NASA-CR-176594 

19860011600 

A Reproduced Copy 

OF 

Reproduced for NASA 

by the 

NASA Scientific and Technical Information Facility 

FFNo 672 Aug 65 

!.ANGLEY R£S£ARCH CENTER 

LIBRARY, NASA 

HAr.~PTOt't VIRGINIA 

1111111111111 1111 1111111111111111111111111111 

NF00453 
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SlIRFACEENERGY flUXES IN COMPLEX TERRAIN 

Elmar R~ Reiter, Principal Investigator, 

-

John D. Sheaffer and James E. Bossert 

Department of Atmospheric Science 

Colorado Stat~ University fort Collins, CO 80523 

Progress Report NASA Grant NAGW 601 

February 1, 1985 to February 28, 1986 

rUA SA-CE-116554) COMPLEX TEBBAIN ESURFACE ENERGY FLUX'S IN 

:985 - 28 Feb. tge~o~~ess Eeport, l F~b. 42 P HC ACJ/MI A01. clocado state Univ.} 

CSCL QIJS 

March 1986 

G3/47 

N86-2to71 

Unclas 

05605 
.. 

A. INTRODUCTION 

the -emphasis of our 1985 NASA project activity was on field .measurements. 

Initiatives included a 19 station mountaintop monitoring progr-am. tes.ting and 

reffnfng the surface flux monitoring -systems and packing and shipping equipment to the Peopl e I s Republ ic -of China in preparation for the 1986 Tibet 

-Experiment~ -Other work jncluded more extensive analyses of the 1984 Gobi Desert 

and Rocky Mountain observations plus som~ pr~liminary analyses -of the 1985 

mountaintop network data. Details -of our field efforts are summarized in Section 

B and results of our data analyses are in Section C. For convenience and to 

avoid lengthy and redundant descriptions of our monitoring systems and prior 

work. we refer you to our First Annual Progress Report (Reiter. et al., 1985) 

B. FIELD WORK 

1. Rocky Nountain Peaks Experiment (ROMPEX) 

In April 1985 we were informed by Chinese officials that logistical 

problems would require a one-year postponement of our planned 1985 monitoring 

program on the Tibetan Plateau. We imm~diately began,work on 3n alternative 

study of the Rocky Mountains, which was designed to examine both the plateau 

heat balance over a broad area and an apparent low-level jet phenomenon 

observed at mountaintop in our 1984 observations at Mt. Werner (Reiter et al .• 

1985) . 

Wind data collected at Mt. Werner in August 1984 revealed a distinct 

diurnal cycle with very strong and perSistent nocturnal winds. These winds 

tended to flow away from the core of the dominant highland are~, (Continental 

Divide) which was approximately 100 km to the southeast of our station. We 

noted that these winds were most pronounced when: (a) broad high-pressure 

systems in the mid-troposph2re encompassed the western plateau region and; 
#-A'P& 

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." 2 

(b) an active monsoon was present with strong and widespread afternoon 

thunderstorms over the highland areas. 

The persist~nt nighttime winds at Mt. Wer~er often exceeded 20 m/s 

when nigher level winds inferred from nearby soundings were- comparatively 

weak. It was concluded that a stron~ regional scale circulation was being 

generated-by the diurnal heating cycle over the plateau. Hence,-we 

decided to use the time and equipment availaMe to us because of the 

Tibet program postponement to obtain more information on these winds wnile. 

at the same time. doing a br.oad-scale surface heat balance study. 

After extensive negotiations with several agencies. including the U.S. 

Forest Service. the Bureau of Land Management and the National Parks Service. 

and then subsequently with the operators of various ski resorts. we obtained 

access to 19 mountaintop sites. These sites. as shown in Fig. 1. were 

scattered over the central Rockies from southern Wyoming to north-central 

New Mexico. The approximate dimensions of the overall data network were 

600 (N-S) by 300 (E-W) km and 200 by 100 km for the inner. heat balance 

network. Our preference for ski resorts in these studies was based on ease 

of access to mountaintop locations which were. at the same time. comparatively 

secure from vandalism. 

Because of a shortage of time and staff for planning and preparing for the 

field program. we were unable to inspect most of the sites prior to actual deployment of the instruments. Consequently several of the monitoring sites were 

less than ideal. The most notab10 case was site C5 (Crested Butte) where a 

dense stand of 15 meter spruce trfes covered the true peak of the mountain. We 

were obliged to place this radiation flux monitoring station in a relatively 

small. 50 by 50 meter clearing. which was 30 meters below and 200 meters west 

of the true peak. The problem was subsequently overcome by placing a 20 meter 

----.. 
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Fig. 1. 

F1 

.... ·0 

.... 

o ••• 

. . . . . .. . . .. • a:. • •• •• a-' ........ . ..... ••• • ······F2 

C1* :::0: ............. 

· .......... . •••• • •••••••• ~. P1 ••••• ..... •• ~~'« • 

.. ;~*; C3 .• ~.!;.:G: P2 ... •••• • !t.l..' .-~ •••• 

AO." ·C2 ·~r: ::::a: P3 · .......... . ............•. 

C4 ::: :: :::::::::::::: .:8;;::::::"':::::::: ~- . ••••••• • _ •••• %:8. ••••••• 4" 

. . . · . .. . 

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• • • • ~ ••••••••• ~ L2 • •• ~ •••••••• ,\:a!- · ............... . ••• La' •. . .... . 

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· .. .. · .. . · .. .. · .. . LS·::-: .:0: 

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Locations of the ROMPEX-85 monitoring stations. The stations 

are keyed to descriptive data in Table 1. Shading indicates 

elevations greater than 2700 meters (9000 feet). The four 

locations indicated by stars were sites for surface energy 

balance measurements. 
,-

= 

4 

tower on the true peak. Thi.s tower was instrumented at three levels (5. iO 

and 20 meters) for UVv/winds and at four levels (0.1. 5. 10. 20 meters) 

for temperature and humidity-. SiteC4 -was also relatively far removed from 

the. true peak. However, a: .catastrophic failure occurred .at this site when 

stray- -cattle topp1 ed the 5 meter tower ana destroyed the instruments. A1-

thougn all other- sites enjoyed good exposure. some data loss oc~urred ~ue 

to wind damage to the -UVW anemometers 1stat-ions -C& and C7) and due to 

_occasional failure 'Of the CSU satellite ground station for satellite- telemetered sites (Fl. F2 and -M1). 

Spe~ific information concerning the location, elevation and measurements made at each monitoring station are given in Table 1. As noted. 

stations Pl. P2. P3 and M1 were already in place as part of other ongoing 

studies. Stations Ll through L6 were installed and operated by personnel 

from Los Alamos National Laboratory under the direction of Dr. William 

Clements. This collaborative aspect of the study \-/as motivated by Dr. 

Clements' involvement in the ASCOT program which is assessing the potential 

for transport and diffusion of pollutants in the complex terrain ~f the 

Rocky Mountain Plateau region. 

Deployment of instrumentation began on June 24. 1985 and the last of the 

instruments were removed on October 3. 1985. The -principal network observation 

period wherein all stations were in place was from July 24 through September 9, 

a total of 47 days. Data from the network of heat flux monitoring stations 

were obtained from July 10 through September 11, a total of 62 days. 

In addition to the surface observations, two intensive piba1 sounding 

experiments were conducted to examine the variation with height ot the wind 

speed and direction over the mountain peaks. The first of these efforts was 

coordinated with personnel at los Alamos. Du~ing the afternoon and evening 

(1500 to 2400 mst) of August 12, 13 and 14 piba11 soundings were made hourly 

--
TABLE 1. Station Data. 

Station(l) Name Elevation 

(Meters. msl) 

Cl 

C2 

C3 

C4 

C5 

C6 

C7 

C8 

Fl 

F2 

L1 

L2 

l3 

L4 

L5 

L6 

Ml 

Pl 

P2 

P3 

Mt. Werner 

Flat Teps Vail 

Powder Horn 

Crested Butte 

Monarch Pass 

Pikes Peak 

Crested Butte Tower 

Elk Mountain 

Rocky l10untain 

National Park 

Cuchara 

Holf Creek Pass 

Nesa Verde 

Purgatory 

Santa Fe Mt. 

