GEOB 102 - Textbook Notes - Physical Geography

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Geographical Biogeosciences
GEOB 102
Carlos Gaitan

GEOB 102 CHAPTER 3 - ROTATING EARTH A) Earth’s Rotation: 1. earth - oblate ellipsoid (bulge @ equator, flat @ poles b/c centrifugal force) 2. counter-clockwise (north america → europe) 3. causes Coriolis effect - makes wind/ocean deflect to right in the north, left in the south B) Geographic Grid - spherical coordinate system w/ parallels and meridians 1. Parallels run parallel to equator, perpendicular to axis of rotation, east-west a. latitudes (specific parallel) i. angular distance north & south of equator; goes from 0-90 in each hemisphere ii. equator = only great parallel = 0 ° b. degrees work by imposing 3D cartesian system, x-axis = equator, y = north-pole/south-pole 2. Meridians runs perpendicular to parallel, north-south a. Greenwich = prime meridian (0 °) b. degrees work similarly to parallels, except one axis = Greenwich c. longitude meridians = angular distance east & west of prime meridian 3. minutes - 1/60th of a degree 4. seconds - 1/60th of minute; divisions are for precision 5. great circle - circle intersecting center of sphere; has same radius as sphere 6. small circle - non-great circle 7. Global Positioning System - locational info for about a 10x15m accuracy using 24 satellites C) Map Projections - methods of representing 3D sphere on 2D plane 1. polar projection - circular map centered on North/South pole 2. Mercator projection - rectangular map; meridian = straight vertical, parallel = straight horizontal; classical map 3. Goode projection - mathematical curves/sine curves & ellipses to represent earth D) Time Zones - global time; based on meridians to create Standard Time system. 1. 24 hour circle 2. on 360 circle, each time zone is 15 degrees 3. based on number hours each time zone differs from Greenwich (Greenwich Mean Time GMT) 4. west is NEGATIVE; east is POSITIVE 5. Coordinated Universal Time (UTC) - accounts for differences in the year 6. Daylight Savings Time (DST) - set clocks ahead in spring, set back in fall; DST in western civilizations; except China, Australia, Japan, India and tropicals E) Rotation: 1. orbital motion of earth around sun = revolution; elliptical but almost spherical 2. 1 revolution = 365.242 days; OR 365 + ~6 hours 3. UTC accounts for the decimals and corrects it. *** IMPORTANT 4. seasons caused by tilt towards the sun a. summer (North Hemi.) = North hemi tilted towards the sun 5. perihelion - earth nearest to sun (Jan 3) 6. aphelion - farthest from sun (July 4) 7. Tilting of Earth’s axis: a. plane of the ecliptic i. plane which Earth travels when going around sun ii. 66.5 ° iii. AKA, 25 ° from vertical 8. Solstice - 25 ° away from sun @ December solstice, opposite in Summer/June solstice 9. Equinox a. equi = equals; midpoint between solstices; axial tilt neither towards nor away 10. - subsolar point - point on surface where the sun @ noon is directly overhead falls 11. - during equinox, subsolar point = on the equator 12. - sun’s declination = latitude of subsolar point 13. - circle of illumination - circular boundary separating earth into light and dark halves 14. - during solstices, goes from Arctic Circle (parallel @ 66.5°N) to Antarctic Circle; subsolar points are at 25 ° GEOB 102 - CHAPTER 4 - THE GLOBAL ENERGY SYSTEM A) Net energy balance 1. incoming = outgoing a. during day → has positive net radiation (warming surface b/c K↓ > L↑) b. during night → negative net radiation (cooling surface b/c L↑ > K↓) 2. maintained by radiation, absorption, scattering, albedo & poleward heat transfer B) Radiation 1. Stephan Boltzmann: M = δT^4 (M = energy flowW/m^2; δ = 5.67e-8W/m^2K^2; T=tempK 2. Wien’s Law: λ=b/T (λ = max wavelength of radiation (micron); b = 2898micron; T= tempK 3. Electromagnetic radiation → primary form of radiation a. characterized by wavelength (λ) and frequency; transverse b. visible light → 400nm - 700nm c. shortwave radiation - solar; UV d. temp of radiation ∝ 1/wavelength i. sun - short wave (UV, visible) ii. earth - longwave (infrared) 4. Insolation - incoming solar radiation a. ∝ angle of Sun ray striking Earth b. greatest @ subsolar point (sun