JAPCA 38: 163-170 (1988) .~eprinted from APCA Journal, Vol. 38, No.2, February 1988

M. Segal, C.-H. Yu and R. A. PielkeDepartment of Atmospheric ScienceColorado State UniversityFort Collins, Colorado

A numerical mesoscale model was used to simulate meteorological fields in the Lake Powell

area during the summer, providing an input to a Lagrangian-type transport/dispersion model

evaluation. The main objective of the study was to use these modeling tools in order to

evaluate the local effect of thermally-induced circulations on large-scale transport of polluted

air masses into that area. Results indicated a substantial modification of the transport

characteristics due to the local terrain-forced circulations. Most noticeable are: (i) trapping

of pollutants within the Lake Powell valley, (ii) upward and downward venting of pollutants in

convergence/divergence zones associated with these circulations, and (iii) slowing of cross-

valley transport as compared to equivalent situations involved with flat terrain.

study is designed specifically to providean evaluation of modifications to long-range transport by mesoscale effects inthat area during the summer using themodeling tools outlined in the next sec-tion. Generally, the impact of mesoscalethermally-induced circulations on long-range transport of a polluted air mass isunaddressed in the literature. Therefore,although the present study provides aspec;:ific evaluation for the Lake Powellarea, it also provides some insight as tothe related impact of valley circulationsin the general case.

Observations in the Lake Powell areahave indicated that a significant visi-bility impairment often exists in thisarea located in southern Utah andnorthern Arizona (a schematic illustra-tion of the area is provided in Figure 1).Since several National Park areas with-in this region are mandated by federallegislaton as Class I areas under thePrevention of Significant Deteriora-tion (PSD) of the federal air qualityprogram, considerable research efforthas been devoted in recent years to un-derstand the atmospheric processes af-fecting visibility in that area. Studiesevaluating the potential contributionof local sources in the area to the visi-bility impairment is reported, for ex-ample, in Bluemental et at.,l and Yuand Pielke.2 Most of the focus in recentyears, however, has been directed tovisibility oriented studies includingevaluations of the impact of long-rangetransport of polluted air masses intothe area during the summer. Duringthe summer, a shallow thermal lowdominates the lower atmosphere of thesouthwest United States (e.g., Tangand Rieter3). Studies reported, for ex-ample, by Pitchford,4 Macias,5 Fluci-hini et at.,6 Ashbaugh et at.7 suggestthat southwest synoptic flow associat-ed with that meteorological systemmay lead to the long-range transport ofpolluted air masses from southern Cali-fornia and southern Arizona into the

Modeling Aspects

A numerical mesoscale meteorologi-cal model was applied in a two-dimen-sional domain along a northwest-southeast cross section in the LakePowell area (crossing through Page,Arizona; see Figure 1 for an illustrationof the cross section location) as adopt-ed in Yu and Pielke.2 In this region, theterrain acquires a general two-dimen-sional symmetry (i.e., uniform terrainalong the lake direction), thereby justi-fying using a two-dimensional modelversion for the preliminary study re-ported in this paper. The model com-puted meteorological fields are used asinput for a Lagrangian particlesscheme to predict their transport/dis-persion.

Numerical Mesoscale Meteorological

Modeling

The formulation of the numericalmesoscale model used in the presentstudy is given in detail in Pielke,9Mahrer and Pielke,10 and McNider andPielke,l1 and also is summarized inPielke.12 The model was validated suc-cessfully in studies of mountain/valleythermally-induced flows similar to thesituation considered in the presentstudy (e.g., Segal et al.,13 McNider andPielke,14 Abbs,15 among others).

C"pyright 1985-APCA

Lake Powell area. Also, these studiessuggested situations involved withsoutheast synoptic flow advecting pol-luted air into the Lake Powell areafrom New Mexico and Texas. This sec-ond common transport situation is as-sociated with flow around the west sideof a subtropical ridge which is situatedto the east of the thermal heat low.

All of the transport studies in thisregion, however, have been bas~d onobserved synoptic wind data. The tem-poral and spatial resolution of suchdata is typically insufficient to evalu-ate the impact of mesoscale generatedcirculations (i.e., mountain/valleyflows with typical horizontal scales ofless than several hundred kilometers)on the large-scale transport. Therefore,in those studies, the transport modifi-cation of a pollutant mass by mesoscalecirculations were not considered. Alsoin those studies, turbulence processeswere not considered. Hence, whilethese synoptic transport evaluationsprovide bulk information concerningair movement over mesoscale domains,additional evaluations are requiredwhen thermally-induced circulationsexist along the path of the pollution(see, for example, Pielke et at.,8 for adetailed evaluation and discussion ofthis aspect).

The Lake Powell area, which is locatedin the Colorado River basin, is affectedby valley-induced circulations. Our

February 1988 Volume 38, No.2 163

initial height was 600 m and its hori-zontal extent 15 }l:m. The volume wasdifferentiated graphically into threelayers indicated by a (bottom layer); fJ(the medium layer); and 'Y (the upperlayer) as illustrated in Figure 4a.Transport simulations for this situa-tion are listed in Table II (Cases 1-4).They consist of a release of the volumeat various hours of the day with andwithout turbulent effects. This cross-valley simulation provides an illustra-tion for situations involved with pollut-ant air transport to the Lake Powellarea from New Mexico and Texas.

The second situation reflects asouthwest synoptic flow of 2.5 ms-l(i.e., along the valley direction). Parti-cles were released in this case from themiddle of the valley as illustrated inFigure 9a. The particles volume had aninitial horizontal extent of 30 km anddepth of 600 m. The simulated trans-port cases for this situation are list~d asCases 5-7 in Table II. These cases pro-vide an illustration for situations in-volved with pollutant air transport intothe Lake Powell area from the direc-tion of southern California.