Mt. San Antonio 

Mines Peak 

Hard 

Roll insville 

Squaw Mt. 

3250 

3441· 

3350 

2987 

3352 

3597 

4297 

3382 

3383 

3660 

3290 

3590 

2610 

3200 

3660 

3320 

3650 

3048 

2749 

3505 

(1) Station Designations 

c: Operated by E.R. Reiter and Staff, CSU 

F: U.S. Forest Service equipment made available 

by D. Fox, Ft. Collins, CO 

L: Operated by W. Clements and Staff, Los Alamos 

National Laboratory, NM 

M: Operated by T. VonderHaar, CSU 

P: Operated by NOAA, Environmental Research 

Laboratory, Boulder, CO 

Parameters (2) 

Observed 

A 

A 

A 

6 

A 

B 

B 

o 

B 

a 

c 

c 

.. , 

, c' 

c' 

c 

C 

B 

B 

B 

B 

U1 

(?) Index of parameters 

A: Radiation station, WS~ WD., Radiation, Air 

and soil temp. and humidity (see Reiter 

eta1.,1985) 

B: WS, WD~ Humidity and Temperature C: WS, WD, Temperature 

0: . Flux tower: UVW at three levels; Temperature ~nd humidity at four levels. (see Reiter 

et a1., 1985) 

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at both Los Al-amos and on top of Mt. Werner, A similar experiment was conducted. 

on August 28 and 29 at Mt. Werner ortly. 

~e are obtainin~ a large amount of additional data for the ana1ysis 

portion of our work. These data include digital tapes of routine NWS surface 

obsei"vations -and soundings, weather and radar analyses, lightning strike data, 

and observation from remote station networks operated by the Forest Service 

and the Bureau of Land 11anagement. Personnel at the NOAA Environmental -Research 

laboratory in £oulder~ CO have agreed to loan us high quality satellite imagery 

for the period. Also~ we are .preparing finaT data tapes of our 1984 and 1985 

radiation observations for transmittal to NAS.I\, Langley. We are establishing a working relationship with that laboratory (Dr. Tom Charlock) through 

which we will be able to obtain AHVRR data for use in our studies. 

2. Tests and Modification of Flux Monitoring Systems 

Certain deficiencies in the tower portion of our flux monitoring systems 

were described in our first annual report (Reiter et al., 1985). Specifically 

the turbulent fluxe! of sensible and latent heat estimated by eddy correlation 

~tatistics were often an order of magnitude smaller than anticipated values 

for various conditions. A series of field tests were conducted between March 

and June 1985 to systematically examine a number of instrument configurations 

that were suspected of contributing to the problem. 

These tests quickly demonstrated that the primary source of error was 

strong damping and thermal inertia of the thermistor/hygristor shelters. 

This problem was corrected by developing a remarkably durable "hat" of 

fiberglass and styrofoam. This hat permitted good. unbiased exposure 

of the sensors and was small enough to allow us to locate them adjacent to 

the UVW anemometers with effectively no mechanical interference. However. 

----- --
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. even with this modification -the observed turbulent fluxes were still as much 

as 50 percent low under strong wind conditions. 

Next we examined the effect of-increasing the tower height and the height 

abov.e ground of the sensors and, thereby ~ decreas lng the proportion -of turbulent 

ene.rgy in the hi.gh frequency portion of the spectrum beyond the measurement 

capabil ities of the system. In this regard we were fortunate to acquire two 

20 meter towers from. the. Los· Alamos National Laboratory. With this change we 

now pbtained turbulent fluxes which YJere approximately SO- percent of -what is.. 

required for closure. of the energy budget fnr most conditions. 

Prior to our Tibet-B6 program we plan to conduct several additional tests 

of the turbulent flux system. These will include adjustments to the wind data 

for response variations wi th the angle of attack (cosine cOI'rections) and stability dependent estimates of the high frequency turbulent component beyond the 

range of the UVW anemometers. We hope to employ borrowed sonic anemometers 

and fast response thermistors for this work to perform an effective calibration 

test of the entire system. 

In addition to the surface flux stations and radiosonde systems. we have 

acquired a multiwaveband solar photometer for use in our Tibet.-B6 program. 

We hope to supplement our soundings and other data by making extensive measurements of atmospheric extinction due to particulates, water vapor and ozone for 

premonsoon, monsoon and break monsoon conditions. These measurements should 

be quite useful in the interpretation of our surface-based measurements of 

solar fluxes and atmospheric emittance. Moreover, because feN high elevation 

measurements have ever been made with this sort of instrument. the data wi". 

provide basic information on pressure effects in atmospheric "later vapor 

determinations. Because of the potential importance of these data and also 

because of a few minor mechanical flaws, this instrument was returned to the 

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manufacturer in NDvember 1985 fDr repairs and careful calibratiDn against 

local (Tucson, AZ) radiosDnde data. This calibration w·n1 be cDmp1eted in 

March 1986, at which time we will- also- obtain thDrough instruction in its 

prDper use. 

C. DATA ANALYSIS 

In this sectiDn we briefly summarize DngDing wDrk with Dur 1984 data 

set-s and- preliminary ana1yses of our 1985 ROMP EX data. Hhile the emphasisof this work is ~n the analysis Df cDmpDnents Df surface energy budgets in 

remDte and cDmplex terrain, we are also. loDking at periDdic oscillatiDns in 

the heat balance and the role of mDist processes in fDrcing an apparent 

low-level jetphenomenDn over the Rocky MDuntains. 

1. The Enel'gy Balance Df a Shal1Dw Mountain Snowpack 

Our first annual repDrt (Reiter et al., 1985) cDntains a detailed 

descript.ion Df an energy balance mDnitDring prDgram in a mDuntain val1E'Y 

area called Pingree Park. Briefly, this site was in a clear-cut area near 

·the edge of a largely fDrested :no',mtain valley at 2800 meters a.m.s.l. The 

experiment,. which ran fDr'130 days, experienced heavy snow CDver at the 

site during the first 60 days (March 14 ti11May 9). 

The data frDm the radiation statiDn (see Reiter et a1., 1985) have been 

carefully analyzed for three pDrtiDns of the spring period (Table 2) when 

fairly heavy and unifDrm snDW cover was observed belDw the flux monitors. 

Detailed results of this study, summarized below, \~il1 be the subject of 

a forthcoming journal article (Sheaffer and Reiter, 1986). The results 

include: 1) Analyses of ShDtt-term variations of the heat balance and 

integrated effects Df meltin~ and evapDration of the snowpack; 2) Observations of strong infrared divergence frDm a very shallow layer Df moist air 

just abDve the melting snDW surface; and 3) Analyses Df the appropriate 

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TABLE 2. Summary of mean values for key energy flux parameters, Pingree 

P'ark sno\'/ pack, Spring 1984 . 

P~rameter (

1 ) 

Q* (w/m2~ 

K* 11 

1.* II 

V* It 

N* Ir 

Hs II 

Hl II 

Evap. (total. cm) 

Thaw II 

Air T. (Oe) 

Rel. Hum (%) 

WS (m/s) 

Ri(2) 

.March 23-28 

8.6 

-37.6 

44.6 

-8.2 

-29.4 

-7.3 

9.8 

0.2 

Study Periods 

April 4-15 

-16.6 

-n.6 

5a.5 

-19.S 

-57.9 

-10.0 

20.1 

0.8 

-1. 5 (net freeze) 0.5 

-4.5 -0.5 

63.9 46.3 

2.7 3.6 

.05 .10 

(1) See Table 3 ana text for explanation of symbols. 

April 23-May 6 

-23.3 

-67.0 

42.8 

-17 .0 

-'53.3 

-14.7 

22.9 

0.7 

3.5 

-1.4 

62.6 

3.9 

.08 

(2) Bulk Richardson number; positive value indicates stable conditions, 

negative for unstable. 
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roughne-ss 'factors for scal ing mechanical turbul ence in the Tower boundary 

layer in mountainous terrain. The study also "includes observations of the 

radiative components. winds, air temperature and humidHy. and soil heat 

and m(}istul"e. 

