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Announcements
NO CLASS WEDNESDAY! HAPPY THANKSGIVING!
No office hours this week.
Missing your lab? See the TAs. Apologize for the delays in getting them back
NATS 101 Section 4: Lecture 32
Global Climate
Classifying the global climate and Earth’s climate record is probably not as exciting as learning about hurricanes or
tornadoes, but it important prelude before we get to global warming, the
final topic of the course.
Some reasons why understanding global climate is important
The type of climate in an area is a control on an area’s ecosystem.
Plant and animal species are specifically adapted, physically and behaviorally, to climate.
Climate affects how human civilization has evolved and adapted to cope in various environments. For example:
Agriculture: types of crops and domesticated animalsWater supplyTypes of dwellings and structures builtClothing Social structures, like governments and religions
Climate patterns may change due to anthropogenic (human-related) activities—and this is probably already happening. More on that later…
Survey question: Which of the following statement best represents your position with respect to the potential impact of weather and climate on our modern American civilization?
A) Our civilization is totally resilient to weather and climate.
B) Our civilization is susceptible to disruption from extreme weather and climate events from time to time, for example hurricanes and droughts, but these events are localized and affect a small portion of the population.
C) Our civilization, as a whole, is highly vulnerable to weather and climate. Changes in weather and climate have the potential to cause widespread societal disruption, and, in the most extreme, dramatically alter or destroy our way of life.
Ancient civilizations that
succumbed to climate change
ANASAZIFour Corners Region
Southwest U.S.ARID DESERT CLIMATE
MAYAYucatan Peninsula
MexicoTROPICAL WET-DRY CLIMATE
PROLONGED DROUGHT PERIODS LIKELY LEAD TO FAMINE AND WAR, AND THESE ANCIENT CIVILIZATIONS WENT INTO DECLINE.
We’ve already discussed many of the controls on global climate
in previous lectures.
I’ll briefly review those and then describe a formal global climate
classification system.
Climate control #1: Latitude
January Average Temperature
What it does:
Controls the intensity of incoming solar radiation.
Effects
Temperatures decrease with increasing latitude. Effect is more pronounced in wintertime.
Largest annual changes occur at higher latitudes.
Temperature does not change much in the low-latitude tropics
Climate Control #2: Land-Sea distribution
January
July
SIBERIASIBERIA-60 -60 °F°F
SIBERIASIBERIA50 50 °F°F
Maximum Temperature
What it does:
Water has a higher heat capacity than land, so it heats and cools more slowly than the surrounding land mass
Effect on climate:
Locations closer to a large water body will:
1. Have less of a seasonal temperature range.
2. Have a later occurrence of annual maximum and minimum temperature.
Climate control #3: Ocean Currents
What they do:
Giant convective circulations (gyres) transport heat from equator to pole.
The warm side of a gyre is typically along the east coast of a continent.
The cold side of a gyre is typically along the west coast of a continent.
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California
California
Hu
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Hu
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Bengulas
Bengulas
Can
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Effect on climate
Climates on east and west coasts of continents margins are respectively modulated by the presence of warm and cold ocean currents.
Climate control #4: the general circulation
What it does:
Governs the locations where air converges or diverges on a global scale.
Effect on climate
It is the primary control on the global distribution of rainfall.
(UNC Charlotte)
SAHARA DESERTSAHARA DESERT
SAHELSAHEL
CONGOCONGORAIN FORESTRAIN FOREST
KALAHARI KALAHARI DESERTDESERT
SAR
ENG
ETI
SAR
ENG
ETI
CONGOCONGO
KALAHARI DESERTKALAHARI DESERT
SAHELSAHEL
SARENGETISARENGETI
SAHARA DESERTSAHARA DESERT
Climate control #5: Terrain
Example of rain shadow effect
What it does:
Mountain valley circulations.MonsoonsOrographic uplift
Effect on climate
All of these factors can be potentially very significant controls on the precipitation occurring at a regional scale.
As we discussed earlier, these factors are really important for understanding Arizona’s climate!
Köppen climate classification system
Wladimir KöppenGerman climatologist
Developed a climate classification system based on common vegetation types observed throughout the world.
Goal was to explain climate in areas that had few or no station observations.
Basic Types
A = Tropical moistB = DryC = Moist temperateD = Moist coldE = PolarH = Highland
Notations for subtypes derive from German.
