Lecture 8 Flashcards
(45 cards)
1
Q
What are tropical cyclones?
A
- 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
2
Q
What are extratropical cyclones?
A
- 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.
3
Q
What is a tropical disturbance?
A
-a large area of low pressure with unsettled weather
4
Q
What is a tropical depression?
A
-an unorganized area of thunderstorms
5
Q
What is a tropical storm?
A
-an organized area of storms with wind of 65-119km/h
6
Q
What is a hurricane?
A
-an area of low pressure with wind of at least 120km/h
7
Q
What are the components of a hurricane?
A
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
8
Q
How are hurricanes named?
A
- 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)
9
Q
How do hurricanes typically move?
A
- 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
10
Q
How do you determine where wind speed is highest?
A
-opposing arrow will tell you the side of the hurricane with the weakest wind speeds
11
Q
What is the most devastating component of a hurricane?
A
-eyewall
12
Q
What is the most devastating effect of a hurricane?
A
- 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
13
Q
How are hurricanes classified?
A
-hurricanes are classified by the Saffir-Simpson Scale based on wind speed
14
Q
What regions are at risk for hurricanes?
A
- 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
15
Q
Describe Hurricane Juan
A
- Sept 29 2003
- it was a category 2 hurricane when it made landfall near Halifax
16
Q
Describe Hurricane Hazel
A
- 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
17
Q
What is weather?
A
- the state of the atmosphere at a specific time and place
- components of weather: temperature, pressure, humidity, wind, clouds, visibility, etc.
18
Q
What is climate?
A
- the average state of the atmosphere over a long period of time
- climatic averages are calculated from data over a 30 year period
19
Q
Describe the interactions between the components of the “spheres”
A
- atmosphere: gases
- hydrosphere: oceans, large bodies of water
- lithosphere: plate tectonics, orogeny
- cryosphere: glaciers, ice sheets, snow cover
- biosphere: vegetation, animals, humans
20
Q
Describe climate change
A
- 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
21
Q
When was the last glacial period?
A
- 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)
22
Q
How has climate changed in recent history?
A
- there has been a rapid rise in temperature over the past 100 years
- this corresponds to human industry and the increase of greenhouse gases
23
Q
What are the causes of climate change?
A
- variations in solar radiation
- changes in composition of the atmosphere
- changes in Earth’s surface
- variations in Earth’s orbit
24
Q
Describe what variations exist in solar radiation
A
- 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
25
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
26
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
27
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
28
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
29
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
30
What is eccentricity?
- changes in the shape of Earth's orbit from circular to elliptical (100000 year cycle)
- this cycle accounts for ice ages
31
What is precession?
-the wobble of Earth's axis (23 000 year cycle)
32
What is obliquity?
- changes in the tilt of Earth's axis
- 41 000 year cycle
33
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
34
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
35
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
36
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
37
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
38
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
39
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
40
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
41
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
42
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
43
The recurring nature of ice ages can be explained by what?
milankovitch cycles
44
45
