AFGL-TR-81-0237 SIO Ref. 81-33

LEVEK;L )

SPRING AND FALL MEASUREMENTS

OF EUROPEAN VERY LOW ALTITUDEVOLUME SCATTERING COEFFICIENTS

L=k

Richard W. Johnson

Approved for public release; distribution unlimited.

Scientific Report No. 17August 1981

Contract No. F19628-78-C-0200OF[ Project No. 7670Ci A [ I F G RN I Task No. 7670-14

"A' : SAW. DIEGO [ I Work Unit No. 7670-14-01

V •Contract Monitor, Major John D. Mill, USAF

/L& Optical Physics Division

LA. Prepared for

Air Force Geophysics Laboratory, Air Force Systems Command.United States Air Force, Hanscom AFB, Massachusetts 01731

I NST• I, TI 1

OCEANOGRAPHY VISIBILITY LABORATORY La Jolla, California 92093

OTICDEC 2 8 1981

I iI j

tI .

Qualified requestors may obtain additional copies from the Defense Documentation Center. All i!others should apply to the National Technical Information Service.

t

r i

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L ••,•

SECUR I' Y CLA"0I00-eATION VF rH__'_ PAGE (Wh_ _ __a_ _ _.ne_ _)

REPORT DOCUMENTATION PAGE1 READ INSTRUCTIONSBEFORE COMPLETING FORM

. REPORT NUMBER GOVT ACCESSION NO• • RECIPIENT'S CATALOG NUMBER

AFGL-'R-_ !-0237 )__A r4 TITLE (and Subf(rI; 5. TYPE OF REPORI 6 PERIOD) COVERED

SPRING AN[) FALL MEASUREMENTS OF EUROPEAN Scientific- Interim

VERY LOW ALTITUDE VOLUME SCAITERiNC Scientific Report No. 1I6 PERFORMING ORO. REPORT NUMVIER

COEFFICIENTS SIO Ref- 81-33 -

7 AUTHOR(s) S1. CONTRACT OM OGRNT NUMIIER(.)

Richard W. Johnson F19628-78-C-0200

9 PERFORMING ORGANIZATION NAME AND .DDRESS 10 PROGRAM ELEMENT. PROJECT, TASK

University of California, San Diego AREA s WORK UNIT NUMMERS

Visibility Laboratory 62101FLa Jolla, California 92093 7670-14-01

II. CONTROLLING OFFICE NAME AND ADDRESS 12ý REPORT DATE

Air Force Geophysics Laboratory August 1981--Hanscom AFB, Massachusetts 01731 13 NUMBER OF PAGES

Contract Monitor: Major John D. Mill/OPA 1814 MONITORING AGENCY NAME & ADDRESS(If different from Controlitng Office) 1S. SECURITY CLASS. (of thle report)

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Approved for public release; distribution unlimited.

17. DISTRIBUTION STATEMENT (of the abetrct entered in BfocA 20, It different from Report)

IS. SUPPLEMENTARY NOTES

It. KEY WORDS (Continue on reverse aide It neceessla, ad Identify by block number)

Atmospheric Scattering CoefficientSurface VisibilitySlant Path Contrast Transmittance

20. AISTRACT (Continue on reverse side If neceeeary and Identify by block nuwber)

-- This report presents measurements of atmospheric volume scattering coefficients collected

during twenty-five low altitude flights made mostly during the Spring and Fall seasons of 1976and 1977 at four different European locations. The measurements were conducted during aninstrumented aircraft's final approach and landing at its staging airbase, The measurementswere made using a pseudo-photopic spectral response and thus are suitable I. :omparison withdata associated with standard visual determinations of airfield visibility.

DO ,j•. • 1473 moo-iot OP I NOV 6i 1SSOLTI. UNCLASSIFIEDS S/N 0102-014-6601 SECURITY CLASSIFICATION OP THIS PAOR ('3Sles Data UIffw*

UNCLASSIFIEDSECURITY CLASSIWC•P ION OF THIS PAUZ (Ulwme Dal ESheIe.d)

20. ABSTRACT continued:

-- 'The data illustrate that in twenty-two of twenty-five cases, there was little or no significantvariation in the value of scattering coefficient as the aircraft approached the surface from analtitude of several hunared meters.

I I

UNCLASSIFIED

SECURITY CLASSIFICATION OF THIS PAO'rhMeln DOa Entem4r6

SA,(,I.-IR •d ('• SIO Ref. 81-33

SPRING AND FALL MEASUREMENTS OF EUROPFANVERY LOW ALTITUDE VOLUME SCATTERING COEFFICIENTS

Richard W. Johnson

Visibility LaboratoryUniversity of California, San DiegoScripps Institution of' Oceanography 4

La Jolla, California 92093

Approved- Approved:

Roswell W. Austin, Director William A, Nierenberg,

Visibility Laboratory Scripps Institution of Oceanography

CONTRACT NO. F19628-78-C-0200Project No. 7670

Task No. '007-14Work Unit No. 7670-14-01

Scientific Report No. 17August 19dl

Contract Monitor

Major John D. Mill, Atmospheric Optics Branich, Optical Physics Division

:;;=- ....... Approved for public release; distribution unlimited.40.. 0e- 1on F'or. i

DTIC TARBUnannouice(A 0 Prepared forJustification ] D T IC

- AIR FORCE GEOPHYSICS LABORATORY ELECTEBy______, __ AIR FORCE SYSTEMS COMMAND DE 28 .. 8. E!"l D-ll Olutn/ ' UNITED STATES AIR FORCE, ,., ]UIIAvailability Codes HANSCOM AFB, MA$SACHUSETTS 01731

A ali d/orDDisat Specea D

5i

SUMMARY

This report, which describes portions of the Visibility Laboratory's Project OPAQUE effort, was prepared underAFGL Contract F19628.78-C-0200. It contains a presentation of 25 low altitude scattering coefficient profiles and relatedmeteorological data that were measured mostly during the Spring and Fall seasons of 1976 and 1977 at four differentgeographical locations. The measurements were conducted during an instrumented aircraft's approach and landing at fourof the staging bases associated with the overall OPAQUE program, Johnson, etaL -(1979). Similar data covering theWinter and Summer seasons of 1978 have been presented in an earlier repor<AFGL-TR-81-0154, Johnson (1981a).

The nephelometer measurements of total volume scattering coefficient which ar e-pesetedd'in this report were madeusing a pseudo-photopic spectral response having a mean wavelength of 557nm, and are thus suitable for comparison withdata associated with standard visual determinations of airfield visibility. The temperature and dewpoint temperaturemeasurements were made using an AN/AMQ-17 aerograph and a Cambridge Model 137-C3 Aircraft Hygrometer System.Measurements of horizon and terrain luminances which were also made during these aircraft descents are itot included inthis report, but are available in the Visibility Laboratory's basic data base should their subsequent analysis becomedesireable.

The reported data illustrate that in twenty-two out of twenty-five cases, there was little or no significant variation inthe photopic scattering coefficient a one approaches the surface from an altitude of several hundred meters. Thusmodelling approximations of low altitude haze properties based upon near surface measurements are in general appropriatefor the range of meteorological conditions extant during these flights.

FMID~MG PAGE BLAhENOT FILM~

v

TABLE OF CONTENTS

SUMWEARHE. SUM. ARY..................I.................. ......... I.............. .- .................................... v

4. LISTA OF RLLSETRATIONS...........................I.......I....................................................................

