Climate Classifications

October 28, 2014

Weather vs. Climate

• Weather – state of the atmosphere at a specific place and time on Earth’s surface.

• Climate – average values of weather elements, such as temp and precipitation, over an extended period of time

“Climate is what you expect, weather is what you get.” –Mark Twain

Variables that Influence Climate• Latitude – intensity of radiation, length of day

• Seasonality – annual variation of sun angle

• Air Circulation – predictable – weather systems

• Maritime/Continental – proximity to water can increase precip. and reduce temp range

• Topography – local topography can impact climate, e.g. windward vs. leeward side of mts.

Köppen Climate Classification System• Describes world climates based on:– Avg monthly temp

– Avg monthly precip

– Total annual precip

• 6 major climate groups based on latitude:

A-E & H

• Further subdivided by temp and precip.

• Primary Letter – based on latitude– Exceptions: B and H climate types

• Secondary letter – based on seasonal changes in precipitation

• Tertiary letter – based on seasonal changes in temperature– Exceptions: A and E climate types have no

tertiary letter

Köppen Climate Classification System

Köppen’s Climate Classifications

• Tropical Climates (A)– Average temp of every month > 18ºC

• Mesothermal Climates (C)– Coldest month average temperature < 18ºC but >

-3ºC– At least 1 month average temperature > 10ºC

• Microthermal Climates (D)– Average temperature of warmest month >10ºC– Average temperature of coldest month < -3ºC

Primary Letters

Köppen’s Climate Classifications

• Polar Climates (E)– Average temperature of all months  < 10ºC

• Dry Arid and Semiarid Climates (B)– Evaporation > precipitation

• Highland (H)

Primary Letters

Köppen’s Climate ClassificationsSecondary Letters

• These letters are based primarily on seasonal precipitation:– f = adequate rainfall all through the year, no distinct dry

season

– w = winter dry (keep in mind the hemisphere), if 70% or more of annual rainfall occurs in summer

– s = summer dry, if 70% or more of annual rainfall occurs in winter

– m = extremely wet summer = monsoon. A climate only.

Köppen’s Climate ClassificationsSecondary Letters• For B climate only:

– S = semiarid = steppe– W = arid = desert– which results in either BS or BW.

• For E climate only:– T = tundra– F = perpetual frost = permanent ice– which results in either ET or EF.

Köppen’s Climate ClassificationsTertiary Letters

• The third letters in the system are based exclusively on seasonal and annual temperature:– a = hot summer, warmest month > 22°C; C and D only

– b = warm summer, warmest month < 22°C; C and D only

– c = cool summer, < 4 months over 10°C; C and D only

– d = very cold winter, coldest month < -38°C; D only

– h = dry-hot, annual temperature > 18°C; B only

– k = dry-cold, annual temperature < 18°C; B only

Köppen’s Climate ClassificationsExamples of Combinations• Af = Tropical Rainforest climate type

• Am = Tropical Monsoon climate type

• BWh = Low-Latitude Hot Desert climate type

• Cfa = Humid Subtropical climate type

• Csa = Mediterranean climate type

• Dfb = Humid Continental climate type

• ET = Tundra climate type

Tropical Climates (A)

•Straddle Equator from 25º N to 25º S

•Avg. Monthly temp. exceeds 18ºC (64ºF)

•Subdivided by precipitation:

•Af – tropical rainforest – wettest

•Am – tropical monsoon

•Aw – tropical savanna - drier

Af

HawaiiTropical Rainforest - Af

Northern AustraliaTropical Savanna -

Aw

IndiaTropical Savanna -

Am

Arid/Semi-Arid Climates (B)• Poleward of A climates on all continents

• Subsiding air from STHs - Moister on fringes

• Subdivided by temp & moisture:

– BWh – 15-30º N & S – hot - little precip

– BWk - <15 cm precip/yr – high temp range

– BSh – more temp range & precip than BWh

– BSk – rainshadow – convectional precip – high temp range

Arid Climates (BWh)

Semiarid Climates (BWk)

BWh

BWk

Semiarid Climates (BS)

BSh

BSk

Jordan – Hot, Low-latitude Desert - BWh

Northcentral China – Cold, mid latitude Desert - BWk

Eastern Colorado, USACold, mid latitude Steppe - BSk

California, USA - Hot, low latitude Steppe - BSh

Mesothermal Climates (C)• 20º- 60º N & S – where most people live

• A warm and a cool season

• Cfa, Cwa – Humid Subtropical - hot, humid summer – east side of continents – 20-35º N & S

• Csa, Csb – Maritime - near 35º N & S – winter wet season, dry summer

• Cfb, Cfc – Mediterranean - west coast of continents – 35-60º N & S – mP air & orographic processes

Humid Subtropical

Cfa

Maritime

Mediterranean

Csa

Southern California – MediterraneanDry-Summer Climate - Csa

Western Washington – MarineWest-Coast Climate - Cfc

Microthermal Climates (D)

• Poleward of C climates, 35º- 60º N & S• Long winters, limited summer warmth,

continental climates• Dfa, Dwa – large annual temp range – jet

stream & cyclonic precip, most in summer• Dfb, Dwb – very large annual temp range –

mild summer, harsh, dry winter• Dfc, Dwc, Dwd – long, bitter winters - short,

cool summers – little precip – highest annual temp range on Earth

Microthermal Climates (D)

Dfa

Dwa

Eastern US – Humid ContinentalHot-Summer Climate - Dfa

Northern Michigan – Humid ContinentalMild-Summer Climate - Dfb

Central Canada -Subarctic Climate –

Dfc

Polar Climates (E)

• Latitudes >70º N & S

• Long, cold winters w/little precip.

• 2 Subcategories:

– ET – temp moderated by ocean – precip mostly June-Oct.- polar high dominates

– EF – interior Greenland and Antarctica – always brutally cold – polar desert

Polar Climates (E)

ET

EF

Highland Climates (H)

• Associated with large mtn ranges, e.g. Andes, Rockies, Alps, etc.

• Cooler/colder than surrounding lowlands, even in tropical or equatorial regions

• Often wetter than surroundings due to orographic precip.

North American Climates