Transcript Intro to Atmosphere

Intro to the Atmosphere
• The layers of gas that surround the other
spheres of influence on our planet
• Interacts frequently with
-
Hydrosphere- Clouds,Humidity,Rain
Lithosphere- Weathering,Wind Erosion,Dust Particles
Exosphere- Blocks incoming Solar Radiation
Biosphere- Us!, plants, animals
How do we know about the atmosphere?
• Measuring instruments
- Thermometer- temperature
- Barometer- pressure
- Geiger Counter- radioactivity
- Chromatograph- chemical composition
• Space missions
- satellites
- aircraft
• Theory
- physics and chemistry
Origins of Earth’s atmosphere
• Early on- volcanic activity is
responsible for atmospheric gases
- rich in CO2 (carbon dioxide)
- very different from today’s atmosphere
• simple plants and bacteria as planktonic life
forms (phytoplankton) changed the
atmospheric composition over 2 billion years
- increased the oxygen content in oceans then air
• Solar radiation also contributed
- created other atoms by irradiating
existing components- ozone layer
Composition (modern)
N 2 (nitrogen) = 78 %
O 2 (oxygen ) = 21 %
Ar (argon) = 0.93 %
an inert gas
CO 2 (Carbon Dioxide) = 0.035%
a greenhouse gas
Aerosols and Water
• dust and moisture particles small
enough to stay up in the atmosphere
The structure of
the atmosphere
• divided based on
• the temperature
Ionosphere
Composition is
unchanging here
Clouds
form
here
Ozone Layer O3
Aurora Borealis
& Australis
Ionosphere &
magnetosphere
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AURORA BOREALIS
movies
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are needed to see this picture.
Factors associated with the atmosphere
• Heat
- different from temperature (avg. kinetic energy)
- usually measured as the temperature of the air
- F, C, K scales
- a function of the kinetic energy (molecular motion).
• Moisture
- Measured as relative humidity
- a function of temperature and availability
- expressed as a percentage
• Pressure
- Measured in millibars, pascals, or inches
Heat transfer
One of the big things the atmosphere does!
Conduction
• contact between air and ground
Convection
• mixing due to temp related density changes
Radiation- also known as radiative or
electromagnetic energy
• absorbed and emitted by all objects
Conduction
Heat transfer (2)
• contact between hot & cool
- transfers E from hot to cool
• solids > liquids > gases
- atmosphere poor at
conduction
Convection (& Advection)
• "mixing" of hot & cold
- Usually in currents
- Con- is vertical; Ad- is horizontal or lateral
Radiation
• Sun is the source of most radiation
- visible light = intermediate-wave radiation
- infrared (heat)= Longwave radiation
- X-rays, gamma rays, etc= very shortwave
• Earth also gives
off some radiation
• Living things also
give off radiation
• Angle of approach
and reflective
properties are
critical factors
Air Pressure
The "weight" of the air pressing
down on the Earth's surface
A simple barometer
• measured by a Barometer
- inches (or mm) of mercury
rising up in a tube
• adjusted according to height
above avg. sea level
- less air pressing down from above at higher
altitudes
• also takes into account motion of air
- sinking vs rising
Atmospheric Density
120 km
• air is "thinner"
aloft- less atoms
of it
• Pressure is
lower aloft
• Important for
heat and pressure
transfer
0 km
Surface isobar map with fronts
Moisture- the other main thing
• dependent on temperature
- warmer = hold more water vapor
- colder = holds less water vapor
• results from
- evaporation of liquid water
- cools surface and adds heat to air
- sublimation
- direct transformation from solid water
(ice) to vapor
• Acts as a trap for longwave radiation (heat)
• Transports heat
• Acts to transport water
Interaction of Radiation,Pressure,Moisture at macro, or
global, scale
Weather patterns are dictated by
moisture, pressure and temperature
differences in various air masses
• A hurricane
(shown at
right) is an
extreme low
pressure
system that
draws energy
from warm
water
Interaction of Radiation,Pressure,Moisture at meso scale
Sea Breeze- Interaction of Radiation,Pressure,Moisture at
micro scale
animation