4.1 I R DUatandFiON........ y.............................................................................................I

2. 2 PRO escitofDURE IN TRUM eNTATIrphN...............................................................................2

4. Su3.pEATHE eSUM ary......tres..........................................................................................36

. DATA PRESENTATION............................................... ......................................................... 6 1

4.1 Su maData ...a...d..............S..m..ary....................................................... ............................ . 6

6.. CKDATAGEMNDISCU SSIO N........................................................................................... ...... 101

7. REFERENCES ....................... ......... ........ .............. ...................................................... 11

APPENDIX A: Meteorological Glossary & Abbreviations...................................................................... 13

APPENDIX B: VisLab Contracts & Related Publications ......... ......................................................... 14

waoMrID PAGE BLANK..NO FILb=

Vii

LIST OF TABLES AND ILLUSTRATIONS

Table No. Page

1.1 Fligh t Iden tification D ata ................................................................................................................... I

2. 1 Geographical & Seasonal Distribution of Low AltitudeScattering C oefficient Profiles ........................................................................................................... 2

3.1 Comparison of Aerodrome & C-130 Data Differences .................................................................... 4

3.2a Standard M eteorological Table, W unstorf, Germany ....................................................................... 4

3.2b Standard M eteorological Table, Vaerlose, Denm ark ...................................................................... 5

3.2c Standard M eteorological Table, M ildenhall, England ....................................................................... 6

3.2d Standard Meteorological Table, Lorient, France ...................................... 6

51 Summary of Conditions for Flights Profiles IllustratingLow A ltitude H aze Structure ...................................................................................................... 10

5.2 Comparison of Station Reported Visibilities andN ephelom eter D erived V isual R ange .............................................................................................. iJ

IAI

Fig, ,. Page

2 - q ync::,; O A,.Q t io t F ligh t l'ra ,k. ; ......................... 3.................................................. 3

.1 Appro,,:h Profile,, graphic and tabular. Wunstorf, Germ. . ................ 7

2 •-.ppr'i .�Pron!Ik.. galiiL and .~ular Vaerlose, Derin: ..

t ' l ,ic P' - ii-.'' . 'traphic ax d tabular, Mildenhall, Etv, . , . 9

""¼tpr,'.ch 'i.. P1 rifc -"n.d •ahuiar , L,,riett, Fran(:,., ............................. 9

Son+,111 roit¢e , and derived visual ,, .................................. ii

ix

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SPRING AND FALL MEASUREMENTS OF EUROPEANVERY LOW ALTITUDE VOLUME SCATTERING COEFFICIENTS

Richard W. Johnson

1. INTRODUCTION Spring-Fall report in conjunction with the previouslypresented Winter-Summer data set are intended to reduce

In the increasingly sophisticated world of electro- substantially the uncertainties in the structure of the nearoptical detection, search, and guidance, the requirement surface scattering coefficient profile.for establishing and predicting atmospheric influences onsystem performane continues ato develop nas a primary An identification of the flight data included in thisSSpring-Fall report is provided in Table 1,. 1As in theoperational necessity. It is in support of this general con- Sing-Fallmrer s preie table 11 Asuinth

tex tht te Vsibliy Lbortor incopertio wih, nd Winter-Summer set, these data represent measurementstext that the Visibility Laboratory in cooperation with, and made following each experimental data flight during theunder the sponsorship of tne Air Force Geophysics instrumented aircraft's approach and landing sequences.Laboratory has maintained an extensive program of air- The flights indicated in Table 1.1 are mostly from theborne optical and meteorological measurements. In recent OPAQUE 1, 11 and Ill deployments, Duntley et al. (1977,years this program has been c._,aducted as an independent 1978a and 1978b). For completeness, two flights made atbut cooperative effort [Johr )n et al. (1979)] in conjunc-tion with the NATO program OPAQUE (Optical Atmos- included with the summer of 1977 data.pheric Quantities in Europe), Fenn (1978). During thetwo year interval spanning the years 1977 and 1978, over80 missions were flown documenting the vertical structureof the visible spectrum tota' volume scattering coefficientin the lower troposphere. Since a thorough awareness of itIdentfication Data

this vertical structure is essential to the prt;diction of A-rodome- jh-it T LandingTmeatmospheric influences on contraest transmittance throu~gh___e.•_o. __,_ •_ Gr

this regime, these data have been presented in a series of Wunstorf. Germian 381 25 MNov 76 14 2803

andgN 985 392 23Nov 76 13 .13 2technical reports, the most recent of which is entitled "Air- S7m MSI. 39. 2 Nov 76 1 153sborne Measurements of Atmospheric Volume Scattering 394 iS No. 76 13 S 834Coefficients in Northern Europe, .'rmmer 1978", Johnson 3% 22 Nov76 i 05 50397 23 Nov 76 14 10 33

and GordGn (1980). 414 2 Jul 77 1 592 2

The optimum use of the experimental data 41 29Jul,77 1249 11

presented in reports such as Johnson and Gordon (1980) 416 4Aug77 103630

is surely to establish the baseline assessment of those opti- 419 4 Aug 77 1647 35

cal characteristics most influencing slant path contrast Vaerloe. Denmark 378 12 May 76 1148354

transmittance, and to develop from these assessments 5-46N' 12*20' 379 17 May76 1401 33

realistic predictive models. An initial effort in this model IBM MS 391 26Oct 76 13 27 37development, using both surface and profile data from the 421 10 Aug 77 14 37 54

OPAQUE program is discussed in Johnson et al, (1979), 47 2 Sep 7 1642 27and the further application of these data to contrast 479 26 Sep 73 131647

transmittance modelling is illustrated by Hering (1981). Mildenh, Englan., 377 10 May 76 1345 145222TN 0029E

As discussed briefly in the earlier issuance of this 1 MSLtwo report series, ie. AFGL--R-81-O154, Johnson(1981a), there has been a systematic gap in the data 4746N. F3*33V 400 4 Dhc 76 132742describing the vertical variations in low altitude atmos- 2m MSL 401 5 Dft 76 14S1O4

pheric scattering coefficients, which has been particularly i 402 6Di 76 is 526 16I41 4 Jul 77 1304352troublesome when addressing the performance of low 4-111 6 Jul ?77 1 5452

flying electo-optical systems. The data contained in this -

2. PROCEDURES & INSTRUMENTATION As noted in Johnson (1981a), a special measure-ment sequence was associated with most flights discussed

The general flight sequences conducted during the in these earlier reports, but its resultant data were notOPAQUE measurement program have been reported in included as part of the standard fight package, norseveral preceding reports as noted in bottom row entries included in those reports. These specialized data resultedof Table 2.1. In these earlier reports, measurements of from having the airborne optical, meteorological, and dataatmospheric volume scattering coefficient and natural irra- logging instrumentation operational during the aircraft'sdiance levels were presented for a broad variety of geo- landing approach and touchdown. Thus, since the aircraftgraphical and seasonal conditions. The general locale for was stagng out of an airfield generally remote from thethese data missions is illustrated in Fig. 2-1 which has standard OPAQUE flight tracks shown in Fie. 2-1, two

been abstracted from Johnson ci a!. (1979) The aero- separate and independent data sets were collected duringdromes at which the approach data were measured are most missions. The first was the rather extensive, multi-indicated by the symbol, *, whereas the flight track loca- spectral set of measurements made along the indicatedtions for the previously reported data are indicated by tracks between 6.0 and 0.5 kilometers in altitude, and theshort solid lines e.g. near Birkhof. second was the smaller more selective set made at the