The pollutant mass as representedby the particles was assumed in bothsimulations to be initially horizontallyuniform in order to represent long-range transport into the region withoutmesoscale or turbulent dispersion up-stream. This was done so that the influ-ence of the mesoscale and turbulentflows in the Lake Powell area could bebest visualized. In reality in both simu-lated cases, it is expected that interven-ing complex terrain between the sourceand the Lake Powell area would sub-stantially influence the dispersion andtransport in a similar manner as occurswithin the Lake Powell area itself.

The terrain cross section used for thesimulations, which consists of elevationvariations larger than 1000 m, is illus-trated in Figure 2. The meteorologicalconditions simulated reflect July con-ditions in that area. Table I providesthe general information related to themeteorological model simulations. Twobackground flow situations were simu-lated: 1) southeast synoptic flow of 2.5ms-l (i.e., crossing the valley perpen-dicularly) as a background flow; and 2)southwest synoptic flow of 2.5 ms-l(i.e., along-valley direction).

Simulation Results

meteorological model and U'i are turbu-lence velocity fluctuations parameter-ized statistically based on the meteoro-logical model boundary layer predic-tions.

The turbulence velocities are provid-ed by the relation:

u,;(t) = u,;(t -fJt)R(fJt) + u" i

i = 1,2,3 (2)

where R(fJt) is the Lagrangian autocor-relation function at time lag fJt and U"iis a random component with a Gauss-ian distribution of zero mean and vari-ance defined by the local turbulencevariance. A validation of the scheme isreported in McNider6 and McNider etaV8

A set of transport simulations as out-lined in Table II were carried out. Inthe cross-valley (i.e., southeast) synop-tic flow situations, a volume of pollut-ant, represented by particles, was lo-cated initially at the southeasternboundary of the simulated domain. Its

Cross-Valley Synoptic Flow-Meteorological Fields

Representative meteorological fieldsin the simulated cross section for the

Table I. Input parameters for the meteorological model.

Transport/Dispersion Modeling

Using the wind and turbulence fieldscomputed by the meteorological mod-el, a Lagrangian approach is applied toevaluate the transport and dispersionof pollutants. This dispersion andtransport considers both the synopticand mesoscale (i.e., valley circulation)flows. The detailed formulation is giv-en in McNider16 and described also inPielke et al.,17 and McNider et al,18;thu8, it is outlined in this paper onlybriefly. The model consists of trackinga release of a large number of particlesrepresenting a pollutant air mass ad-vected and diffused, in the general caseof a three-dimensional domain, usingthe formulation:

Xj(t + bt) = Xj(t) + [Uj(t) + ui(t)] bt

i = 1,2,3 (1)

where Xj(t) is the oldx,y, andz positionof a particle and Xj(t + bt) is its positionfollowing time interval bt (in thepresent study bt = 20 sec); Uj are the u,v, and w velocities computed by the

Simulated domain top-9600 mLowest terrain height within the simulated domain~ 1300 m ASLDomain horizontal extent-150 kmModel horizontal grid interval-5 kmIntegration time step-60 secModel vertical number of levels-28Simulation start hour-2100 LSTSolar declination for the simulated day-July 10Initial boundary layer depth-250 mInitial potential temperature lapse rate ao/az:

a) 0 K/1000 m for z :5 250 mb) 2 K/1000 m for 250 < z :5 2450 mc) 4 K/1000 m for 2450 < z :5 9600 m

Latitude-37°

JAPCA164

S91.G 'ON '9£ awn lOA886~ AJenJqS;:j

eq~ ~UO{U JehU{ UO!SJeAU! pesuq-eJUjmS{OOJ h{eA!~U{eJ 'A\Onuqs U jO S~S!SUOJ('ijZ em~!.!I) prey 'ijm~uJedwe~ {u!~ue~odeq.1 .(Sen{UA h~!JO{eA {UJ!~JeA eA!~U~eU~JeueJ s'ijm~y p~ues'ijJd eq~ nu U! SUO!~-J'ijS pepuqs su neA\ su smo~uoJ peqsep~uq~ e~ou) JZ em~!.!1 U! UA\oqs su sedo{s

eq~ ~UO{U pe{epow S! se!~!JO{eA {UJ!~JeApJUA\UA\Op q~!A\ JehU{ A\Onuqs V 'UO!~-u{nJJ!J peJnpU!-hnUWJeq~ henUA eq~q~!A\ UO!~JUJ~U! puu ~J'ijjj'ij J!WUuhPu!uJJe~ o~ Gnp do~ henUA eq~ ~u h{~q~!{Sh{UO peqm~Jed S! A\OU J!~dOuhS eq.1.(UZ em~!.!I) I-SW {UJeAeSjO speeds q~!A\A\Onuqs eq O~ pe~UJ!pu! S! A\OU e~UU!UJp'po!Jed {uum~Jou eq~ jO PU'ij eq~ ~v

.uZ em~!.!1 U! p~UJ-!PU! SU 'I-SW 96 jO peeds PU!A\ U q~!A\

h{Je~sueq~nos S! A\OU J!qdoJ~soe~ eq.1'z em~!.!1 U! UeA!~ eJU (.18'1 001'1 ~U)ew!~up 'ijq~ puu (.18'1 0090) 'ijW!~~q~!U

'papnl:>U! S! a:>ualnqrn~ Sa~l1:>!pU! .L :papnf:>u! s! UO!~:>aAp11111:>!~JaA Sa~l1:>!pU! m:papnl:>u! s! UO!~:>aAp111~uOZ!Joq S~l1:>!PU! n 'sa!pn~S aSl1:> ~JOdSUl1J~ JO ~S!'I °11 alqu.L