Components of -the surface neat balance at the 'Site are given in 

.equation 1-. 

H + H + Hr = Q* + HL H g, so· - s 

where 

Hg = soil heat flux 

Hsn =.snow neat flux 

HT = ·heat flux for thawing or freezing snow 

Q* = net radiation 

HL = latent heat 

Hs = sensible heat 

During this experiment the soil temperatures (dewn to 40 em.) never 

varied from OOC, indicating little or no heat flux to or from the soil 

beneath the snow (hence Hg = O). Also. Hsn was determined to be comparatively smol1 in most cases and was effectively zero for most 24 hour periods. 

Therefore. in the present results we treat Hsn as part ofHT• or "T = 

HT + Hsn' Sensible and latent heat were computed using the bulk formulations: 

HL = pL Cd (qs - qa) (2) 

Hs = P Cp Cd Ua (Ts - Ta) <!>i (3) 

where P = air density 

L = 1a tent hea t of vaporization 

Ua = wind speed 

Cd = drag coefficient 

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Cp = specific heat of .air at constant .pressure 

T~ = air temperature 

T9 = snow surface temperature 

¢!'j =s-tabil ity dependent scal ing term 

qs = saturation mixing ratio of snow surface 

qa = mixing rat10 of air 

The valuesfor Cd are scaled for variations in stability, using terms 

suggested by Oke (1978), 

·41 = H 5 Ri)2 s 

$ = (1 - 15 Ri)3/4 u 

where sand u desi9nate stable and unstable conditions respectively, 

and Ri is a local Richardson-number obtained by assuming that the wind 

speed is lero at the surface. 

The mixing ratio at the snow surface was diagnosed from the 

Iffective ~lack ~ody Iemperature (EBBT) of the surface. The procedure 

involves first applying the Stefan-Boltzmann law to the upward infrared 

emittance and then applying empirical formulae by Lowe and Fricke (1974). 

Allowing that snow is not a perfect emitter, the EBBT at which the snow 

surface was assumed to take on the characteristics of liquid water was 

lowered to 271.8°K, corresponding to an actual emissivity of 0.98. 

It should be noted that the snow surface EBBT often exceeded the presumed 

o . maximum value of 273.15 K by as much as 3 degrees or more. It is unlikely 

that the thin film of liquid water on the snow surface can assume these 

values. Various studies have shown a sharp increase in the air temperature 

near melting snow surfac~s. typically reaching a maximum within one meter 

above the snow. Halberstam and Schieldge (19Bl) have observed this effect 

and demonstrated that strong absorption of radiation in a shallow moisturerich layer just above the surface is the probable cause of the warming. 
: 

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12 

This layer must be associated.,l'lith it strong infrared divergence just 

above the surface which probably accounts for our anomaloJs surface EBST 

values~ In addition. the enhancement of the snow EBBT is observed to .t-~ 

generally diminished fDr increased wind speeJ. We h0pe to gather more 

data on this effect using collocated rauiometers at several ievels -cbove 

the surface in a series :af tests scheduled {or Spring 1936. 

Whereas the snow temperature was restrictec to a value no greater 

than 213~150K ~for calculation of the surface mixing ratio. the vertical 

gradients of temperature and virtual temperattJre (for diagnosing the 

Richardson number) are based on the observed EBBT value. 

Time ~eries estimates of HL• Hs and thaw for the ~hree e~perimen_tal 

periods are shown in Figs, 2. 3 and 4. Figures 5. 6 and 7 show time series 

for the cumulative melt/freeze and evaporation of the snow pack for these 

same periods. The effects ·of occas'onal systematic errors in net radiation 

(Q*) are entered as modifications to the net thaw (TF) in Figs. 6 and 7. 

These effects are due to the iormati~n of frost on the upward looking 10n9-

wave radiometers resul ting in an upward bias in the estinlated Mt cool ing. 

(Syn~ptic data and other site parameters did not indicate the presence of 

h~avy cloud cover or snow during these periods. hence the presence of 

fr05t is assumed.) The cumulative effect of these errors h: inClcated by an 

asterisk at the end of each time series. Average diurnai values for all 

heat parameters for all three periods are given in Table 2. 

Although significant thawing and refreezing of the spow occurred :hrough 

the period. little net thaw occurred prior to May 1 (Day 122). The final. 

complete tha~ of the ;now pack occurred rapidly when a fairly moist air 

mass 'rrived ard lingered over the area for s~ve~~l weeks. The moist air 

tended to ir.cret'se the net atmospheric in; j"ared emittance which. in turn, 

~ ___ r .e'Ia..A_ Ioo"'Io~OIt....-....t __ a_'~ _ "-..,. -'-,-" ' __ .~ _ . ____ _ 

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Fig. 2{b). 

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Day" 83 - 68 

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C:w -, . ". - ... I • 

3CO "T"""JI -b-:=;"-- -' -- -~ -,.... --= ~ C 

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ORIGiNAL PI~Ge r.; 

OF POOR QUALITY 

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• .. .. .. - . ' .. l::C! Tl~C~~O~~S) 

Time series 0f energy consumea for efaporation/sublimation 

(HL) and thaw-freeze (iF) of th~ snow pack at Pipgree Park 

between March 2~ apd ~arch 28. 1984. The sign conv~ntion 

for this 'lnd ott.er !Jlots is positive for fluxes directed upw~rd from the ~now and negative for fluxes into the snow; 

hence negative values of FT ccrrespond to heating and 

melting of the snow Pdck. 

As in Fig. 2a. but for latent (HL) and sensible heat fluxes 

(Hs) • 
=----= 

.. " 

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14 

a 

Ooys .9S - 106 

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Lc:ol 

. . 1J~_~-e~~c' ~ ~ ~ - ~ ~ -

.. • _ r _ " IC£ 1111 ,Col au IQ.I lC" lOt 

Locol ~l~~<~~~-S' 

Fig. 3. As in Fig. 2 except for April 4 to April 15. 1984. 
- - _. 

" ". -_~."~ .!~.~...,. ... -..... \,;...:..;:-_ .. :....-.-.~ , .~·~.'t·a"'~."""~· 

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"' IU II' "' U· tI. II' U( 11'1 '" II. 

III "" III ."' II" II' III lie II: III .n UI .'" "I :1· 

Lcccl il~.\~~~~S) 

Fig. 4. As in Fig. 2 except for April 23 to May 6. 1984. 
c 

m 

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f 

W 

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Cum. Evop/Thow 10 I 

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Doys 83 88 

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BB T 

Local Time(hours) 

Fig. 5 Cumulative evaporation (E) and thaw (T) of the snow pack at 

Pingree Park between March 23 and March 28. 1984. expressed 

as em. of water. A negative trend in the thaw curve in this 

figure corresponds to a net freezing of melt water in the 

snow. 
r. 

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OF POOR QUALITY 

Evep/Thov,", 

Dcys 95 lC5 

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07 01 gQ ICO 101 102 IO!! ICC 

Local Time(hours) 

Fig. 6. As in Fig. 5 but for April 4 to Apr-il 15-,. lStS". The dashed 

corrections to the T curve represent estimate'd actual cooling of the snow where L~ values were biased by frost or snow on 

the radiometers. The astrisk at the end of the T curve 

sholt.s the estimated cumulative correction due to this problem. 
c 

m 

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W 

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t 

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Cum. Evap/Thaw 

-ooys 114 127 

Oi\lmN;~L PhGE 1$ 

OF POOR Q1JALtTY 

E 

, Ii' i " ,P i j I j , I J • j iii i • , , 1 ' Iii ' i I I ' i ''''-''--'-' , Ii'. i 

I" 115 lit! 117 118 I:; 120 ::1 122 123 12. IZ= 12~ 127 

Locol Tlme(hours) 

Fig. 7. As in Figs. 5 and 6 but for April 23 to May 6. 1984. 
:. 

--

19 

inhibited cooling and refreezing of the snow pack at night after ~ay 1. By 

May 9 (day 130) the snow under the station was completely gone. 

