GEOG10001 Lecture Notes - Lecture 3: Intertropical Convergence Zone, Atmospheric Circulation, Ocean Current
16 May 2018
School
Department
Course
Professor
LECTURE 3: FOOD PRODUCTIVITY V POPULATION
• Zimbabwe: floods, then drought (70 dams burst)
• Crops: growth related to climate and soil
o Lower in LDC’s + climate zones
CLIMATIC ENERGY
• Earth has an eccentric orbit + rotation = fluctuations in insolation reaching Earth’s surface
o Variation: daily, annually + 1000’s of years
• Radiation: Incoming – shortwave, Outgoing – longwave (comes in as light, goes out as heat)
• Oceans + atmosphere: redistribute/recirculate energy
o This recirculation of energy distribution of wet + dry/ cold + hot climates
Atmosphere (Winds)
• Reliable data
• Heat on the globe redistributed by winds + atmosphere, through atmospheric circulation
• Land heats up faster that water, creating cells which lead to circulation
• Hadley Cell: closest to equator
Global Air Masses: 7 different types
• Important: (m) = maritime, (c) = continental
• Maritime: as you travel higher latitude = larger variations in temp annually, however
usually rather constant + stable
• Continental: as you move higher latitude, larger fluctuations, unstable + larger
seasonality
Oceans
• Less certain data
• Move energy around, through ocean circulation systems (gyres)
o Currents move in relatively predictable ways
• High energy on surface (warm sea surface temperatures) + lower energy deeper down
• El Nino: create huge convective storms that cause changes in atmosphere + shift oceans
o Redistribution of energy influences climate
CLIMATE ZONES
• Classified based on precipitation + temperature
• FAO suggests 6 climate zones in Africa: desert, arid, semi-arid, sub humid, moist sub humid and humid
Precipitation Regimes
Equatorial + Tropical Zones
• Wet equatorial: stable
• Monsoon: massive seasonal variation
• Wet-dry tropical: variation, not as extreme
• Tropical desserts: no rain
Subtropical + Mid Latitudes
• Summer maximum: very even, still seasonality
• Winter maximum: also even, still seasonality
• If a country is used to constant rainfall, the rely on this to sustain water systems
o E.g it only takes 3 weeks of no precipitation for England to go into drought
• Dense populations in regions rely on consistent precipitation
POPULATION RELATIONSHIPS
• Global distribution of humans
o ½ of Earth’s potentially habitable land area is thinly populated (less than
2% of human pop. at densities of less than 10ppl/km2
o Other ½ at extremely high population densities
• Physiographic relationships (see blue box) stronger than climatic ones
• Regions with higher annual variability in precipitation are densely populated areas
(experiencing Indian and East Asian Monsoons)
o Consistency of precipitation important for areas without irrigation
▪ However, snowmelt runoff can offset variability in precipitation
• Population density increases exposure to catastrophic events
LECTURE 4: CLIMATE CHANGE V POPULATION
Inter-tropical Convergence Zone
(ITCZ)
• Direct insolation changes
seasonally between tropics of
Capricorn + Cancer
• Shifts up + down seasonally
• Winter monsoon = dry
conditions, summer monsoon =
wet conditions
• Provides a predictive set of
climatic conditions over the
year
• Allowing farmers to know what
crops to grow, + when
Koppen Classification
• Climate classification, based on vegetation
• Created zones based on monthly temperature + precipitation, and their variation across the year
• Group B: Dry (arid + semi-arid) climates, desert like
o Generally low populations, hostile landscapes
Population Diminishes Rapidly with:
• Increasing elevation
• Increasing distance form
coastline
• Increasing distance from
major river
Document Summary
Lecture 3: food productivity v population: crops: growth related to climate and soil. Earth has an eccentric orbit + rotation = fluctuations in insolation reaching earth"s surface: variation: daily, annually + 1000"s of years. Radiation: incoming shortwave, outgoing longwave (comes in as light, goes out as heat: oceans + atmosphere: redistribute/recirculate energy. This recirculation of energy distribution of wet + dry/ cold + hot climates. Heat on the globe redistributed by winds + atmosphere, through atmospheric circulation. Land heats up faster that water, creating cells which lead to circulation. Global air masses: 7 different types: maritime: as you travel higher latitude = larger variations in temp annually, however. Important: (m) = maritime, (c) = continental usually rather constant + stable: continental: as you move higher latitude, larger fluctuations, unstable + larger seasonality. Oceans: move energy around, through ocean circulation systems (gyres) Less certain data: currents move in relatively predictable ways.