-lOA eq.L .(W}{ gI) SIBAJe~U! P!J~ eeJq~jO~u~xe fB1UOZ!Joq 11 pUB W 009 jO q~depB q~!fr\ U!BWOP eq~jo (Bt eJn~!.!I ees) AJB-punoq UJ~Slle eq~ ~B AIIB!~!U! pe~B:>°1S! sel:>!~rnd eq~ jO ewnloA eq.L .0 eSB~)esBeleJ .LS'l 0060 B q~!fr\ peAloAU! eJn~

-Bej uo!sJeds!p eq~ sep!AoJd I:: eJn~!.!I.Ufr\oqs eJB 'peJou

-~! eJefr\ s~:>ejje e:>uelnqJn~ q:>!qfr\ U!eBB:> B ~u!pnl:>U! '~U!UeAe eq~ U! euo pUt?

sJnoq ~U!UJOW eq~ U! sesBeleJ eeJq.L.UO!~Bn~!S S!q~ JOj pep!AoJd eJB seJn~-Bej ~JOdSUBJ~ jO SUO!~BJ~snII! In°.!l

IJodsueJIIUelnIlOd-MOI:f A9I1eh-SSOJ:)

S! uo!~sIn:>J!:> henSA pe:>npU!-hnSWJeq~eq~ ueqA\ J,S'l OOtl JOj pe~ueseJd eJS

seJn~sej Is:>!~oIoJo~ew ew!~sp eqJ,.pe:>np

-eJ s! e:>ueInqJn~ eq~ eJeqA\ wo~~oq

henSA eq~ pJSA\O~ suedeep q:>!qA\ sedoIs

.S10{d eq~ U! pesnuo!~n{oseJ {B:>!~eA eq~ JO eSnB:>eq eJn~yeq~ U! ~Uep!Ae ~OU eJB eJn~:>nJ~s eJn~BJed

-m~ pUll PU!M pUnOJ~-JBeU eq~ JO S{!~

-ep eq~ ~Bq~ ~U!~OU q~JOM S! ~! 'hIIBU!~.Jnoq p~ueseJd eq~ JoJ m}{ gOZ-Z punoJBS! 'eJn~:>nJ~s eJn~BJedm~ eq~ hq p~B:>!P-U! S1I 'q~dep JehB{ AJBpunoq eq.L .JehB{

~Bq~ JOJ fB:>!dA~ S! q:>!qM UO!~B:>!J!~BJ~S{BmJeq~ {BJ~neU-JBeU eq~ q~!M pe~B!:>-OSSB S! SJnO~uo:> eq~ JO UO!~~Ue!JO pJBM-dn uy .(q~dep ~u!x!m) JehB{ AJBpunoq

eq~ JO q~dep em!~hBp eq~ e~B:>!pU!oz eJ~!~) SJn~uo:> ern~BJedm~ fB!~-u~od eq.L .pe:>unouoJd osfB S! SUO!~B{

-n:>J!:> edo{sdn eq~ q~!M peA{OAU! he{fBAeq~ JO e{PP!m eq~ JeAO J!B JO ~U!}{U!S

.(PZ eJ~!~) SeJn~BeJ h~!:>O{eA {B:>!~eAeq~ U! e{qBe:>!~OU S! edo{s UJ~SBeq~noseq~ ~UOfB SMOg pe:>JoJ-hIIBmJeq~ pUll:>!~dOuAS eq~ ueeM~eq ~u!{dno:> eq~ ~enp e:>Ue~JeAUO:> {~UOZ!Joq eq.L .(epn~

-!~{B ~Bq~ ~B MOg :>!~dOUhS ~sBeq~noseq~ pUB UO!~B{n:>J!:> UJn~eJ eq~ JO UO!~-!sodJedns B hq peSnB:> S! l-sm L pUnOJBJO peeds PU!M }{Bed B O~ ~JO{B UO!~

-B:>Y!SU~U! MOg eq~) SMOg edo{sdn {eAe{MO{ eq~ O~ esuodseJ U! peSnB:> SBM q:>!qM

qZ eJn~!~U! m}{ f: ~noqB ~B peJe~ue:> MOgUJn~eJ eq~ O~ enp edo{s UJ~SBeq~noseq~ JeAO ~JO{B MOg eq~ JO UO!~B:>!J!SUe~U!

eq~ S! p{ey MOg eq~ U! eJn~BeJ ~UB:>Y!U-~!S y .edo{s UJ~SBeq~nos eq~ ~UO{B MOg:>!~dOUhS ~U!SOddO UB q~!M SMOg edo{s-dn eq~ JO ~u!{dno:> eq~ SB IIeM SB edo{sUJ~SeM Jedee~s B ~ p~nq!J~~B S! q:>!qM

'(qZ eJn~!~) edo{s UJe~SeM eq~ ~UO{B

esoq~ UBq~ edo{s UJ~SBeq~nos eq~ ~UOfBeSU~U! SSe{ ~BqMemos eJB SMOg pe:>np

-U!-hIIBmJeq~ edo{Sdn .}{Bed S1! pUnOJB

3.01!~QO~§!".."".,::: I b u~ ~

1.8 I

1,4 I

3.0

I ~l5T 2.6 d

2.2

1.& I

1.4

1.0

0.60.2

"-..". ,. .' .' ~

:~.""""~""

"~ i":~' r'

Figure 3. Features of pollutant particles dispersion at several selected hours for a release at 0900 LST.Southeasterly synoptic flow; only advection is considered (Case 1).

for the incorporation of turbulence,and particles were released at 0500LST (Figure 4). By 1100 LST the parti-cles were advected somewhat downslope. The strong vertical mixing with-in the boundary layer is pronounced;however, the vertical velocity impactillustrated in Case 1 is still noticeablein the particle distributions. At 1700LST the particles become mixed withinthe deeper boundary layer along both

slopes; however, the southeastern por-tion is somewhat deeper as this regionis affected by upward venting withinthe convergence zone. The synopticflow over the shallow drainage flowduring the night causes the pollutantmass to reduce its depth and to be ad-vected gradually out of the domain asillustrated in Figure 4d.

