Lesson 1 Flashcards
Location of tropics
- 23.5 North and South
- Tropics of Cancer and Capricorn
- lots of South America and Africa
- Little bit of Asia and Australia
- Tiny bit of North America
Average temperature in the Tropics
- 25-25 but used to be 24
- hottest to coldest month varies by 2-5
- hottest to coldest time of day varies by 8-9
Amount of rainfall in the tropics
Tropical rainforests: >100 mm every month and >1500 mm every year (no dry spells)
Megathermal: >2000 mm per year
Tropical seasonal forests: some months get 60 mm or less
- Tropical Dry Forests/ Monsoon forests have 2-5 dry months
- Tropical Deciduous Forests have 5-7 dry months
Hadley Cells
- air rises at equator
- flows poleward at 10-15 km above earth
- descends in subtropics
- returns to equator near Earth’s surface
- ascending moist air releases moisture; descending dry air absorbs moisture
- produced by solar radiation and evaporation of ocean water
Intertropical Convergence Zone (ITCZ)
- “doldrums”
- zone of low pressure 5 degree N and S of equator where trade winds converge and create heavy convectional precipitation
- location changes slightly with seasons bc of earths tilt
- can also vary by 40-45 lattitude due to land masses
- low pressure
- high humidity and cloudiness
- light variable winds and heavy rain
- thunderstorms
- occasional periods of where wind disappears for a while
El Nino Southern Oscilation
Usually:
- trade winds go E to W
- push warm water West with help of ocean current
- warm water evaporates and causes lots of rain in the west
- cooler, dry air goes back to the east
- since the warm water is pushed west, cold water from deeper in the ocean rises to the top in the east
El Nino
- weaker winds and warmer water in the Pacific
- less push of warm water to the west
- warm water and heavy rainfall happens closer to the east
- causes flooding in the east and droughts in the west
- also screws up the wind patterns–> now its going W and E from the middle
El Nino’s role in climate and its consequences
-Mechanism by which Earth regulates heat distribution and determines rainfall patterns globally
- Usually the cold water that comes to the surface in the East is nutrient rich –> during El Nino, this doesn’t happen so there’s less nutrients, less phytoplankton, less fish
- also affects coral reefs
Trade winds vs jet streams
Trade winds blow E to W in the tropics and are closer to the Earth’s surface
-Hadley cells + Earth’s rotation create NE and SE tradewinds and maintain rain at equator
Jet streams typically blow W to E and are higher in the atmosphere
Holdridge Life Zones
- Originally Merriam was like: elevation changes alter plant communities the same way latitudinal changes do
- Holdridge defined communities in relation to precipitation, biotemp (avg of temps above freezing), and evapotranspiration (used PET/ mean annual precipitation)
Evapotranspiration
- water transpired by plants + evaporated from surfaces
- PET = amount of evapotranspiration that would occur with unlimited water supply
Orographic rainfall
- Wind carries warm, moist air up one side of a mountain
- releases precipitation on that side of the mountain
- cool, dry air comes down other side of the mountain
Why is the location of continents significant?
- It alters ocean currents and ITZC to make El Nino events
- topography can also alter precipitation and limit rainforest locations
Why is transpiration important?
- it maintains atmospheric moisture
- globally, transpiration is 10% of atmospheric water
- in tropics, 25-75%
Factors that dictate tropics
- Planetary Arrangement
- distance from sun and tilt
- rotation around axis (W to E) - Abiotic factors
- phys and chem properties of water and atmospheric composition - Physical location and surface of continents
- location w/in tropical lattitudes
- topographic variation - Biotic factors
- evapotranspiration
Planetary arrangement
- Distance from sun determines amount of solar radiation (343 W/m)
- tilt determines area that gets directs sunlight (90*)
- rotation around axis (W-E) creates wind patterns and ocean currents –> includes Coriolis effect
