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MET 112 Global Climate Change - Lecture 6
Controls on Climate II
Dr. Craig Clements
San Jose State University
March
June
Sept.
Dec.
Northern Summer
Northern Winter
Seasons Review
 A season is one of the major divisions of the year,
generally based on yearly periodic changes in weather.
 In temperate and polar regions generally four seasons
are recognized: spring, summer, autumn (fall), and
winter.
 In some tropical and subtropical regions it is more
common to speak of the rainy (or wet, or monsoon)
season versus the dry season, as the amount of
precipitation may vary more dramatically than the
average temperature.
 In some parts of the world, special "seasons" are
loosely defined based upon important events such as a
hurricane season, tornado season or a wildfire
season.
Earth’s energy: latitudinal
perspective
 A majority of the sun’s energy enters the Earth
system in the tropics.
 The tropics thus become quite warm, while the
poles relatively cool.
 The atmosphere attempts to bring the tropics
and high latitude into equilibrium
– Weather systems ultimately act to bring
warm air to higher latitudes and cold air
to lower latitudes.
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Controls on Climate
 Seasonal temperature and precipitation patterns
are generally attributable to:
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Latitude
Mountains and highlands
Land and water location
Prevailing winds
Pressure and wind systems
Ocean currents
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Questions
 Indicate the warmest and coldest areas of the
Earth.
 Consider the temperature at 60N latitude.
Indicate on the map the coldest and warmest
places at 60N.
 What is the temperature difference between
these locations
 What factors might explain this temperature
difference?
 Why is there not a similar difference seen at 60S?
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Annual Average Surface Temperature
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Climate controls:
Latitude/Mountains
 Latitude
– Higher latitude climates are generally
(cooler/warmer)
– Lower latitudes climates are generally
(cooler/warmer)
 Mountains
– Higher altitudes climate are generally
(cooler/warmer): cooler temperatures
– Windward side of mountains are generally
(cooler/warmer) and (wetter/drier), than
leeward side
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Controls on Climate: Oceans
 Ocean Temperatures
– Coasts of continents are affected by ocean
temperatures: Generally less temperature
extremes compared to interior of continents
– Cold oceans:
generally produce cooler/drier conditions
– Warm oceans:
generally produce more warm/humid conditions
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Cold ocean
Warm ocean
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Controls on Climate: Pressure
systems
 Rising and sinking motion associated with low
and high pressure affects climate
 Areas where pressure seasonally low,
–
Tropics: rainy
 Areas where pressure seasonally high,
– Subtropical high (30N/3OS): warm and dry
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January Average sea-level Pressure and surface wind pattern
July Average sea-level Pressure and surface wind pattern
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Diurnal Temperature
 Given a location, the temperature changes
throughout the course of the day.
 This is a result of the changes in insolation at
the surface.
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Measurement of Air Temperature
 Air temperature is measured using a
thermometer housed in a shelter to limit the
effects of: Solar Radiation
 The temperature needs to be measured some
distance above the ground. Typically this is
about 2 m above ground level (AGL).
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Temperature /
Relative Humidity
probe
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