Phys geog lec 2 - chaps 3 - 4
• Chap 3 - Atmosphere
•Intro
•Air a mixture of gases
•nitrogen
•oxygen
•Atmos not uniform density
•concentrated at surface, thins out to space 2% by 16 miles up Fig 3-2
•Instrumental in providing environment for life
•I
Composition of Atmosphere
A. Gases in atmosphere
•N = 78% of air
•O = 21%
•Ar = 1%
•other gases important too - Table 3-1
•some helpful
•H2O - water vapor (yes, it is a gas)
•CO2 - carbon dioxide (absorbs infrared radiation; “greenhouse
gas”)
•O3 - ozone (absorbs harmful UV radiation; important “protector” of
humans) Fig 3-4
•some harmful:
•CO - carbon monoxide
•SO2 - sulfur dioxide
•NO2 - nitrogen dioxide
B. Particles in Atmosphere
•Mostly H2O (water & ice)
•Some dust
•collectively known as “particulates”
•natural and anthropogenic (human) sources
•2 major effects on weather/climate
•hygroscopic (water absorbing), very important to cloud formation)
•absorb and/or reflect sunlight (decrease amt energy reaching
earth)
II. Vertical Atmospheric Structure
A. Temperature profile Fig 3-6
•layers of air with different temp profiles, not just a simple decrease of T
with incr height
•exosphere
•thermosphere
•mesosphere
•stratosphere
•troposphere
•note the patterns of incr or decr Temp with height in the layers
•2 major warm spots, in troposphere at base and stratosphere at
top
•tropo base warm because earth surface heats it
•strato top is warm because UV energy is absorbed by
ozone here
most of book will focus upon troposphere & effect on weather
B. Pressure profile
•press defined - weight of column of air 1” x 1” square and variable height
•units = lbs / sq in (pounds per square inch)
•since air is compressible, it becomes more dense and heavier
close to surface (sea level vs Mt Everest-where do climbers need
air packs?)
•Fig 3.8
•this profile smooth, not like temperature Fig 3-9
•initial press decline rapidly away from surf of earth, then rate of change
slows
•stats:
•50% of atmospheric mass (the gas molecules) is below _____?
•90% is below_____ ? Look them up!!!
C. Composition of atmosphere
2 major divisions Fig 3-10:
1. Heterosphere (above 50 miles -heterogeneously layered)
2. Homosphere (below 50 miles - homogeneously mixed)
•in the heterosphere, the layers form according to density - N at bottom, then O,
then He, then H
•brief mention of ozonosphere (9-30 miles up)
•and ionosphere (40-250 miles up)
•look at all the atmosphere profiles at once fig 3-13
D. Human-Induced change
•mostly summarized as “introducing impurities into the atmosphere, at a pace
previously unknown”
E. Weather and Climate
•weather is short term
•moisture
•temp
•wind
•pressure
•etc
condition of variety of variables (“elements”):
•climate is the “long-term aggregate” (average) of weather conditions
•so to describe climate you need a historical database about the weather
• Controls that cause variations in wthr/climate:
•latitude (more sun near the equator)
•land vs water setting
•atmos circulation (refer to Earth Sci notes for explanation)
•ocean circulation Fig 3-16
•elevation above sea level
•topography (mountains as barriers)
•storms
Chap 4 - Insolation and Temperature
A. signif impact on the “landscape”
•organisms (incl humans)
•patterns of evolution
•soil development, weathering
B. Solar energy - the source
•supports all life
•energizes atmosphere
•stat: sun produces more energy in a single second than ALL energy used
by mankind TOTAL to date!
•Energy gets to earth by energy transfer process known as radiation (vs
conduction or convection)
•energy type is known as EM or electromagnetic Fig 4-4
•3 portions we are interested in are next to each other:
•UV (ultraviolet)
•Visible (ROY G BIV)
• IR (Infrared)
•note that terrestrial energy re-radiated from earth is all IR
(important in terms of global warming)
•most incoming solar radiation is short wave, potentially harmful
C. Basic processes in heating and cooling
•radiation fig 4-6, 4-7
- the hotter the object, the shorter the wavelength of
energy
•absorption
•reflection fig 4-8
•in gen, good radiators are good absorbers, good reflectors are poor
absorbers
•scattering - change direction but not wavelength fig 4-10
•transmission - wave passes through the medium
•important point - sometimes, transmission through a medium is
wavelength dependent; eg, shortwave radiation goes through auto
windshield or a green house, but re-radiated, longer waves can’t escape
back out through the glass Fig 4-11
•this of course is the “greenhouse effect”, and is the essence of global
warming
•conduction - molecule to molecule Fig 4-13
•convection - heat transfer via a moving substance (air, water, etc)
•known as advection if the mvmt is mostly horizontal Fig 4-14
•convection very common method of heat transfer in atmosphere
•adiabatic cooling/warming fig 4-15 air cools as it rises
•latent heat - evaporating water takes in heat, condensation releases it
D. Heating the Atmosphere
•get to the specifics Fig 4-17
•we think there is in general a global heat balance (global warming is slight
relative to the total system)
E. spatial and seasonal variation
•the variations in the generalized sequence
shown are responsible for weather
and climate variations
•main cause for weather and climate is that unequal heating is present on earth
•unequal heating due to diffs in latitude and diffs in seasons
•diffs in latitude cause diffs in angle of incidence fig 4-18 excellent
•diffs in length of day
•diffs in path length traveled through atmos fig 4-20
•land and water contrasts important too
•big diffs in temp over ocean vs land (ocean less extreme) fig 4-25
•several reasons behind the diffs
•specific heat or heat capacity very high for water
•depth of radiation penetration deep in water
•dispersion in water
•evaporation of water
F. Temperature as a Measure of Heat
•definitions:
•heat is energy
•temp is a measure of that energy, but temp is not energy
G. Mechanisms of heat transfer
•several:
•atmos circ - 75-80% of all heat transfer from tropics to poles
•Earth Science lec notes/Figs in Chap 5 will expand the
discussion
•oceanic circ - the rest
•how heat transferred? Warm water nr equator moves
toward poles, cool water nr poles moves toward equator Fig
4-27
•oceanic gyres are huge circulation cells, view them as 4sided boxes, each side an ocean current
•example - Atlantic gyre - Equatorial current, Gulf Stream, N.
Atlantic current, Canary current
•a signif link between atmos currents and oceanic currents
H. Vertical Temp Patterns
•lapse rate - what you typically expect in the troposphere Fig 4-29a
•inversion - warm air over cool air (big problem in Denver)
I. Global Temp patterns
•controls include:
•altitude (the higher the cooler)
•latitude (the higher the cooler)
•land vs water (water less extreme)
•ocean currents (what current is carrying warm or cold water)
•seasonal shift of isotherms, much greater range over land than over water Fig
4-34
•by far biggest temp extremes in interiors of continents Fig 4-35