Nearly 35 -percent -of the moi~turepresent in the ~now beneath -the station 

was computed to have evaporated,\-/ith- the remainder melting and- 'Seepi-ng into 

the soil or nearby deeper sno\'1 cover. Peak rates of evaporation occurred on 

ChinooR days when warm,dry \'1inds swept d-own from higher elevations to the 

\'1est. Energy consumed for -evaporation of snow- occasionally exceeded 150 -\'/atts 

per square meter on these- days, a -rather strong rate of transfer over a 

smooth surface under slightly stable conditions. 

It is significant that a drag coefficient value of 2.5 K 10-3, 

typical of values cited for smooth snow, provides what appear to be 

fairly accurate results for this mountain environment. Our claim of 

accuracy in this case is based on the reasonable values obtained for 

specific situations and for the cumulative computed thawing of the snow 

pack. On days 117 and 118 (Fig. 2) for example, rather cold air temperatures and strong winds suggested that little heating and probably no thawing 

of the snow pack occurred. Ba~ed on the thermal properties of the snow and 

also on data for similar conditions (Brazel and Marcus, 1979) we estimated 

that the total daytime snow heat flux is well approximated by the values shown 

for days 117 and 118 in Fig. 2. - Furthermore, measurements of the depth and 

observations of the condition of the snow pack on day 114 indicated the 

presence of approximately eight to ten em. of water equivalent. Although protrucing rocks and twigs preclJded accurate flux computations after day 127. 

extension of the calculations through day 130 suggest a total melt and 

evaporation of ju'st over 8 crn. of moisture. Varying the estimated drag 

coefficient between values of 2.0 X 10-3 to 3.5 X 10-3 leadsto either 

unrealistically low or high estimates of the short-term fluxes and significant differences from the estimated total evaporation and thaw for the 

period. 

/ 
.1 

I 

20 

~e not~d in our original proposal that the normal procedure for 

dealing with large-scale roughness effects of mountainous terrain in 

numerical.models i~ to use a large drag coefficient to ·characterize 

forced mechanical turbulence in the lower boundary layer (see Zhang and 

Anthes. 1982). The present flux data were obtained using a comparatively 

small ~rag coefficient in persistently damped mechanical turbulence (i.e. 

stable condition5). therefore. -a· rea~istic treatment of surfa(;es in 

mountainous terrain would appear to require t~e use of a smaller roughness scale appropriate to local surface cover in the lower boundary layer. 

Mountain scale roughness effects such as large mechanical wakes and thermal 

p1umes ~u1d then require a separate stability-dependent treatment for 

fluxes in the outer boundary layer. We hope to further investigate these 

findings in newly acquired data for several additional mountain settings 

described in Section C4. 

2. Analyses of the 1984 Gobi Desert Heat Balance Observations 

An in-depth analysis of our measurements of the surface energy budget 

in the Gobi Desert during the spring a~d summer of 1984 has recently been 

completed. The objective of this study was to observe the heat balance 

components of the arid Gobi landscape for different seasons and hence 

for different solar ~eating rates. Ultimately this work will provide 

baseline information for diagnosing broad-scale desertification processes 

by remote means . 

In contrast to the dry spring period, the summer observation period 

was marked by considerable atmospheric moisture, cloud and rainfall. The 

wet summer conditions strongly influenced the absorption and partitioning of 

radiant energy into latent and sensible fluxes and precluded simple 

quantification of the response of the surface system to increased solar 
1 

I 

1 i . 

1 

I 

i 

i 

! 

--

2"1 

radtatton. Moreover~ the effects of deep atmospheric moisture reduced 

and redistributed the solar flux such that the net heating at the surface 

in surrunerwas e(JuivaJent to that for early spring. A- separate report 

(Smith -€taL~ 1986) which pre'Sents 'i1etails of this sttldy has- -been 

submitted- to the Journal of Climut€ and Applied Meteorology. 

Additional work 'with tile -Gobi data is being performed by Mr. ltl longhua 

of the Academy of -Meteorological Science, Shan9hal, PRC. Expanding on 

prior Chinese studies. Hr. lu is performi:19 extensive aut(}oand crossspectral analyses of the Gobi radiation station data (see Reiter et al •• 

1985). Although this work is still rather preliminary some interesting 

results have been obtained. In addition to what is assumed to be a 

synoptic scale periodicity of 7.5 days, a very strong 3.2 day periodicity 

has been observed in a number of parameters including nearly all of the 

radiative flux terms and the 5ensible heat flux. The significance of this 

apparent 3.2 day oscillation lies in the fact that a similar periodicity has 

been reported for the development and eastward propagation of mesoscale 

vortices over the Tibetan Plateau. The latter observatio~ is based on an 

intensive 90-day upper air study performed by the Chinese during the summer 

of 1979 (Shen and Huang, 1984). Hopefully, the same analyses can be performed 

with our two-year, multistation data set for the Rocky Mountain Plateau. 

Possibly a related, though presumable different, characteristic frequency 

can be identified and linked to the interaction beb~en the atmosphere and 

the heat balance of the elevated terrain areas. 

Higher frequency spectra of the Gobi data reveal strung periodicities 

at approximately 30. 80 and 150 minutes. We asslJme that the 30-minute 

spectral peak is related to the time scale of larger turbulent (thermal) 

eddies but implications of the longer period oscillations is not immediately 

cl ear. 

--
22 

3. The 1984 Rocky Mountain low-level Jet 

Observations of strong nocturnal winds at mountaintop were described 

by Reiter et al. (1985) and also in sections B-1 and C-4 of this report. 

We have recently begun a study to examine the possible r~'e of moist 

thermodynamic processes 'in the forcing of these winds. This work ir.volves 

the analysis- -of time variations of equivalent potential terr.perature and 

saturation point at mountaintop- in relation to the onset of strong winds. 

The analysi~ is based on concepts outlined by Betts (1982a~ b) for identifying the thermodynamic signatt;res of specific atmospheric heating processes. 

Preliminary results tend to confirm our belief that outflO\'1 from organized 

regional scale convection is, at least in part, resoonsible for the strong 

and persistent mountaintop wind events (see also Section C-4 below). More 

extens.ive work with our 1984 data sets should further clarify this issue . 

.. , .. ---.----,_._---
t _ 

-, 

i: 

- -- • -~ .... - I ..... 

23 

(-4 Preliminary Results -of R0I1PEX-85 

Final processing and assimilation of the RO~PEX-85 data into several 

data base archives has not yet been completed. Nevertheless we feel that 

we have once again -obtained a great deal of unique and high qual ity .data 

- from our remote .area monitoring HorR. Seve-ral preliminary studies of both 

the wind field and energy balance data have yielded some very promising 

result-s. 

1. Mind Analyses 

Resu1t~ of initial work with the ROMPEX wind data tend to confirm our 

prior conclusions concerning the- nature of the mountaintop low-level jet 

phenomenon, described in Section B1 and in Reiter et a1. (1985). In ROMPEX, 

as in 1984, we find that a fairly strong plateau monsoon in conjunction with 

a stationary regiona1_ anticyclone appear to be necessary conditions for prl)-

mounced occurrences of the low-level jet. Our selection of August as the 

principal R011PEX study period was based, in part, on the fact that the plateau 

monsoon typically reaches its maximum during this month (Tang and Reiter, 1984). 

Unfortunately, in August 1985 the mensoon was nearly nonexistent. Several 

-

intermittent but fairly intense monsoon periods did occur -in July 1985, hm'lever, 

which allowed us to collect some useful regional-scale observations. 

Average diurnal cycles of wind direction at Mt. Werner (Station el) for 

August 1984 and 1985 are shown in Fig. 8. The time series of I1t. Werner 

winds in Fig. 9 show details of typical 19S4 nocturnal wind events, most 

notably on days 225,227,228 and 231 (August 12, 14,15 and 18, 1984). 

Although thera is a modest direction cycle in the averaged data in Fig. 8b. 

both the strength and frequency of the wind reversal events in August 1985 

\ 

, 

; 

-, 

--~ I 
~.J 

Fig. 8(a) 

Fig. S(b) 

-:.. .- -- --':'" "'-

o 

360 

330 

3CO 

1 UO ,. 

~ -210 

~ 190 

~ 150 

d 120 8-

9 90 

24 

MT.WERNER WIND DIRECTION 

: I ~~~~~~~~~~~~~~'~i~i ~i~i~i~i~i 

350 

330 

270 

o 

1 240 ,. 

