Climatic Controls

Latitude Altitude Continentality Prevailing Wind Air Mass Variability Topography Ocean Currents Land Use / Land Cover Change

Empiric classification: Köppen and later modified by Thornthwaite and Trewartha

looked at the global distribution of different plant and animal species and attempted to see how weather variables correlated with these patterns.

Temperature and precipitation

Köppen climate classification

Five primary categories– A Tropical– B Dry– C Mesothermal- “moderate”– D Microthermal- “low”– E Polar

BASIC WORLD CLIMATES

A climates

Mean temperature of coldest month is above 18°C (64°F)

Essentially, no freezes– Tropical Rainy: no dry season– Tropical Wet-and-Dry: short dry season– Tropical Monsoon: long dry season

TROPICAL RAINFOREST

Annual precip > 80” No real seasons Sticky, humid air, with little wind High sun angle all year

Tropical Savanna and Monsoon

Savanna– alternating 3 month wet and dry periods

dominated by movement of ITCZ

Monsoon – 5 - 7 month wet and dry regime

Both have 40 – 80” precip/year and average temps above 64°F every month

B climates

Arid and Semi-arid P < PE

– BW (Desert):– BS (Steppe):

Steppes

Dry short grass regions surrounding deserts There are cold and hot steppes Hot steppes are subtropical

– South Texas Cold steppes are at mid latitudes

– Montana Both have approximately 10 – 20” annual

precip

Deserts

Hot and Cold deserts just like Steppes Both have < 10” precip/year Abundant sunshine Hot desert

– Sahara

Cold desert– Gobi

C climates

Essentially, it freezes but snow is not permanently on the ground in winter.– Mediterranean: dry summer– Wet-and-dry: dry winter– Humid: no dry season

Humid Subtropical

Mild winters with temperatures frequently dipping below freezing (northern limits) to infrequent freezes (southern limits)

Hot summers Abundant precip throughout the year

– SE U.S.

Mediterranean(dry summer subtropical)

No summer rain Very little late spring/early fall rain Cool moist winters and warm summers Climate moderated by cold water Abundant sunshine

– Southern Cal

Marine West Coast

Cool/cold and moist winters Pleasant summers with temps generally not

exceeding 85°F Summer is drier Persistent fog, drizzle, gray skies for the

majority of the year– Seattle, London

D climates

Coldest month is less than -3°C; warmest month above 10°C.

Essentially, where snow remains on the ground for part of the winter.– Wet-and-dry: dry winter– Humid: no dry season

Humid Continental

Cold winters and warm summers Precip in every month

– Northern U.S.

Humid Continental (cool summers)– Located farther north with colder winters

Southern canada

Subarctic Boreal or Taiga

Brutal winters Coniferous forests Short cool summer with average temps

breaking 50F and frequently reaching the 70s

Not much precip 10 – 20” Northern Hemisphere only

– Most of Canada, Russia

E climates

Warmest month below 10°C. Essentially, where it’s too cold for trees to

grow– Tundra: it thaws in summer– Ice Cap: it doesn’t

Tundra and Icecap

Tundra is treeless Average temps do not break 50°F Small flowering plants, lichens, mosses, Horrible insects in summer when permafrost thaws

Icecap is frozen year round Occasionally temperatures will rise above freezing

Alpine or Highland

Complex climates because of altitude Can be a little of everything depending on

the elevation

WORLD CLIMATES

ANNUAL PRECIP