engineer), Robert Simpson (Director of National
Hurricane Centre (USA))
Tropical Storm Classification:
- Saffir-Simpson Scale 1-5 rating scale
o 1 119-153km/h (33-42.5m/s), > 980 mb
o 5 greater than 249 km/h (>69m/s), < 920 mb most crucial
o Wind speed and pressure is used to differentiate the categories
o The lower the pressure, the stronger the tropical storm!!!
o **note down all 5 category classifications!**
Dynamics:
- How do hurricanes form? intense low pressure-system
o Tropical storms fueled by sea surface temperatures (source of latent heat) and latent heat
release (**26.5degC threshold** is necessary but not sufficient)
Below 26.5deg. C, there is hardly any possibility of formation of hurricanes
o What is latent heat? heat that is released or absorbed due to change in phase
o Convergence at the surface another main thing you need for low pressure system to
occur
Convergence at the surface, divergence aloft
Warm air expands, causing divergence aloft
Wind generated waves, increasing spray, increasing evaporation and latent heat
formation fuel for the storm
- Tropical Storm Development – Atlantic Basin:
o Begins as a tropical wave (originates in East Africa) in the Intertropical convergence zone
(ITCZ)
o June through November
o Latitudes 5-20deg North
o Group of thunderstorms that become organized and self-sustaining and if the conditions are
favourable, they can turn into hurricanes
- Requirements for the formation of tropical cyclone:
o Threshold of 26.5deg. C
o Convergence at the surface
o Divergence aloft
o Rising air released latent heat, warms upper atmosphere, causes air to diverge
o Eye forms in the middle where air is sinking only storm that has this is hurricanes!
- What affects the length and strength of a tropical cyclone?
o SSTs the warmer the surface, the stronger and longer the storms are
If the SSTs is not favourable to hurricanes, then that will affect the length and
strength of the storm
When 26.5deg. C, hurricanes are average, normal – but is this SSTs sustains over the
next several weeks, the hurricane gets the chance to get stronger and longer
stronger hurricane increase in category
o Upper wind structure strong upper level winds inhibit tropical cyclone longevity
QBO – quasi-biennial oscillation of the winds in the stratosphere
If at westerly phase stronger
Easterly face weaker
El-Nino – affects winds in Eastern Pacific (EP) and Atlantic (ATL) hurricanes
(Enhances EP, suppresses ATL)
Kind of the opposite of QBO
o i.e., Toronto, El Nino year we will see much less hurricane
Toronto, non- El Nino year much more hurricanes occurring
Landfall cuts off cyclone from both sources of energy (SSTs and water vapour),
increases surface roughness (friction)
Examples: Atlantic Hurricanes and ENSO:
1997 El Nino year hardly any hurricanes
1998 Non-El Nino year almost double the hurricanes
o Sea surface temperatures has opposite phases for el nino and non el
nino years
The mixing of the east and west ocean water – during el nino
year, most of the eastern oceanic water where you have up or
down oiling of deep ocean water, the east and west water
mixes so east ocean water is warmer, so when it mixes with
west water, and therefore, the west water is hotter than usual
During non-elnino year, the water does not mix, therefore, we
feel cold
Tropical Storm Distribution:
- Why do tropical storms not occur in the South Atlantic and the southern Eastern pacific?
o Where is the hurricane originating and what is the threshold, where is it 26.5deg. C
threshold?
Note temperature distribution of the world ocean all regions of hurricane
development exceed 26.5deg C
o ***However in 2004…there was an exception:
CYCLONE Katrina: March 26-27, 2004
First hurricane-strength storm observed in the South Atlantic (category 2)
(somewhere you never see storms – South Atlantic)
Why now? combination of SSTs and atmospheric flow
o
o Canadian Hurricanes:
Eastern provinces occasionally are hit by tropical storms – as far west as the Great
Lakes
Not an issue in the Western provinces
Canadian Hurricane Centre in Halifax
Eastern provinces starts in mid-June and ends in October
In terms of the time frame (1900-2000), avg. number of hurricane activity is
increasing
o What is happening that is different in the recent year(s) that is
causing the hurricanes to be more frequent and stronger?