The instrumentation used during these flight local staging base between about 0.7 and 0.0 kilometers.episodes has been described adequately in the previously This second set of measurements, made only in the photo-referenced reports [Johnson and Gordon (1980), etc.] and pic spectral band, is nominally referred to as thewill not be further elaborated upon herein. Suffice it to APPROACH data, and is the subject of this report, thesay that the entire instrument system was mounted on an second in a two report series.Air Force C-I30 aircraft and included, but was not limitedto,The general operating procedures employed durinthese APPROACH flight sequences were similar in nature

to those described in each of the reports listed ina. A multi-channel, multi-spectral nephelometer for the Table 2.1. A few specific, but minor, variationm in the

measurement of atmospheric total volume scattering procedure are discussed in the companion Winter-Summercoefficient and directional scattering functions, report, Johnson (1981a).

b. multi-spectral scanning radiometers for the measure- Post deployment data processing of these data hasment of sky and terrain radiances,Potdpo etdtarosinoftsedthsbeen handled in a manner similar to that described inc. a multi-spectral, two channel flat plate irradiometer Johnson and Gordon (1979). Calibration data for each

for the measurement of upwelling and downwelling deployment set is the same as was used for the parent datairradiance levels, and sets as referenced in each of the Related Data Report

d. meteorological transducers for the measurement of entries of Table 2.1. Readers are referred to these mot,-ambient temperature, dewpoint temperature and detailed reports for supplementary background informa-atmospheric pressure. tion where required.

Table 2.1.

Geographial and Seasonal Distribution ofLcw 4ltitude Scatterins Coelkient Proflm

Attempted Low Altitude Data SequencesAerodrome Locations,•

(see Fig 2-1) Spring, 19S" Fall, 1976 Summer 1977 a 1978 Winter 1978 Totals

SiIonlla, Sicily (SIG) 0 0 4 4

Lonent, France (LOR) 0 4- 3- 0 7

Menminngen Germany (MEM) 0 0 3 6 9

FWunsorif, Ge@mMny (WiUN) 3. S. 13" 4 25

Soatetbari., Nethetrands I 0 0 0 1

Mikdenhal, Eaujand (MIL) 4' 0 3 6 13

Vaerloe, Denmark (VAR) 2" 41 0 7

T-*al _1W to 30 20 10

Related A3IL.TR-7?-0163Data Reports AFOL-TR-77.0007 AFOL.TR-77-0239 AFOL-TR-WO0207 L AFrjL TR-79-0159 APOL.TR.79O028.

*Astenik todiestea those sub-sets rrom which the data in this report ware chosen.

2

a~t ODea OSE

MILDENHAL.L i

A M S T E W U N S T O

Y OVIL

ORE T

R I H

41.

Pn

\Ni

NV

•+d i t •r area•n Se'a

Fig. 2-1. Typical OPAQUE Flight Tracks.

3. WEATHER SUMMARY vided by the U.S. Air Force Environmental TechnicalThe weather conditions existing during each nf the Applications Center (USAFETAC) at Scott Air ForceTlghe weathodesrom coitos ch theAPPROACHprofis thae Base, and the National Oceanographic and Atmospheric

flight episodes from which the APPROACH profiles have Administration via the National Climatic Center in Ashe-been extracted are discussed in detail in Johnson and Gor-don, 1979 and 1980. These parent reports include data ville, North Carolina.from daily surface and 500 millibar charts, surface obser- Comparisons between the C-130 and RAOB air-vations, pilot reports, vertical cross sections and borne measurements oi temperature, dewpoint tempera-radiosonde launches. The bulk of these data were pro- ture, and the derived values of relative humidity for each

3

of the flights preceding these APPROACH episodes have Tale 3.1been made in the parent reports referenced above. How- Companmtn of Aerodrome A C.130 Ias Diffawnm (Measurements Duing LAvI,*)ever, several additional comparisons are summarized Rioat Temperature Disl ftihl [hilft-herein which relate more directly to the actual landing cir- Asiilomme Number A (TC) A* ('C) Ap (mb)

cumastances._ _

muntto" 331 +0.6 .21 -)93 415-2

Measured values of temperature (t), dew.oint tern- 97 +04 t 1i .4perature (dp), and atmospheric pressure (p), that were 414 +1.4 +57 .4

415 .15 +2.5 .4recorded at the exact moment of landing touchdown have 4s 2. .been compared with the equivalent values reported by t4h +3 +5.0 -hostbaerodromp forfifteenhof the fvlihtls reported in the 41: +1.4 +6. -.host aerodrome for fifteen ow the flights reported in Sec- 4 + .0 +6o -5tion 4. These flights were those for which the flight vaeos 371 -.09 .- .

dynamics data permitted a specific and unambiguous 379 +0.1determination of the exact instant of landing. Those 421 +0. +406flights for which the landing time was for any reason non- 422 +06 +49 .0

specific were not included in the comparison, even though Lorin. 402 +03 MSG .their data might in fact be suitable in all other respects. 410 +14 +14 -0These comparisons are listed in Table 3.1, In all cases the Mldnh-,I 37 +3 5 -1 sdifferences, At, A4, and Ap, represent the aerodrome .4

measurement minus the C-130 measurement. Overall is +10 OPQ I&Ii iO 111 -49Awe age rights - 0 -1 481 +4b

The data summarized in Table 3.1 indicate that the ^,,___ ___, ,-____+airborne and aerodrome measurements were on the aver- . A, is poritive 14/15am. implymn tame aetifwat a ,.ee

age in reasonable agreement, although not as closely the Winter-Summer data (Johnson. I1lsarelated as were the measurements during OPAQUE IV & 2.."p is neglative in all came impiyng sysitceitti offwt owu target then•

V (Johnson, 1981a). The temperature data indicate a sys- Winter-Summer data.

tematic difference of about IoC between the C-130 and A*ilfmQI.ll fowOPQIIIaerodrome measurements. The dewpoint and pressure Witer-Summer data. amatl and vab•ttlemeasurements indicate substantially larger offsets.

There was an instrumentation failure in thedewpoint hygrometer system during flight C-399 (6 De, measured differences, Adp, are similar in sign and magni-1976) that may have influenced the data during the tude for the OPAQUE , II, IV and V ,yata, while theimmediately preceeding OPAQUE 1I missions. Intermit- differences for the OPAQUE ill set are systematicallytent evidences of system failure were first noticed in the positive and large. There is no evidence of malfunction orflight C-395 (19 Nov 1976) data, and were deleted during calibration error associated with the dewpoint system dur-post-mission processing (Duntley etal., 1977). However, ing the OPAQUE III interval, so at this time thea residual artifact of this system failure, and its subsequent apparently anomalous behavior is unexplained.repair may be evidenced in the data of Table 3.1. In an Since the staging aerodromes for most of theseexamination of the dewpoint differences, one notes that flights were generally remote from the primary data tracks,the differences associated with the OPAQUE I and 11 selected supplemental weather data related specifically to

deployments, (flights 370 through 402) are all negative in the APPROACH site have been included herein. Shortsign and mostly small in magnitude. In contrast, the summaries of the meteorological observations taken at thedifferences associated with the OPAQUE I. deployment staging aerodrome, at or near the time of landing are(flights 410 through 422) are all positive in sign and gen- presented in Table 3.2. A glossary of the most often usederally larger in magnitude. One may compare the data in symbols is included in Appendix A for the reader's conTable 3.1 wit' the equivalent data presented previously in venience. All data were reported in Greenwich Civil Timethe companion Winter-Summer report, (GCT), which is equivalent to Greenwich Mean TimeAFGL-TR-81-0154. In this comparison it appears that the (GMT), the terminology used in Table 3.2.

