Download doc midterm 1 review notes 2009

Atmosphere:
 Composition:
 Global energy system:
 Air temperature:
 Winds:
 Atmospheric Moisture:
 Precipitation:
 Weather systems:
Drainage Basin:
 Precipitation:
 Interception: Biomass that intercepts
 Evapotranspiration:
 Infiltration:
 Runoff:
 Water stores:
Effects of changes in land use:
 Urbanization:
 Deforestation:
o Transmission: passage of radiation through transparent atmosphere
o Atmospheric scattering: redirection of radiation through reflection/refraction off
particles in atmosphere
o Atmospheric absorption: particles in atmosp absorb radiation and heat up.
o Atmospheric constituents that trap IR radiation: carbon dioxide, methane, nitrous
oxide, ozone, CFC’s, water vapour. <-33ºC diff between theoretical radiating
temp and real, so heat being trapped in atmosphere for greenhouse effect.
o Albedo: shortwave rad being reflected back into atmosphere.
o Incoming solar rad goes to heating atmosphere, heating earth (directly and
diffusely), reflected off atmosphere, refle off clouds, reflected off earth’s dif
surfaces (earth’s avg albedo is 31%).
o More light will be absorbed around equator where sun hits earth directly.
o Outgoing radiation (69%)by ozone layer, latent heat (evap), convective transfer,
surface radiation, direct heat loss to space. Sensible (heating of nearby bodies,
conduction) heat loss.
o High clouds heat up earth’s surface, and low clouds cool surface.
o Max insolation at earth’s surface over desert areas b/c of cloud cover. Max daily
net radiation at top of atmosphere is over equatorial oceans.
o Net Radiation Q* = Kin – Kout + Lin – Lout. Q* splits into Qe (latent) + Qh
(sensible) + Qg (ground). Splitting affected by ability of surface to
absorb/emit/reflect/transmit/refract/conduct/convect and availability of moisture.
o Dark wet soils have low albedo, high conductivity, high heat capacity. Snow is
high albedo, low heat conductivity.
o Global patterns in Q*: highest in equatorial oceans. Patterns in LE: greater over
equatorial oceans and affected by currents (gulf stream). Patterns in H: occurs
over equatorial land, affected by ocean circ patterns (el nino).
o Atmospheric T lapse rate: 6.4 ºC/km. so higher altitude’s have lower mean T and
greater variability.
o Clouds are most variable factor affecting earth’s radiation budget. Cloudy areas
have generally less variable Ts.
o Maritime Effect: more constant T annually and daily because water moderates
temp.
o Continental Effect: more variability in temperatures.
o Controls for water: evaporation, transparency, specific heat, movement/currents,
sea-surface temperatures. Light hitting water is heating ~60m deep.
o Thermal equator: line of all highest mean temps. Bends down in January and up
in july.
o Low pressure creates strong winds, high pressure creates light winds. So high to
low creates big gusts.
o Coriolis effect: earth spins so linear things become parabolic centered roughly at
equator. ITCZ is meeting of these two differently rotating air masses (cloudy).
Bends down in jan, up in jul.
o Low press @ equat goes up and toward poles, stopping at subtropical jet stream.
o Earth spins right. From bird’s eye of north pole, counter clockwise. So circulation
of atmosphere is opposite.
o Equatorial low pressure trough: moist hot air rising and expanding and cooling.
Produces condensation, heavy rainfall.
o Subtropical high pressure: 20-35 º latitude. Hot/dry high pressure zone of
descending air. Cloudless.
o Subpolar low pressure: dominant in winter, disappear in summer. Contrast btwn
cold air from poles and warm air from tropics forms polar front.
o Weak polar H pressure cells: frigid dry deserts without much energy (weak).
o Thermohaline circulation: important transfer of heat from equator to poles,
bringing warm water from surface at equator to high latitudes where it becomes
dense with salt and sinks. Moves water btwn oceans.
o El nino: switching of winds/currents from west to east in equatorial pacific btwn
south America and Australia. Precipitation over south America and dry over new
guinea. El nino events coincide with faster rises in global temp. *Read about El
Nino
o La nina: opposite of el nino, when more cold water from east goes west towards
guinea so excess rain falls on guinea.
o Relative humidity: actual H2O content/max as %.
o Adiabatic processes: T changes that occur from pressure changes in atmosphere
as air parcels rise or fall that result in a change in temp from changing sizes.
Affects environmental lapse rate. MAR < DAR because moisture regulates temp
better.
o Convergent lifting: air hit low P and lifts upwards.
o Convectional lifting: maritime air hits continent and lifts from land heat.
o Orographic lifting: physical features such as mountains.
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Frontal lifting(?): warm and cold air meet and warm air is pushed up.
most rain falls on equator or on coasts or near mountains.
Air Mass Classes and Koppen Climate Classes: see lecture 6.
Warm surface temperatures are conducive to hurricanes. *Read about
hurricanes
Measurement of stream runoff by finding area of cross section and measuring
flow. Drainage basin: P = ET + R + dS. P is precip, ET is evapotrans, R is runoff.
Interception of precip comes from vegetation that absorbs water into capillaries.
Reduces intensity and amount. Throughfall goes directly to ground. Stemflow
comes down stems of plants. Porous soils can percolate more water more quickly.
Soil Moisture: gravitational water, field capacity, capillary water, hygroscopic
water. Wilting point: only hygroscopic water left.
AET = PET – D when soil moisture < field capacity. Factors on PET are
humidity, radiation, mean T, wind speed.
Lysimeter: measure soil moisture * read about lysimeter
Soil water deficit: in summer. Precip doesn’t match demand.
Water table: dividing saturated and unsaturated ground soils
Active spring: natural emergence of ground water at ground surface. Effluent
conditions when ground water feeds stream. Influent conditions when spring
feeds ground water.
Aquifer: any geologic strata that allows for movement of groundwater.
Aquitard/Aquiclude: strata that inhibits movement of groundwater.
When water is drained from aquifers we remove support: land subsidence,
cracked house foundations, changes in drainage.
Runoff: Streams: perennial or intermittent. Originates from surplus surface-water
runoff, subsurface throughflow, groundwater. Highest runoff, globally, is near
equator. Lowest runoff at subtropical deserts.
Measurement of runoff using weirs or readings and then stilling well with staff
gauge.
Flood frequency analysis: Tr = n/m where Tr is recurrence interval, n is # years of
record and m is number of floods of given magnitude or larger.
If rainfall intensity > infiltration capacity then Horton overland flow. Infiltration
capacity controlled by soil texture, soil composition, vegetation, and antecedent
moisture condition.
Effects of deforestation: reduced interception, less transpiration, leads to greater
runoff, changes in flowpath. Generally area will experience warming, increased
albedo, and less precipitation. Increased runoff can be corrected as new vegetation
grows in, possibly even go into negative increase from species changes.
Urban Climate: dust dome, disrupted air flow through buildings, air circulation
and turbulence. Photochemical smog when NO2 reacts with VOC and UV to
make Ozone and bad shit. More clouds, more rain, less snow, less radiation, more
contaminants, higher temp (urban heat island), less humidity, less wind speed,
sewers and impervious land lead to increase floods and decreased low flow runoff
<-creates urban rivers.
Urban heat island differences greatest after sunset because city is still releasing
heat. Affected by pop size. Strategies to combat UHI: increase biomass, increase
surface albedo, reduce heat loss from vehicles and buildings, install air
conditioning, increase access to healthcare.