Lecture 7 Climate

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Lecture 7 Climate
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• Meteorology Study of climate and weather
• Weather daily variations in precipitation,
  winds, temperature, etc.
• Climate overall combination of temperature,
  precipitation, winds etc. of an area/region
• Subject to many factors
• Amount of sunlight
• Topography
• Rotation of earth
• Major variations in climatic patterns
• Seasonal
• El Nino Southern Oscillation (ENSO)

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• Movement of Air Water Masses
• Uneven heating
• Drives air circulation patterns and consequently
  precipitation patterns.
• Warm, moist air rises.
• Adiabatic cooling moisture condenses and falls
  as rain.
• Cooler, dry air falls back to surface.
• Rainforests found near equator.
• Major deserts found near 30o N / S.

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• Temperature impacts moisture content of air
• Equilibrium vapor pressure function of
  temperature
• As temp. drops amount of water that can be held
  in the atmosphere drops precipitation forms

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Solar-Driven Air Circulation
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• Coriolis effect
• caused by moving N or S on rotating Earth
• earth is rotating from left to right (eastwards)
• Motion faster at equator than towards poles
  (think parabola)
• so as one moves toward equator, one enters a
  faster region from a slower one
• objects in motion seem to be deflected to left as
  they are moving slower (to the right) than their
  surroundings
• moving away from equator, one enters a slower
  region from a faster one
• objects in motion seem to be deflected to right
  as they are moving faster (to the right) than
  their surroundings

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• Intertropical Convergence
• Latitudes near equator associated with sun-warmed
  moisture laden surface air
• subtropical high-pressure belt
• ca 30º /- equator dry upper atmosphere air falls
  to earth ? arid regions

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• Ocean Currents movement of large masses of water
• Driven by
• Uneven heating
• Steady winds, interrupted by land masses
• Thermohaline differences
• Gyres large circular movements that circulate
  around an oceanic basin
• counterclockwise in southern hemisphere
• clockwise in northern hemisphere

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• Impact of Gyres
• move warm waters northward or southward ? warm
  the climate of the land
• example is the Gulf Stream in the North Atlantic,
  which so warms western Europe that palm trees
  grow in southern Ireland
• move cool water south
• Example California Current ? cools west coastal
  climate

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• Marine Upwelling
• Develop as winds bring nutrient rich waters to
  surface
• CA coastal regions occur during summer months
  driven by winds offshore
• Nutrients stimulate food chain causing massive
  increases in krill (tiny crustaceans)
• Accounts for presence of sea bird and whale
  populations in Monterey Bay through summer/fall

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• El Niño Southern Oscillations The Christ Child
• Prevailing condition east-to-west trade winds
  push warm surface water westward ? upwelling off
  coast of Peru
• El Nino conditions winds drop/cease ? Fishers in
  Peru, Ecuador and Chile get some time off!

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• An El Niño winter - unusual weather patterns all
  over the world

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• La Niña
• Not as well known as El Niño
• Causes extreme effects that are nearly opposite
  to those of El Niño
• In the US, effects are more apparent in winter
• Northwest is wetter and cooler than normal
• Southeast is dryer and warmer than normal

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• Long-term Climate Trends
• Human observational records 200-500 yrs
• Other sources
• Tree ring/growth
• Isotopic analysis
• Pollen analysis of sediments
• ice core analysis
• Fossil evidence

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• Summary
• Circulation patterns both in the atmosphere and
  in the oceans are impacted by differential
  heating due to solar radiation and rotation of
  the earth
• As a consequence of these circulation patterns
  various biomes as well as localized climates may
  be recognized
• Local climate conditions may be impacted by
  topography and other interactions of local
  weather patterns
• Many unique local ecosystems exist due to
  localized climatic conditions and factors