Table 3.2a Wunstorf, Germany Standard Meteorological Data Sheet Lat. 52028N Long. 09*25'E El. 57m

Spring 1976

Weather and WindTime Visibility Obstructions Temp. Dewpoint Direction SpeedGMT Cloud Cover (Kilometers) To Vision ('C) (VC) (00-36) (mps) Remarks

F1lit No. C-3ut Date: 25 May 19761344 Clouzd Ntae Unknown 11.2 14.nl 7.0 L 1. Ceiling 500 Feet

4

I • • .. . . ..-- • .:•. i " ... .. -: -• . - " . . .. + ....

j•I Table 3.2t (Con't.) Wunsto;f, Germany

Fall 1976

Fight No, C-393 Date: 2 Noventifr 19761144 2000 11.2 13.0 7.0 22 6.61244 ?000 11.2 13.0 6.0 24 6.6Ighat No. C-394 Date: 18 November 19761444 15409 1.7 F- 5.0 2.0 07 2.5 Sky Overtast Type

MiMingFlight No. C-396 Date: 22 November 1976

1144 Cloud Data Unknown 11.2 RW- 5.0 0.0 29 6.6Flight No. C-397 Date: 23 Novcmber 1976

1444 Cloud Data Unknown 11.2 2.0 0.0 28 6.6 Ceiling 2500 FeetRain Shower DuringPast Hour

Summer 1977

Flight No. C-414 Date: 28 July 19771144 Cloud Data Unknown 11.2 19.2 11.2 33 1.0 Ceiling 8000 Feet

Flight No. C-415 Date: 29 July 1977

1244 Cloud Data Unknown 11.2 19.2 11.2 u 1.0 Ceiling 27000 Feet

Flight No. C-416 Date: I August 19771644 Cloud Data Unknown 11.2 19.2 13.2 31 6.1 Ceiling Unlimited

Flight No. C-418 Date: 4 August 19771044 Cloud Data Unknown 6.0 H 21.2 16.2 30 1.6 Ceiling Unlimited 4

Flight No. C-419 Date: 4 August 19771644 Cloud Data Unknown 4.9 H 23.2 16.2 03 0.5 Ceiling Unlimited

Table 3.2b Vaerlose, Denmark Standard Meteorological Data Sheet Lat. 55046'N Long. 12*20'E El. 18m

__ __ __ _ Spring 1916Weather and Wind

Time Visibility Obstructions Temp. Dewpoint Direction SpeedGMT Cloud Cover (Kilometers) To Vision (°Ci (*C) (00-36) (mnps) RemarksFlight No. C-378 Date: 12 May 19761200 25(Du-(DI (D 40.0 13.0 5.0 16 7.2Flight No. C-379 Date: 17 May 1976

1250 Cloud Data Unknown 11.2 16.0 5.0 12 2.5 1/8 Cover1320 Cloud Data Unknown 11.2 170 4.0 09 1.5 1/8 Cover

Fall 1976Flight No. C-391 Date: 26 October 1976

1420 E190 7.0 F- 08 5.6

Summer 1977Flight No. C-421 Date: 10 August 19771420 Cloud Data Unknown 11.2 21.2 14.2 15 4.1 Ceiling UnlimitedASO Cloud Data Unknown 8.0 H 20.2 15.2 17 4.6 Ceiling Unlimited

Flight No. C422 Date: I I August 19771150 Cloud Data Unknown 8.0 R- 19.2 162 01 2.5 Ceiling 8000 Feet1200 Cloud Data Unknown 8.0 R- 19.2 16.2 01 2.1 Ceiling 8000 Feet

Summer 1978flight No. C478 Date: 25 September 1978

1650 Cloud Data Unknown 11.2 R- 13.2 8.2 24 7.2 Ceiling 8000 Feet1750 Cloud Data Unknown 11.2 11.2 8,' 25 6,6 Ceiling Unlimited

Fligbt No. C-T79 Date: 26 September 19781250 Cloud Diat Unknown 11.2 14.2 8.2 24 7.3 Ceiling 7000 Feet1 J50 Cloud Data Unknown 11.2 14.2 8.2 23 7.2 Ceiling 9000 Feet

i'5

111k

Table 3.2c Mildenhall, England Standard Meteorological Data Sheet Lat. 52°22'N Long. 0029'E El. lore

Spring 1976

Weather and WindTime Visibility Obstructions Temp. Dewpoint Direction SpeedGMT Cloud Cover (Kilometers) To Vision (C) (1) (00-36) (trps) Remarks

7l110t No. C-377 Date: 10 May 1976

1400 Cloud Data Unknown 6.0 H 18.0 11.0 33 6.6 Ceiling 2300 Feet

Table 3.2d Lorlent, France Standard Meteorological Data Sheet Lat. 47"46'N Long. 03*33E El. 52m

Fall 1976

Weather and WindTime Visibility Obstructions Temp. Dewpoint Direction SpeedGMT Cloud Cover (Kilometers) To Vision (0C) ('C) (00-36) (mps) Remarks

Flight No. C-398 Date: 2 December 19761500 Cloud Data Unknown 8.0 RW- 8.0 6.0 32 6.6

Flight No. C.400 Date: 4 December 19761400 15()u-(I) E2300 11.2 7.0 3.0 30 4.11500 15(Du-(D E2300 10.0 6.0 4.0 28 2.6

Flight No. C-401 Date: 5 December 19761400 11.2 9.0 4.0 22 3.61500 25Du-(D/(D 20.0 9.0 3.0 24 3.1Flight No. C-402 Date: 6 December 19761500 Cloud Data Unknown 10.0 11.0 8.0 24 12.41600 Cloud Data Unknown 11.2 24 13.3+ Gusts to 20.55

Summer 1977

Flight No. C-410 Date: 4 July 1977

f 1500 3501200/@ 5.0 TRW. 21.2 19.2 24 3.1Flight No. C-411 Dhte: 6 July 19771200 3501200/0 50 26.2 19.2 06 3 6

4. DATA PRESENTATION Figs. 4-1, 4-2 and 4-3. The spring, fall and summer meas-4.1 Data and Flight Summary urements at each of four aerodromes appear grouped by,

location for ease of comparison.During the S:,ring of 1976 ,2 April through 26

May), thirteen flights were made in northern Europe, of The scattering coefficient profiles represent neasure-which eight contained ise3ble profile data. These data ments made continuously during each final descent whichwere reported in Duntley ei al. (1977). Of these thirteen, have been averaged vertically to yield one data point everyfour contained recoverable approach profiles. These four 30 meters in altitude. The measurements were all madeare listed in Table 1.1. using a pseudo-photopic spectral response having a mean

wavelength of 557 nm. Altitudes are reported in metersDuring the foilowing fall (25 October through 6 above ground level (AGL).

