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
- abundant overhead sun
(insolation)
- shifts with the seasons
(extends 30 N & S)
- never below 18 degree
C (64.4 F)
- less extensive on West
Coast due to cool currents
- more extensive on East
Coast due to Trade Winds
- three (3) major distinctions
based on amount & distribution
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
- Turkestan, Taklamakan,
Gobi, Patagonia
- 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