Hurricane Damage in Canada: emergency preparedness Canada
8th costliest natural disaster in Canada
19 from 1990 to 1999
136 fatalities, 1868 evacuated
1.15 billion dollars of damage
o 2010 hurricane hit Newfoundland hurricane IGOR
Forecasting Hurricanes:
- (William) Gray Index – forecasting Atlantic Basic Hurricanes
o The only reliable forecast measure in North America
o Statistical Methods employed
o Factors Affecting Hurricanes:
ENSO (El Nino Southern Oscillation)
QBO (quasi-biennial Oscillation)
SSTs (sea surface temperatures)
Sahel rainfall (related to larger scale air flow which affect hurricane development)
o Gray forecasted in 2004 there will be 15 named storm (observed 14), Cyclones 9
observed 8
2005: 15 (27), 8(15)
2005 – poorest forecast on record for Atlantic tropical storms
First time number of storms exceeded available names (Alpha to Zeta used)
Year when New Orleans was swept off by Hurricane Katrina
2006: 11(9), 6(5)
2007 Summary: 14 (17)
Hurricane Dean (5) hit Mexico
Hurricane Felix (5) hit Nicaragua and Honduras
Hurricane Humberto (1) hit Texas
**notice how the intensity (category 4,5) of hurricanes have been increasing
by the year (mainly after year 2000)**
2008 Hurricanes:
9 named hurricanes
5 of them are category 5 hurricanes
Bertha (5) hit Bermuda and is the longest-lived July Atlantic tropical cyclone
that died after 17 days
Hurricane Dolly (5) made landfall two times at Texas and also near Cancun
Hurricane Gustav (5) made landfall at Haiti
Hurricane Hanna (5) hit South Carolina and Haiti
Hurricane Ike – third deadliest, affected part of Eastern Canada
o Comparisons of the hurricane seasons of 2005 and 2009:
2005 had the busiest season on record
A lot of activity in 2005, not so much in 2009
o 2009 Hurricanes: El Nino Year
Forecasters expected 12 tropical storms
Six of these were expected to become hurricanes
Two of which are expected to be major hurricanes
Where are all the storms/hurricanes???
El-Nino #1 cause (b/c it affected SSTs) – the pacific warm-water pattern
that tends to limit the formation of tropical storms and hurricanes in the
Atlantic
Wind shear marked by criss-crossing winds at different layers of the
atmosphere, can kneecap the rotation of brewing storms
Dry air high in the atmosphere that sinks down and tends to sap the
thunderstorms which fuel the hurricane dynamo
*Only exception was Hurricane Bill*
Global temperature temperature increased more than 26.5deg. C
o Same kind of results as an el nino year, but not actually el nino,
maybe because of the fluctuating global temperatures
o 2010 Hurricanes PREDICTIONS:
Forecasted Atlantic hurricane season will be “above-average” in activity
Transition year from el nino to non el nino
This will cause more hurricanes to occur in the Atlantic Basin
11-16 tropical storms, including 6 to 8 hurricanes
3-5 would become major hurricanes of category 3 or higher
o 2009 vs. 2010: why was the forecast for 2010 must more aggressive from 2009? What are
some of the assumptions/observations made behind such forecast?
Because of the transition from el nino to non el nino – affect the SSTs and will occur
increase in hurricane activity
o 2010: above-average (prediction corrected)
Highest number since 2005
Four category storms, forecast was 3-5
Therefore, prediction was almost perfect
Perspective on Recent Storms:
- 2005: Emily, Katrina, Rita, Wilma are these storms unusual? (all category 5 storms –
unprecedented)
- Hurricane Katrina: 23-31 August, 2005
o Direct damage of a category 3 storm
o Indirect damage due to flooding resulting infrastructure failure (80% of city)
o Over 75$ billion in damages (insured and uninsured) – some estimates over $100 billion
o 1417 deaths (deadliest since 1928)
o Aftermath of Katrina: what was so different about this hurricane that made it so severe
(than the other hurricanes that occurred in the same year)?
Are we prepared adequately for hurricanes in terms of infrastructure, emergency
preparedness?
Is the nature of hurricanes changing?
Two theories natural cause vs. global warming
Hurricanes and Climate Change:
- Scientific Community divided:
o William Gray (AMO –Atlantic Multi-decadal oscillation)
Variation in the 3-D circulation of the Atlantic Ocean
At one phase higher, at one phase lower temperature
Leads to decadal variations in temperature
Warm temperatures in 40’s and 50’s more frequent hurricanes
**”a result of the multi-decadal increase in strength of the Atlantic Ocean
thermohaline circulation (THC)”
Problems with Gray’s position:
Maintains that a strong thermohaline circulation in the Atlantic leads to
higher SSTs in the tropics and vice versa
By his reasoning, the current THC should be stronger than usual
Bryden et al. 2005 indicate THC was 30% weaker
So why are tropical SSTs warmer???
o There has been an increase in greenhouse gases (carbon dioxide)!
o Kerry Emanuel (global warming)
“very likely a response to increasing anthropogenic greenhouse gases”
Hurricane Damage: Natural Disaster or Human Folly?
