2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 Hence it is with unusual satisfaction that I am able to report the

2

SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL.

94

SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94, NO.12, PL.2

View Showing the West and North

Sidesof

the Observatory

AND the

Dwelling,

Mount

St.

Katherine

NO. 12

MOUNT KATHERINE

STATION

ABBOT

₃ struments, almost, indeed, adequate to observe the solarconstant of radiation, and they spent weeks and even

months

in observing at

some

of the

more

promising stations. In this

way

they visited the

Cape Verde

Islands,

many

peaks in

South-West

Africa, and finally

Mount

St. Katherine, about lo miles

from Mount

Sinai in Egypt, havingan altitude of about8,500 feet.

No

station visited proved as promisingasthelastmentioned.

Mr.

and Mrs.

Moore

observedthere on about 100 days duringthe

months

of March, April,

May,

June, andJuly,1932.

As

aresultI

was

convincedthat

Mount

St.Katherine hadafairchanceofprovingtobe nearly as satisfactory as

Montezuma

inChile for solar-constant observations.

With

further support

from Mr.

Roebling, and withthe generous gift

from

the National Geographic Society of the apparatus which had formerly beeninstalled at

Mount

Brukkaros,

Mount

St.Katherine

was

occupiedinthe

summer

of 1933,andregularobservations of the solarconstant of radiationwere beguntherein

December

_1933.

It is a pleasure to acknowledge the great aid received and the cordial relationswhich haveprevailedatalltimeswithHis

Eminence

Porphyrios III,Archbishop of

Mount

Sinai,and withthe

monks

of St. Katherine's Monastery, under his direction, on

Mount

Sinai.

During Mr.

and Mrs. Moore's reconnaissance, the

monks

placedan existing structure on

Mount

St. Katherine at the disposal of these observersand brought

them

supplies.

When

a permanentoccupation

was

undertaken, the authorities of theMonastery built the observa- toryand living quarters of stone on Gebel Zebir, a spur of

Mount

St. Katherine, built trails, and developed water.

They

stillcontinue to transport suppliestothestation

from

the

Red

Sea,and arehelpful inuncounted ways.

The

station

was

built, equipped, and occupied under the supervi- sion ofHarlan

H.

Zodtner,ourfielddirector, assistedby Frederick A.

Greeley. Mrs. Zodtner and their

two

children

accompany Mr.

Zodt- ner,andshe

makes

a

home

forthe expedition.

Plates I and 2

show

the inhospitablemountainsite, andthe build- ings erected bythe authorities of the Monasteryforthe instruments andobservers.

Records of the observations

made from December

1933 to April 1935 have

now

been reduced under the direction of

my

colleague, L. B. Aldrich.

A

short

method

similartothosein useatourstations

Montezuma

and Table

Mountain was

developed by

him

forSt.Kath- erine. Also

some improvement

based on additional observations has recentlybeen

made

by

him

in the reduction tables for

Montezuma,

and

more

correct

new

values, differing by a

few

thousandths of a

4 SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL. 94 calorie

from

thosefirstcomputed, have beensubstituted for the broad- casted

Montezuma

observations of the solar constant of radiation for the past

few

years.

Our

firstcare

was

to reducethe St. Katherineresults tothe same average scaleas

Montezuma. The

scaledepends ontheadoptedcon- stantsof the pyrheliometers, and

no

favorableweather for determin- ing these

was

available in

Washington

before the departure of the Egyptian expedition.

The

scale correction

was

obtained by comput- ing the average difference for i8o individual days of good quality at both stations.

The

^resulting

mean

difference, 0.034 calorie,

was

subtracted

from

all St. Katherinedaily values.

Next

the average

mean

difference of the daily results of good quality

common

to the two stations

was

computed for each

month

without regard forsign,as

shown

intable i,together withthe

num-

Table I.

—

Monthly Averages of Daily Differences, Montezimia Minus

St.Katherine

Year Jan. Feb. Mar.Apr.MayJuneJuly Aug.Sept. Oct. Nov. Dec.

(MeanValue 7

'^^^

1Numberdays 4

{MeanValue 4 8 7 14 12 9 5 7

711

7 8

Numberdays 4 7 10 i3 S

n

'9 19 ^6 14 (i 8 1935^• MeanValue 13

Numberdays 9

General mean, 182days, 0.0086calorie.

ber of days represented in each mean.

The

values given are in thousandthsofacalorie.

Thus

the general

mean

^{of allthe}daily dift'erences, numbering 182 inallandcovering a period of 17months,isapproximately_{0.45 per-} cent of the solarconstant, taken as 1.940 calories. Omitting 6 aber- rant values,itis0.0079calorie,orapproximately0.40 percent. Divid- ing by

V^, we

^find the average daily accidental error of a single stationis0.30 percent.

It

was

particularly important to determine whetherthe daily dif- ferences,

Montezuma minus

^{St. Katherine,}

show

a yearly period.

Accordingly

mean

values of

them

were computed monthly having regardto sign.

The

resultsare givenin table 2.

They

areexpressed inthousandthsofacalorie.

Table^2.

—

Monthly Averages of Daily Differences, Montezuma Minus St. Katherine Takenwith Regardto Sign

Year Month Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

1933 Mean +i

1934 Mean

+3-4

^{o +14 +12 —4 +1} +2 -3 -9 +4 +2

1935 Mean +13 —i —6

—

6

4

SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL. 94 calorie

from

thosefirstcomputed,have beensubstituted for the broad- casted

Montezuma

observations of the solar constant of radiation for the past

few

years.