overhead) ∴ greatest @ noon when sun @ zenith above horizon i. imagine light as limited quanta ii. smallest area light falls on = greatest concentration of quanta (which would be directly overhead) iii. larger areas are result of lower angles (think shadows) c. insolation patterns over course of year i. non-tropics: max/min @ solstice; average @ equinox ii. tropix: max @ equinox, min @ solstices d. ∝ duration of exposure (more → greater) 5. counterradiation a. radiation absorbed by atmosphere released in all directions b. is directing back towards earth (opposite to longwave) B) Absorption by Atmosphere 1. present: 78% N 2, 21% O 2, 0-4% H O 2. oxygen & ozone absorb UV rays shorter than 0.3micron → warms the atmosphere 3. 1.3 micron 1.9 micron b/c CO2 & H2O absorption 4. long wave radiation - thermal infrared radiation emitted by earth a. 6-8, 14-17, >21 micron absorbed by atmosphere 5. Ozone: a. measured w/ Dobson Units b. 300 - 3mm of ozone in given area c. found in stratosphere d. can be destroyed/trapped/dissociated by chemicals; esp CFC e. O2 + UV → O + O; O + O2 → O3 f. toxic to humans C) Scattering 1. turning aside of radiation by particle so direction is changed a. selective/Raleigh - scattering caused by particles < wavelength; blue = 10x more b. Mie/nonselective - b/c large particles scatter all wavelengths indescriminately 2. diffuse radiation → scattered radiation moving in all directions 3. diffuse reflection → scattering such that radiation goes back to where it came from D) Reflection 1. reflective surfaces (ie. white/light/shiny) reflect radiation back 2. calculated w/ albedo → % of light reflected back a. range from 0.0 (blackbody) - 1.0 (perfect mirror) b. high albedo = snow, ice, some concrete (>0.85) c. low albedo = pavement E)Poleward Heat Transfer: ASSORTED RANDOM THINGS: 1. @ north pole, sun traces small circles around horizon to 23.5° above horizon 2. development of atmosphere a. primordial atmosphere: He, H NH3, CH4 b. volcanoes added CO2, N2, SO2, H2O c. O2 added via photo-dissociation of H2O b/c of UV; more b/c photosynthesis GEOB 102 - CHAPTER 5 - AIR TEMPERATURE & AIR TEMPERATURE CYCLES 0) Definitions 1. air temperature - temp of air observed @1.2m off ground 2. types of movement of air a. conduction = flow of sensible heat from warm substance to cold substance w/ direct contact b. latent heat transfer - water evaporating @ surface, removal of heat stored in change of state from liquid to vapor c. convection - heat distributed in fluid by mixing 3. Surface Energy Balance Equation: R shor+ R lon+ H LATEN+ H sensib+ H so→ outgoing = positive a. During Day: Short (-), everything else is (+) b. During Night: Short = 0, Long (+), everything else (-) A) Atmosphere Components 1. Layers: a. troposphere i. decrease in temp w/ decrease in height ii. contains a lot of water vapor → lots of clouds & precipitation iii. contains aerosols - minute particles b. stratosphere i. increase in temp w/ inc. height ii. contains ozone → absorbs UV rays & shields life c. mesosphere i. temp falls w/ elevation d. thermosphere i. increase in temp w/ inc. height e. first 100km of atmos (tropo, strato, meso, lower thermo) → homosphere → mixture of air molecules i. >100km → layer’d by molecular weight & charge → heterosphere B) Latitude 1. daily insolation patterns → heat up atmosphere → heats up ground 2. temperature peak @ midafternoon not @ peak insolation b/c convection 3. summer → higher curves; winter → lower curves 4. surface temperatures = most @ extreme a. conduction moderates soil temp b. convection moderates air temp 5. equatorial variation → very little 6. pole variation → great range C) Surface Type 1. rural a. transpiration - water taken up by plant roots & moved to leaves → cools leaf surfaces & surrounding air b. moist soils → evaporation 2. urban a. darker & more absorbant (pavement absorb 2x as plants) b. vertical surfaces c. concrete, stone, asphalt holds heat better than soil → nighttime warm temp d. human impact → air conditioning in summer e. urban heat island i. elevated temperatures in urban environment compared to surrounding rural ii. desert = exception, b/c evapotranspiration w/in city > in desert D) Location 1. maritime a. minimizes temperature