- Three factors for insurance payouts from hurricane damage:
o Nature of the physical disaster Frequency of hurricanes appears unchanged but intensity
and duration are increasing
Therefore, less number of hurricanes, but the less amount of hurricanes that are
occurring are of a higher intensity (category 4 and 5)
o Where people live “Coastalization” of American population
If you live near dam or coastal area, that is going to put you on risk during a storm
That is the individual’s problem, because they have chosen to live there
o Relative wealth Americans are increasingly wealthy and stand to lose more when a
hurricane hits
o Latter two have caused most of the increase in insurance payouts
- Foreshadowing (Sheets and Williams, 2001)
o New Orleans is at a vulnerable stage, even if a category 1 hurricane hit them, they would
still be highly affected because city was 5 feet below sea level
They did not get any warning about the storm, and they did not take any precaution
o “the vulnerability of New Orleans is legendary and scary”
o “the highest surge on the storm’s right side would push Lake Pontchartrain – north of the
city – over the fifteen foot levees and into a part of the city that’s as much as five feet below
sea level”
New Orleans:
A city below sea level, a city built on a flood plain recipe for disaster
New Orleans was supposed to be prepared for a Category 3 Hurricane:
Katrina was a Category 5 storm, but downgraded to category 3 when it hit
New Orleans
Infrastructure not good enough – dams and levees were breached, flooding
the entire city
Hurricane Research:
- Who? W. Gough and graduate student, Paul Steenhof
- What? Linkage between hurricane activity in the Atlantic Basic and sea surface temperatures
(SSTs)
- Where? Climate Research Lab, UTSC
- When? Began in 2001, Persistent difficulties in getting paper published (refer to scientific
controversy above), publication in 2007
- Why? to quantify the impact of SSTs on hurricane activity in the Atlantic Basic, to provide insight
on how climate change may affect hurricane activity in the future
o Forecast what is the impact of climate change in hurricane activity in the Atlantic Basin
- How? from previous literature, a main development region (MDR) was identified for Atlantic
Basic hurricanes, 10-20deg. North, 30-60deg. West
o Looked at SSTs for the MDR from 1940 to the present were extracted from global data sets
o Hurricane activity was counted for the same period of years
o Data set split into two parts, 1940 to present and 1965 to present reflecting the advent of
satellite technology in the more precise identification of hurricanes
o Compared Ten warmest years were compared to ten coolest years and the different was
tested for statistical significance
o Correlation analyses were done on SSTs and hurricane activity data through statistical tests
o Future Projections of SSTs in the MDR were obtained from the Canadian Climate Centre
(CCCma) coupled climate model
o Using derived relationship projections of future activity was estimated
- Results
o In terms of correlation, with SSTs and NTC – strong correlation
o Between 26.5-27.6 hurricane activities increasing
o NTC Index and SSTs NTC as a function of SST, increase particularly notable for higher SSTs
o considerable “noise” (ENSO, QBO)
- Projection:
o Climate modeling results (CCCma):
MDR temp. will rise 1.7def. C than current climate
Projected for 2050 30deg.C
2005 was 0.75def.C above 60 year avg. and was most active hurricane season to
date
o Does not bode well for future:
Some mitigating mechanisms which suggest linear analysis may not be appropriate
Minimum threshold for hurricane formation may increase and this would reduce
hurricane activity
It is not good for the future, because 30deg. C is way above the threshold
(26.5deg.C), then it will not favour the hurricane activity
Eastern Pacific Hurricanes and Climate Change: Some research done on Eastern Pacific hurricanes in UTSC
Climate Lab by W. Gough and graduate student Trisha Ralph
- Sometimes referred to as the “forgotten hurricanes” – not as damaging as others as most storms
go out to sea
- Occasionally impacts Mexican coast
- Study: WDR and EDR, compared 5 warmest to 5 coldest years
o EDR closer to the land
- Results: for EDR, the SSTs is way above the threshold, for WDR – normal threshold (26.5deg. C)
- Discussion:
o Two distinctive regions of hurricane development in the Eastern Pacific
o Western Development Regions demonstrates more sensitivity to temperatures than Eastern
DR WDR closer to temperature threshold (26.5deg.C)
Therefore, we should be careful to what the future hurricane activities can cause to
this region
o Climate models indicate that WDR will warm faster than the EDR
o Likely to see more hurricanes in the Eastern Pacific especially from WDR
Summary of Hurricanes:
- Increases in Atlantic Basin attributed by some to Global Warming, others to AMO (Atlantic Multi-
decadal oscillation)
- Eastern Pacific Hurricanes:
o Sensitive to SSTs (sea surface temperatures)
o EDR intensity increases with increasing SSTs
o WDR frequency and intensity increases
Answer to Quiz #1: How upper level wind is different from surface wind?
