World Geography / Unit 2: Physical Geography
2.3 Weather, Climate and What Controls Them
Notes
Weather is the condition of the atmosphere at a particular time and place. Climate is the average pattern of weather over many years (usually 30 or more).
- Latitude: places near the equator get more direct sunlight and are warmer.
- Elevation: air gets cooler with height, about 3.5°F per 1,000 feet (6.5°C per kilometer).
- Nearness to water: oceans heat and cool slowly, giving coastal places milder temperatures.
- Ocean currents and prevailing winds carry warmth or cold. The warm Gulf Stream and North Atlantic Drift keep northwestern Europe mild.
- Mountains cause a rain shadow: wet air rises on the windward side and drops rain, leaving the far side dry.
- Worked example: a city at 5,000 feet is about $5 \times 3.5 = 17.5$°F cooler than a sea-level city at the same latitude.
Practice
Which statement correctly separates weather from climate?
Climate is the long-term pattern, while weather changes day to day.
A city at sea level has an average temperature of 70°F. Another city at the same latitude is 4,000 feet higher. About what temperature would you expect there?
$4 \times 3.5 = 14$°F cooler, so about 56°F.
Why is the land on the leeward (downwind) side of a tall mountain range often dry?
This is the rain shadow effect.
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