Case 3 is the same as Case 2 exceptthe release of the particles was at 1100LST; thus, the impact of the daytimevalley circulation in this case would ap-pear immediately following the release.By 1400 (Figure 5a) the particles wereadvected somewhat in the downslopedirection. The mass is noticeably af-fected by the upward and downwardvelocities at the slope convergence lo-cation and the mid-valley divergencezone following the patterns illustratedin Figure 3. It is worth pointing out thatthe sinking motion above the valleycauses the particles aloft to be venteddownward, otherwise, particles maynot have been trapped within the valley.The dominance of the convergence/di-vergence effects leads by 1700 LST to adivision of the mass into two branches(Figure 5b). Similar nocturnal featuresshown in Case 2 are also obtained forthis case, while the mass is advectedgradually toward the northwest andout of the domain (Figure 5c,d).

Case 4 is the same as Cases 2 and 3;however, particles are released at 2100LST (Figure 6). By 0600 LST the pre-sented particle distribution had beenestablished mostly due to horizontal

3.83.4 b

3.02.6

2.2

, .8, .4 I

3.B

3.4 J

3.0

2.b

2.2

'j 1.BN

1.4

r~

1700 LST3.83.4 C

3.0

2.6

2.2

] 1.8N

1.4

1.0

0.6

3.8 0200

3.4,~QO~$~ 3.0

2.b

2.2

1.8

1.4

1.0

O.b

0.2

.-: ;::..':r'I .".:,: '

'.:,' ;"," ,, , ", \,.','

,', ',,"',..' ;' ,:; :,'::; , " ', '",' ,., , ,

~:: ,:',', ',;', ,,', "'- '"

.'~.~ .

,.. ." .., " '

;. :.~'

:'..:~~:;-f ':~

'. c -

...,

~:. .',ir ,,'.: .

,; ""

~ t ."

, ',',

,,'

.:

'.',. ".-;- ..~ : :!I

, "

'I,' '/..,

Figure 4. Features of pollutant particles dispersion at several selected hours for a release at 0500 LST.

Southeasterly synoptic flow; advection and turbulence are considered (Case 2).

ume is differentiated graphically intothree layers, enabling an evaluation ofthe mesoscale impact on each layerseparately. The particles are advectedby the u (cross-valley wind component)and w (wind vertical velocity) with theturbulent contributions ignored (i.e.,u' = w' = 0). The motivation for thissimulation is the evaluation of the im-portance of the advection processes ascompared to the turbulence processesin the studied cases. This objective canbe accomplished by a comparison ofthe dispersion features presented forCase 1 with those obtained in the casesin which turbulence is considered. By1200 LST the simulated pollutant massis vented upward intensely in the con-vergence zone. By 1500 LST upwardventing within the convergence zone isinvolved with the a layer particles,while the fJ and 'Y layer particles, whichhad been advected to the middle of thevalley are sinking in the downward ver-tical velocities there. By 1800 LST thea layer particles also become trappedin the sinking motion, with the fJ and 'Yparticles located at the low elevationsof the valley as a result of the down-ward venting. Affected by the finalstage of the daytime upslope circula-tion, the sinking particles were advect-ed westward, while the fJ and 'Y parti-cles were advected eastward and vent-ed up the western edge of theconvergence zone. As the nocturnal cir-culation is established following sun-set, the particles effected by the rever-sal in the valley flow and their interac-tion with the synoptic flow, resulttoward the end of the night in the parti-cle distribution shown for 0300 LST inFigure 3d.

Case 2 is equivalent to Case 1 except

JAPCA166

, .~.,';1, ,,

,"~. ,f" ~',f '

I,,"~\'", ~.~,i;;;'

L91.~ 'oN 'S£ ewnlO/\996 ~ AJenJqa::l

iv 9Se:) p9J9PiSUO:J 9Je 9:JU9InQJnj pUB UO!I:J9I\pe :N\011 :J!ldOUAS AIJ91See41nOS"lS1

OO~~ Ie 9Se919J e JOI SJn04 p91:J919S leJ91\9S Ie UOiSJ9ds!p S91:J!!Jed Iuelniiod 10 S9Jnje9,j "9 8An61,j

.:':""" ... ....: ;'.:"; ..c...

, .

..\ ~. L

8. L

Z'Z

P .q.Z"'.' tsloOTiloo£

t. ~N

S.I!~'Z

.~. :> ..q.Z"" l~.obzt'u'£

-!.lUW!.ld S! ~ueuodwo:> PU!M edoIs-sSO.l:>eq~ '.leAeMoq ~(~U!U.ln~ PU!M UUW){~ O~enp 'OeO!) .le.\uI .\.lupunoq eq~ U! pe.l.ln:>-:>0 ~ueuodwo:> .\eIIuA-ssO.l:> u o~ MOU :>!~-dou.\s eq~ Jo uo!~nq!.l~uo:> IIuWS V "UO!~-:>es S!q~ U! pe.lep!suo:> S! (MOU :>!~dou.\s

~seMq~nos 'OeO!) UO!~:>e.I!P .\elreA eq~~UOIg I-SW g"& JO PU!M :>!qdo.l~soe~ V

SP181:t le~I6010JO8.8W-MOI:t A.8I1eA-8uoIY

"AeI[BA et{1 U! peddBJ1 1I!1SeJeM seI:>!1J11d ff pUB v et{1 jO awos eI!t{M

'U!BWOP et{1 jO 1nO pe1:>eApB ueeq pBt{saI:>!1rnd J.. et{1 Jnot{ 1Bt{1 AH ".LS'I 001'6