- At upper level there is PGF and CF are exactly in balance, so at upper level the wind blow parallel to
the isobars
- There is friction at the surface, so it is a three way balance among friction, PGF and CF, and wind
blows at a curved path
- At the upper level the wind speed is usually much higher compared to the surface because the
pressure decreases as we go up and the differences in pressure between the isobars cause the
isobars to be steep and the wind is much stronger, vice versa at the surface
Wind Lecture 4: Midlatitude Cyclones
Hurricanes in the Great Lakes: Analysis
- Relatively rare – return rate to Great Lakes
- Data readily available on Web (i.e., Environment Canada)
- Examine records of hurricanes in North America (Atlantic Basin) since 1951 to 2000:
o 10 hurricanes in Great Lake region: 1 every 5 years
o Never more than 1 per year
o Clustering:
0 hurricanes from 1969-1987
5 hurricanes from 1988-2000
According to Gray’s index, this is maybe linked to North Atlantic Oscillation (NAO)
o Some examples:
1954 Hazel, 5-18 October
121.4mm at Toronto Pearson Airport
The 6 examples occurred approx. in September and October, and over the great lakes
o 2006-2007 no great lake hurricanes
o 2008 Hurricane Ike’s effect
The major difference between when storms pass oceans and lakes is that Great lakes
are not affected by strong currents
o Snow storm in 2011: U of T was closed for the day (midlatitude cyclone, “gulf low”)
Originated form gulf of Mexico
Huge damage in Texas
From Texas, it went to 2-3 more states of US, then over to Canada
Forecasted 30cm of snow
What actually happened was: wasn’t as bad as what the forecast was
Midlatitude Cyclones:
- Commonly referred to as a “low” or “low pressure system” or “frontal system”
- Major weather maker in midlatitudes (35-60deg)
- Most storms in Southern Ontario in the fall, winter, spring are midlatitude cyclones (not summer!)
- Occur approx. every 4 to 7 days
- Characteristics:
o 100s to 1000s km in extent (larger than hurricanes!)
o Less intense winds
o Can have thunderstorms and tornadoes associated with them (cold front)
o Stays only 4-7 days then goes away, whereas hurricanes have a longer time-span
o Differences between hurricanes and midlatitude cyclones: Intense wind in hurricanes than
cyclone, hurricanes longer time-span, cyclones are larger
Large Scale Flow:
- Polar front region between Polar and Ferrel cells (30-60deg – air rises at 60 and sinks at 30 for Ferrel
cell)
o Air Masses:
Midlatitudes – battle ground between cP (continental polar) and mT (maritime tropical
air masses (air masses cover a huge area therefore anything can change at any time)
Toronto: dominant air masses are cP or DP and mT or MP and DT
For hurricanes sea surface temperatures, and convergence and divergence
Fronts: division between air masses
- Stationary front:
o Stable
o Low pressure trough
o Horizontal wind shear
o Alternating blue triangles and red semi-circles
o Stable because it doesn’t’ have any disturbances lack of latent heat to fuel storm
- Cold front:
o Cold air pushing into a warm air mass (cP (cold) & mT (warm))
o Designated by blue line with triangles facing warm air
o Frontal slope 1:50
o 15-25 knots (7-13m/s)
o Heavy precipitation along the front where mT air is forced up
o Criteria for Identification:
Strong temp. gradient
Change in moisture (dew point)
Shift in wind direction
Pressure change
Cloud and precipitation pattern (the line shows this, where the line is there, that is the
place of the most cloud and precipitation)
- Warm front:
o Warm air pushing into a cold air mass – battle ground between the cP and the mT air
o Designated by red line with semi-circles pointing toward cold air
o Slope 1:150 -1:300
o Gentle precipitation (drizzle)
- Occluded front: most intense storm!!!
