1	Earth System Climatology (ESS220)
2	Course Description This course offers an overview of Earth's climate system by describing the major climatological features in the atmosphere and oceans and by explaining the physical principals behind them. The course begins with an introduction of the global energy balance that drives motions in the atmosphere and oceans, then describes the basic structures and general circulations of the atmosphere and oceans, and finally look into major climate change and variation phenomena.
3	Syllabus
4	Earth Climate System
5	Circulation of the Solid Earth
6	Lecture 1: Atmosphere Composition
7	Thickness of the Atmosphere The thickness of the atmosphere is only about 2% of Earth’s thickness (Earth’s radius = ~6400km). Most of the atmospheric mass is confined in the lowest 100 km above the sea level.
8	Vertical Structure of the Atmosphere
9	Vertical Structure of Composition
10	Ionosphere and AM Radio The D- and E-layers absorb AM radio, while the F-layer reflect radio waves. When night comes, the D-layer disappears and the E-layer weakens. Radio waves are able to reach the F-layer and get reflected further. The repeated refection of radio waves between Earth surface and the F-layer allows them to overcome the effect of Earth’s curvature.
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12	Origins of the Atmosphere When the Earth was formed 4.6 billion years ago, Earth’s atmosphere was probably mostly hydrogen (H) and helium (He) plus hydrogen compounds, such as methane (CH₄) and ammonia (NH₃). Those gases eventually escaped to the space. The release of gases from rock through volcanic eruption (so-called outgassing) was the principal source of atmospheric gases. The primeval atmosphere produced by the outgassing was mostly carbon dioxide (CO₂) with some Nitrogen (N₂) and water vapor (H₂O), and trace amounts of other gases.
13	What Happened to H₂O? The atmosphere can only small fraction of the mass of water vapor that has been injected into it during volcanic eruption, most of the water vapor was condensed into clouds and rains and gave rise to oceans. è The concentration of water vapor in the atmosphere was substantially reduced.
14	Saturation Vapor Pressure Saturation vapor pressure describes how much water vapor is needed to make the air saturated at any given temperature. Saturation vapor pressure depends primarily on the air temperature in the following way: è Saturation pressure increases exponentially with air temperature.
15	What happened to CO₂? Chemical weather is the primary process to remove CO2 from the atmosphere. In this process, CO2 dissolves in rainwater producing weak carbonic acid that reacts chemically with bedrock and produces carbonate compounds. This process reduced CO2 in the atmosphere and locked carbon in rocks and mineral.
16	Carbon Inventory
17	What Happened to N₂? Nitrogen (N2): (1) is inert chemically, (2) has molecular speeds too slow to escape to space, (3) is not very soluble in water. The amount of nitrogen being cycled out of the atmosphere was limited. Nitrogen became the most abundant gas in the atmosphere.
18	Where Did O₂ Come from? Photosynthesis was the primary process to increase the amount of oxygen in the atmosphere. Primitive forms of life in oceans began to produce oxygen through photosynthesis probably 2.5 billion years ago. With the concurrent decline of CO2, oxygen became the second most abundant atmospheric as after nitrogen.
19	Where Did Argon Come from? Radioactive decay in the planet’s bedrock added argon (Ar) to the evolving atmosphere. è Argon became the third abundant gas in the atmosphere.
20	Formation of Ozone (O₃) With oxygen emerging as a major component of the atmosphere, the concentration of ozone increased in the atmosphere through a photodissociation process.
21	Ozone (O₃)
22	Other Atmospheric Constituents Aerosols: small solid particles and liquid droplets in the air. They serve as condensation nuclei for cloud formation. Air Pollutant: a gas or aerosol produce by human activity whose concentration threatens living organisms or the environment.
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24	Air Pressure and Air Density Weight = mass x gravity Density = mass / volume Pressure = force / area = weight / area
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27	Units of Atmospheric Pressure Pascal (Pa): a SI (Systeme Internationale) unit for air pressure. 1 Pa = a force of 1 newton acting on a surface of one square meter 1 hectopascal (hPa) = 1 millibar (mb) [hecto = one hundred =100] Bar: a more popular unit for air pressure. 1 bar = a force of 100,000 newtons acting on a surface of one square meter = 100,000 Pa = 1000 hPa = 1000 mb One atmospheric pressure = standard value of atmospheric pressure at lea level = 1013.25 mb = 1013.25 hPa.
28	Units of Air Temperature
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30	Variations in Tropopause Height
31	Dry Adiabatic Lapse Rate
32	Moist Adiabatic Lapse Rate
33	Stratosphere
34	Ozone (O₃)
35	Ozone Distribution The greatest production of ozone occurs in the tropics, where the solar UV flux is the highest. However, the general circulation in the stratosphere transport ozone-rich air from the tropical upper stratosphere to mid-to-high latitudes. Ozone column depths are highest during springtime at mid-to-high latitudes. Ozone column depths are the lowest over the equator.
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