EARTH SYSTEM SCI
EARTH SYSTEM SCI ESM 203
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This 10 page Class Notes was uploaded by Weston Batz on Thursday October 22, 2015. The Class Notes belongs to ESM 203 at University of California Santa Barbara taught by Staff in Fall. Since its upload, it has received 21 views. For similar materials see /class/226966/esm-203-university-of-california-santa-barbara in Environmental Science and Resource Management at University of California Santa Barbara.
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Date Created: 10/22/15
Infiltration theory of runoff We have seen that the in ltration capacity of the soil surface is the critical variable that partitions water from rain or snowmelt into subsurface or overland ow What is in ltration and what surface characteristics affect it Imagine an initially dry soil water is held only in the finest pore spaces and therefore the capillary suction holding it there is strong see lecture notes from ESM 203 As the soil becomes wetter larger pores become filled and the suction is less When many raindrops enter a soil they increase the moisture content ofa layer near and the 39 ure action of gravity creating a more or less distinct wening front which becomes less distinct as the antecedent moisture content ofthe soil increases Why does in ltration capacity ol a soil decrease through time during a storm Rainfall at intensity 1 l Surface l2 Wem mg fro t Infiltration f in the absence ofmacropores and on the widely occurring uniform at surface involves vertical percolation in units ofvolume per tim area and me aw therefore depth pert We can equate fwith Qa in Darcy s L 1 where H is the hydraulic head that we covered in ESM 203 In this general case hydraulic conductivity K depends on the moisture content 9 up to a maximum 9 which is saturation ie Kmax the saturated hydraulic conductivity familiar to you from ground water hydrology as K or Ksat Since head consists of the sum of the two components of potential energy that due to elevation z the effect of gravity and that due to pressure p which you will remember from the soil physics lecture in ESM 203 depends on soil moisture content 0 the drier the soil the greater is the suction or negative pressure H z 2 pg fKe I Ke 1agf lt3 fKFfE Thus there are two forces driving water into the soil gravity the first term and capillary suction Approximating apaz with the pressure gradient between the surface and the soil immediately beneath the wetting front makes km mml 02 AZ 5 If the two pressures remain constant but AZ increases monotonically as the wetting penetrates deeper as more water infiltrates then f is going to decrease through time and converge on the value K Remember that pdryso is negative and patmos is zero by definition 10022007 ESM 203 EarthSun energy balance Temperature measure of energy storage gt sens ble heat energy OUt doing work i e motivating energy in some change In a system 0 Energy and heat are equivalent Energy in energy 0 requires nergy latent heat Aenergystorage Igt melt A energy storage E either A temperature A phaseH of water solid liquid gas condense lt gives up energy less Lam 39 lt Y alreng 74 Wmquot 65 all imriist radiate wermsr imriist more I I370Wm72 intemctions depend on wavelength o Conduction moleculeto molecule T Some fraction 2030 is re ected by atmosphere and surface s hot to cold temperature s i Remainder7080 is absurbed and emitted at longerwavelengths cnnmr nn mixing in a 0 d I day water enhances transfer typical soil sensible tempemture difference emPem Jl es between warmer and colder uid a latent change of phase ofwater Ewes heat durin mixin Vapor g g gig ESM 203 Earth Sun energy balance Temperature steady Ener converts water Osteam WHKH leaves me pot Latent neat Temperature rising energy stored in water Sensible sot Water tempemture C Time gt Input of energy heating 10022007 Wavelength i c gt traviolet gamma rays 1039 10 quot2 10 quot 1 10 Y 1039 1 04 gquot Xrays rays infrared rays For radiation in the climate we usually use um micrometer 0 m or nm nanometer IO m to measure wavelenan shortwave radar m TV AM Ana sMu InLA An 0 If the atoms are receiving or generating a lot of energy ie they are hot they emit photons in large numbers and frequently Thus both the intensity energy per unit time and the frequency of emission are hig 0 Since energy travels through a vacuum at a constant speed h is Planck39s constant ESM 203 EarthSun energy balance 1 102 10 I Wavelength meters Visible Light a e httpwwwyorkucalexelspectrumgif 7 2hcZ hc L1 5 Where x 1 ex e1 MT Peak radiation or hotter objetcis higher and at horter wavelength E c speed oflight 30 x ioE msquot ii Planck39s constant 663 x IO 3 Js k Boltzmann39s constant 38 x IO 23JKquot Hotter object radiates more ac all avelengths wvelumlh 10022007 Sun 5mm Radiance Wm zam sr emissivity ratio of radiation rrom the material to