Smithsonian miscellaneous collections

SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOLUME

87,

NUMBER

9

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IRoeblino 3Funb( ^may 24 1932

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PERIODICITY IN SOLAR VARIATION

(With Two

^Plates)

BY

G. G.

ABBOT

Secretary, SmitlisonianInstitution

AND GLADYS

T.

BOND

Statistical Assistant, Smithsonian Astrophysical Observatory

(Publication 3172)

CITY

OF WASHINGTON

PUBLISHED

BY THE SMITHSONIAN

INSTITUTION

MAY

24, 1932

SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOLUME

87,

NUMBER

9

IRoeblino jfwnb

PERIODICITY IN SOLAR VARIATION

(With Two

Plates)

BY

C. G.

ABBOT

Secretary, SmithsonianInstitution

AND

GLADYS

T.

BOND

Statistical Assistant,Smithsonian Astrophysical Observatory

?c%'Nc/?i:

fi^\

(Publication 3172)

CITY

OF WASHINGTON

PUBLISHED

BY THE SMITHSONIAN

INSTITUTION

MAY

^{24, 1932}

BALTIMORE, MD.,V.8. A.

IRoebliuQ fwn^

PERIODICITY IN SOLAR VARIATION'

By

C. G.

abbot

Secretary, Smithsonian Institution

AND

GLADYS

^T.

BOND

Statistical Assistant, Smithsonian Astrophysical Observatory

(With

2 Plates)

Long

ago,Secretary

Langley

induced Congress to supportthe study of solarradiation at the Smithsonian Astrophysical Observatory.

He

pointed outthatalllife

and

^allweather

depend

on it.

He

held out the possibility

and hope

that asufficient

knowledge

of solar radiation

and

ofits behaviorinour atmosphere might evenenable meteorologists to forecast long in advance the fat years

and

the lean years as Joseph is said tohave

done

in Egypt.

After

40

years of research,

we

have results

which seem

^{to us to} justify in

some

degree Langley's hope.

We

have not yet, it is true, triedtheboldventure oflong-range forecasting, but

we

have evidence to present tothe

Academy

today that the sun's output of radiation is

variable; that itsvariation is periodic; thatthe United States weather departures

from normal

are periodic;

and

that nearly^allof theranges of weather departures

from normal

are comprised ina series of peri- odicities

which

are identicalwith those

found

ⁱⁿ the sun.

We

expect todiscover

by

a little

more

research whether

we

have here real cause

and

effect. If^it should prove so,

we

need not emphasize the value of suchknowledge.

For more

_{than 25} years the staff of the Smithsonian Astrophysical Observatory has been

measuring

the intensity of solar radiation.

At

first, in

Washington,

w^e further developed the

method

devised

by Langley and

used

by him

about 50 years ago at Allegheny

and

at

Mount Whitney. We

devised the silver-disk pyrheliometer for ordi- nary daily

measurements

of thetotal intensityofsolar radiationatthe station.

We

also devised the water-flow

and

the water-stir standard pyrheliometers,

whereby we

reduced the scale of

measurement

to

^Paperpresented before the National Academyof Sciences, April 26, 1932 Smithsonian Miscellaneous Collections, Vol. 87, No. 9

SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL.

8/

NO. 9 PERIODICITY IN

SOLAR VARIATION

AllBOT

AND BOND

₃

standard caloriesper square centimeter perminute.

We improved

the recording spectrobolometer ofLangley sothat inlessthan lo minutes

itcould furnishanexcellentrecord of theintensitiesofall

wave

lengths in the solar spectrum

from

about 0.35

micron

in the ultra-violet to about 2.5 microns in the infra-red.

We

devised graphical

methods

196

195

192

191

1.90

4 SMITHSONIAN MISCELLANEOUS COLLECTIONS

^VOL.

87

of the sky about ^{the sun,}

which we named

^the pyranometer.

By

its

aid

we

have devised a ^brief empirical

method

for estimating the ^at- mospheric transparency ^{in all}

wave

lengths.

We have

also devised a spectroscopic

method

for estimating the quantity of precipitablewater heldinthe

form

of vaporintheatmosphere.

From

our determinations of atmospheric transparency

we

have checked ^exactly with other

methods on

^the determination of the

number

of molecules ^{per unit} volume.

As

the temperature of the earth

and

the fundamental factors of climate

and

^weather

depend on

^{the intensity of solar radiation,}

we have made

^{earnestefforts}over a longperiod of yearstosecure accurate

measurements

^{of it.}

When ^{we began}

^this

^work

ⁱⁿ 1903, authorities

were

ⁱⁿdoubt over^theentire range as

between

PouiUet's value of 1.76 calories,

and Angstrom's

value of 4-0 calories for thesolarconstant of radiation.

