Struggle for Existence pt. 4 Flashcards
Most important environmental variable
temperature
Highest density of photons
at equatorial regions (perpendicular to rays)
Seasonal variation occurs as a result of
the earth’s tilted axis (as the earth revolves, different parts of the earth experience the sun directly overhead). At spring and autumn equinox, sun is directly above equator.
October - March is cold season/dry season for northern hemisphere
April - September is warm/rainy season for northern hemisphere
Tropic of Cancer
23.5°N
Tropic of Capricorn
23.5°S
Does light have to travel longer through the atmosphere at higher latitudes than near equator? Does it affect its energy?
Yes, a photon travelling to Toronto vs Costa Rica will travel through more air, however because most energy from sun is light energy and air does not absorb light, the longer distance doesn’t really matter much.
Where does energy transfer occur?
Energy transfer occurs when lights hits surfaces other than air (solid surfaces, water). Absorbed-> reradiated as infrared waves (heat).
Where does solar energy heat the earth?
Closest to the surface because of the IR waves that are reradiated after light is absorbed. Heating is strongest near equator. The fact that heat is strongest closest to the surface of the earth and not near top of atmosphere is super important because heating from the bottom of a fluid (air) makes the air near the bottom less dense and more buoyant. It rises displacing cold air which falls to surface only to be heated again (circulation patterns).
Review: How do Hadley cells work
Heat up air closest to eq, it rises creating a partial vacuum underneath it, thus surface air from north and south is drawn to solar equator, hits atmosphere and slides towards poles, cooling (because there is less pressure to compress the gas) and falling (warming as it does) pulled back to eq.
adiabatic lapse rate
altitude gain = temperature drop (extension of ideal gas law). For 1 km of altitude gained, air temp drops about 5°C in humid air and 10°C in dry air.
Low pressure weather systems =
lots of precipitation
Hadley cells deliver
the wettest and driest weather (vapour in humid packets of air condense to fall of eq regions, as it rises most of the vapour has been wrung out so dry air is delivered to 30°N and S)
Where does the air that falls from Hadley cell go: poleward or towards eq?
Both. Airflow is indiscriminate. Air flow that goes towards eq is pulled back into Hadley cell, dry air that goes to poles moves across surface picking up moisture and rising creating another pair of rainy/snowy low pressure zones at 60°N and S (Ferrel cells).
What closes the loop of both Hadley and Ferrel cells
Air that flows towards equator. The airflow is indiscriminate when it hits the atmospheric ceiling and goes both south and north. Equatorward air closes the loop, poleward air starts another cell. Polar cells result from the poleward air from top of Ferrel cells (which explains why they are the weakest).
Westerlies
Explains why Toronto weather blows in from the prairies. Air being pushed straight north by ferrel cell is being pushed over spinning sphere thus it overshoots. West curving to east.
Equator zones are subject to easterlies or westerlies and why?
Easterlies, equatorward air falls behind its destination because equator is moving faster than zones close to poles.
Prevailing winds are strongest and weakest where?
strongest at the latitudes in the centre of the atmospheric cells
- 15° and 45° (roaring forties at 45°S because no significant lan masses in southern oceans) weakest where air is rising
- 0° and 60°) and falling (30°)
Doldrum
Windless equatorial region
Horse latitudes
windless regions where air is rising 30°N/S
Jet streams
concentrated and narrow westerlies
Oceans provide
inertia for nearby land masses
gulf stream
brings warm water from Caribbean to northern latitudes (including UK)
Frost sensitive crops are cultivated often in…
maritime climates (thermal inertia provided by water)
Seasonality in the triopics is dictated by
Precip not temp. Temperature is uniform throughout year and in some places the ITCZ doesn’t move and rainfall is uniform but when it does move, there are rainy and dry seasons.
Cold ocean currents correspond to
the driest deserts because moisture does not evaporate from cold bodies of water as much as it does from warm water. Canary current gives Sahara desert, Benguela to Kalahari, etc.
Most extreme deserts are on…
western coasts of continents + cold offshore currents
The Rockies cause…
a rain shadow for essentially all of North America, but it is most pronounced east of the Rockies (prevailing westerlies). On the flip side though, water comes from rivers that are fed by run off from the Rockies.
Riparian vegetation (gallery forest)
vegetation supported by permanent rivers
ex. cottonwoods
Orogenic precipitation is much more pronounced…
on oceans than land thus oceanic islands with mountains have severe rain shadows (Hawaii)