December) thirteen additional flights were made in thesame general areas, of which twelve contained useable 4.3 Supplementary Data Entriesprofile data. These data were reported in Duntley et al.(1978a). Of these thirteen, ten contained recoverable In the taibular displays, four additional cntries hiavrapproach data. These ten are also listed in Table 1.1. been included ts peripheral information. The first iL t1.c

local visibility reported by the station meteorologist wlriDuring the following Sunimet of 1977 (4 July abstracted from Table 3.2. The second is the ground te-,'l

through 11 August) another thirteen flights were accom- scattering coefficient (sW, as measured b) the C-130plishea and subsequently reported in Duntley etal. nephelometer, converted to approximate visual ran,:(1978b). From this third set of flights, an additional nine (VR) via the expressioncontained recoverable approach data. These nine arelisted in Table 1.1 as are two additional flights from the VR ý-3/sSummer of 1978 deployment (flights 478 & 479, 25 and as discussed by Douglas and Young (1945), Middlecin26 Sep 1978). (1952) and Gordon (1979). A comparison was anticipated4.2 Description of Data Tables and Graphs between these measured values and the visual estimate.;

made by the aerodrome meteorological observer, howeverThe flight data for the APPROACH sequences listed for eleven of the twenty-six landing intervals, the

in Table 1.1 are prescnted both tabularly and graphically in meteorological report was truncated at 11.2 km (7 statute

6

.+_.3

LG. _ WUNSTORF. GERMANY SPRING 1976

C- -381 Tow Vol. smw3n421 Cae.tui. 1a-

Almus. -__9 (m) AGL C311

450 2 762E-04420 251704

370 , ?IE.ONf300 2 76E11.0427O 272 1.04

2l0 2 337E-04so4 27 41P-04

10 20 271iE:04go 2 687E-0460 21 25E.0450 2 3)E-040 24006-04 ____ ____

Reson•d Vmblity (knm) 5 2 I

SI~umnallson (liv) 55 $400 ---- ___

a adm T~e 2001 1428

oio" 10TOTAL VOLUMNE SCATTERING COEFFICIENT

PER IM)

LEGEND2o- C-3,2c - C-393

-C-394 WUNSTORF. GERMANY FALL 1976C-396C--397 AToNI Vmlolr.m S•iutwmn Col11, (C-

2)

Z 0 AOL C392 C393 C394 C396 0247

5 4 171-0 2E-04 I190E740

420 3 44J4' 10.671109-280 461449 .10013 2224714-

2360 2104 16143 2E04 212244420 3 22IE104 374?E-03 I 114E,4 9 263S264

300 2226144 IE-4 3142 2OE3 4731.04 ,2023144

620 4 325E94 I 5113..04 3 22SEO14 I 154E-04 3 174•74.! 240 33,1IE'04 3Sl4E-04 32406E.03 I 17SEA 2 921E-1

210 5 353E-04 3 270E-04 3 914E703 I I6-E4 47.E-04IIso 11Em04 , I12E-0 4 O39E-03 2 1129.04 2 23E-0

I SluOna leEo) 2550 32-0 52ME00 1IO 2~ 23004

m 0 3 21611-m4 3 722E402 14025E25 2 02E5444

30 (PEE-04A 9 I 2l -04

0 55515-04 1670 .04- 11( 2 12 I17 111 Il

,1+ b.. (kii) 1•__Wll• 11 l 11

" • , ~ViwuW Runl (k.i) -- 6.0 'a1 91 26

:_. , l _ ___L ERMANY SUMER l7

TOToL VOLUVom SCSoToTERING COEFFICIENTtPER mi'

c!o.C-414C i+.Cts WUNSTORF, GERMANY SUMMER 1976

. -C-416 1- - -S-C-11, Tomll Vohlm SI- C.le (-I

*-C-4l9 Almude - -_____

(Ml )AL C414 C4125 C416 C418 0449

480 6401644 I 397E.3450 4 0451.04 63331.04 14521-05 794E-03

9 52 6050-04 632?01.0414105 8113300 52,1.04 67 - 0E.04 143 1621436690 01-04 117E104 E5510 2777143

220 523 l16.-04 b 426E-04 223E403 ;6E-03)00 3661E-04 6 122E.104 12121:53 174545270 42167E-04 60O01-04 22470-03 I1747E-03240 - 599E.104 2 92144 222E103 I 716E-032 2o 4021,-04 60OIE024 3 230E-04 5I2 2 E.-03 I 7441-0120 4 14221.04 7375064 5322144 42451103 729E-03

25.0 39201-004 55E41-4 0721-04 24116f-03 632E-03220 4 037E.04 5 411E-04 3+0iE44 . 2-OS 259E-03

*95 4 W41-04 17E0-04 3 074E-04 E40560 4611-0540 42206-504 57741E44 55431E-04 249671-0 26521E-0320 40641-04 60531-04 3 266E-04 I 440E-03 2449003

_ 0 4480F044 64066-04 3 2256-04 24221-03 2%59E-01

S Rmon'dV,.92,Is 2lm1 s222 5422 5222 59

IIu.intomw (l1.0 49300.: 580 )4200 53400 2

S 4464-ri(96 i 1211014) 459 2249 24E36 206 27

I ....

IO* , .

'0, -- -

TOTRL vOL1.N9 SCATTERINO COEFTICIENT

Graphic Tabular

FIg. 4-1. APPROACH Profiles - Wunstorf, Gemurty.

7 +

C-379 VAIRLOW DIENMARK 1ft35 197

.4) 5494-0

270 :m430 51446.0IN, 11594 1.5133

I29 14431.0'

5319631144 551010

IY44 31 1 I045343.4

b..a0 Cmi a) 7900 350

T5PC1 LK WTrERI, NI crriC I ENT(PER III

I ~VAEFLS33. DENM1ARK FALL. 1954

AkftftTil Vk .W.g fti0 Cooed" W 1

(0) An'. C391

39o. 75393.04

6.9503.035o. 490.04m530. 4937344

530. 43203.

40 47046.04

T0- 9 VVmLUMNkau 43~.RN C.rUI

VARILWIE. DENMARK SUMMOER 1977 A 5970

0:C -421 rous vp. Sooumnsft Co46ewI W 105* C-422 Afti~i4___ _ _C-479 m)oo AOL C421 C4322C' C

450. 3 937E-04 9.73SE450420 11,41104 100211.04j340 3W4.304 9,4951430 93721.03

304.41.04 07301.03 5001403.0

370.5444.04 7371.03 9 347343

550 4334 3440164494 3 55441340. 4.451144 5433244 9302E43 5334144410, M 4410 5 S43 .4 0043 43 53579-44111 431701104 1537114d394 0577343 5353044

:s. SS44 00 49 031431 15533.00. 33542106 153411,04 95931243 5043444~~ ~ ~~ 17414YW44y(o 4 50 ".0W54

V t.Sagm 3."U 4 6444 334 ý %E141

0 La 0q~,535 501437 [1U4 I_ 5537 542 25

150 10 1 U.2

TOiTAL VoLUPY SCATTERING COMMENIC3T

Graphic Tabular

Fig. 4-2. APPROACH Proffim - Vaeriame, Denmark.

MILD0041ALL. 11IOLAWD 103182 If%

tm) AOL C)" ______

15741044

540 1004W

42311,6114

410 12434M

Ia 112404)

110 10903

.10 :311434

020 11471143

0 1123114)

50' 5 Vwi m0 Z 041 24

(PER1 III Lm4"%o~n TIOT(G 1249

Lemm LORIENT, FRANCE FALL 1916

a - C-390 Tol.I Vokemme 113u01 C..o~k~~ (a-

-C-401 W,, AOL Cm0 C400 Cal Cat2

*C-4026w 01411.05570 00911405 64342M510 7)4)14 oem-s4M9 M41)14 012"15 1130430 :01474.4 6104 1130

4)0 a ISIMOS 01W"4 14514S44'Note 70:17015 o~S45 101

Scoi0 27 4 99345 "0M45 I 8144

Change 270 5021145 1 047344 0)0HIM 1 112145t

240 04045U, 0F4414 :0277305 210142 QWS0 1 001m 00ZVI 2044

mm5 0)145 "7E."0 ow-I* 9014 00 "1146

*0 0012113.

a,. 5 ,*o _____ 2 w 1011141d 0 II.,n~1o,(0l 9 2357. 310945 10 100U4

so 103SE-0 96I4 10 -__ I

L0, AO Mel CM41IIýx

C1 11011 Sm44

4O0 0)4104 041054

410 0745 92)2E4 0

400 6 041E.04 90511J44

200 711)7054 2115.0

270 7.173 .05 777203442 90)4044 7921144

1110 520.0311N 14)20 1020E103 9920144

00 :022W034 6,01941!4:

00 10 71-0

Graphic Tabular

P15. 4-3. APPROACH Proflesa Mildenhall, England & Lotient, France.

