Weather and Climate basics Charles Darwin Climate Symposium 14 October 2011 Joel Lisonbee NT Climate...
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Transcript of Weather and Climate basics Charles Darwin Climate Symposium 14 October 2011 Joel Lisonbee NT Climate...
![Page 1: Weather and Climate basics Charles Darwin Climate Symposium 14 October 2011 Joel Lisonbee NT Climate Services Centre Bureau of Meteorology.](https://reader036.fdocuments.us/reader036/viewer/2022062320/56649d365503460f94a0e347/html5/thumbnails/1.jpg)
Weather and Climate basics
Charles Darwin Climate Symposium14 October 2011
Joel LisonbeeNT Climate Services Centre
Bureau of Meteorology
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Weather and Climate basics
Goal: To explain and define basic weather and climate terms
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• Weather: “The state of the atmosphere…the short-term (minutes to days) variations in the atmosphere” AMS Glossary of Meteorology
• Climate: “The slowly varying aspects of the atmosphere-hydrosphere-land surface system” AMS Glossary of Meteorology
– Often taken as a 30 year average
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Air Pressure
• Force = mass X acceleration, F=ma
• Pressure: net force per unit area, P=F/A
1 m
1 m
ma
• Air has mass
• Gravity pulls air down
• Air Pressure is the force exerted by the column of air directly above you.
•Measured by a barometer
•In millibars (mb)
•Hecto Pascals (hPa)
•Sometimes inches of mercury1 m
AIR
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Side note: air pressure and altitude
• If air pressure is weight of air above you
• Then less air above you means lower air pressure
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L
AIR
AIR
Air pressure (cont.)
AIR
AIR
AIRA
IR
H
DivergenceConvergence
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Air Pressure
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Pressure lines (isobars) on a weather chart
L
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Air flow around Low pressure system
L
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Hot Air Rises…Cold Air Sinks
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Atmospheric layers%
of atmosphere above that level
• Temperature change with height
– Troposphere• 6.5 °C/km
– Dry air parcel• 9.8 °C/km
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L HH
Sea Surface Temperature (SST): The temperature of the ocean surface
Convection
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•Over Simplified model•Other Complications include:
•Spinning planet•Tilted axis•Land masses/oceans•Water vapour
North/South Circulation
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Global Circulation
• Forces from Earth’s rotation create: – 6 circulation
cells– Bands of high
and low pressure
– Easterly and westerly winds
L
L
L L
H
H
H
H
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L HH
East/West circulation
Winds are named for the direction they came from:
West wind / westerlies East wind / easterlies
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Walker Circulation
• Walker Circulation: a patterns of rising and sinking motion in the Tropics which creates east/west circulation
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climatology average conditions and anomalies
• Climate: “The slowly varying aspects of the atmosphere-hydrosphere-land surface system” AMS Glossary of Meteorology
– Often taken as a 30 year average
• Climate variability: “any variations of the atmosphere/ocean system around a mean state” AMS Glossary of Meteorology
• Climate Change: “Any systematic change in the long-term statistics of climate elements sustained over several decades or longer” AMS Glossary of Meteorology
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Mean climate and anomaly
Measured
Expected
Anomalies
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Mean Climate and anomaly
Climatology: mean, average, or expected
conditions
Negative Anomaly
Positive Anomaly
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Climate Variability
• Example: El Niño/La Niña– Seasonal SST
Changes in the Pacific
– Seasonal to annual effects
– Drought or Flood?• Australia or Pacific
Islands
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Climate Change: Trends in past climate
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Climate Change in Australiawww.climatechangeaustralia.gov.auwww.bom.gov.au/climate/change/