Lecture 8 Flashcards
What are tropical cyclones?
- these form over warm water at latitudes 5-20degrees
- they include tropical depressions, tropical storms, and hurricanes
- they contain high winds, heavy rain, and storm surges
- they require a water temperature of at least 26 degrees Celsius
What are extratropical cyclones?
- these form over land or water in temperature regions at latitudes 30-70 degrees
- they are associated with fronts and are also called mid-latitude cyclones
- they contain rain, snow, freezing rain, etc.
What is a tropical disturbance?
-a large area of low pressure with unsettled weather
What is a tropical depression?
-an unorganized area of thunderstorms
What is a tropical storm?
-an organized area of storms with wind of 65-119km/h
What is a hurricane?
-an area of low pressure with wind of at least 120km/h
What are the components of a hurricane?
Eye: a region in the centre with light winds and clear to partly cloudy skies
Eyewall: a ring of intense thunderstorms that whirl directly around the eye
Spiral Rain Bands: rings of tall clouds and heavy rain that exist throughout the hurricane
How are hurricanes named?
- names were first assigned to hurricanes in 1953
- alternating male and female names are used in alphabetical order (5 letters are skipped: Q, U, X, Y, Z)
- the name is retired if the hurricane produced notable damage (ex: Andrew, Katrina)
- names were exhausted for the first time ever in 2005 when 27 hurricanes occurred (final 6 that year were named after Greek letters)
How do hurricanes typically move?
- hurricanes typically travel very slowly (less than 20km/h)
- because wind in a hurricane rotates counter-clockwise wind speed varies over the area of the hurricane
How do you determine where wind speed is highest?
-opposing arrow will tell you the side of the hurricane with the weakest wind speeds
What is the most devastating component of a hurricane?
-eyewall
What is the most devastating effect of a hurricane?
- it is the most devastating effect of hurricanes
- it results from powerful winds creating an abnormal rise in sea level
- hurricane Andrew (1992): 23ft storm surges were repeated in Florida
How are hurricanes classified?
-hurricanes are classified by the Saffir-Simpson Scale based on wind speed
What regions are at risk for hurricanes?
- in North America areas at highest risk are found along the Atlantic coast and the Gulf of Mexico coast
- the official hurricane season ranges from June 1st to November 30th
- many hurricanes occur in August and early September because this is when the water is warmest
Describe Hurricane Juan
- Sept 29 2003
- it was a category 2 hurricane when it made landfall near Halifax
Describe Hurricane Hazel
- Oct 15 1954
- it killed 81 people when intense flash floods in Toronto swept away homes; no other disaster has caused that many deaths in Canada to this day
- flooding of the Humber River caused the most damage
What is weather?
- the state of the atmosphere at a specific time and place
- components of weather: temperature, pressure, humidity, wind, clouds, visibility, etc.
What is climate?
- the average state of the atmosphere over a long period of time
- climatic averages are calculated from data over a 30 year period
Describe the interactions between the components of the “spheres”
- atmosphere: gases
- hydrosphere: oceans, large bodies of water
- lithosphere: plate tectonics, orogeny
- cryosphere: glaciers, ice sheets, snow cover
- biosphere: vegetation, animals, humans
Describe climate change
- through Earth’s entire history (4.6 billion years), the climate has always been changing
- over the last billion years, there have been several worldwide ice ages
- between ice ages, the global climate was at times slightly warmer than it is today
- the concern today is not the actual temperature; it is the rate of temperature change
When was the last glacial period?
- all of Canada was covered with ice 18000 years ago (except for Northern Yukon)
- lower sea levels at that time exposed the Bering land bridge (between Russia and Antarctica)
How has climate changed in recent history?
- there has been a rapid rise in temperature over the past 100 years
- this corresponds to human industry and the increase of greenhouse gases
What are the causes of climate change?
- variations in solar radiation
- changes in composition of the atmosphere
- changes in Earth’s surface
- variations in Earth’s orbit
Describe what variations exist in solar radiation
- the sun tends to emit more energy during periods of high sunspot activity
- sunspot: a cool region of high magnetism on the Sun
- sunspots occur in cycles and reach a maximum every 11 years
- sunspots are surrounded by faculae (bright areas that emit high amounts of energy)
- solar output regularly changes on the order of 0.1-0.2% in relation to sunspot cycles
- with more sunspots there is increased solar output
- Maunder minimum (1645-1715): a time period with no sunspots; this corresponds to a time period known as the Little Ice Age
What are changes in composition of the atmosphere?