9

miles) i.e. VV>11.2 km was reported as 11.2 km. This Sinci the profile data upon which the Hering modelcommon aeronautical practice precluded the accumulation was developed terminated at 500 to 1000 ft. (150-300m)of as large a comparative data base as was desired, how- above the ground, the confidence with which one couldever there are seventeen instances of reasonable simul- specify the low level scattering properties from these datataneity that may be representative of the overall cam- was somewhat compromised. The data presented in sec-parison listed in Table 5.2. The reported visual estimates tion 4 of this current report, in addition to that presentedare also included in the supplementary data for the in Johnson, 1981a, specifically address the resolution ofreader's convenience, the uncertainty in this specification. They support the

The third peripheral item is the measurement of contention that in most cases, midday measurements of

total downwelling illumination at the time of landing. atmospheric volume scattering coefficient made within the

These measurements, also made in the pseudo-photopic 150-300m AGL altitude regime may be reliably extrapo-

spectral band, are reported in units of ha (Iumol/m2 ) and lated down to the surface with only marginal risk of

can be compared directly with standard tables of natural significant error within the context of overall model per-illumination such as Brown (1952) by utilizing the location formance. Of the twenty-five scattering coefficient profiles

and time information listed in Table 1.1. These specific illustrated in Section 4, only four, two in the Fall and two

comparisons however, have not been included in this in the Sutmmer seasons show marked structure within thereport. low level haze. Thus, as summarized in Table 5.1, there

are only seven flights out of the total fifty-one reported inThe final supplementary entry is the time of landing these two companion reports which illustrate clearly dis-

touchdown. These times, indicated in GMT, have been cernible variations in the magnitude of the near surfaceextracted from Table 1.1 and truncated to hours and haze profile.

ff minotes only.There were twelve instances within the twenty-five

landing episodes where the station visibility was reported5. DATA DISCUSSIONas less than 11.2 km and therefore could be approximated

As noted in the introductory remarks of section I in by the derived value of visual range (VR - 3/s) as dis- =boththi reortand t'sWiner-umme copanon, cussed in Section 3. These twelve values plus the five

Johnson, 1981a, the accurate specification of the atmos- available from the companion Winter-Summer report areJ volume scatte characteristics at vr low alti- summarized in Table 5.2 and illustrated in Fig. 5-1. TheS pheric vouescattering cactrsisat verylo ati

tudes can be critical to the determination of slant path data points for two flights 378/VAR and 398/LOR have

contrast transmittances through this near surface regime. been omitted from the graphical display since they areIt is of major importance for one to know, or be able to substantially beyond the scale of the plot at visual ranges ireliably deduce, the occurrence of major variations in the greater than 20 '::n. Whereas one might expect bettervertical structure of the atmospheric aerosol. The flight comparisons between these pseudo-simultaneous deteri-data representea in the earlier referenced reports, Johnson nations, there are good and sufficient reasons to anticipate

and Gordon, 1980 et., have provided extensive samples a fair degree of spread within this small uncontrolled sam-

of these variations and thus have served as the case stu- pie. Johnson (1981b). The trend in the comparison is

dies required for developing reasonable modelling reasc nable for the most part, although the data tend to

representations. A preliminary discussion of a proposed illustrate clearer derived values than those reported by sta-modelling technique was originally discussed in Johnson tion observers.

et aL 1979, has been amplified upon in Johnson and Her- As an artifact of the site-season mix within theing, 1981, and is described further in Hering, 1981. o,,erall data set, only the Wunstorf site has a substantial

Table S.1.Summary of Conditions for Fliglts Proffinl Illustrating Low Altitude Haze Structure

DewpointSurface Haze Top Wind Depression

Scat Coef Altitude Direction-Speed Obstructions STA C- 130

FLT NOISTA Season (m-1

) (m AGL) (deg) • mvc -I to Vision (C) ('C)

435/MEM Winter 2.6 E-4 100 180- 3.6 6 5.1436/MEM Winter 3.8 E-4 ISO 060- 2.5 8 6.2439/MEM Winter 6.4 E-4 100) 030- 15 H 5 1.2

394/WUN Fall 3.3 E-3 350 070 - 25 F- 3 0.7"397/WUN Fall 1.7 E-4 350 230-66 RW 2 0?2

410/LOR Summer 1.5 E-3 300 240. 3.1 TRW- 2 2.0411/LOR" Summer 6.3 E-4 I1 , 060- 3.6 7 79

Haziness increasing with increasing altitude.

"CAM-137 Dewpoilnt Hygrometer failed during the OPAQUE II deployment, and examination of thedewpoint temperature memurements indicates the high problability of an amplifter offs equivalenit toapproximately MC during the Interval peaeding the failure These indicated dewpoint depreslonstherefoe may be too small

1o

Table 5.2. profiles are remarkably constant within this near surffeCompaiaow of Station Reported Visbilitie, regime. As noted in the previous Winter-Summer report,and Neapielometer Derived Visual 3*- 8 these data by and large represent midday measurements

T eporteDer] uved and thus ase based in favor of good convective mixingVisibilSty Visu•,, Rm induced by solar heating of the ground surface.FLT NOISTA Smown (kin) i (kin)

394/WUN Fail '76 1.7 0941|/WUN Sum, ner '77 6.0 2.1 5.1 Su•ulma419/WUN Summer '77 49 1.94/WUN Winro '78 2.5 2 Twenty-five vertical profiles of fte photopic atmos-37VVAR Fall '76 40 216 pheric volume scattering coefftcient represnting Sprlin,391/VAR Fall '76 70 4.3 Fall and Summer conditions at four septrate European421/VAR Summer '77 8.0 5.6422/VAR Summer'77 .0 4.6 aerodromes have been presented for evaluation. The

basic question to be addressed is whether or not the402/LOR Fall '76 10O 294 scattering coefficient profile remains reasonably constant as4021LOR Fall "76 10 12.0

410/LOR Summer '77 5.0 2.0 one approaches the surface from an altitude of several411/LOR Summer '77 5.0 4.8 hundred meters, and if not, what is the character of the460/SIC Summer '78 5 12 vertical structure. These data indicate that in twenty-one461/SIO Summer '78 8 13 out of twenty-five instances, the profile is essentially con-

stant in value and thus the modelling approach proposed377/MiL Spring '76 6.0 .4 by Hering (1981) is in fact an appropriate procedure.475MIL Summer '78 Il 13 When combined with the data from the companion4391MEM Winter '78 5 5

Winter-Summer data set, Johnson (]981a), forty-sevenout of fifty-four (87%) of the profiles are represented bystable, nearly constant values of scattering coefficient

20 1 i 1 1 1 1 , 1 1 within this very low altitude regime.

