Lecture 4-Earths atmosphere and energy

Lecture 4-Earths atmosphere and energy - Earths Atmosphere...

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Earth’s Atmosphere and Energy (Ch. 2, 3 (pp 50-87)
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The Atmosphere Insolation moves through our atmosphere to the surface of Earth… Powers physical systems in atmosphere, oceans, land… Works as a ‘filter’ which removes harmful radiation from sunlight..
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The Atmosphere Today’s atmosphere is not original! ~4 th atmosphere in Earth’s history (Anthropocene) Composition of atmosphere has changed during different phases of Earth’s history… Can you think of any examples?
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Atmospheric structure Our modern atmosphere arranged in a series of ‘shells’ or layers Not a uniform structure! All of these layers are bound to planet by gravity Atmosphere is still a thin envelope! Less than one-millionth of Earth’s total mass! First…important concepts!
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Atmosphere-Air Pressure Atmosphere exerts its weight on our Earth as it is compressed by gravity = air pressure! Motion, size, # of air molecules create air pressure.. Air pressure-weight of atmosphere (force over a unit area). 1 kg/cm^2 (or 14.7 lb/in.^2) at sea level Or 1013.2 mb (millibars)….more later!
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Atmosphere-Air Pressure Air pressure pushes down on us too! Why don’t we get crushed by the mass of air around us?
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Atmospheric profile Atmosphere is denser at Earth’s surface Density decreases with increasing altitude- Over half of total mass of our atmosphere is compressed below 18,000 ft (~3.4 mi) 90% is compressed below 52,500 ft! All but 0.1% of our atmosphere exists within an altitude of 31 mi (163,680 ft!)!
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Atmospheric Density Atmosphere is denser at Earth’s surface-Why? Density = mass volume
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Atmospheric Density Density = mass volume decreases with height due to gravity Density decreases by half every 3.48 mile (~18,000 ft) in height
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Layers of the Atmosphere ‘Top’ of atmosphere = Thermopause (300 mi) Beyond thermopause, near-vacuum conditions = exosphere (“outer sphere”) Extends up to 20,000 mi from Earth!
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Layers of the Atmosphere We categorize our atmosphere into different layers by examining: Composition Temperature Function There is some overlap in these categories! All aspects of the atmosphere combined….
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We can see how the atmosphere is divided into its ‘layers’ according to different aspects… Note the overlap of different layers!
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Composition Divided into two broad regions- Heterosphere 50 mi to top! Gases not evenly mixed Divided into layers Homosphere Surface to 50 mi Gases well mixed what we breathe!
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Composition Heterosphere-less than 0.001% of atmosphere’s mass is in heterosphere! Homosphere-some exceptions to ‘blended’ gas composition! – Ozone layer (O 3 )- 12-31 mi altitude Variations in pollutants near surface
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Atmospheric chemical composition Major Gases – *Nitrogen (N 2 ): 78% – Oxygen (O 2 ): 21% Argon (Ar): 0.9% -Carbon Dioxide (CO 2 ): 0.037% Trace Gases – Ne, He, CH 4 , Kr, O 3 , N 2 0, H, Xe
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Temperature Four distinct zones in atmosphere based on temperature (Exosphere-outer limits)
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