Unformatted text preview: Ch.1 The Earth and Its Atmosphere
1.1 Composition of Atmosphere 1.2 Vertical Structure of the Atmosphere 1.3 Weather and Climate The Big Picture About 14 billion years ago, the Big Bang created the Universe. Universe consists of billions of galaxies. Each galaxy contains billions of stars. The sun is one such star located in the Milky Way galaxy. Our earth is the 3th planet evolving around the sun The Milky Way The Solar System Nine/Eight Planets
Earth is the 3rd planet 150 millions miles away from sun My Very Educated Mother Just Send Us Nine Pizzas Defining the Atmosphere What is sky? What is atmosphere? What is air? The atmosphere is a thin, gaseous envelope It shields us from harmful ultraviolet rays from the sun It is where all weather is created. Defining the Atmosphere cont'd Composition of the Atmosphere
Atmos is composed of 99% permanent gases and 1% variable (trace) gases. Permanent gases are those with constant concentration with time &space. Variable gases are those with varying concentration depending upon where/when you are. All weather and climate are associated the 1% variable gases. Atmos Composition Breakdown by volume Permanent: nitrogen-78% (78.08%) oxygen-21% (20.95%) Others - < 1% Variable: water vapor (H O) 0~4% 2 carbon dioxide (CO2) - 0.038%, Ozone (O3) 0.000004% others Variable Gas Water Vapor
More vapor in warmer locations, less in colder Only substance that exists in 3 phases near the surface (temperature) Phase changes (condensation) form clouds and drive weather Variable Gas Carbon Dioxide (CO2) CO2 increases 0.4% per year From 280 ppm* pre-industrial era to 385 ppm today *ppm= part per million = 1/1,000,000 Main Pathways of CO2 cycles Another Pathways? Variable Gas Ozone
Ozone high in the atmosphere is good blocks out harmful UV rays Ozone here is formed naturally Ozone low in the atmosphere is bad creates photochemical smog Ozone here is created by humans Variable Gas Ozone Hole Lowest ozone concentration or ozone hole 1.2. Vertical Structure of Atmosphere
Although atmosphere is thin compared to earth itself, it has vertical structure, revealed as different layers. Atmosphere has no definite top, rather thinning out gradually. Changes in atmospheric properties describe vertical structure. Vertical structure determines weather and climate. Air Density
Atmosphere is more dense closer to the surface, with density decreasing rapidly with height Density = the amount of matter (mass) in a given space (volume) mass wight density = = volume volume water: 1gram per cubic centimeter (1g/cm3) air: 1.2 kilogram per cubic meter (1gk/m3 ) Air Pressure Air pressure is measure of weight of atmos column over area It is defined as force divided by the area
gravity force weight pressure = area area Pres=1.47 lb/in2 or 1 bar ~1000 mbar, at surface Air Density
Pressure decreases with height exponentially Half of the atmos is below 5.5 km or 3.4 mi Air Pressure Vertical Profile of Temperature
Temperature profile is not monotonic due to surface heating and gas absorption of solar radiation Layers of the Atmosphere
All weather occurs here Strong turbulent mixing forced by surface heading Stratosphere
Very smooth due to increasing temp with height Most jet airplane fly here because of smoothness 1.3. Weather and Climate We live under weather and talk about weather and climate almost on a daily basis. What are they? Weather map for the general public Cyclone Anticyclone Simplified weather map for meteorologists What is Weather?
Weather is the current state of the atmosphere at a specific time and place. The current state of the atmosphere is described by: Temperature Pressure Humidity Precipitation Visibility Winds Weather always changes What is Climate?
Climate is "average weather" at a particular location. accumulation of daily and seasonal weather events over a long period (e.g., 30 years) Annual or seasonal mean temp, precipitation Climate change very very slow Weather Events Severe weather Summary Atmos is composed of 99% permanent gases (nitrogen-78%, oxygen-21%) and 1% variable gases
(water vapor, carbon dioxide, ozone, etc.). All weather and climate are associated the 1% variable gases that are also called greenhouse gases. The lowest two atmospheric layers are troposphere (0-11 km) and stratosphere (11-50 km). Turbulent tropos, in whcih temp decreases with height, is where all weather occurs while stratos, where temp increases with height, is stable and supports no weather. Weather changes everyday while climate that is long-term mean of weather only changes over decade on longer. ...
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This note was uploaded on 03/18/2012 for the course UNDERSTAND 212 taught by Professor Qi during the Spring '12 term at Saint Louis.
- Spring '12