- the addition of greenhouse gases (carbon dioxide, water vapour, methane) increases global temperature
- carbon dioxide has a long residence time in the atmosphere (100 years)
- therefore, even if we reduce carbon dioxide today, the effects will not be felt for decades
- a warming climate appears to be inevitable during our lifetimes
What are ice cores?
- the width of an ice layer provides insight on the temperature and snowfall of that year
- each year, a new layer of ice forms
- bubbles of air are trapped in the ice
- ice cores provide climate data for up to 600 000 years in the past
What is dendrochronology?
- this is the study of tree rings
- wider tree rings correspond to warmer or wetter years
- tree rings provide climate data for up to 1000 years in the past
What is the theory of plate tectonics?
- the continents have moved over time
- the collision of converging plates results in uplift and the creation of mountains
- this affects wind, temperatures, and precipitation patterns of the surrounding landscape
What is the Milankovitch theory?
- the theory proposes that three separate phenomena relating to Earth’s orbit lead to climate change
- they are referred to as the three Milankovitch cyles: eccentricity, precession, obliquity
What is eccentricity?
- changes in the shape of Earth’s orbit from circular to elliptical (100000 year cycle)
- this cycle accounts for ice ages
What is precession?
-the wobble of Earth’s axis (23 000 year cycle)
What is obliquity?
- changes in the tilt of Earth’s axis
- 41 000 year cycle
What is the greenhouse effect?
- greenhouse gases allow solar radiation to pass through but they absorb infrared radiation
- main greenhouse gases: carbon dioxide, water vapour, methane
Describe the enhancement of the greenhouse gas effect
- the greenhouse effect itself is not a concern, however the enhancement of the greenhouse effect by humans is a concern
- adding greenhouse gases results in climate change
- increasing the amount of carbon dioxide enhances the greenhouse effect
- more infrared radiation from the Earth is absorbed by the atmosphere
- carbon dioxide emissions are rapidly increasing in China and India as the economies in these countries continue to industrialize
Describe the positive feedback of snow and ice
- a process in a system that encourages the continuation of the original process
- less snow/ice decreases the reflectivity of solar radiation (because snow is highly reflective)
- therefore after snow/ice melts more solar radiation is absorbed rather than reflected
- as snow and ice melt, more energy is absorbed which therefore encourages more snow and ice to melt
- this leads to continually warmer conditions
- it is the reason why the polar regions are warming the fastest
What are climate models?
- estimating by how much the Earth will warm is achieved by climate models
- climate models forecast that over the next 100 years, the Earth will warm by at least 1.5 degrees
- models solve a series of mathematical equations
- variables represent greenhouse gases, solar radiation, other climatological components
- to best estimate observed temperatures a climate model must incorporate many different variables
What was the Kyoto Protocol?
- a global agreement aiming to slow climate change
- objective is to reduce greenhouse gas emissions to 5% below 1990 levels by 2010
What are the impacts of climate change?
- polar areas will warm the most
- boreal forests will expand northward, agriculture will shift northward
- precipitation patterns will change thus affecting habitats
- there may be increased intensity of tropical storms and hurricanes
What areas are at risk from sea level rise?
- as sea level rises, erosion is affecting areas farther inland; some areas are eroding at 10m annually
- sea level is projected to rise as global climate changes and ice sheets continue to melt
- north american cities at greatest risk include Vancouver, Miami, New Orleans, and New York
- Maldives is an island nation of 300 000 people in the Indian Ocean
- about 80% of the country is less than 1 m above sea level
- seawalls have been built around many of its islands to protect from waves up to 2m in height
How does climate change impact humans?
- climate change affects food production, tourism, and human health
- the most serious impact of climate change to humans is the spread of malaria
How does climate change impact biodiversity?
-warming temperatures will affect plant and animal habitats: bleaching of corals, loss of flora and fauna, extinction risk for polar bears
How many deaths have resulted from climate change?
- climate change since the mid-1970s is contributing to the cause of over 160 000 deaths per year
- these deaths are attributed to an increase in malaria and malnutrition in less developed countries
The recurring nature of ice ages can be explained by what?
milankovitch cycles