Climates of the world in Köppen system
Rest of the lecture is taking the “tour” of this map…
Type A: Moist Tropical Climates
Characteristics
Year-round warm temperatures (above an average of 64 °F)Abundant rainfall (about 60 inches a year)Wet and dry seasons controlled by the position of the ITCZ.
Where located
Equator to about 15 – 25° latitude.
Subtypes
Af = Tropical wetAm = Tropical monsoonAw = Tropical wet and dry
Tropical Wet (Af)
These regions are tropical rainforests.
Typically near the equator.
Wettest time of the year is typically during the equinoxes when the ITCZ is nearest to the equator.
Temperature hardly varies through the year.
Tropical monsoon (Am) climates similar, but have a bit more variation in rainfall.
Example Regions:Tropical Wet (Af) Climates
\
AMAZONAMAZON CONGOCONGO INDONESIAINDONESIA
Tropical Wet-Dry (Aw)
About 5 - 20° latitude, on the periphery of the ITCZ.
Strong annual variation in rainfall, controlled by ITCZ position Summer wet season Winter dry season
Savannahs, or large grasslands with scattered trees, like the Sarengeti in Africa.
Example Regions:Tropical Wet-Dry (Aw) Climates
\
BRAZILIAN BRAZILIAN HIGHLANDSHIGHLANDS
SAHELSAHEL
SARENGETISARENGETI
Type B: Dry Climates
Characteristics
Low precipitation most of the year (less than 20 inches).Located under the subtropical high most of the time.Favored on the west side of continents because of cold sea surface temps.
Where located
About 20 - 40° latitude
Subtypes
BW = Arid DesertBS = Semi-arid or steppe
Arid desert (BW)
Receives less than 13 inches of rain per year
Hottest temperatures on Earth (e.g. greater than 120 °F)
Plants that live in these areas are xerophytes, capable of living long periods without rain.
THIS IS THE CLIMATE FOR MOST OF ARIZONA
Example Regions:Arid Desert (BW) Climates
\
ATACAMA ATACAMA DESERTDESERT
SAHARASAHARA
KALAHARIKALAHARI DESERTDESERT
SONORAN SONORAN DESERTDESERT
ARABIAN ARABIAN DESERTDESERT
GOBI DESERTGOBI DESERT
AUSTRALIAN AUSTRALIAN DESERTDESERT
The driest spot on Earth…where is this??
Semi-arid or Steppe (BS)
Receive about 8 to 16 inches of rainfall.
Short grasses and scattered low bushes and trees.
Can get cold in the winter, if in the mid-latitudes.
Areas typically are good for grazing animals.
In the tropics, typically the transition zone from tropical-wet dry to arid desert.
Example Regions:(Mid-latitude) Steppe (BS) Climates
\
PAMPASPAMPAS
GREAT GREAT PLAINSPLAINS
CENTRAL CENTRAL ASIAASIA
Type C: Moist Temperate Climates
Characteristics
Humid with mild wintersAbout 20 to 40 inches of precipitation per yearVery different subtypes depending on continental position.
Where located
About 25 - 40° latitude
Subtypes
Cfa= Humid subtropicalCfg = West coast marineCs = Mediterranean
Humid Subtropical (Cfa)
Typically along east coasts of continents, on the western side of the subtropical ridge.
Wet all year round, but slightly more rain in the summer.
Hot, muggy summers
Supports thick forests or agriculture.
Example Regions:Humid Subtropical (Cfa) Climate
\
EASTERN EASTERN ARGENTINA ARGENTINA
AND AND URUGUAYURUGUAY
SOUTHEAST SOUTHEAST U.S.U.S.
SOUTHEAST SOUTHEAST CHINA AND CHINA AND
JAPANJAPAN
NORTHEAST NORTHEAST SOUTH AFRICASOUTH AFRICA
EASTERNEASTERNAUSTRALIAAUSTRALIA
West coast marine (Cfb)
Located at 40 – 60° latitude
Rain throughout the year, especially in winter. More so if on the windward side of mountain range.
Receive rain from mid-latitude cyclones hitting west coasts.
Proximity to water moderates the climate
Example Regions:West Coast Marine (Cfb) Climate
\
SOUTHERN SOUTHERN CHILECHILE
PACIFIC PACIFIC NORTHWEST NORTHWEST
NORTHERN NORTHERN EUROPEEUROPE
NEW ZEALANDNEW ZEALAND
Mediterranean (Cs)
Located equatorward of the west coast marine climates (30 - 40° latitude)
Under the subsiding branch of the eastern side of the subtropical high in summer, so hot and dry then.