1B UO!1nq!J1S!P 1UB1nlIod et{1 Aq 1Uep!AaS! sJnot{ 1xeu et{1 ~u!Jnp SSBW 1uB1nI

-Iod et{1 jO UO!1:>eApB 1UB:>!j!U~!S "Jnot{S!t{11B sedoIs t{10q WOJj SPU!M pa:>npu!-AIIBwJet{1 Aq pe1:>ejjB aJB AelIBA et{1U! peddBJ1 ~u!aq seI:>!1JBd ff pUB V et{.L

'AJBpunoq 1SeMt{1JOU et{1 pJBM01 'SSBW

pe1nlIod P91:>eApB et{1 jO 1UOJj et{1 1BeJB 'Ja1SBj pe1:>eApB eJeM SJnot{ Je!IJBe

et{1 ~U!Jnp t{:>!t{M 'seI:>!1JBd J.. et{1 'JeAe

-MOt{ ~SJeABI lIB S1:>ejjB ~U!x!W IB:>!1JeA.LS'I 00'61 AH "seI:>!1JBd JeABI J.. et{1 WOJjUO!1B!1uaJajj!p eIqBe:>!10u B U!B1U!BW1I!1S t{:>!t{M 'sJeABI ff pUB V et{1 81:>ej

-JU ApSOW ~U!x!W IB:>!1JaA (q9 eJn~!d).LS'I 0060 1V 'Jnot{ 1Bt{1 Aq UO!1BJn~!J-uo:> IB!1!U! J!et{1 aAJeSUO:> AIe~JBI sJeABIJ.. pUB ff et{1 eI!t{M 'peJJn:>:>o AelIBA at{1

jO W0110q et{1 1B e:>Ua~JeAUO:> MOU 01enp seI:>!1JBd V et{1 jO SpJBMdn ~U!1ue A

"<nBWS S! e:>ueInqJn1 IBUJm:>ou et{1Aq uo!snjj!p SB) 1JodsUBJ1 IB:>!1JeA pUB

t" ~N

tj"~!l'l

q"l

"" , , , , ,e I1Sl 0090 0"£

~ aq~Jo ~sow .LS'1 OOtl AH "UB~aq SMOUadoIsdn aq~ SB p~JaJJB AlqBaJ!~ou ~SowaJaM sJaABl f:f pUB ~ aq~ .LS'1 0080 ~V"asBalaJ .LS'1 0090 B q~!M pa~Blnw!s S! A~

-!JolaA IBJ!~JaA alq!~!I~au aJaqM 9 asH:)q~!M paAloAu! ~uawdolaAap aq~ 81uas-aJd 8 aJn~!d "B6 aJn~!d U! pa~BJ!pU!S! SSBW ~uB~nuod aq~ Jo UO!~BJOI IB!~!U!

aq~ 'MOU J!~dOuAS AaU~A-~uoIB aq~ uI"uo!~JaJ!p AaUBA-SSOJJ aq~ U! salJ!~JBd

aq~ Jo uo!~nq!J~s!P IB!~Bds aq~ U! UO!~B-J~lB U1I aSnBJ o~ pa~Jadxa aJB 'aJual-nqJn~ ~ UO!~!PPB U! 'SMOU [BwJaq~AaUBA-SSOJJ Jo ~uawdQlaAap aq~ AluO'aJoJaJaq.L "Alsno!AaJd ~no pa~u!od SBJOU!W S! ~OdSUBJ~ Aal[BA-ssOJJ uo ~JBd-W! 81! '(AaUBA aq~ ~uoIB '"a"!) AIJa~saM-q~nos S! MOU J!~dOuAS aq~ aJu!s "AaUBAaq~ ~U!JaAOJ awnlOA Ja~JBl B Jo uo!~odB ~JauaJ ~q~!W ~I "AaUBA aq~ Jo UO!~

-BAala JaMol aq~ U! pa~BJol AUB!~!U! S!salJ!~JBdJo awnlOA B UO!~Bn~!S S!q~ uI

.JodsueJl .ue.nIlOd-MOI~ 1.911el\-6uOIV

"q'} JO UO!'}B.I'}Snu! UB ~U!P!AO.Id) .LS'I

0090 '}B SPI"!J IB:>!~OI°.IO"'}"w "q.L

'MOU h"UBA-~uoIB :>!'}dOuhS"q'} hq hpq~!IS hIuO P".I"'}IB "q O'} P"-'}ud!:>!'}UB ".IB SPU!M h"UBA SSO.I:> p,,:>np

-U! hUBW.I"q'} "W!1hBP pUB "W!'}'}q~!U"q'} 'UO!'}BInW!S sno!,,".Id "q'} "J[!IUn 'h"I-IBA ~UOIB S! MOU :>!'}dOuhS "q'} "811:> S!q'}

U! ":>U!S +"suns pUnO.IB UB~"q UO!'}BIn

-W!S "q.L .S'}:>"JJ" IBW.I"q'} hq p,,:>npu! hI

if: 9Se::» p9J9P!SUO:J 9Je 9:JU9lnqJm pue UOII:J9J\pe :MOII :J!ldoufi.s fi.IJ9lSe94lnos

181 OO~ ~ Ie 9Se919J e JOI SJn04 P91:J919S reJ9J\9S Ie UO!SJ9dSIP S91:J!lJed Iuelnilod 10 S9Jme9:j 'S 8Jn61~

;:'~'~,.; I ~::~"'"",' ; ;:", ': ., .., i" '. ',' ,I,

" , ,:. "'. ,,':.. "

.,,~...

..f.. ~

:~~. ",,' .'", ','" ;',.,'

" "",~.t" ~

N

B" ~;co!

