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RGPL 103 Global Cities:Planning and Development

Dr. Hoch

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Earth’s Orbit Around Sun

152.5 Million Km 147.5 Mil. Km

SUNEARTH

AphelionJuly 6 (12:00)

PerihelionJan 3 (00:00)

Dates for 2010

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Earth Rotation

23 1/2°

Ecliptic Plane(Plane of earth revolution around sun)

Earth’s axis

N Pole

Northern Hemisphere Seasons

• Summer• North pole tilted toward Sun• Days are longer than the nights• Get more energy - higher temperatures

• Fall• Neither pole tilted toward the Sun• Days about equal with nights• Less energy than in the summer• Cooler temperatures

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Northern Hemisphere Seasons cont.

• Winter• North pole tilted away from the Sun• Days shorter than the nights• Get less energy-Cold temperatures

• Spring• Neither pole tilted toward the Sun• Days about equal to nights• More energy than winter- Warmer temperatures

Global regions

• Tropics (23 ½°N ‐ 23 ½°S)

• Low latitudes (30°N ‐ 30°S)

• Mid latitudes (30°N ‐ 60°N and 30°S ‐ 60°S )

• High latitudes (60°N ‐ 90°N and 60°S ‐ 90°S )

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Key positional relationships

•Tropic of Cancer - 23 1/2° N•Highest latitude in the Northern Hemisphere that the suns

vertical rays ever reach

•Tropic of Capricorn- 23 1/2° S•Highest latitude in the Southern Hemisphere that the suns

vertical rays ever reach

•Arctic circle- 66 1/2° N•24 hrs of daylight-summer solstice•24 hrs of darkness at winter solstice

•Antarctic circle- 66 1/2° S•24 hrs of daylight-winter solstice•24 hrs of darkness at summer solstice

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Circle of illumination

Equinoxes and Solstices (2010)

Day  Date  Sub‐solar Point 

Summer solstice  June 21  23 1/2° N 

Autumnal equinox  Sept 23  0° 

Winter solstice  Dec 21  23 1/2° S 

Vernal equinox  March 20  0° 

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Equinox

Solstices

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Earth

1

3

1

1

= 100%

= 33.3%

SUN

Higher latitudes get LESSENERGY per unit of area

Solar Heating

Most of the Sun’s Energy is Received in the Equatorial Region of the Earth

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Global‐scale circulation system

• The equatorial and tropical regions receive far more solar energy than the midlatitudes and polar regions

• This heat energy is redistributed from warmer to colder areas by means of atmospheric air circulation (60%) and ocean currents (40%)

Hypothetical non‐rotating earth circulation

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Idealized global circulation

The global circulation model

Consists of three ‘cells’1) Tropical cell2) Midlatitude cell3) Polar cell

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Midlatitude and subtropical jet streams

Cross‐sectional view of jet streams

BLUE arrows and lines represent

areas or fronts of HIGH pressure

and rotate clockwise

RED arrows and lines represent

areas or fronts of LOW pressure

and rotate counter-clockwise

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Cyclic changes in upper air flow

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Inter‐Tropical Convergence Zone (ITCZ) World Map

The Intertropical Convergence Zone (ITCZ)

The location of the ITCZ gradually varies with the seasons, roughly corresponding with the location of the thermal equatorAs the heat capacity of the oceans is greater than air over land, migration is more prominent over land Over the oceans, where the convergence zone is better defined, the seasonal cycle is more subtle, as the convection is constrained by the distribution of ocean temperatures

The Intertropical Convergence Zone (ITCZ), known by sailors as the doldrums or the calms, is the area encircling Earth near the Equator, where the northeast and southeast trade winds converge

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Worldwide Rainforest Depletion

• Reported in 2012, more than 200,000 acres of rainforest are 

burned every day

• That is more than 150 acres lost every minute of every day, or 78 

million acres lost every year

• More than 20 percent of the Amazon rainforest is already gone

• More is severely threatened as he destruction continues

TropicOf 

Cancer

TropicOf 

Capricorn

Amazon BasinRain Forest

Congo BasinRain Forest

South EastAsiaRain Forest

Rainforests also help to stabilize Earth's climate

They absorb carbon dioxide

The reduce the effects of worldwide anthropogenic climate change

They also home to about half of the species of plants and wildlife on the planet

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https://news.mongabay.com/2014/12/tropical‐deforestation‐could‐disrupt‐rainfall‐globally/

The Earth at NightMan‐made light shining at night is used as a metric to measure the amount of urban development

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Central Place Theory

• Provides a conceptual mechanism for understanding the role of the city as a service center.

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