: 210. 

~ IBO 

a 

n 150 

d 120 

• 9 90 

fiO 

30 

• , • ~ • • ., , • • ~ .1 II It .& II d It " ~ • ~ • • • 

Local Tl~a(hour.> 

MT.WERNER WIND DIRECTION ~ Day. 

O~~~~~~~~~~~~~~~~~~ 

• , • • • • • t • • It ., II I' .& .1 II " 'I II ~ " ft • " 

Local Tl~a(ho~.) 

-.~.-

Mean diurnal cycle of wind direction at Mt. Werner (Site el) 

for August 1984. The outer pair of curves represent f one 

standard deviation of the daily mean values. 

As in Fig. 8(a) but for \uyust 1985. 

/ 
I 

t 

!, 

I 

I 

I 

I 

» 

I 

- - .-

Fig. 9(a) 

:. 

25 

VEL 

30 a 

v 

- ~ 20 

-0 

C 

~ 15 

~ 

II 

r- 10 

• .. 

c 

5 

r t t . -~ . - / ~~ ~I . ., f il,. . I, I, 

~ ~ - TI_(.Jullon ~ ~ day> - - .--

o--~----------------------~~ ~ - - T, .... ~ (.Julian - -dey> - . -

Time series of mean, maximum and minimum wind speed for 15 min. 

time periods (5 sec. scans) at Mt. Werner for August 12 to 

August 19, 198~. The large tic marks on the abscissa correspond to local nidnight. 

Fig. 9(b). As in Fig. 9(a) but for wind direction 

~ ; 

£I 

ij 

iL---------
'. 

,-

.~ . 

; ,! 

26 

-

wer.e-great1y diminished_ The averaged August wil'ld speeds in -Fig. 10 

also show this same tendency wherein 1985 daytime (westerly) winds are -

strongest in contrast to the 1984 n;ghttim~ (easter1;) maximum. Results 

for two stati.ons (Cl t Mt. Werner and C3,- V'3il Mountain) for portions 

of J-u1y 1985 are shown in J"ig. 11. These data. oS noted previously. 

represent a more a~tive monseon period and shew a much mOie pronounced 

diurnal cycle. Mean nocturnal wind speeds fer the July 1985 peried \-Iere 

415-0 str.o:1ger than- the afternoon values. 

A,!lalyses .oJ regional data fer severat tirr-e peried') .011 the 14+.h of 

July 1985 are sho\"m in fig. 12. At l:!OO MST (Fig. 12a) strong regional innow 

toward the highlands can be .observed at the stations fur which data are 

presently avai1ab1e. This inflew had continued through the ~fternoon but, by 

1900,streng c.onvecti.on ever thp eastern portien .of the network ~ad begun 

t.o cel1apse. At 0100 I-IST on July 15, a strong and fairly \O/e'l organized 

outflew pattern can be .observed. The eutflew persisted fer several hours 

and gradually relaxed to a weak anticyclonic circulation by the fellO\'/ing 

merning. 

As stated previeusly, we ( ~till expanding and refining .our data 

base tb include additienal statiens (the "PH and ~l" sitei in Fig. 1). 

We hope to generate animated analyses (cemputer movies) of the wind field 

for the entire experiment. Hopefully, more and better cases s"imilar te 

that shown in Fig. 12 will be .observed when detai1ed anal}ses are complete. 

One additional analYSis has been done for the period during which 

pibal soundings were made at Mt. Werner and Les AIJmos. Ne~ MexicD. 1hese 

results, shown in Fig. 13, reveal an interesting and unexpected effect. An 

apparent mesoscale wave can be ebser~ed moving through the northern portion 

.of the network on the evel'ling of August 14. 1985. Rather strong west-south-, 
,.. 

" ... ' 

:";':.1 

... - ,.. .. '. i 

;;j 

,.",., 

;! 

~: ~. 

,:" ~ ~ 

;}.:. 

--

V 

• 1 

-Q 

C 

, 

to 

~ 

'II: 

I 

• • c 

v 

• 1 

a 

c 

, 

to 

~ 

III 

I 

• • c 

ttl 

g 

e 

7 

6 

5 

" 

:3 

2 

27 

MT.WERNER \~IND SPEED 

244 a Ooy. 21'4 - 1984 

"' ,. - oJ "- , I 

'" 

1-- ,-, /,/ /""' __ J-:", , I .... -

• a I • • • , 1 • • ~ " U MM. ~ It M ~ • • • • M 

Local T' •• (hour.) 

MT.WERNER WINO SPEED 

10 b 

g 

213 - 243 

1985 

e 

• • • I • I • , • • " ., U Q ,_ q M " M •• • • • • ~ 

Local T,,,,q(hour.) 

.. 

Fig. lO(a) Diurnal cycle of average wind speed at Mt. Werner for August 1934. 

The dashed cuter curves represent ± one standard deviation of the 

daily mean values. The solid outer curves represent! t.he average 

standard deviations of the actual wind fluctuations. 

Fig. 10{b) As in Fig. 10(a) but for August 1985. 

~ 
330 

330 

3::0 

270 

0 

I 240 .. 

• 210 c 

t. lBO I 

~ 150 

-

d 120 

• 9 90 

60 

30 

0 

:3 

I 

I 

I 

, , , , , , , " """""" I 

• , • • • • • , • • II I. ~ II •• •• ~ ~ ~ ~ • ~ • • ~ 

Local Ttm.(hov~o) 

V A I L M TN. vII NO~ I R. 

b 

• I I • • • • , • • 10 II II I' ,. " ,e ,,. ., " ID II oil n .. 

Local Tl~D(~ourc) 

1 

I 

I 

I 

Fig. ll(a) Average diurnal cycle of wind direction at Mt. Werner for 

July 1 to July 16. 1985. 

Fig. 11(b) As in Fig. 11(a) but for Vail (Site e3) for July 8 to July 

16. 1985. 
c:. ..... v'4ll:~·H .. ~'.-.a...-;~ ..... '"' __ ,.._ .... ~~_·_: ~t_ .. ~ .. _ .. -+:, __ . ___ ~'::"'~ .. ::':;;;;';';"~;""'':'"'-'' •. ''' '·1' .. :~'w...~sJ,:i':. ,( ,~.,fi.:.Q·1 ~ ~.=..~~.-i~_'~--=,;'~I-J'~:·.·. _:';..=f.;~.::-,,;~. __ ...:_"~. ""'~.'" ....... '~~"'!;; 

• 

A 1200 MST 14 JULY 1985 

. .... . \ ' .. ...... '.' I a .... 

t·· .. • :! .•• ;,_ ...... :! .. 

::-". i.······ , : ····l : 

-:-4 N" ~ '" ...... ~ \~ ..... : . ....... : .... .... .... :/lJ .' ~'''''''' 

':. . :. ···X: : ". . .; ...... '.. ...... .' ... ' 

'.,\\ :." .... "'::" . .. . . . ..... ~. ~ ! ':\i ::~ . .' . ' .......... . ,.. . . .. ' .. . ., - '0 I 

. . 

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

.. . . . . 

.. 

. : .. 

..... 

5 • 5 ,MIS 

10 

B 0100 MST 16 JULY 1985 

.... " 

'. . = ... : .. 

~ 

.. ';\". ". : f "~ ..•.. : 

~ 

..... : .. ' , ... ., .".' .. .-. ' .:. . • ., ... \. I ••••• ' lit : ... . .. ' \ -... .. . • ..... : ·.i ~ .... ...... "'", 

• • • . Ii".. . • ...' ." I 

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

. ':" ...... "':' . ... : '.' ...... : ...... . • • II' • ". f. :: , ... . ........ , J'" : ". • • : I : 

. . . . 

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

1,5 • 5 'I M/S 

10 ' 

Fig. l2(a) Analyses of averaged wind speed (15 min. means) at ROMP(X sites (for 

which data are presently available) ofr 1200 on July 14, 1985. The 

arrows indicate the direction of airflow and the len~th of the arrows 

is proportional to speed. Strongest winds in these figures are 

slightly greater than 10 m/s. The point of each ~rrOw indicates 

station locations. 