o Cold front catches up with warm front
o Warm air forced above surface, so you start to get latent heat (fuel for the storm)
o Warm front-style precipitation
o Alternating blue triangles and red semi-circles
Polar Front Theory: mechanism of the formation of the midlatitude cyclone
- Low pressure or cyclone is the principal weather maker at midlatitudes
- Development of a low pressure begins with a small perturbation or disturbance along the polar front
(division between polar and Ferrel cells)
- Step ONE:
o Disturbance stable stationary front becomes unstable
o cP (northeast) and mT (south west) colliding with each other disturbance unstable
o huge pressure gradient between cP and mT air that creates this disturbance low pressure
system develops
o Stationary front with a strong horizontal wind shear
o Wind shear is horizontal gradient of wind direction and can be unstable
- Step TWO:
o Under certain conditions a kink or small disturbances forms along the polar front
o A “cold front” of cold air pushes to the south and warm air “warm front” pushes to the north
interaction between cP and mT = PIVOT POINT
o The pivot point is the lowest local pressure and is the low pressure centre temperature
drops and low pressure system is getting intense (storm is building)
o Precipitation begins
- Step THREE:
o Fully developed wave
o The wave moves east or northeast – it takes 12 to 24 hours to reach this stage of development
o The centre pressure continues to drop
o Large bands of precipitation have formed (fuel for the storm)
o A “warm sector” has formed in the region between fronts
- Step FOUR:
o The faster moving cold front catches up with the warm front, reducing the size o the warm
sector
- Step FIVE:
o Occlusion occurs as cold front catches up with warm front This is the most INTENSE part of
the storm
o There is widespread precipitation the storm is losing its fuel, therefore starting to weaken
- Step SIX:
o Storm dissipates after occlusion the source of the energy (mT air) has been cutoff (i.e., no
more latent heating)
o Storm gradually weakens and dissipates
Midlatitude Cyclones in the Great Lakes Region:
- Great lakes storms:
o Major precipitation events – lake levels, happening because of the midlatitude cyclones
o Major cause of erosion, sediment transport
o Ship and property damage
- Great lakes storm climatology: ***LOWER PRESSURE = STRONGER STORM***
o Reference: Angel & Isard (1998); Isard et al. (2000)
o Storm Climatology: Frequency and Intensity (Angel & Isard (1998))
Cyclone track data since 1900
Seasonal distribution of storms
All snow storms that occur in the winter are ALL midlatitude cyclones
# of cyclones are greater and more frequent in the cold season
Surface pressure is decreasing over time
o Where do the storms come from?? Isard et al. (2000) studied this issue
Origin of air masses are highly linked to the different midlatitude cyclones
mT Gulf Low
cT air masses Alberta clipper, Colorado low
in terms of latitude:
midlatitude cyclones (30-60deg North)
frequency of storm types over the Great Lakes Basin;
Which storm is most dominant?
o Alberta Clipper we don’t experience a lot, mostly at south of the
border
o Gulf of Mexico (gulf low?) – Jan. 2011 rare therefore forecasting was
poor
o Great Lakes covers a huge part, approx. 20% is originating from the
Great Lakes
Famous Midlatitude Cyclones:
- SS Edmund Fitzgerald: sunken ship
o November 10, 1975
o Sank as a result of a strong midlatitude cyclone
o 29 lives lost
o The Wreck of the Edmund Fitzgerald – Gordon Lightfoot
“when the skies of November turn gloomy”
“when the gales of November came early”
“could it be the north wind they’d been feeling”
“in the face of a hurricane west wind”
- The Perfect Storm:
o October 1991 Hallowe’en Storm
o Cold air from US west meet with warmer air mass from Atlantic
o Formed Nor’easter or Hatteras Low (empty air coming from over the Ocean)
o Midlatitude Cyclone Formed from Hurricane Grace 25-29 October
Hurricane #8 Oct. 28 – Nov. 2
Midlatitude storm formed from remnants of Hurricane Grace
Later transformed to Hurricane #8 – the “unnamed hurricane”
o Hundreds of millions of dollars damage along east coast of US
o Loss of life (Andrea Gail – 6 fisher men dead, Others – 4)
o 1997 Sebastian Junger Book, “Perfect Storm”
o 2000 movie
- Ice Storm, 1998:
o January 3-10, 1998
o 80mm of freezing rain
o Worst natural catastrophe in Canadian History
o 28 lives lost
o 3 million without electricity
o 15,857 troops deployed
o $4.2 billion in economic loss
o $1.5 billion in insurance claims
o Midlatitude cyclone
Commercial cloud developing
Within 12 hours, it turned into the occluded form (most intense part of the storm)
Toronto Blizzard, 1999:
- Gough (2000):
o A climate perspective on Toronto’s blizzard of ‘99
o CMOSB.doc
o Regional topography:
Toronto cradled by local topography including Niagara escarpment, Oak Ridge’s
Moraine
Compared to NYC, buffalo, etc., they get more lake effected snow because we
are protected by the Oak Ridge’s Moraine
o We get 20 cm less snow in average
o So what happened in 1999, that the Moraine could not protect us from
extreme snow fall?