that from an ideal blackbody39 at same empemture 0909 for most natural materials but 00 005 for aluminum foil for example Energy from the Sun T 5800 K 64 X 07W n39r2 m4 1 0 Energy from Earth T 288 K 390Wm 2 See Dingmm Fig 3 amp3 Bu 3 Wavelength urn W Let E Energy generated at Sun o R Sun s radius 77R2 Watts 0 P radius of Brth s orbit That same amount of energy spreads out over the surface of a sphere at a distance of Earth s radius 477P7 So energy at Earth is Z 2 Sn E W E 47RquotZ P mZ ESM 203 Earth Sun energy balance 10022007 EV can be converted to heat speci c heat of water is 4 85 jdegkg a calorie is 4 85 J Latent heat correct term is enthapy of fusion meltfreeze is 335000 Jkg vaporization is 25 millionjkg 0 Rate of energy exchange is called powerAWatt W is a Joule per second 6 A person uses about 2500 kilocaloriesday IO millionjoulesday 20Watts m lrfnldllnu ind lullnu an IM Hm Inn quotMMMIHTJIAII39MIOZIM lawnm Solar Radiation an Eanh Haa39i Radiation 1mm Eath n 7 emission 24 25 20 15 O 5 0 9 5 Waveiength 1pm 1 0 1 5 2 O Wavelength um absorption scattering NASA Goddard Institute for Space Studies httgWwwgissnasagov ESM 203 Earth Sun energy balance 10022007 less I I l I l I l370Wm 1sg l l i Total solar radiation 50 m2 Total surface area over which the rotating earth spreads the radiation 39 Average intensity of solar radiation 504 342 Wm z This value averages zones where the radiation falls from nearly overhead diam 0quot 3 Fla PerPendin l to 5quot my I m high and m Wide Sox X l Radiation on I m wide plane tilted at angle 909 to sun39s rays i tropics to grazing angles towards poles L ms Radiation on tilted plane so eos 9 5 th sun39s height above the horizon latitude and season 9 lnmnsity ol solar radiation varies wi Arltlc Grub Height of sun above horizon at noon 908 6 ugh 31quot r enmne Latitude at which sun is directly overhead van es seaso Hy DuxburyA c amp DuxburyA a law An lmaduman m theWa d39s knoll ESM 203 Earth Sun energy balance An A atmosphere Ml m39ldayquot 10022007 5 solar mdiation a planetary average a bedo F infmred mdlation T planetary surface temperature wnole planet ie net allwave radiation 0 e liar F gaT4 4 T soT 43 17 00 5039 i E R4 090095 17 567Xl0 c3 0 5 I370W m 2 normal to Sun a Divide by 4 to average over Earth 3425 Wm 2 o Abedo m 027033 see Charlson o ThusT m 255 K 8 C Visible 04 07 Mn scattered by air molecules dust soot salt clouds Scattering by air greater for shorter wavelengths blue Nearinfrared 0 730 m from Sun scattered less but absorbed by water vapor especially at L4 and 9 um and by clouds Middle infrared 35 m from Sun and Earth and thermal infrared gt5 Mn from Earth absorbed by clouds water vapor carbon dioxide methane ozone and other greenhouse gases Some windows 3540um and 0525um when no clouds ESM 203 Earth Sun energy balance qvnrqun rnmnnrqtllrn chnlllrl hp qhnllt I8 C Near the surface average air temperature is measured to be about l6 C The discrepancy must be due to the role of the atmosphere in absorbing energy and storing it near the surface 10022007 In 1000 39l lt 0lum absorbed by N2O2 N O m in in gt 0 5 54 A lt 02m absorbed by 02 gt upper 03 absorbs A lt 03l um gt and l 8 um lower A gt 03lum warms surface which surface mdiates and warms atmosphere 25 27 Layered atmosphere most infmred absorption in lower es in atmos heric layer temperature ifvarious controlling a some solar absorption in quotwe gnarl balancehfor factors were to c nge atmosphere an 5 atmOSP ere eg solar radiationalbedov or the o Sens ble and latent heat from absorbing capacity oi the atmosphere surface up into atmosphere caused by changes in concentrations 0 working Pm Latent heat estimated lrom giobai o p ecipitation W e concerned about such changes because we have come to recognize that 0 Also includes energy released o man activities although negligi e 0 This is a steady state model v no time element r in contrast with a transient model Graedel T E and N Cruucn i 99SAzmoxphere cimze and change 25 23 ESM 203 Earth Sun energy balance 7 10022007 sawW Upper layer Tu Surface 72 F 5quot mm mm m spac x mm mm mm spun 39 a ummplm Minnow nmm my by 14 Np cm 0 Abmmlwn MIN by Hm GmedelT E and M Cruuen i 99Azmmphere Climate and Change 3i Top boundary T xyz Surface lower boundary Layers eg atmosphere er nd mass uxes into and out of each must balance Temperature affects some of the uxes so T can adjust to make them alance 0 Fluxes are Radiative Convective vertical and advective horizontal gt Bot sensible and latent Conductive not important in atmosphere mm nmuy m me To 0 mmnhm quot 539quot quotquot RWave mdiation relatively large asymmetric ecules although natural Addvimmhlnnwhan are augmented by pollutant mum CH o 4 gase mam an lfwe change these 0Ho vyC concentrations expect more Radiumnu hum mtgquot F any 1 mm x A m 1 Wavnlnngth pm GmedelT E and M Cruuen i 99Azmmphere Climate and Change 32 ESM 203 Earth Sun energy balance