Lecture 4-Earths atmosphere and energy

Lecture 4-Earths atmosphere and energy - Earth’s...

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Unformatted text preview: Earth’s Atmosphere and Energy (Ch. 2, 3 (pp 50-87) 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.. 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? 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! 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! Atmosphere-Air Pressure • Air pressure pushes down on us too! – Why don’t we get crushed by the mass of air around us? 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!)! Atmospheric Density • Atmosphere is denser at Earth’s surface-Why? • Density = mass volume Atmospheric Density • Density = mass volume • decreases with height due to gravity • Density decreases by half every 3.48 mile (~18,000 ft) in height 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! 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…. We can see how the atmosphere is divided into its ‘layers’ according to different aspects… Note the overlap of different layers! 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! Composition • Heterosphere-less than 0.001% of atmosphere’s mass is in heterosphere!...
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This document was uploaded on 11/04/2011 for the course GEO 2200 at FSU.

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Lecture 4-Earths atmosphere and energy - Earth’s...

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