Wet, mild winters.
Short scrubby vegetation with a few trees.
Good climate for winemaking!
Example Regions:Mediterranean (Cs) Climate
\
CENTRAL CENTRAL CHILECHILE
CALIFORNIA CALIFORNIA
MEDITERRANEANMEDITERRANEAN
CAPE TOWN CAPE TOWN AREAAREA
SOUTHWEST SOUTHWEST AUSTRALIAAUSTRALIA
Mediterranean Climate and the Roman Empire
Relatively similar and agriculturally productive climate conditions exist throughout much of the Mediterranean.
Same crops that grew in one place would also grow in a another place.
FACILITATING FACTOR IN THE EXPANSION OF THE ROMAN EMPIRE AND DEVELOPMENT OF WESTERN CIVILIZATION!
Type D: Moist Cold Climates
Characteristics
Warm to cool summers Cold winters with snowLarge seasonal temperature rangeAbout 30 - 40 inches of precipitation per year.
Where located
About 25 - 70° latitude
Subtypes
Dfa and Dfb = Humid continentalDfc = Subpolar
Humid continental (Dfa and Dfb)
Typically more toward the eastern side of a continent, poleward of moist subtropical areas.
Regular precipitation throughout the year.
Summer precipitation maximum.
Summers can be sometimes hot.
Favorable for deciduous forests and agriculture
Example Regions:Moist cold (Df) Climate
\
NORTHEAST NORTHEAST ASIAASIA
MIDWEST AND MIDWEST AND NORTHEAST NORTHEAST
U.S. U.S.
EASTERN EUROPE EASTERN EUROPE AND SOUTHEAST AND SOUTHEAST
RUSSIARUSSIA
Subpolar or Boreal (Df)
Very cold winters
Fairly low precipitation (less than 20 inches per year)
Typically supports large evergreen boreal forests, or taiga.
Example Regions:Boreal Forests (Df)
\
NORTHERN NORTHERN SCANDANAVIA SCANDANAVIA AND SIBERIAAND SIBERIA
NORTHERN NORTHERN CANADA AND CANADA AND
ALASKAALASKA
Type E: Polar Climates
Characteristics
Cold temperatures year round.Tundra, permafrost, or ice cap.Very little precipitation.
Where located
Poleward of boreal forestTHESE REGIONS ARE CHANGING RAPIDLY DUE TO RECENT GLOBAL WARMING.
Type H: Highland Climates
Climate changes experienced with increasing altitude. Farther up, the typically more “polar” the climate gets.
THESE REGIONS ARE ALSO CHANGING RAPIDLY DUE TO THE RECENT GLOBAL WARMING—PARTICULARLY MOUNTAIN GLACIERS.
Example Regions:Highland Climates (H)
CENTRAL CENTRAL ASIA AND ASIA AND
TIBETTIBET
ROCKY ROCKY MOUNTAINSMOUNTAINS
ANDEANANDEANALTIPLANOALTIPLANO
WE’LL SEE WHAT HAS HAPPENED TO MOUNTAIN GLACIERS INTHESE PLACES LATER…
Summary of Lecture 32The major controls on climate are latitude, land-sea distribution, ocean currents, the general circulation, and terrain.
Climate is classified by the Köppen system.
TROPICAL MOIST (A): Either rainforest near the equator or savannah farther polward. Precipitation influenced by the ITCZ.
DRY (B): Deserts typically located under the subtropical ridge and/or near the west coast of continents. Steppes are grassland transition zones.
MOIST TEMPERATE (C): Specific subtype depends on continental position (east vs. west). Moist subtropical on eastern side, west coast marine and Mediterranean on the western side.
MOIST COLD (D): Poleward of moist temperate climates, with large seasonal shifts in temperature. Includes boreal forest.
POLAR (E): Tundra, permafrost, or ice cap.
HIGHLAND (H): Colder climate due to higher elevation.
Reading Assignment and Review Questions
Reading
Chapter 16 (last Chapter to be covered)
Chapter 17 Questions
Questions for Review: 1,2,3,4,5,7,8,9,10,11,12,13,19 (8th ed.) 1,2,3,4,5,6,7,8,9,10,11,12,13,14,20 (9th ed.)
Questions for Thought: 2,3,5,6