Z"Z

Q"Z

0"£

t"£

.."" " " " " " :>, ,ISlOO£Z 11"£

"ApmS 9SU:>

MOll :>!~dOUAS A911UA-SSOJ:> 9q~ JOJ p9-~JOd9J 9S0q~ O~ JUI!UI!S 9JU (JL 9Jn~!.!I)

9Jn~UJ9dUl9~ re!~U9~Od 9q~JO S:>!~S!J~:>U

-mq:> 9q.L "UO!~UIn:>J!:> 9IU:>SOS9U1 9q~ JOq:>UUJq re:>!~J9A 9q~ S~UJ~Snll! (P L 9Jn

-~!.!I) UJ9~~Ud A~!:>°I9A IU:>!~J9A 9q.L "(qL

9Jn~!.!I) UO!~nq!J~S!P PU!M ~u9uodUlO:>n 9q~ Aq ~U9P!A9 su s9dOIS q~oq ~UOIU

p9dOI9A9P puq UO!~UIn:>J!:> p9:>npU!-AIIUUlJ9q~ IU:>!SSUI:> U .LS'1 OOt1 AS

"(9L 9J~!.!I) SJn:>:>o osIuUO!SJ9AU!

9:>uJJnS IuuJn~:>ou MolluqsU '(uo!~uInUl!s A911UA-SSOJ:> 9q~ '"9"!)

Apn~s 9SU:> SnO!A9Jd 9q~ o~ JUI!UI!S ":>'u L

S9Jn~!.!I UlOJJ ~U9P!A9 9JU SJ9AUI Moll

9~UU!UJp MolluqS "L 9Jn~!.!1 U! p9~uJ~snI-I! 9m '(~q~!U ~U SPI9!J Iu:>!~OIOJ09~9U1

0

0

v' ~N

8.~!Z'Z

9.Z

0.£

,O£e

t~ObfJt.8'£

"j::, '~,' .~,',: ~i:':,'., .,.,) . ,~- . ..~ . ::r-' ' , :',

," ..., . .."T .' ".. .,..' \.', ' ""r.,..," .,. "v ,.. " .~t

,~~:~~t:::

'.:. i~''. "

~

trapping of the pollutant mass over thevalley 24 hours following the release(0500 LST second day).

For Case 7, where the release was at2100 LST, the particular redistributionfollowing 12 hours (0900 LST) is illus-trated in Figure lOa. By that time thedevelopment of boundary layer verticalmixing and upslope flows were notice-able in the redistribution of the parti-cles. Following an additional 12 hours(2100 LST), the vertically well mixedparticles over the valley were similar tothose obtained in Case 6 by that hour(Figure 9).

'\ '

:-mf'1./

0.1

0.2 ~ I

-0.:

1m:;

Summary and Conclusions

Two cases of the influence of meso-scale circulation on long range trans-port that are likely to be involved withthe Lake Powell area during the sum-mer were evaluated using a modelingtool. Pollutant mass was representedby particles which were differentiatedgraphically into three layers (lX, fJ, 'Y)enabling a more detailed evaluation asto the transport features in each layer.The simulations provide insight as tothe impact of valley thermal circula-tions and dynamic effects in that areaon long-range transport. The resultsalso illustrate expected influences onlong-range transport of thermally- anddynamically-forced mesoscale flows as-sociated with complex terrain in gener-al. Additional work, of course, is need-ed to quantify the influence of suchcharacteristics, such as the aspect ratioof the valley, synoptic flow intensityand atmospheric stability (or theFroude number) on the modification ofsynoptic long-range transport. Three-dimensional simulations of the LakePowell area, and other geographic re-gions which incorporate both meso-scale and synoptic influences, and tur-bulence effects are, of course, needed.Nonetheless, the two-dimensional sim-ulations presented here demonstratethe expected major importance of me-soscale and turbulence effects on long-range transport across complex terrain.

The main conclusions of the present

mosphere at the valley bottom, as wellas the advection of some of the particlesout of the domain, mostly from thewestern boundary where the upslopeflows were stronger. In the nocturnalperiod, relatively strong but shallowdrainage flow was capped by a deep butlight reversal flow aloft. This led to a

particles were advected toward theboundaries of the domain, but were de-celerating in the east, at the conver-gence zone. The a layer particles wereaffected by a less intense upslope andtheir advection toward the boundarieswas slower.

Figure 9 presents a time sequence forCase 6 of the alteration of mass (initiallyreleased at 0500 LST) including diffu-sion by turbulence processes whichshould cause alterations in the basicfeatures as obtained in the previouscase. Following 9 hours from the release(Figure 9b), the development of upslopeflows and a well mixed layer were evi-dent by the generation of two separateand well mixed pollutant volumes alongthe slopes. The a, (3 and 'Y layer particleswere vertically well mixed up to an ele-vation of about 2.5 km above the valleybottom. Additional impact of the day-time upslope on the particle distribu-tion was seen at 1700 LST. It consists ofthe generation of a relatively clear at-

3.1' .O8~O.LSJ 2. a

2.

I

(

,81

]N

.~'It .

[:-.."" .01

,..,

Figure 8. Features of pollutant particle dispersion at two selected hours for a release at 0500 LST.

Southwesterly synoptic flow; only advection is considered (Case 5).

168 JAPCA

.0 1400 LST,bl b' ., , , .""" ';,21

-

81

4~W"0

b

l2

691.c .ON 'S£ ewnlo/\996~ f.JenJqe~

iL 9Se:) P919P!SUO:J 91e 9:JU9lnqlnj pue UO!j:J9i\pe ~MOII :J!jdoul.s 1.I19jS9M4jnOS

IS1 OO~l je 9Se9191 e 101 sln04 P9j:J919S le19i\9S je UO!S19dS!p 91:J!jJed jUejnllod 10 S91nje9::! 'O~ 91n6!::!-Jaq~ E.anUA-SSOJ:> E.q pa~:>ajJB SUM~JOdSUUJ~ aq~ 'UO!~U~Ua!JO S~! ~UOIUE.anUA aq~ U!q~!M ~JOdSUUJ~ SSUW~uu~nnod q~!M paAIOAU! sasu:> aq~ UJ .