o How did it happen?
Series of 4 storms passed to the south of Toronto in early Jan., 1999
The fourth pressure system is so intense, that it passed over Lake Ontario and
took all the moisture and hit Toronto
Storm centre to the south of Toronto, allows for east to southeast winds
Winds sweep across lake Ontario gathering moisture and energy
Leads to larger than normal snowfall
Midlatitude cyclone with enhancement from Lake Effect
o Research Question: how unusual was the January snowfall in Toronto?
o Research Method: examination of snowfall record for Toronto using data from the University of
Toronto weather station – 1840 to present (longest record in Canada)
Monthly data examined, have 100 cm months occurred before? When? How
frequently?
o Total snowfall: 118.4 cm (U of T site) – record for January
Mean annual: 139.2cm
January mean: 36.4cm (THEREFORE, 118.4cm is WAY ABOVE AVERAGE!!!)
Other months > 100 cm
Snow/Total precipitation Ratio: are we getting less snow?
Total precipitation is not varying significantly but the proportion that is snow is
declining (more precipitation through rain, and less through snow)
o Conclusions:
Unusual event – does not appear to be part of a trend for such events
Therefore, we would not forecast this type of storm to occur at this time any
time soon in the future
Excessive snow due to 4 successive storms which has pathways that led to enhanced
snowfall due to passage of wind over Lake Ontario
Concept Maps
- A means of organizing knowledge
- Concepts linked together with phrases to illustrate their relationships
- Help to clarify or “sort out” complicated topics, and to identify areas that are poorly understood
- Illustrated way of communicating information
- Helps to organize thoughts, ideas, and themes
- IMPORTANT: there is no “right” way to craft a concept map
- Construction Tips:
o Often hierarchical:
Most general, inclusive at the top
Least general, most specific at the bottom
o Make a list of important concepts:
Afterward, rank the list (roughly)
o Look for cross-links
Be selective!
o Describe relationships by thinking of phrases that describe two concepts
- Criteria for Evaluation:
o Clear, easy to understand
o Limited in text
o Uses simple wording to show connectivity or interrelationships
o Demonstrates an extended level of thinking – beyond basics!
- Concept maps in “WIND”:
o Will be used in some participation assignments
o Will also appear on Midterms and Final Exams!
o Will be asked to use concept maps to summarize topics and research studies and/or connect
themes or theories presented in the course
- Example: Hurricanes Create a concept map describing hurricanes including the following concepts:
SOLUTION GIVEN IN SLIDES*** NOT A FLOW CHART – MORE LIKE A WEB
Wind – ESSA09 – Lecture 5: Thunderstorms and Tornadoes
Thunderstorms:
- Also known as Convective storm caused by surface heating
o Suburban areas around the GTA are getting more warmer than the areas in downtown
- Common in Southern Ontario in summer
- Only storm that has thunder and lightning
- Large thunderstorms can spawn/turn into tornadoes
- Four categories: differs in strength of the wind
o Ordinary:
Often develop within large air masses
Not necessarily near a frontal system
Little vertical wind shear (don’t need large air masses)
Change of horizontal wind speed with height
Three stages:
Cumulous stage: Differential surface heating induces upward flow in unstable
air, updraft, cumulus cloud formation
o Warm surface air rises (updraft), condensation starts (formation of
cloud), change of phase, and latent heat released which starts to fuel the