Fig. 12(b) As in Fig. 12(a) except for n10n. 15 July 1985 and the tail of each 

arrow is now at the station location. 

........... 

" ~., 

, 

, 

N 

\,() 

, , 

" 

, ,'i 

" 

, ' 

" ", 

, , 

.! ,', • 

" 

'" 

': 

" 

" , 

" 

'r, 

I 

" 

, , 
-

f 

" . "--.: ' ..... 

.. .-' 

' .. 

;''' 

~~ 

(-l 

11 

~i 

ti '. "I 

~I 

;1 

;1 

I 

" t 

1 

i-

, 

I 

\ 

~j 

:j 

:; 

! 

) 

I 

'.~ 

,I ,j 

-- .. - - .'.--

31) 

westerly winds were onserved aloft during this period. Our analyses of 

piba~ data taken at Mt. Werner suggest that this brief southerly shift 

of the winds. which began at ~bout 1900 MST. extended through a layer at 

least one kilometer thick. The analysis in Fig. 13 suggests a wave 

length scale of about 200km. and a propagation speed of about 50 km./hr. 

Although the diurnal heating cycles of plateau areas have been s~spected 

before of causing vorte)\ phenomena similar to what appears to occur in 

Fig. 13 (Shen et a1.. 1985). little observational data have been obtained to 

document their existence. Allowing that such vortices are also believed to 

propagate downwind and provide upper 1 evel support for the deve'lopment of 

mesoscale convective complexes in low-lying areas. the possibnity may exist 

for observing such effects in real time at mountaintop. Hopefully. a 

complete analysis of the data will clarify this prospect. 

2. Heat Balance Analyses 

During the RO~lPEX-85 program the surfac! energy balance was monitored 

at four mountaintop sites as shown in Fig. 1 We have recently completed 

a preliminary study of the principal radiative components for these sites 

for August 1985. These results are summarized in Table 1 which also includes 

comparable data for ~lt. Werner (site Cl) for August 1984 .. 

Inspection of Table 3 reveals that the interannual differences between 

1984 and 1985 at Mt. Werner arc generally greater than the local differences 

between the 1985 sites. '~he notable differences between 1984 and 1985 at 

Mt. Werner include both lower incoming and net solar fluxes and enhanced 

terrestrial infrared fluxes in 1984. In addition to these differencl's the 

smaller visible albedo and slightly larger near infrared albedo at Mt. 

Werner in 1984 may all be attributed to the presence of increased atmospheric moisture and precipitation. 
n ~ -

~ 

, 

!j . , 

,'-

r 

' . 

.. 

,./ 

-~ 

-'. 

0.1800 MST 14 AUG. 1985 

\} n 

·····1 .:/ '·._1 .. ~ .. : 

I 5 . «' lUIS 

10 

C.OOOO MST 15 AUG 1985 

----., •.. : I .... ~ 

\,;.t;' i .,'1. : 

..... , .: .... ..... : .. -.;. 

~"', 

.. IS • IS ,II IS 

10 

31 

: 

b. 2100 MST 14 AUG 1985 

'-....: .. " '-.\ 

····1. 

.~~~:(:~ 6\ .,~ :. ! .. /.... : ".- : , ':', -: ::::.!.~ ... : ..... . ....... ~ :'./.!.' ..... '~ .. ' ~.~ \:.:(:." .... (-::r; 

! -.............. ~ :~': , ' .. /-.-

tIS. IS I MIS , 10 

d.0300 MST 15 AUG 1ge5 

Fig. 13. As in Fig. 12(a), but for ft.ugust 14 and 15, 1985. 
I' 

TABLE 3. August heat ~a1ance statistics for ROMPEX-85 plus 184 Mt. Werner data. . .. " ' 

-Stations-

" Parameter Mt. Werner (C1) Mt. Werner Vail (C3) Flattops (C2) Crested Butte (C5) " , 

1984 (320Om) (3353m) (3441in) c:nS3m) . ' ' , ,I 

'; ,I) " .. ' 

... I' :, I 

W/m2 Radiation ' " 

Total Solar K -247.5 -284.6 -272.4 -2a6.6(L) -272.3(5) ;1 I , , 

Visible (V) -118.1 -136.1 -130.0(5) -138.4(L) -133.2 ,', ... ','. " , , 

Near IR (N) -129.7 -148.6 -142.4 -148.7(L) -139.1(5) ',' 

" 

Atmospheric IR (L~) -315.0 -284.6(L) -266.8 -261.1(5) -279.0 ," I 

Surface IR(L+) +385.0 378.0 363.4(5) 366.4 +381.1(~) 

, , 

, . , ' ' 

, 

Net Radiation {Q*} -134.8 -140.1(L) -118.4(5) -124.5 -124.6 " ~i' I 

I" ,,' 

K* -204.5 -233.8(L) -215.3(5) -229.5 .2~6.5 . I, ':' "\ 

V* -113.2 -127.4 -122.6(5) -128.0(L) ., 123.4 " 

fl* -96.1 -106.4(L) -92.5(5) ·1111 \ 5 .. 103.1 :,""., ' 

L* 70.1 93.5(5) 96.6 10S.3(L) 102.1 ' : ' I 

. , ' 

" I r' 

Albedos (%} ~ 

~ '1 

Ak 17 .4 18.0 21.3(L) 20.5 16.4(5) 

Av 4.3 6.3 5.9 7.4(L) 6.3(S) , ' 

An 29.5 28.6 35.5(L) 31.4 26,6{S) , " ' 

~J3_BTemps (oK) ";,. 

E B(3T t 272.6 266.0(L) 261.7 260.4(5) 264.5 

EBBT 1 286.5 285.3(L) 28:!.4(S) 282.9 285.2 

Wind Speedo(m/s} 4.69 4.25 4.S4(L) 3.53 1.70{S) 

Air Temp ( C) 11.4 12.1(L) 11.6 10.6(5) 11.8 \' 

Rel. Humidity (%) 47.5 39.3(5) 42.8 45.4(L) 44.5 

" ,,' 

'(L) and (5) designate the largest and smallest 1985 values,respectively. 

~:: I 

" -

'\ 

'" 
f 

t 

j 

! , 

I 

I 

L 

! 

" - . ~ - -

,. " - - ~ ~-.-

". ~ 

-- - - - - - - \ 

33 

The results for 1985 indicate that Station C2 (flattop) experienced 

a generally dryer atmosphere than the other sites. Evidence for the latter 

-observation include both the -smalTer mean atmospheric emittance and- larger 

solar flux components at that site. Whereas Mt. Werner (site -(1) experienced 

the strongest mean atmospheric- emittance, the incoming solar components 

,were also .comparatively strnng. This condition suggest that a- detailed 

comparative study of time series data for eachsitewnl be required to 

determine how the-mean values in Table 3 are actually obtained. 

Figures T4 throug!; 17 show the mean diurnal cycles of radiative components 

for August at each of the 1985 stations. The August 1984 data for Mt. Werner 

are also included. To simplify intercomparison between these ploi;s, we have 

superimposed the diurnal cycle of several key components of the 1985 Mt. 

Werner data onto each figure. 

The effects of our compromises on sit~ selection can be observed in the 

analyses for Crested Butte (C5) and Flat Tops (C2). The early morning data 

for both of these stations and afternoor data at Crested Butte show undulations due to the presence of shadows cast by nearby trees. In addition to 

these problems th~ atmospheric emittance data at Crested Butte appear to 

be contaminated by infrared emittance from nearby trees in the early afternoon. 

One interesting result in these data is the strong decrease in the 

atmospheric emittance at Mt. Werner between 1984 and 1985. The 1984 data 

sho'rl the presence of the active monsoon in the form of greater afternoon 

cloud cover and a much wetter/warmer nocturnal atmosphere. A decrease 

in the net solar fluxes ij also evident in 1984 data in Fig. 14. 