Our

firstcare

was

to reducethe St. Katherineresults to the

same

average scaleas

Montezuma. The

scaledepends onthe adoptedcon- stantsof the pyrheliometers,and

no

favorableweather for determin- ing these

was

available in

Washington

before the departure of the Egyptian expedition.

The

^scale correction

was

obtained by comput- ing the average difference for i8o individual days of good quality at both stations.

The

resulting

mean

difference, 0.034 calorie,

was

subtracted

from

allSt. Katherinedailyvalues.

Next

the average

mean

difference of the daily results of good quality

common

to the

two

stations

was

computed for each

month

without regard forsign,as

shown

in table i. togetherwiththe

num-

Table I.

—

Monthly Averages of Daily Differences, Montezuma Minus

St.Katherine

Year Jan. Feb. Mar.Apr.MayJuneJuly Aug.Sept. Oct.Nov. Dec.

(IMeanValue 7

'''^^

1Numberdays 4

JMeanValue

487

^{i4 12}

9577 ^{n "8}

'^''^

(Numberdays 4 7 'o 13 5 11 19 19 26 14 'i 8

(MeanValue ¹³ 12 8 12 '^^^

(Numberdays 9 4 7

n

General mean, 1S2days, 0.0086calorie.

ber of days represented in each mean.

The

values given are in thousandthsof acalorie.

Thus

the general

mean

ofallthedaily dift'erences, numbering 182 inallandcoveringaperiod of 17months,isapproximately0.45 per- cent of the ^solarconstant, taken as 1.940^calories. Omitting 6aber- rant values,itis0.0079calorie,orapproximately0.40 percent. Divid- ing by

V^, we

find the average daily accidental error of a single stationis0.30 percent.

It

was

particularly important to determine whether the daily dif- ferences,

Montezuma minus

St. Katherine,

show

a yearly period.

Accordingly

mean

values of

them

were computed monthly having regardto sign.

The

resultsare givenin table2.

They

areexpressed inthousandthsofacalorie.

Table 2.

—

Monthly Averages of Daily Differences, Montezuma Minus St. Katherine Takenwith Regardto Sign

Year Month Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.

1933 Mean +'

1934 Mean

+3-4

^{o +14 +12 —4 +1 -f2 -3 -9 +4 +2}

193s Mean +13 —i —6

—

6

Fig.I.

—

Comparisonofsolar-constantvaluesfromtwo stations 7,000 milesapartonopposite sides of theEquator. Onepercentequals fourverticaldivisions.

NO. 12

MOUNT

ST.

KATHERIXE

STATION ABBOT ₅ Exceptfor the largepositivevalues found sporadicallyinJanuary 1935, andApriland

May

1934, there seemstobenoevidence of ap- preciable yearly periodicity.

For

the differences are

no

largerthan would be expected as the result of unbalanced experimental errors.

During

the

months

justexcepted

somewhat

unsatisfactoryconditions prevailed at one or both stations. This general conclusion ishighly satisfactory. It

means

thaton

good

daysthe differences ofexposure ofinstrumentscausedby unequal altitudesof the sunandthediffer- ences ofprocedureand magnitudesinallowing foratmosphericlosses at

two

independent stations in opposite hemispheres, separated by nearlya third thecircumferenceof the earth,produce nodifferential periodicityinexcess of

two

or three tenths of i percent of the solar constant of radiation. Accordingly the yearly range of systematic error forone station,being half as great as the combined ranges of

two

stations, is surely negligible.

Summer

with its increased heat, haziness,andhumidity,opposed bywinterwithitsgreatercold, clear- ness, and dryness, and besides these the observation of the sun at different angles above the horizon at the constrasted stations, have altogether failedtoproduce differences inthe results which indicate that systematic errors are certainly appreciable.

Finally, the individual dailyvalues atthe

two

stations duringthe five best months, June to October, 1934, have been tabulated in table3, and plottedin figure i. In computingthe

mean

values and deviations in the table, I have included a

few

fairly good values

marked

^"unsatisfactory^"which were excludedintables i

and

2.

A

heavylineinthe figure gives the best value of the

march

of the solarconstant of radiation.^

The

independentresultsof the

two

sta- tions are indicatedbyalighter line for

Montezuma and

adottedline for St.Katherine.

The

closeaccord

shown

bythese

two

remoteand contrastingstationscannotbutencouragethebelief thatthe observa- tionsof thevariabilityof thesunhithertoreported

from Montezuma

areveryclose tothetruth.

Every

day but six withinthis interval of 152 days

from

June to October 1934^is coveredbygoodobservations atonestationor both.

The two

stations obviously support each otherindisplaying in

com- mon many

variations of the intensity of solar radiation.

The

most conspicuous variation of long period

shown

has a periodicity of a little

more

than 40days, perhaps even 45days, andhasan amplitude ofabout_{I of} I percent. Thiseffectisdoubtlesstobe associatedwith thatsolarperiodicity ofabout 45 days^towhich Ionce

drew

attention

^Thetable and diagram wereprepared independentlyandmay differ slightly.

6

SMITHSONIAN MISCELLANEOUS

COLLECTIONS VOL.

94