storm
Mature phase: Development of a downdraft with precipitation
o precipitation, cold air starts to sink therefore you have a downdraft that
forms at the same location (therefore, easier for DD to cutoff UD) of
ordinary thunderstorm
when it is raining, you start to lose latent heat
o Gust front develops as downdraft air spreads along horizontal surface
o Gust front forces more air up into the updraft
o Updraft and downdraft form a convective cell (change of heat)
Dissipation stage: Downdraft cuts off updraft and storm loses energy source and
dissipates
o When the gust front moves past the updraft, the updraft weakens
o Rain starts to fall into the updraft, cutting off the rising humid air
Life Cycle:
Relatively short-lived
Less than 1 hour
Diameter is 1km or less
o Multi-cell:
Similar to ordinary except moderate wind shear
Storm tilts
Downdraft forms downwind of updraft (does not form at the same location,
therefore, harder for DD to cutoff UD)
o As a result DD does not cutoff UD right away, it cuts it off in about 5 or 10
hours Storm lasts longer
Gust front of one storm initiates or induces another storm
o Super-cell:
Form with strong vertical wind shear (need strong large air masses)
Surface winds (mT air) from south/southwest
Upper level winds (cP air) from north/northwest
Along cold front of a midlatitude cyclone
Midlatitude cycle is dying down and at the tail of the cyclone you will see the
development of a super-cell thunderstorm
100-600 m in diameter
Tornadoes can spawn
Midlatitude cyclone super-cell thunderstorm tornado
Downdraft does not cutoff updraft Storm can last for several hours
Location of the DD is far away from the location of the UD
Hail can form
Microbursts can also form
i.e., almost like a shower-head, where water drops down straight the ground and
then when it hits the ground (bathtub), the water curves up (rises up again) and
falls at angles all around
Localized DD (energy is concentrated in one single space)
o Radial burst of surface wind (when localized strong wind with formation
of localized thunderstorm)
Aviation hazard
o Airplane crash, Aug. 1985 at Dallas-Fort Worth Airport, 100 lives lost
Plane view of thunderstorm
Areas of UD and DD
Gust front
Up level blow off (anvil extent)
o Mesoscale convective complexes (MCC):
Multiple thunderstorms
Little wind shear ?????
Circular fashion
Covers over 100,000 square km
12 hours or more, self sustaining
Heavy precipitation - therefore, favourable to farmers
Good for farming, these types usually form over prairies
- Squall Line: strong of thunderstorms along a cold front
o Nov. 15, 1989 – The Huntsville Tornado is an example
o Hail and tornadoes formed
o Super-cell thunderstorms???
Lightning:
- Special characteristics of thunderstorms
- Charge separation occurs in the cloud (charge is carried by the cloud droplets or ice crystals)
- Smaller particles tend to go to top of storm with positive charge, larger ones with negative charge to
the bottom negative charges attracts positive charges on the ground
o Acts like a magnet to attract positive charge at the surface
- Most (90%) lightning starts at cloud base and goes to the surface
- First step – Stepped leader a path of multiple 50m or so is ionized by 3 million volts of electricity
o Further steps of 50 to 100m until surface is reached
o As surface is neared, positive ions from the surface more upward
When the two connect, the luminous return stroke is seen
Several cm in diameter
Process can repeat leading to forked lightning
Air heats to 30,000deg. C
Generated shock wave thunder!