1_ - The identification of the conditions resulting in theseven profiles showing variations within their vertical

16-- structure will require additional analysis. A supplementaryset of precision local meteorological observations including

S 2// local trajectories would be beneficial.

6. ACKNOWLEDGEMENTS

o-/ This report has been prepared for the Air Force8 -, SIG

0 MEM Geophysics Laboratory under Contract No.0 F19628-78-C-0200. The author wishes to thank the

X + MIL members of the Visibility Laboratory technical staff forU 4 - X x VAR their assistance in preparing these data, and in particular

4/ LOft to acknowledge the contributions of Mr. Nils R. Persson,S •- our senior computer specialist, and Ms. Alicia G. Hill and

20/ Mr. John C. Brown our specialists in computer assisted0 4 a 2I I 16 20 document preparation.

REPORTED VISIBILITY (KM)7. REFERENCES

Fig. 5-1+ Comparison of reported visibilities and derived visual ranges.

Brown, D. R. E. (1952), Natural Illumination Charts,Report 374-1, Project Ns-714-100, Department of

number of profiles appearing in both of these two com- the Navy, Bureau of Ships, Washington, D.C.panion reports. Thus, an enlarged commant upon the Douglas, C. A. and L. L. Young (1945), "Development ofpossibility of a higher seasonal variation in scattering Transmissometer for Determining Visual Range",coefficient existing during the Winter, as indicated in the U.S. Department of Commerce, Civil Aeronautics .Winter-Summer report, is probably not justified. Within Administration, Washington, D.C., Technicalthe composite nineteen flight Wunstorf set. 4 Winter, Development Report No. 47.1978, 4 Summer 1978, 6 Spring and Fall 1976, and 5 Duntley, S. Q.. R. W. Johnson, and J. 1. Gordon (1977),Summer 1977; there does not seem to be any significant "Airborne Measurements of Atmospheric Volumedifference in the degree of scattering coefficient variation Scattering Coefficients in Northern Europe, Springas a function of season. There is however a broad spread 1976," University of California, San Diego, Scrippsin the range of values encountered, as one might well Institution of Oceanography, Visibility Laboratory,expect, and in all but two of these nineteen instances, the SIO Ref. 77-8, AFGL-TR-77-0078.

,,

Duntley, S. Q., R. W. Johnson, and J. I. Gordon (197h), Symposium ol the AGARD Electromagnetic Wave"nArborne Measurements of Atmospheric Volume Propagation Panel on Special Topics in Optical Propa-Scattering Coefiocients in Northern Europe, Fall gation, Monterey, California. (April, 1981)1976," University of California, San Diego, Scripps Johnson, R. W., W. S. Hering, J. 1. Gordon B. W FitchInstitution of Oceanography, Visibility Laboratory, and J. E. Shields (1979), "Preliminary Analysis andSiO Ref. 78-3, AFGL-TR-77-0239. Modelling Based Upon Project OPAQUE Profile and

Duntley, S. Q., R. W. Johnson, and J. I. Gordon (1978b), Surface Data", University of California, San Diego,"Airborne Measurements of Atmospheric Volume Scripps Institution of Oceanography, VisibilityScattering Coefficients in Northern Europe, Summer Laboratory, SIO Ref. 80-5, AFGI.-TR-79-0285.1977", University of' California, San Diego, Scripps Johnson, R. W. and J. 1. Gordon (1979), "Airborne Meas-Institution of Oceanography, Visibility Laboratory, urements of Atmospheric Volume ScatteringSIO Ref. 78-28, AFGL-TR.78-0168. Coesffcients in Northern Europe, Winter 1978",

Fenn, R. W. (1978), "OPAQUE - A Measurement Pro- University of California, San Diego, Scripps Institu-gram on Optical Atmospheric Quantities in Europe, tion of Oceanography, Visibility Laboratory, SIOVol. I The NATO OPAQUE Program", Special Ref. 79-25, AFGL-TR-79-0159.Reports No. 211, AFGL-TR-78-0011, Johnson, R. W. and J. 1. Gordon (1980), "Airborne Meas-

Gordon, J. 1. (1979), "Daytime Visibility, a Conceptual urements of Atmospheric Volume ScatteringReview", University of California at San Diego, Coefficients in Northern Europe, Summer 1978",Scripps Institution of Oceanography, Visibility University of California, San Diego, Scripps 1nstitu.Laboratory, SIO Ref. 80-1, AFGL-TR.79-0257. tion of Oceanography, Visibility Laboratory, SIO

Hering, W. S. (1981), "An Assessment of Operational Ref. 80-20, AFGL-TR-80W0207.Techniques for Estimating Visible Spectrum Contrast Johnson, R. W. (198,a), "Winter and Summer Measure-Transmittance", Paper presented at the 25th Annual ments of European Very Low Altitude VolumeTechnical Symposium of the Society of Photo-Optical Scattering Coefficients", University of California,Instrumentation Engineers, Seminar on Atmospheric San Diego, Scripps Institution of Oceanography, SIOEffects on Electro-Optical, Infrared and Millimeter Ref. 80.00, AFGL-TR-81-0154.Wave System Performance, San Diego California. Johnson, R. W. (1981b), "Daytime Visibility and(Aug. 1981) Nephelometer Measurements Related to its Determi-

Johnson, R. W. and W. S. Hering (1981), "Measurements nation", ATMOSPHERIC ENVIRONMENT, 15,of Optical Atmospheric Quantities in Europe and 10/11, 1835.Their Application to Modelling Visible Spectrum Middleton, W. E. K, (1952), Vision Through the Atmo.Contrast Transmittance", Paper presented at the 29th sphere, Chapter 10, University of Toronto Press.

12.

12

APPENDIX A

METEOROLOGICAL GLOSSARY AND ABBREVIATIONS

SKY AND CEILING VISIBILITY (VV)

Sky cover symbols are in as-ending order. Figures pro- Reported in kilometers.ceding symbols are heights in hundreds of feet abovestation. Sky cover symbols ate:

WEATHER AND OBSTRUCTIONTO VISION SYMBOLS

O Clear: less than 0.1 sky cover

(D Scattered: 0.1 to less than 0.6 sky cover A Hail IF Ice fog

0 Broken: 0.6 to 0.9 sky cover AP Snall hail K Smoke

(P Overcast: more than 0.9 sky cover B9 Blowing dust L Drizzle

- Thin (when prefixed); light (when suffixed) OI Blowiig sand R Rain

-- Very light (when suffixed) BS Blowing snow RW Rain showers

-X Partial obscuration: 0.1 to less than 1.0 sky hidden D Dust S Snow

by precipit.Jion ar obstruction tu vision (bases E Sleet SG Snow grains

at surface)EW Sleet showers SP Snow pellets

X Obscuration: 1.0 sky hidden by precipitation or

obstruction to vision (bases at surface) F Fog SW Snow showers

GF Ground fog T Thunderstorms

H Haze ZL Freezing drizzle

Letter preceding height of layer identifies ceiling layer IC Ice crystals Z Freezing rain

and indicates how ceiling height was obtained. Thus:

A Aircraft CLOUD ABBREVIATIONS

B Balloon (pilot or ceiling) Ac Altocumulus Cs Cirrostratus

D Estimated height of cirriform clouds on basis of As Altostratus Cu Cumulus

persistencyCb Cumulonimbus Ns Nimbostratus

E Estimated height of noncirriform clouds CCc Cirrocumulus Sc StratocumulusM Measured

Ci Cirrus St StratusR Radiosonde balloon or radar

U Height of cirriform ceiling layer unknown WIND

V Immediately following numerical value indicates a

varying ceiling (also used with varying visibility) Direction in ten's of degrees from true north, speed in

W Indefinite, sky obscured by surface base phenoirenon. meters per second (rps). A 0000' indicates calm. A

e.g. fog, blowing dust, snow 'G" indicates gusty, A '0" indicates squall. Peakspeed of gusts, when reported, follows G or 0. The

contraction WSHFT in remarks followed by time group

(GMT) indicates wind shift and its time of occurrence.