range b. processes global changes slowly; max/min @ Aug & Feb instead of Jul/Jan (max/min insolation) 2. continental 3. causes of differences a. penetration of radiation (into depth of water vs soil) b. specific heat capacity of water 3x> than land c. convection currents mixing water d. evaporation E) Elevation 1. lapse rate = decrease in temp in increasing latitude (° C/1000m) 2. environmental temperature lapse rate - actual measured lapse rate a. avg ELR = 6.4K/1000m 3. temperature inversion a. temp increase w/ altitude; thus colder air sits ontop of warm air (like cwc sammich) i. eg: killing frosts when temp fall below 0° C ii. found along west coast of continent iii. found at polar regions → buildup over long nights iv. suppress vertical mixing → holds pollution 4. higher elevation → less air a. less scattering/reflection/absorption by air particles b. more extreme temperature ranges; low temps @ night F) Global Warming 1. greenhouse gasses: NO 2, CO2, CH4 2. human activity greatly increase the g.g.s & of aerosols (reflect solar radiation) a. by clearing away forested lands; burning fossil fuels GEOB 102 CHAPTER 6 - ATMOSPHERIC MOISTURE & PRECIPITATION A) OVERVIEW air rise -> expansion & cool b/c lower pressure moist air -> clouds! B) HYDROLOGIC CYCLE 1. hydrologic cycle - movement of water 2. evaporation -> condensation (rain) / sublimation (ice crystals) -> precipitation (rain/snow/hail) 3. hydrosphere - all water on earth, 97% = ocean water; 2.15% in ice sheets, 0.63% in ground water 4. storage of water - most (glaciers, groundwater, lakes/river, water vapour/stuff) least. 5. global water balance a. total = 0 b. positive balance for land → more precipitation than evaporation (110k - 70k = 40k km 3) c. negative balance for ocean → more evaporation (380k - 420k = -40k km^3) d. remaining 40k end up back in ocean in runoff 6. precipitation mostly in equator C) Humidity 1. %water in air = humidity 2. Daltons Law of Partial Pressure: pressure of mixture of gasses = sum of pressures of constituents 3. Quantity of water increases as temp increases (rest taken up by ice) 4. saturation vapor pressure (SVP) = max amount of water vapour held by atmos. 5. specific humidity (g water/kg air) - actual quantity of water vapour in air parcel (g/kg) a. measure of amount of water available for precipitation b. greatest @ equator & lowest @ poles 6. saturation specific humidity - max specific humidity @ specific temp 7. dewpoint temperature - temp @ which water saturated air will start forming dew 8. frost point temp - when dewpoint is below freezing 9. relative humidity - amount of water vapour present / total amount possible 10. wet&dry bulb thermometer, sling psychrometer, hair hygrograph E) Adiabatic Processes → turns water vapor into precipitation 1. gas expansion = cooling 2. gas compression = warming 3. heating/cooling due to pressure = adiabatic process 4. precipitation forms only when lots of air falls far below dewpoint 5. abundant -> air be above troposphere (thus cooled by adiabatic processes) 6. dry adiabatic lapse rate (DALR) - rate of temp change as func. of height for unsaturated air (10deg/1km) 7. altitude for which air = saturated = lifting condensation level 8. saturated adiabatic lapse rate (SALR) - 4 - 9 deg/1km 9. above lifting condensation level, condensation happens & releases heat 10. adiabatic cooling > latent heat release by condensation A) Clouds 1. made from water drops/ice crystals, 20 - 50 mm in size 2. form around cloud condensation nucleus (CCN); 0.1-1mm 3. in clouds, water is a supercooled liquid 4. freezing occurs (earlier) when there’s ice nuclei to start making ice 5. types: a. stratiform - layered clouds; massive area; low lying b. cumuliforms - big air parcels; huge vertical height, poofy, globular, c. mid-level = alto-something d. highest- cirro-something or cirrus e. bottom = strato/nimbo- C) FOG TYPES 1. layer of stratus @/close to surface 2. smog = polluted fog 3. radiation fog - formed @ night when air = below dewpoint 4. valley fog - formed b/c lowlying air is cool & chills moist air above 5. precipitation fog - rain falls into cold air & evaporates; happens @ warm fronts 6. steam fog - warm water evaps. & condenses 7. advection fog - warm moist air moves over cold 8. sea fog - warm air cooled by cool water currents D) PRECIPITATION 1. collision-wake capture - when water drops get too big, they fall through cloud a. - big drops can also collide w/ other particles & drag it down 2. Bergeron (Bergeron-Findeisen) process - snow/ice originates from this process a. w/o freezing nuclei; ice needles form when cloud is < -35deg. b. w/ these crystals, supercooled water will aggragate to nuclei c. b/c of collision-wake capture, will get bigger 3. if cloud warmer than air layer below; grains of ice/sleet get formed 4. frozen ground layer & lowest air layer frozen -> ice storms 5. hail = 5-50mm (approx) 6. virga - streaks of rain/snow fall, but evaporate before reaching ground 7. drifting snow - wind <35km/h; restricted to below 2m 8. blowing snow - 35km/h < wind < 39km/h; >2m height; visibility < 10km 9. blizzard - > 40km/h wind, <1km visibility, < -10deg E) PRECIPITATION MEASUREMENT rain -> rain gauge F) PRECIPITATION PROCESSES 1. orographic precipitation a. wind move moist air over mountain -> forces higher -> cooled @ dry adiabatic rate -> forms cold clouds -> precipitation -> moves leeward down mountain (over the peak) -> gets warmer (takes up heat) -> water evaporates -> dry & warm b. Chinooks - warm winds caused by this process 2. convergent precipitation a. convergence between two air masses (warm meets cold air front) 3. Convectional Proceses a. rising air cools; then rains b. caused by “localized pockets of air rising b/c warm less dense than cool” c. still warmer than air around even when rising d. @ dewpoint, makes cumulous clouds 4. rain shape: MOAR ATMOSPHERE and shit. A) Atmospheric Stability stable air parcel - denser than surrounding unstable - less dense than surrounding ETLR - Environmental temperature lapse rate; is the temp. of surrounding air 4. DALR/SALR - temp of rising air 5. absolute stability result of rising air surrounded by warm air; ALWAYS exists in temperature inversion 6. absolute instability -> result from warm rising air => convection process 7. neutral stability; ETLR = DALR; thus air parcel changes @ same rate as surrounding air does 8. conditional instability - ETLR is between DALR and SALR B) THUNDERSTORMS convective (????) storms caused by cumulonimbus clouds w/ strong updrafts latent heat keeps storms going; drives air parcels higher supercell - most dangerous -> single cell thunderstorm 20k-50k across lasting 3-4hrs - has ROTATING UPDRAFT core - large enough = mesocyclone 4. microbursts - sudden sharp downdrafts ****!! AS A RESULT OF LATENT HEAT THERE IS PRECIPITATION, thus latent heat moves from ocean -> land; but convection currents goes back to ocean GEOB 102 - CHAPTER 7 - WINDS AND GLOBAL CIRCULATION SYSTEM A) Pressure 1. unit of pressure: pascal (Pa) = 1N/m^2; measured usually in kPa 2. 103kPa = sea level pressure = 1 atm = 1013 millibar (mb) 3. measured w/ barometer, recording barograph, sensors 4. Air = compressible; mass & density & pressure decreases w/ altitude 5. Thus: PV = nRT 6. constant pressure surfaces (WHAT IS THIS??!?!?!) 7. pressure gradient caused by heating & density a. pressure decreases less rapidly in warm air than cold B) Wind Overview 1. wind = horizontal motion of air currents; vertical = up/downburst 2. characterized by direction & velocity; given as direction FROM which wind blows a. e.g. westerly wind goes from west to east 3. causes: a. difference in atmospheric pressure b. ∴ pressure gradient force moves air from high pressure→ low pressure c. Coriolis effect (earth’s rotation; essentially atmosphere & surface not connected) i. deflect winds clockwise in north ii. counterclockwise in south iii. strongest @ poles; weakest at equator 4. cyclone = low pressure center @ bottom; high @ top a. cloudy/rainy weather b. b/c high pressure centers are moving towards low pressure c. counterclockwise inspiral in NORTH, clockwise in SOUTH d. goes from lower atmos → higher 5. anticyclone - high pressure center a. fair weather b. CLOCKWISE in NORTH c. COUNTERCLOCKWISE in SOUTH d. goes higher → lower e. linked w/ cyclone by convection loop by inflow/outflow C) Global Surface Wind Patterns 1. equat
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