Climates

Climates

Overview

climate is long-term weather patterns
precipitation & temperature - major weather elements used as indicators of climate
Köppen system most used climate classification - based on precip. & temperature
- specific designation of temperature & precipitation levels
  - (e.g. tropical never fall below 64.4 F on average)
  - (e.g. polar never rise above 50 F on average and no trees)
- used letter system to designate major climates
  - A = tropical; B = deserts; C = temperate; D= severe; = polar: H = highlands
  - upper case designation correlates to latitude change except highlands
  - lower case: s = summer drought; w = winter drought; f = wet year-round
  - lower case: a = hot; b = cool; c = cold summer periods
- ( western & eastern hemisphere climate zones)

Tropical Climates

Tropical Rainforest (Af)

constant heat & humidity (no variation)
steady, year-round rains associated with doldrums & convergence
- daily afternoon rain showers due to convection
- near oceans associated with greatest precipitation in world
produces true "selva" or canopy rainforest (not jungle)
greatest climatic stability and biodiversity in world

Tropical Monsoon (Am)

reversal of winds associate with shifting of ITC
summer lands heat and draw in moist ocean air
- further exacerbated by orographic lifting
short dry season (winter) followed by intense rainy season (summer)
more jungle like vegetation and less biodiversity

Tropical Savanna (Aw)

flanks tropical rainforests & monsoons areas
abundant rain received during the high sun period (summer)
little to no rain during the low sun period (winter)
- prone to winter drought or unpredictable weather conditions
- precipitation caused by the shifting ITC (i.e. shifting sun)
classic savanna grasslands, strange trees and shrubs
home to large ungulates(grazing animals) & predators
- African Serengeti, Venezuelan Llanos, Brazilian campos
hardpan soils called "laterites" leached from heavy rains
- not well-suited for agriculture yet under population stress
home to last nomadic people and animal herders like Masai

Deserts (subtropical deserts & inland deserts)

emphasis on precip. not temperature
- world contains both cold & hot deserts
- Great Basin (snow in winter) and Arabian Desert (130°F)
great consistency along western continental edges
- due to subsidence and the high pressure zones
- increased aridity from cold coastal currents
Atacama, Namib, Kalahari, Baja deserts
larger ones: Sahara, Arabian, Ausrailian and Thar
- removed from oceanic moisture (continental effect)
  - Great Basin & Great Plains
achieve high temperatures (abundant insolation)
two major divisions:
- true deserts (BW)
- semi-arid deserts (steppe - BS)

Dry Desert Climates (BW)

based on precip effectiveness - actually available to plant
low relative humidity (less than 1/2 potential evapotranspiration)
when precip comes, it comes all at once (yearly level - one day)
high temps and shallow soils produces hardy, drought tolerant plants
- "xerophytic" vegetation has thick bark, no leaves, large storage
- prickly cactus, Joshua trees, creosote bush
large deserts correlate with subtropical high cells

Steepe Climates (BS)

fringes of deserts with controls such as continentality, rain-shadow, high pressure
greater precip but never reaches potential evaporation (deficit of moisture)
received between 10 and 20 inches
found in cold regions, like Montana and Nevada, with slightly higher humidity
- i.e. (greater than 1/2 potential evapotranspiration but less than full evap.)
excellent for grasslands and large ungulates (grazers)
delicate system of fragile life-providing crust and bunch grasses
vulnerable to overgrazing and easy destruction
while native vegetation is drought tolerant, crops can easily fail

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