RELATIVE HUMIDITY (RH) Examples: 0109 is 010degrees. 9rmps.

3607G11 is 360 degrees. 7 rps, peakReported in percent and computed from temperature and speed in gusts of 11 rps.

dewpoint.

MSG Data missing in original source.

13

F7>VISIBILITY LABORATORY CONTRACTS IDuntltw, S Q R~ W Johnson ndlt 1. I (ijdotl%~

ADRLTDPUBLICATIONS: Sbhon Re. 78-3, AFGL-rR -ul3 oln

"Airbore Meauremets ofOpticl Atmspherc Satering Coetlkients in Nrtctiý Eutopc, SumalProprtis i Souher Gemany Unverity f Cti-19~76" 1 niversity of' (alilorni- dti Sn Ditcgc, Scripps

Fornia atSan Dieg, F19p628- ti76io4o401en0g Institution of' OceanographyN, NVisihiih! 1 Laboratorv.raph, Vsiblit Laoratry,510 Ref 7264,SIO Ref. 78-28, AFGiL-TR1- 77.0239

AFCRL72.025. Iuntley, S. Q., R. W. Johnson, and I. I Ooirdov (19781,Duntley, S. Q., W. W, Johnson, and J. i. Gordon (1972), "Aithorne Measurements of tosptLLW k Vtostuhnr

"Airborne adroiBsdMeasurements of' Oppic- Proophei cterties, Summary asnd Revliew I-'~ll e SunivcrialAmshrcProperties in Cot~r ermntr"l UniewrMetiof , Cai 97,UieslCalifornia at San Diego,, Scripps Isiuino

UieitofClforniia at - San Diego, Scripps Instituino'cao-Intuioof Oceanography , Visibilit\ Laborator>,SC)Rt '.

tuino caoraphy, Visibility La b~oratory, SIO e'726,SORl 8-, AFGL-TR-78-028b,AFRefL271- FR722-046. Fintch, B. Q., T. W. Cie 17ss 191), "Masurement1 ( of ero

Duntley, S. Q., R. W. Johnson, and J. I. GordJon (1972). sAol Si eaDstributints in the LowrTopshreoe"Airborne adGoa-ae Measurements of Optiaftopeic Nroprthern Eummrope", evcwI University o lfri.%ca Atopei Properties, umr and Review Nw exc", Unlversity at San Diego., Scripps Institution ofOenorp.UiestofCalifornia at San Diego, Scripps Instituio Ocanfapy Visibility Laboratory, SIO Ref 71189AG-TRtuino Oceanography, Visibility Laboratory, SIC' Ref. 72-2, 80-0192Rf727,AFCRL-72-0493. Gordon, B. W., T. S. Haris(91, Sr. eands.uremDntseyof1W'3),

Duntley, S. Q., R. W. Johnson, and~ J. 1. Gordon (1973), "MSieaDsuring ton Earthto-pae Contras Tranosmpthnereoe"*Airborne Measurements of Optical Atmospheric fromthGrond Statio n iversiOt. 12, C317-or324.Propertiesi Southerynd Il vinoi", University of' Cai- Godn, Dieg, SC. p F Indg stitutiand S. Q.Duntley1975)Clfornia at San Diego, Scripps Institution of Viaog siignl-igty Naooramor, J Opt Sof.118 Am. 5,11-TOcaoraphy, Visibility Laboratory, SIO Ref. 73-824, 8-18.AFCRL-TR73-0593. Gordon, J. I., (1979) "HaytimeSr, n VSibliy A. ontlep093)

Duntley, S. Q., R. W. Johnson, and J. 1. Gor'Ion (1973), RMevsuinw g UiearsityofS Caionrnasat SransDiegoc"Airborne adGon-ae Measuremetnts of Opti-a Soshri ripm Irondstittions of.p Ocaorphy. Visibility24alAmshrcProperties in Southern Illinois", UnvritabCai oratory. I, SC. RF. Edg-to, aFGd S.Q- utR-7- (1975),

Uiiest fClforniia at San Diego, Scripps Instituino cao- Johgnsongh R.ora" J and. S.IGron. (179. "Airbornetu~no 'caoraphy, Visibility Laboratory, SIO Mesuemnt of24 Atophrc1oue8cttrnKef. 74T-2573CQL-TR-4-29. Coroefficients in99) orthen Europeit, WiCn:eter198"

Duntley, S. Q,, R. W. J.ohnso~n, and J. 1. GordIon (1975), eiw, University of California at San Diego, SrpsIsi"Airborne n run-ae Measurements of Optica Atopcripp Inttution of Oceanography, VisibilityLaotrySIcalpcAtmospheic W rsterntWeshingSothnUiers lityofs" Laborat79-2, AFGL-Ref. 8-01, 59.T-9-2Uiiest fCalifcrn ia at San Diego, Scripps Instituino Johnson, R. W., WaSHrnd , J. 1. Gordon, B179. "A itchnettoe of 'kgranohv ph, Visibility Laborator.SORef. 75-24 Man.s.uSheldns (1979to"phrecVlmnr Analysrisn&Rf742,AFCRL-TR-74-3414. ModeiiengtBse Uporten P urojet OPQEPoilter and8

')untley, S. Q., R. W. Johnson, and J. I. Gordon (1975), ufc aa, University of California at San Diego, ScipIIsi"Airborneý M.easuerements oif Optical Atmospheric Srps nitution of Oceanography, VisibilityLaotry I

L . ~~~Properties i Wstern Washand gton.~ ", University of Laborat-ry, SIO -Ref. 80-59.FLT-7-25California at San Diego, Scripps Institution of Johnson, . W., W. and erng J. 1. Gordon (90, "iBorn Meas-chOceanography, Visibility' Laboratory, SIO Ref. 75.26, urmntd of Atmoiel s(17)"PhericmVolum Scatterin&AFCRI.-TR-75-04S7. Codellising Northerpn Europet SPAUmmroier 1978"

Duntley, S. Q., R. W. Johnson, and J. 1. Gordon (1976), ufc aa, University of California at San Diego, SrpsIsi"Airb. t'e Measurements of Optical Atmospheric Scip nttution of Oceanography, VisibilityLaotry 0Properties, Sinm Notend G vermaNy", University of Laarai-y Ref. 80-20 FL-R80-5,0207. 79025Clfornia at San Diego, Scripps Iinstitution of Oeng Johnson, Rt. W, n .1.Gro (1980a), "Winerbndrumer Mefrsu-Ocaoraphy, Visibility laboratory, SIO Ref. 75.-26, urments of European heryioc lttd Volume SatrnAFGRL-TR-76-01 88. Sfcattering Coefficernt, Euniverst ofme Caliorni,

Duntley. S. Q., R. W. Jo'hnson, and J. 1. Gordon (1977),UnvriyoCafriat San Diego, Scripps Instituino-caorpy I"Airborn-e Measurements of Aptmopica Vtolumeri Re. %-0; FLTR8-1

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