"(~JOdSUUJ~ PU!M E.IJa~suaq~nos'"a"!) sasu:> PU!M E.anUA-SSOJ:> SnO!JUA

aq~ JOj punOj uuq~ Ja~SUj S! SsaJ~-OJd jO a~UJ S!q.L "sJnoq 91 ~noqu

U!q~!M U!UWOP aJ!~ua aq~ passoJ:>aAuq PlnoM ssuw ~uu~nnod aq~'s~:>ajja alu:>sosaw ou pUll u!uJJa~~uU q~!M 'E.pn~s ~uasaJd aq~ U! su

wJ[ 091 jO ~u~xa [81UOZ!Joq jO U!UW-oF U pUlll-SW 9-Z jO MOU :>!~douE.sU q~!M "~lnsaJ ssuw jO Ja~ua:> J!aq~

jO uo!~uJala:>ap PUg uo!~uJala:>:>u'E.lsno!AaJd pau!l~no su 'E.l~uanbas

-uoO "U!UJJa~ ~uU ~uolu UO!~:>aApu jOasu:> aldw!s PUg uowwo:> aq~ WOJj

~! qs!n~u!~s!P Suo!~uln:>J!:> luwJaq~pa:>npu! aq~ ~ anp uo!~nnod aq~jO uo!~nl!p lU~UOZ!Joq PUg lu:>!~JaA .

" (sJaE.ul

pa~nnod p~uAala aq~ E.IJuln:>!~Jud)E.nun~uaAa E.alfBA aq~ jO ~no pa~Jod-SUUJ~ aJaM 'E.anuA aq~ U! padduJ~

q~noq~lu 'MOU :>!~douE.s E.anuA-SSOJ:>q~!M paAloAu! sasualaJ aw!~~q~!N .

"E.al-luA aq~ U! (q tZ~) po!Jad pa~ulnw!saq~ JOj padduJ~ aJaM sasualaJ aw!~

-E.up aq~ JOj (pU!M alu:>s-a~Jul E.al-lUA-SSOJ:> u '"a"!) MOU :>!~douE.s ~sua-q~nos E.up Jawwns E.q uaJu naMod

aJ[u'} aq~ O~U! pa~:>aApu ~uu~nnOd .

:aJU uaJu aq~ ~

~JodsUUJ~ a~uuJ-~UOl O~ ~uuAalaJ E.pn~s

zoo

9'0

0" ~

t" ~N

8'~[Z'Z

9"Z

0'£

e t'£, "", " ., " , ,L

ISlO060 8'£

.(1861) &fO~ :91 .uo.l]au:fI .SOW1V ,,'h~-!{1!nb J!U l1InS!h ~u!~:>eJJ8 SJ~:>uJ Jo S!S-hl1lUU l1Iuo!~eH" 'n!t{u:) .J, '!U!t{:>:>°I.!I.H'wIuW .:) .M. 'pJoJt{:>~!d .W 'PioJt{:>1!d.V .f.(VS61) 8&9 ;611 .aaH .la1{1vaM ,{11{1~OW,,'suJe~~ud UO!~uIi1:>J!:> IUUJn!p uos~:>eJJe nu~uId" 'J~!eH .H .~ '~uuJ,.W .&

.(sseJd U!) .UO.l]au:fI .SOW1V,,'ueJu neMod eJ[u'} U! SUO!~!PUO:> uosuesPI°:> :>!~dOUhS ~uu~~s Jepun h~!IunbJ!U el1l:>soseW" 'eJ[Ie!d .V .H 'n}.. .H-.:) .~

.(1861) 9961 :91 .UO.l-]au:fI .SOW1V ,,(V.L.LSIA ~:>eroJd s,Vd~Jo hJuwwns w!Je~u!) h~!I!q!S!h UJe~SeM-t{~nos uo se:>rnos Jet{~o pus ~uuId JeModpeJ!J-Iuo:> u Jo ~:>eJJ~" 'UrUMpJUt{g .S .d'UOSI!M. .~ .M. 'WoJ~s~Jeg .M. .H 'SU!:>uW.S .~ 'sPJUt{:>!H .M. "} '~uewenIg .'}.cr .1

S9:>U9J919H

-JnpOJ1UI .UO!1Bz!IBap! UB S! qJ!qM

'(UO!1JaJ!p hanBA aq1 ~uoIB U!BJJa1UIJO}!Un B '.a1) BaJB pa!pmS aq1 U!

U!BJJa1 aq1 }O hJ1aUIUIhS IBuo!suaUI-!P-OM1 }O UO!1dUInSSB aq1 JapUn1no pa!JJBJ aJaM SuO!1BInUI!s aqJ, .