Radio waves, “sferics”, are produced allowing for lightning detection worldwide
Hail:
- Largest form of solid precipitation and most damaging
- 2nd costliest natural weather disaster in Canada (after 1998 Ice storm)
- Largest: 757 grams found in Coffeyville Kansas
- Canadian largest: 290 grams in Saskatchewan
- Formation:
o Formed in cumulonimbus clouds (thunderclouds)
o Formed through successive deposition of super-cooled water onto an ice core
UP and DD – ice crystals are being coated by UP and DD within the circle of convective
cell
o Recycling through up and downdrafts enable hailstone to grow until it is too heavy for the
updraft
Continues to form until it is heavy enough to drop to the Earth’s surface (ground)
o 10 billion cloud droplets to form a golf ball sized piece of hail
- Distribution:
o Anywhere thunderstorms can form
o Hail days in US range from 0 to 9
o Leeward side of Rockies has most hail days
o Part 3 of lecture examines Canadian distribution of hail
World Distribution of Thunderstorms:
- Distribution in US:
o Maximum number in Florida
Why? Land/sea contrast
Mid to late afternoon thunderstorms
- Worldwide distribution:
o Dai (2001)
o 15,000 stations around the globe, 1957-1997
o Seasonal distribution of thunderstorm probability summer hemisphere
o Land vs. ocean mainly over land
o Tropics and midlatitudes
Tornadoes:
- Rapidly rotating column of air that reaches the ground
- Called “twisters” or “cyclones”
- “funnel cloud” precursor to tornado
o But if it does not reach the surface, then it is not classified as a tornado
- Mostly counterclockwise:
o Tornado started with a super-cell thunderstorm (mechanism associated with mT and cP air,
which is associated with midlatitude cyclone) which came from a midlatitude cyclone
o midlatitude cyclone has frontal system developing low-pressure system forming, and there,
you have wind moving in low-pressure system in a counter-clockwise direction
- 100-600m diameter
- Usually lasts a few minutes
- Peak winds of 220 knots (400km/h) strongest winds on Earth (stronger than hurricanes)
- Formation:
o From super-cell thunderstorms
o Thunderstorms often form along the cold front of a midlatitude cyclone
o Vortex tube is originally horizontal but the strong updraft within super-cell thunderstorm turns
it vertical
o Conditions for formation:
cP air aloft
mT air at surface
explosive development when stable level at 800mb is eroded
wind shear
surface winds from south/southeast
upper level winds from west/northwest
cause air to rotate
vortex tube forms (first horizontally)
o updraft causes distortion of rotating air (vortex tube)
o rotating column takes on vertical component this is the start of the tornado
o fully developed tornadic conditions
o vortex tube becomes vertical
o funnel clouds forms first and becomes tornado when it hits Earth’s surface
- Classification:
o Fujita Scale created by Ted Fujita
7 levels from light damage (weak) to incredible damage (violent)
F0 weak, 64-116 km/h (light damage)
F1 weak, 117-180 (moderate)
F2 strong, 181-252 (considerable)
F3 strong, 253-330 (severe)
F4 violent, 331 – 416 (devastating
F5 violent, 417 – 515 (incredible damage)
F6 violent, more than 515 km/h
Thunderstorms and Tornadoes:
- How are they related?
o Tornadoes are spawned from super-cell (large) thunderstorms
o Tornadoes are formed from the thunderstorm base
o Thunderstorm is a necessary condition for a tornado but not vice versa
Famous Canadian Tornadoes:
- Emergency Preparedness Canada
o Data base of natural disasters
o Tornadoes are 6th on the list of the world’s most dangerous/damaging natural disasters
(hurricanes are 8th)
o 29 damaging tornadoes from 1900 to 1999
o 1.2 billion dollars of damage
- Deadliest Canadian Tornadoes:
o 1st Regina Cyclone on June 30th, 1912 more than 28 people killed
- Edmonton (Alberta) tornado: July 31st, 1987
o F4 tornado
o 27 fatalities
o $350 million in damage
- Barrie Tornado: May 31st, 1985
o Located north of Toronto on the shores of Lake Simcoe
o 41 tornadoes in CND/US
o At least 13 distinct tornadoes in Southern Ontario
o F4 in Barrie
o 12 fatalities (8 in Barrie)
o More than $100 million in damage in Canada and more than $450 million damage in US
- Vaughn Tornado, 2009:
o Up to 45 houses and buildings have been deemed unsafe
o More than 600 homes
Canada’s Hail Climatology: Etkin and Burn (1999)
- Who Dave Etkin (formerly of Environment Canada and now of York University) and Eric Burn (grad.
Student at UTSC)
- What updating Canada’s hail climatology using more recent data with better coverage
- When research done late 1990’s at U of T
- Why recognition that hail damage is a major natural hazard in Canada (2nd costliest in CND)
- How analysis of Environment Canada hail data collected from stations across Canada for period of
1977 to 1993, before 1977 fewer stations reported, after 1993 automated stations started replacing
manual stations and hail was not recorded, data from 2062 weather stations were used
- Study Objectives produce an updated hail climatology, note the difference between maps produced
for 1951-1980 and 1977-1993
- Data sources
o recorded hail days in Canada normalized by the number of observing stations
increase after 1977 reflects from EC directive for climate stations to report hail
decrease after 1994 results from use of automated stations
o distributions of weather stations
- Conclusions:
o data from 1977-1993 show higher frequencies of hail observation throughout Canada than
1951-1980 climatology
more climate data stations reporting hail incidents
o no trends in hail activity except Alberta where hail activity increased (Edmonton Tornado)
**Midterm differentiate between the major storms: tropical cyclones, hurricanes (midlatitude cyclones),
and tornadoes (thunderstorms)