The surface cover of three of the four ROMPEX sites consisted primarily 

of sparse grass and lichens with a fairly large component of bare. rocky soil. 
'!;~. " 

; .... 

~~ : 

'i/~ 

:..-. .i 

~. I' 

, .... " 

~,,' .~ 

~\1 .~ '"-. ~ ~ "4 ~ 

::~ ".: 

,./ 

i ., 

, 

~ " 

ML WERNER RAD. FLUXES ::1--- -.--- Do,. 113-. ~;-;985 -, 

mo -t ICOC 

~ :1 ; 7001 

~ ~OO1 

:~~ 

z .oo~ 

JOO{ 

2«)' 

100 

O~--~~~~~~~~~~----~ .0 ...•................... 

IIc.o 

IW0 1 

~ GDOl 

:: eo:>~ 

'aoo ~ =1 

300 • 

2Ul ' 

'--I TI_"*,,,-) 

IOC! D-'-.--~~~~~~~~~~--~~ • I ................... " ......... .. Laco' T __ ("""",.' 

34 ORimN.~ Pf.S!:; is 

OF POOR QUALm' 

.. .~V~A~l~L~M~T~N~.~~~~~~~ 

.'-No{ 

~ '"~ ~ wUi j ,';~j 

• we ~ 

: 5.:.01 z .00-: 

JC)CJ 

2a~~ , 

CIa,. I 

., 

! 

1""1 

D--~~~~~~~~~~~~----~ . ................................. .. Lecal T ... II_r.) 

FLATTOPS RAD. FLUXES . -"~ .. - ---..... ~--;;-;l~ -.~-;.;--

I~ -

liD:! 

1.;G.;1 , ~ .. ~ "ooj 

; ~GC~ ~ e=1 • 5:lC-

; .~~ 

"x:1 

• I .......... II .......... It ..... II AI ... 

I~OO 

liDO 

1000 

~IIOO 

; ~~11 ~ 6:: 

: :'00 

l '001 

::- ,)1 2001 

Loco! TI_U"IO\.W".) 

UTTE RAD. FL 

Do,. ~J) - 2&3 

l~~~~ ____ ~~~~~~~~~ ____ ~ 

........ I .... " •• II .................. .. 

LOCDI , ... (~.) 

Fig. 14. Diurnal average values for incoming and reflected components of 

solar radiation during August 1984 at Ht. Werner and at the 1985 

ROMPEX sites. label designations are total solar (K). near 

infrared (N), and visible (V). The dashed curve labeled mw 85 

in several of the plots represents the K~ value for the Mt. Werner 

site for August 1985. 

". 
, 

,-

," 

, 

I 'DO .. 

· '100 • 

· ... 

2200 

--

Lt ,,- .... _-, .,- .... . .,- .... -----' --- q 

------------------=~-----

••••••••• M ••••• _ •••••• ~ 

~ol ,,_"-.) 

35 

{ '00 .. •. 

-· 

100 

/ - -

! 

... 

~:~··I ..,; . o!'i -,~._ OF PO" .... 'l~2 IS . OR _QUAL.ny 

VAIL MTN. RAP. FLUXES 

y ...:. •• ..::,. ... ..,: .. ... ~, ...... L1 .,,- ~"' .. :'--":;'=j.=.-::r ..... ::.::.:.: 

----; .. --------.,;.;;.:.:--_._---.... -----_. 

am, L~ --. 

•.........•...........•.. ~IT' __ .) 

;' 

~~WL,~~~~-U~~~~~~~---. MT.WERNER R~O. FLUXES 

Do,. 21' - 2" 11184 

_F ,~L=..!":..:..T:...T~O~P-=S~..!.:R~A~O ..... ....!-F L!:::.:U~X~,E"""S~-.. eoo .... Do,. llJ • 20, 

, 

I .co .. 

• 

• 

· i 200 

100 

;;;;~----·---·--··--·-----·-u·-· 

............. w ••••••••• • 

'--I T'_~ 

, 

I .00 .. 

• 

· · · 2 200 

100 

/'--........ t •• ~ ~" L 

=-----==/.=.-~' ..... :..-::-:: .. ----.p ------.-- , .. ------:.::..=:------_. 

Ll 

••••••••••• u ................ .. 