.sJnoq tz 1SBaI1B JO} BaJB hanBA aq1 JaAO pa1S!S-Jad saIJ!1JBd aq1 'hnBJaUa~ 'JaAa-MOq ~U!BUIOP aq1 JaAO saIJ!1JBd aq1}O UO!1nup 1UBJ!}!U~!S B U! pa1Ins-aJ S!qJ, .JahBI paX!UI naM hnBJ!1JaAB 01 UO!1!PPB il! 'sadoIs aq1 ~uoIBsaqJUBJq OM1 °1U! SSBUI aq1 }O ~U!1-1!Ids B S! aJaq1 sJnoq 1q~!IhBP aq1

~u!Jnp 1Bt{1 MOqS s1InsaJ aqJ, .sJnoqaUI!~Bp eq1 ~u!Jnp aJuaInqJm aq1°1 UO!1!PPB U! 'SMOU paJnpu! hnBUI

°Jem!M UJpUUS Aq peIP-UBq AIqu BUM ~U!dA~ eq.L '1[JOM B!q~ JO

UO!~eIdwo;) eq~ ~U!mp epuw B~UeWWO;)eIqunIuA J!eq~ JOJ peJ(uuq~ eJU Je1[;)O~S

°H pUB UOBJepUeH °a 'WIUW oM' .!ISNeq~ Aq peJoBuodB B! HV:)N °Je~ndwoa1- A VH:) HV:)N eq~ uo pewJoJJedeJeM Buo!~uIn;)Iu;) Je~ndwo;) pUB '91

we~I '[,1 ~uewpuewv '1000HVH18VN~;)UJ~UO;) Jepun e;)!AJes }[JUd IUUO!~-uN eq~ Aq pe~oddnB BUM }[JOM B!q.L

Juaw6paIMOU)!:>'V'

19 9Se:) p9J9P!SUO:J 9Je 9:JU9lnqJnj pue UO!I:J9/1pe :MOIj :J!ldoul.s I.IJ91S9M41nos

"1$10090 Ie 9Se919J e JOj SJn04 p91:J919S leJ9/19S Ie UO!SJ9ds!p 91:J!lJed Iuelnilod jO S9Jnje9:J "6 9Jn61:J

Z'O

9'0

0' I

~' I

8' t

?'Z

9'Z

0.£" .,' ." P ~.£

"""'."'ls1oosoD'£

'\,

'WS!UB1{JaW~U!1UaA S!1{1 1nO1{1!A\ JnJJO PlnoA\

1{J!1{A\ 1B1{1 WOJJ UO!1nq!J1S!P alJ-j1md a1{1 U! suoj1BJa1lB 1UBJ!J!U~!S~U!SnBJ AIIBmuaAa '81uB1nllod Jo~Uj1UaA IBJj1JaA a1{1 uo sauoz aJua~

-JaA!P/aJUa~JaAUOJ 1{1!A\ paAloA-U! samJolaA IBJj1JaA Jo aJuB1Jod-W! a1{1 pa1BJ!pU! ApmS a1{1 'SaSBJpa1Blnw!s a1{~ uo pasuq 'AIIBU!.!I .

.Alqu!JaJddB pa~uu1{Jaq 10uPlno1{s ApmS S!1{1 U! SJj1S!J"1-JBJB1{J uo!sJads!p/1JodsuUJ1 a1{1 Josuo!snlJuoJ luJaua~ 'JaAaA\OH .uoj1-Blnw!s luuo!suaw!p-0A\1 e1{1 1{1!A\pau!l11qo SaJmBaJ a1{1 U! SUOj1J01S!PSnO!JUA 01 pual Plno1{s suoj1BJap!S-UOJ u!uJJa1 luuo!suaw!p-aaJ1{1 ~U!

Pielke, "Influence of diurnal and iner-tial boundary-layer oscillations on long-range dispersion," Atmos. Environ.(submitted 1987).

ing terrain," J. Atmos. Sci. 38: 2198(1981).

12. R A. Pielke, Mesoscale Meteorology Mod-eling, Academic Press, Orlando, FL, 1984.

13. M. Segal, Y. Mahrer, R. A. Pielke, "Ap-plication of a numerical mesoscale mod-el for the evaluation of seasonal persis-tent regiQnal climatological patterns,"J. Appl. Meteorol. 21: 1754 (1982).

14. R. T. McNider, R. A. Pielke, "Numeri-cal simulation of slope and mountainflows," J. Clim. Appl. Meteorol. 23:1441 (1984).

15. D. J. Abbs, "Sea breeze interactionalong concaye coastline in southernAustralia: Observation and numericalmodel study," Monthly Weather Rev.114: 831 (1986).

16. R. T. McNider, "Investigation of theImpact of Topographic Circulations onthe Transport and Dispersion of AirPollutants," Ph.D. dissertation, Univer-sity of Virginia, Charlottesville, VA,1981.

17. R. A. Pielke, R. T. McNider, M. Segal,Y. Mahrer; "The use of a mesoscale nu-merical model for evaluations of pollut-ants transport and diffusion in coastalregions and over irregular terrain,"Bull. Am. Meteorol. Soc. 64: 243 (1983).

18. R. T. McNider, M. D. Moran, R. A.

5. E. S. Macias, J. O. Zwicker, W. H.White, "Regional haze case studies inthe southwestern U.S.-II. Source con-tributions," Amos. Environ. 15: 1987(1981).

6. R. G. Flucihini, T. A. Cahill, M. L.Pitchford, R. A. Eldred, P. J. Feeney, L.L. Ashbaugh, "Characterization of par-ticles irithe arid west," Atmos. Enviro.15: 2017 (1981).

7. L. L. Ashbaugh, W. C. MaIm, W. Z. Sa-deh, " A residence time probability anal-

ysis of sulfur concentrations at GrandCanyon National Park," Atmos. Envi-ron. 19: 1263 (1984).

8. R. A. Pielke, M. Segal, R. W. Arritt, M.Moran, "Mesoscale Influences on LongRange Pollutant Transport," presentedat CIRA Workshop on Acid Depositionin Colorado, CIRA, Colorado State Uni-versity, August 1986.

9. R. A. Pielke, "A three dimensional nu-merical model of sea breezes over southFlorida,." Monthly Weather Rev. i02:115 (1974).

10. Y. Mahrer, R. A. Pielke, "A numericalstudy of the air flow over irregular ter-rain," Contrib. Atmos. Phys. 50: 98(1977).

11. R. T. McNider, R. A. Pielke, "Diurnalboundary layer development over slop-

JAPCA170