Global Climate Patterns and Life Zone Diversity. Importance of physical environment Causes of global climate patterns Temperature Rainfall Water circulation patterns Local modifications of climate Global life zone classification
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Species distribution often determined by physical environment(see lectures on physiological ecology). Example: distribution of coral reefs limited by water temperature (20º C isotherm of ocean temperature, coldest month)
Insolation the physical environment, particularly climate & air/water currents? (heat input to atmosphere & Earth’s surface via solar radiation) maximal at equator, & declines to 40% of maximal values at high latitudes. Insolation drives mean annual temperatures
Visual illustration of latitudinal gradient of insolation the physical environment, particularly climate & air/water currents?
Moreover, seasonality of insolation arises strictly because of tilted axis of Earth’s rotation (spin) relative to plane of Earth’s revolution around sun: Insolation peaks N. hemisphere June 21, in S. hemisphere December 21.
Tropic of Cancer (latitude 23.5ºN), & Tropic of Capricorn (23.5ºS) defined by extreme latitudes at which sun is directly overhead annually--summer & winter solstice, respectively. This corresponds with 23.5º angle of tilt of Earth. Thus “solar equator” (region of maximum solar input) moves relative to latitude seasonally.
The thermal equator, oscillating latitudinally with seasons, drives low latitude patterns of rainfall by establishing zones of low pressure (high rainfall) and high pressure (low rainfall).
The hadley cell (centered on thermal equator) depends on convection currents with updrafts that cause low latitude rainforests, and downdrafts that cause subtropical hot deserts (20º - 30º N, S lat.).
Major latitudinal displacements of surface air currents: convection currents drive Hadley cells, pulling air at surface into Inter-Tropical Convergence Zone, ITCZ); Ferrel Cells driven by low pressure zone at 20º-30º lat.; Midlatitude westerlies converge into jet stream; polar cells driven by high pressure (cold) flows out of polar region along Earth’s surface towards south.
The convection currents drive Coriolus Force causes winds moving north or south latitudinally to deflect to the right in the Northern Hemisphere, and deflect to the left in the Southern Hemisphere. This force causes the “trade winds” moving from higher latitudes towards ITCZ to come from northeast direction north of equator (northeast trade winds) and from southeast direction south of equator (southeast trades).
45º N. latitude: circumference: 17,000 miles
Air mass (yellow) pulled south (e.g., towards ITCZ) deflects right relative to Earth’s surface, because Earth spinning increasingly rapidly beneath it
Equator: 24,000 mile circumference
Earth’s spin (west to east) faster at equator, because of greater circumference traveled per 24 hour day
Major patterns of oceanic surface flow at low latitudes caused by surface drag, caused in turn by winds.
Some specific currents worth remembering (red = cold, black = warm): California Current (7), Humboldt Current (2), Gulf Stream (13), North Atlantic Current (= Labrador Current; 15), Equatorial Counter Current (4)
Ocean currents tend to link up globally into a giant circulation system, or conveyor belt, comprised of shallow currents (e.g., Gulf Stream) and deep currents that tend to be cold, salty (dense).
Air masses originating in north tend to be cooler (P = Polar), those originating in south tend to be warmer (T = Tropical).
Those originating over land tend to be dry (c = continental), those over water tend to be wet (m = marine).
The foregoing principles and forces explain much of the global patterns in vegetation types (depending on temperature, moisture): Wetter vegetation (forests) green, drier (grassland, desert) tan to brown, cold (arctic, alpine) areas white.
30º N. Latitude global patterns in vegetation types (depending on temperature, moisture): Wetter vegetation (forests) green, drier (grassland, desert) tan to brown, cold (arctic, alpine) areas white.
30º S. Latitude
Classification of basic vegetation types = biomes
Classification of vegetation types partially based on kinds of plants, which tolerate different climactic conditions.
Holdridge’s life zone system is one of most widespread, quantitative schemes for classification of vegetation, land types