Transcript Class #34: Monday, April 7

Class #31:
Wednesday, November 10
Climate types of the present
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2010
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Climate
• Is to weather what a friend’s personality is
to his/her mood
• Sums up the weather’s long-term behavior
• Is the collective state of the atmosphere for
a given place over a specified interval of
time
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Climate is defined by
• Location
– Globe, continent, region, city
– Chapter 14: regional and global scale
• Time: a specified interval
– 30 year average is normal
– 100 years or longer for history of climate
• Averages and extremes of variables
– Chapter 14: temperature and precipitation
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Controls on climate
• Similar to controls on temperature in
Chapter 3
• Latitude: solar energy input
• Elevation: air temperature, snow vs. rain
• Topography: moist vs. dry, temperature,
distribution of cloud patterns, solar energy
reaching the surface
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Controls on Climate (continued)
• Proximity to large bodies of water
– Thermal properties of water (absorption, heat
capacity, transparency, mixing) moderate
temperature downwind
• Prevailing atmospheric circulation
– Intertropical Convergence Zone (ITCZ)
– Subtropical Highs
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Classifying Climate
• Hard to do
– No clear boundaries
– Complex natural systems
• How it is done
– Important to life: hot or cold; moist or dry
– Most common system: based on vegetation
• Köppen climate classification scheme based
on vegetation and temperature
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Köppen (KEPP-in) Scheme
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Modified by Trewartha and Horn
Related to geography and global circulation
Uses letters (1, 2 or 3) in Chapter 14
Has many other subdivisions within the
categories shown in our book
• Has 6 major groups: A, B, C, D, E, H
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The 6 major climate groups
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A: Tropical moist
B: Dry (can be subtropical or mid latitude)
C: Moist with mild winters (mid latitude)
D: Moist with severe winters (mid latitude)
E: Polar (high latitude)
H: Highland (rapid climate change with
elevation)
• 2nd letter: usually latitude (except B)
• 3rd letter: differences in temperature
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Tropical Humid Climates:
Af, Aw, Am
• All tropical (A) climates are humid
• Letter “f” means no dry season, rain year
round, usually closest to the equator
• Letter “m” means “monsoonal”, with a
short dry season and a very rainy season
• Letter “w” means “winter dry season”
except no real winter in tropics, just cool
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Tropical humid climates (continued)
• Af
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Closest to the equator
Smallest annual range of temperature
6.9-10 inches of rain per month
Most thunderstorms in afternoon
Linked to ITCZ
Tropical rain forests
• Am
– Seasonal onshore winds during summer monsoon
– Climates with most yearly precipitation
– Jungle vegetation
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Tropical moist climates (continued)
• Aw
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Farthest A climate from the equator
Often border Af
Tropical wet and dry
Wet summers, dry, cooler winters
Linked to the seasonal migration of the ITCZ
Vegetation is savannah or tropical grasslands
with scattered deciduous trees, as in the
grasslands ofClassAfrica.
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Dry (B) climates
• Potential evaporation minus precipitation
<0
• More land of this climate type than any
other
• Lubbock has a B climate
• Descending branch of the Hadley
circulation near the subtropical highs or
• Rain shadow of a mountain range
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Dry climate subtypes
• 2nd letter
– “S” for steppe or semi-arid (like Lubbock)
– “W” for true desert (extremely dry)
• 3rd letter
– “h” for low-latitude, hot (yearly average
temperature >= 64ºF)
– “k” for mid latitude, cool (yearly average
temperature <64ºF)
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Dry climate subtypes (continued)
• BWh Extremely dry and hot; can have large sand
dunes; Sahara, Arabian peninsula, central
Australia, most extreme B climate
• BSk Least extreme B climate; midlatitude steppe,
often high plateau, Lubbock, Denver, San Diego;
often rain shadow
• BSh Much of Mexico, lower latitude, subtropical
steppe
• BWk Central Asia, very dry, midlatitude rain
shadow, continental interior
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C Climate type
• All C are moist, plentiful precipitation
• All C are midlatitudes
• Average temperature of coolest month
between 27ºF and 65ºF
• Have many subtypes; Chapter 14
concentrates on a few
• 2nd letter like A subtypes
– “f” no dry season
– “w” brief dry
period in winter
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C Climate type (continued)
• 3rd letter
– “a” hot summer
– “b” warm summer
– “c” cool summer
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C Climate subtypes
• Cfb, Cfc Marine west coast
– Northwest coast of US, Canada
– Often cool ocean currents
• Cfa, Cwa Humid subtropical
– Southeastern US
– 30-100 inches of rain per year
• Csa, Csb Mediterranean
– Along a coast, mild winter
– Greece
– Dry summer, semi-permanent subtropical high
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D Climate type
Severe (winter) Midlatitude
• Similar to C but severely cold winter
• Average temperature of coldest month
<27ºF
• Snow on ground for extended periods
• Average temperature of warmest month
>50ºF
• Overall, large change in temperature with
season
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D climate subtypes
• 2nd letter
– “f” no dry season
– “w” winter dry season
• 3rd letter
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“a” hot summer
“b” warm summer
“c” cool summer
“d” extremely severe winter
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D Climate Subtypes (continued)
• Humid continental
– Dfa, Dfb, Dwa, Dwb
– Dfa, for example, Chicago
• Subarctic
– Dfc, Dfd, Dwc, Dwd
– Long winter
– Brief cool summer
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E climate type
• Polar climate, very dry and cold
• Poleward of Arctic/Antarctic Circle, latitude
66.5º
• E climate subtypes
– ET Tundra: mosses, lichens, flowering plants,
woody shrubs, small trees, permafrost
– EF Ice caps: no vegetation; Greenland,
Antarctic Plateau
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H climate type: Highland
• Large variation of temperature and
precipitation over small horizontal distances
• Large diurnal temperature variation
• Can be dry or moist, depending on
orientation, humidity, and whether
prevailing winds are upslope or downslope
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