Locel "_I'-rfO) 

~~~~-~~~=-~~~~~~~~---~ CR. BUTTE RAO. FLUXES Do,. 211 - 203 

SDC ,-.... 

F 

I 000 .. 

• 

• 

· · 2 :00 

100 

'" \ I ••••• - .• - •• ~ 

,f'" ....... Lt ----.. -7--•• 1 -::-.::--.:.-::. - - - _ .... __ . __ t. __ . 

lAW! 

. . . . . .................... LocCiI " .. (~.) 

Fig. 15. As in Fig. 14 but for atmosphet'ic infrared radiation. The 1985 Mt. 

for comparison. 

(L+) and surface (Lt) emitted 

Werner data are again included 

\ 

\' 'I 

! 

I 

I 

I 
'00 

JOO 

:00 

IDO , 

) D .. 

~-IOO 

~-lOO 

:"JOO 

. ,-.o:r 

-500 

-600 

-700 

-100 

.ao 

lOCI 

:00 

ICO , 

I D v 

~-ICO 

, -l'DD 

:-"'00 . 

2-400 

-500 

-tIOO 

-700 

-eoo 

:. 

--

MT.V: 5 

18115 

•............ -.........•. 

LocGI '1_1tor9) 

MT.WERNER NET FLUXE 

0.,. 'IA - 'u 11184 

.. ...............•..•.... 

LocGl '1_"--' 

-- --- - j . :- 1 . 

/. 

36 

100 

.. t D+-------~--------------~~----~ ~-ICO 

,-zoo 

:-JOO 

. 

2-'0::1 

-500 

-tIOO 

-7CO 

-IDO .. ~--~~~--~--~~~~--~--~ • • ••••• r ••• M ••••• _ •••••• ~ 

.LocG1 '1_ '-e' 

FLATTOPS NET FLUXES .co 0.,. ,., 

lOCI 21' - :00 L· 

100 UWM , 

I 0 u 

:-ICO 

~::L -500 

-eoo . 

-7CO 

~ ~~--~--~----~--~--~ 

, 

~ 

.. 

:-100 

,-ZOO 

:-100 

. 

2-000 

-500 

-600 

-7CO 

......................... ~I '1_0.".' 

-.oo .. --~--~--~----~~~~--~--~~ ••••••••• It tI ............... .. 

Loco1 Ta_'hOw""'.~ 

Fig. 16. As in Fig. 14 but for the net radiative fluxes. The 1985 L* 

value for Mt. Werner has been added to some of the plots. 

/ 

/ 
,/ 

t-lT 100 

DO. 

-.0 

A 70 I 

b 80 • cI 

~ SO 

P 

• 40 r 

C 

.. 3:) 

.. 

4 -2tT 

WERNER AlBEOO/T (""bb) 211 zu F; Co,," . 1965 

--------= t- ____ A 

EeST t ~ 

[no i • d 

~ 

. " p 

"ZJO ! · r 

~ 

• .. lee , 

10 

0 

A 

I 

b 

• " 

~ 

c 

: :~ 

p 

· r 

c 

.. .. • , :o~ 

.. ..i 

, 

.~ 

, 

. 

UlO 

;0 

.0 

~O 

80 

SO 

40 

.JQ 

:0 

10 

0 

100 

DO 

to 

70 

80 

SO 

40 

JO 

20 

10 

'.-

OniG!~t~.!.. PI,C~'S 

OF POOP. QlIAl1JY 

VAIL :.liN. ALBEOO/T Cob:') I ,~: Do,. Zll - 24' I 

310) 

T 

, 27C ~ .. 

! 

-lJO· " 9 

lao 

ISO ................ -Ie ... It .... II .... 

Locol T._Ihowr.) 

FLATTOPS ALBEOO/T (~bb) )~C Do,. 21) . 241 

JIO 

........ ~~BTr~--.. u- . .:t - - .. -.. ~- .. -.-... ----... 270 b --.. , e. -----.---.:--- II 

! 

2): " • 9 

" 18: 

Il-... ....... -.,...f 0 I I!.C 

.... ............................ . LocI' Ta .. ~.) 

............ " ....................... LDcol h ........... o) 

CR BUTTE ALBEDO/TC(.-tb) 100 3~O Do,. llJ ":: 2.: DO 

110 JIO 

• 70 T I , b . • 110 270 .. 

d b 

0 SO ! p d 

• 4C 

~~-~gj 2)~. 

r 9 < 30 • " 

t·~ .. 

, 2C 

10 

0' 1'0 .................... _.n .......... Locol , ••• (~.) 

Fig. 17. As in Fig. 14 but for the surface albedo and EBBT values for 

each site. The 1985 EBBT curves and a portion of t~e AK 

(total solar albedo) curve for Mt. ~erner have been included 

in some plots . 

... _-------- - .---------

I 

! 

I 

I 

i 

, 

" 
, 

; 

. ~ 

.:." 

.... 

~ 

~ 

. 

-. 

, . ~~. . 

p-

- - - \ 

38 

The -exception -was- at VaH{C31 where -a comparatively dense mixture of grasS" 

and-tundra flowers covered the ground. The surface at Vail had a notably 

larger albedo for near infrared radiation as shown in Fig.- 17 and Table 3~ 

- In spite of th:is value. the -averaged ~lbedo values for total solar radiation 

in Table 3 -are.generany rather similar. The smaller albedo valueS. at Crested 

~uttet- especially for the near infrared • .are probably due to an approximate 

five percent slope of the surface at this site which has not yet been compensated for in the data. 

We had hoped to place the four energy budget monitoring stations in 

sites with effectively equiyalent local exposure to winds and radiation~ 

Constraints imposed by time and staffing. as noted previously. ultimately 

prec·'uded this deployment plan. Consequently we have obtained extensive 

good quality data for sites that are all distinctly different in exposure 

or surface cover. in addition to being 100 km. or more apart. While this 

diversity might be desirable in an advanced stage of our work it complicates 

the present task of computing a complete energy budget by partitioning 

turbulent fluxes into latent and sensible components at each site. 

Allowing that the soil heat flux can be determined fairly accurately 

from"soil temperature and soil moisture values observed at six levels. the 

total turbulent flux becomes the residual after computing the net radiative 

energy balance. Q*. Estimating the surface mixing ratio over diverse 

vegetation cover is a very difficult task. Consequently. we have chosen 

to use surface EBBT data to compute the sensible heat flux. as described in 

section C-l. and then obtain the latent heat as the resid~al component. 

Unfortunately. several complications unique to mountain peak environments 

require that we proceed cautiously in computing the sensHle heat fluxes. 

#-- "- '. 

i 

/ 
:. 

39 

The latter complications include a very limited effective upw.ind fetch 

-for the true. peak sites and several stability regime.s not typically 

encountered in boundary layer research. Tnese regir,les include a) air 

flow from the free atmosphere imp-ingir.g directl·, onto the site when light 

winds and deep valley inversions 1 imit mixing~ In thls case- the site. becomes 

a source region for subsiding slope flol-ls. b) Under strong heating lnd 

'convectiv~~onditions. the peak~ are the upper limit for upslope flows; 

Hence. °in this case the sites may be in the centers of persistent localized 

thermal plumes. c) For modErate winds wah mixed convectioll. large-scale 

mechanical and thermal eddies -may create a turbulence regime at these sites 

which is more typical of the outer boundary layer than the lo~/er boundary layer 

conditions. The extent to whi~h effects of any or all of these regiMes can 

be identified as important at each site is a necessary preliminary step in the 

comp'ete energy budget analysis. 

Detailed multilevel tower data (eight meter tower) collected at Mt. 

Werner during our 1984 program and similar. but generally suoerior data 

collected during 1985 at Crested Butte should :'e useful for these studies. 

The Crested Butte data (20 meter tower) also include advective components 

[tha t 1 S (U'T'), (li'Cj'). etc.] computed from one -second samples. in 

addition to the usual vertical covariance statistics for wind, temperature 

and humidity. In addition. several snowfall periods which occurred during 

August and September 1985 wil~ also allow a limited set of turbulent flux 

studies identical to those in section C-l to be performed at several of 

the sites. 

D. WORK TO BE DONE DURI~G REMAINDER OF GRANT PERIOD 

1. Prior to departure for Ti~et we intend to calibrate the response 

characteristics of the UVW anemometers and thermistors \~ith sonic anemometers 

and high-frequency thermistors. 
, 

. 

;~-----

40 

2... Field tests with_the s-olar photometer will be -carried out in 

Tucson and fort Collins. prior to departure for Tibet. 

3. Our estimates of IR radiation flux convergence above (rr.elting) 

snow surfaces will be refined. These analyses will then be submitted to 

the open 1 iter.atur_e. ]mplications on remote sens.ing frol" space and on-

-spring -runoff predictions and floodfngpotential win be studied. 

4. Short-period variability of radiation ar.d other energy flux 

components fr-Om all -data- sets- wn 1 t,e investigated using frequency spectrt;m 

analyses- techniques. 

5. ihe ROHPEX dat~ will be analyzed b detail to study the variabil ity 

of radiation- fluxes with changes in the synoptic conditions and in the mesoscale wind fields. 

6. The effects of radiation and precipitation on saturatior. point 

and mass characteristics will be investigated for periods with pronounced 

inflow into. and outflow from. convective systems in the ROMPEX 1985 data. 

7. With I.;.~' help of Dr. Torn Charlock \"e will compare our rad~ation 

and EBBT data with AVHRR data for the purpose of providing ground truth 

calibration. This work will be carried out for Rocky Mountain and Tibetan 

locations. 

8. Analysis of Tibetan rad~ation and surface energy burlget data 

which will become available by August lr~6. 

9. We intend to activate the Mt. Werner radiation station and an 

additional station at lower elevations after our return fro~ China. 

These data should give us more indications of interanilual variabil ity and 

of slope effects. 

• _ ... A _____ .~.~. ___ ._ 

4 
\ -

\ 

--. --------~.~-...... - --_._-- --.. -

---

4l 

REFERENCES 

Betts. A.1<., 1982a-: Saturation point analysis of moi-st convecti-ve 

overturning. ~. Atmos. Sci .• 39. 1484-1507. 

Betts. A.K., 1982b: Cloud thennodynamic moC:les in saturation pOint coordinates. ~. AUlos. Sci •• 39.2182-2191. 

Halberstam, I. and- J. Schieldge, 1981: Anomalous behavior- -of the 

atmospheric surface layer over- a melting snow pack. ~_ ~~ 

Meteor., 2-0, 255-265 -

lowe.- P.-R. and J.M. Ficke, 1974: Technical Paper. No. 4-74, Environmental Prediction Research Facility, Naval Post Graduate School. 

-Monterey, C.l\-

Reiter, E.R., E.A. Smith and J.D. Sheaffer, 19S5~ Measurements of 

the surf3ceenergy budget in the southern Gobi Desert of China, 

and in the Rocky Mountains of Colorado. Progress Report, NASA 

Grant NAGW6Ql for Feb. 1984 - Feb. 1985. 

~heaffer, J.D. and E.R. Reiter, 1986: The heat balance of a shallow 

mountain snow pack. For submission to Meteorology and Atmospheric Physics. 

Shen, Rujin and F. Huang, 1984: The spectral analysis of weather 

systems in the middle troposphere over tre Qinghai-Ziang Plateau 

and its adjacent regions in the summer of 1979. Selected papers of the Qinghai-Ziang Plateau Meteorological Experiment (QXPMEX). 

(3), Science Press. Bpijing. PRC. 

Shen. Rtljin. E.R. Reiter and J.F. Bresch. 1986: Numerical simulation 

of the development of vortices over the Qinghai-Xizang (Tibet) Plate~u. Sub~itted to Archives for Meteo. Geoph. & Biocl. 

Smith. E.A •• E.R. Reiter and Y. Gao. 1986: Transition of the surface 

energy budget in the Gobi Desert beth'een spring and summer seasons. 

Submitted to Journal of Climate and Appl. Meteoro •• Dec. 1985. 
'" 

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/ 

I 

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End of Document