Transcript The Earth and Its Atmosphere

Chapter 1
9/2/2009
1
There is no upper limit of the atmosphere, but it rather becomes thinner and
thinner, merging with empty space.
-laughing gas
greenhouse effect = warming that results when solar radiation is trapped by
the atmosphere; caused by atmospheric gases that allow sunshine to pass
through but absorb heat that is radiated back from the warmed surface of the earth.
Water is the only substance that can be found naturally in the atmosphere in its
3 phases (solid->ice, liquid->water, gas->water vapor)
9/2/2009
2
Carbon
Dioxide
cycle
9/2/2009
3
Fig. 1-4, p. 7
Vertical Structure of the Atmosphere

Air Pressure and Air Density
 Weight (force acting on an object due to gravity) =
mass x gravitational acceleration = m x g
 Density = mass/volume (air density at sea level ~ 1.2 kg/m3 )
 Pressure = force/area
 At the Earth’s surface the pressure of the atmosphere is
14.7 lbs/in2 .
 Standard sea level pressure is:
1013.25mb=1013.25hPa=29.92 in.Hg.
 Atmospheric pressure decreases with an increase in
height.
9/2/2009
4
9/2/2009
5
~ 9km
9/2/2009
6
Vertical Structure of the Atmosphere

-
Layers of the Atmosphere
Pressure & Density decrease with height
Air temperature has a complicated vertical profile
 Lapse rate = the rate of change (decrease) in temperature with a change
in height; the average lapse rate in Troposphere = - 6.5 C / 1 km.
 Inversion layer = change in the sign of the lapse rate, + 6.5 C / 1 km.
 Isothermal environment = no change in temperature with height
9/2/2009
7
Layers of the
atmosphere
as related to
average
profile of air
temperature.
9/2/2009
Fig. 1-11, p. 13
Vertical Structure of the Atmosphere

Observation: Radiosonde
 Weather balloon
 Instrument and transmitter
 Air temperature, humidity, pressure
9/2/2009
9
Vertical Structure of the Atmosphere

The Ionosphere
 Not a true layer but an electrified region within the upper
atmosphere (from about 60 km to the top of the atmosphere) where
fairly large concentrations of ions and free electrons exist.
 Ions = molecule with an additional or minus an electron
 Sun light creates layers: F (at 180 km) ,E (at 120 km),D (at 60 km)
layers
 Ionosphere plays a major role in AM radio communications
9/2/2009
10
At night, the F region of ionosphere strongly reflects AM radio waves, allowing
them to be sent over great distances. During the day, the lower D region
strongly absorbs and weakens AM radio waves, preventing them from being
picked up by distant receivers.
9/2/2009
11
(more solar
eruptions)
Based on composition
of the atmosphere
9/2/2009
12
Weather and Climate

Weather: short term changing in air
temperature, air pressure, humidity, clouds,
precipitation, visibility, and wind

Climate: long term patterns and average
weather; not just magnitude but also
frequency
Assignment 1
9/2/2009
13
Weather & Climate

Meteorology
 Study of the atmosphere and its phenomena
 Aristotle 340 B.C. – book on natural philosophy, Meterologica. – Greek
word = meteoros = “high in air” – sum of knowledge at that time
The birth of Meteorology as a natural science did not take place until the
invention of weather instruments: thermometer ( end of 16th century),
barometer (17th century), hygrometer (18th century).
 1843 telegraph invented
 1920s concepts of air masses and fronts
 1940s upper air balloons
 1950s radar and computers
 1960s satellite
9/2/2009
14
Doppler
radar has
the capacity
of estimating
rainfall
intensity.
9/2/2009
15
Weather & Climate

Satellite’s View
 Geostationary satellite: situated at about 36,000Km (22,300mi)
above the earth. Satellite travels at the same rate as the earth spins,
which allows it to remain positioned above the same spot.
 Meridians measure longitude (W-E): lines running
from north to south. Prime meridian (00meridian) runs
through Greenwich, England.
 Parallels to equator (00latitude) measure latitude (N-S)
 Weather maps: pressure cells, fronts, surface stations
9/2/2009
16
Satellite
Image:
clouds+
storms
at surface
9/2/2009
Fig. 1-15, p.1720
Simplified surface weather map that correlates with
the satellite image shown .
9/2/2009
18
Weather & Climate

Weather and Climate in Our Lives
 Two general reasons for studying how weather and climate impacts our

lives: economic efficiency and public safety.
 Crops
 Utilities
 Extreme cold and heat
 Tornados and hurricanes
 Clothing
Meteorologist
 Any person with a college degree in meteorology or atmospheric science;
not just the TV weather person
 Half of 9000 meteorologists employed by the US National Weather
Service
 Researchers and operational meteorologists
9/2/2009
19
Chapters 2 and 19
Energy, Temperature, & Heat
Energy is the ability to do work (push, pull, lift)
on some form of matter.
 Potential energy is the potential for work.
Gravitational potential energy:
PE  mgh


Kinetic energy is energy of a moving object
KE  1 mv2
2
Total energy = PE + KE
 Temperature is a measure of the average speed of

atoms and molecules.
 High temperature  corresponds to high average speeds
Cold, more
dense air
Warm, less
dense air
Energy, Temperature, & Heat

Which has more energy?
 A lake or a cup of hot tea?

Heat is the energy in the process of being
transferred from one object to another because of
a difference in temperature.

First Law of Thermodynamics: Energy cannot be
destroyed or created  conservation of energy
Temperature Scales

Fahrenheit (early 18th century): 32 freeze, 212 boil
 (180 equal divisions)

Celsius (later in the 18th century): 0 freeze, 100 boil
 (100 equal divisions)

Kelvin (19 century): absolute; 0K = -273°C (no thermal motion)
0
C5
0

F  32
9
0
K  0C  273