As

aresultofour work,^carried

on

atall seasons,at stations ranging

from

sea-level to4,500 meters^elevation,

and

checked

by

auto- matic apparatus exposed

from

sounding ^{balloons at} 25,000 meters elevation,thereis

now no

doubtthatthe true valueliescertainly within one percent of 1.94^caloriespersquarecentimeter perminute.

We

^have discovered evidences of variability of the sun's emission.

Having

devised a brief

method

of

measuring

the solar constant,

we

have applied it several times a

day on

^{all favorable}days over a long

term

of years.

We

have occupied

mountain

stations indesert lands

m

Arizona and

^southernCalifornia,in northern Chile,

and

in

South West

Africa. Plate i, Figure i

shows

^{our stationat}

Mount Montezuma

in northernChile, 9,000 ^feet above sea-level. Plate i, Figure 2

shows

a closerviewof the apparatus.

The

pyrheliometers

and

^the

pyranometer

are exposed outside,

and

^thesolar altitude is

measured

witha theodo-

lite.

A beam

of light is reflected into a cave observatory

where

the spectrobolometric

work

^{is done. Figure i}

^shows

^{the close accord}

attained in the

monthly mean

values of the solar constant at three widely separated ^{stations. It is clear} that if the observations at the earth's surface

and

the estimates of losses in the earth's atmosphere

were

correctly made, then determinations of the solarconstant (that

is, the intensity of solar radiation outside the atmosphere) ought to agree ^exactly

wherever made on

the earth's surface. In fact

we

have so far refined our determinations that our

two

best widely separated observatories,

Montezuma,

Chile,

and

Table Mountain, Calif., do agreein their

monthly mean

^valuesovera period of five years within

an

average difference of 0.08 per cent.

The

probable error of the

mean

curve

shown

in Figure i is well

below

o.i per cent.

SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 87, NO. 9,PL. 1

Su«%->ai«>.' \ijM:\^^^1*

Solar radiation station, Alount A'lontezuma, ^Chile.

I, The dwelling; 2, the cave observatory.

0/3

—

00E

NO. 9 PERIODICITY IN

SOLAR VARIATION ABBOT AND BOND

It will be noted that the three stations not only agree closely, but uniteto indicate fluctuationsof the sun's emission.

The

extreme range of variation

shown

inFigure i is 1.2 percent.

On

an earlieroccasion, in 1922, a range of the

monthly mean

values of nearly ₃ per cent

was

observed as indicated in Figure 2,

where

values

from Montezuma,

6

SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL.

8/

ofapproximationis

shown by

the smallness of the residualsincurve B.

It is to be noted that larger residuals are

found

in the earlier years

when

the solar observing

was

lessperfected than it

became

later.

These

results

on

periodicitieshave beenobtained

by Mrs. Bond

with

an

instrument

which we

call the periodometer,

shown

in Plate 2. It

was

constructedwith the aid of agrant of $1,000

from

theResearch Corporation of

New

^{York. Its purpose is to discover}

^and

^evaluate

periodicities in long series of observations. It does not recognize the reality of

any

period until tested,

and

^it evaluates its distribution in amplitude without regard to

any assumed

mathematical expression.

Itappearsto us,forinstance,thatas thecurveof sun-spot frequencyis

well

known

not to be of regular sine form, there is

no

reason to supposethat other solar periodicitiesshould

have

asine form.

Hence

our instrument is designed to evaluate their

forms

as

Nature

fixed them, notaccording to the

forms assumed

in mathematical series

and harmonic

analyzing machines.

Curves

C, D, E, F, G,

H,

of Figure₃

show

the periodicitiesactually discovered in the solar radiation

by

aid of the periodometer. Itwill be seenthat the 21

-month

periodbetraysalso oneof 7 months. Inthe cases of the shorter periods,

we

have beenabletoseparate the datainto several groups

and

independently evaluate the periodicities at several epochs.

These

partial determinations are

shown

in curves Ci, C2, C3, Di, D2, D3. In such cases

we have

been encouraged to find that the

maxima and minima

occur without change of phase in these inde- pendent epochs.

Thus we

regard the periodicities

found

as having reality

and

permanence.

We

ventured in

November,

1930, to

make

a forecast for 193¹

and

1932 of the probable

march

of solar variation.'

Thus

^farithas been wellverified,although itcalled for solar-constant valuesalmostallthetimesince 1930 about oneper centabovethe

mean,

notwithstanding that the values preceding the date of forecast for several years had been prevailingly below the

mean.

It has been of great interest to us to note that several of the periodicities

found

in solarvariationarecloselyrelatedtothe sun-spot period of ii^ years or 135 months. Thus, 68

months

is within its

probable error one-half, 45

months

one-third of 135 months. Again,

if

we

takeaperiod approximately three times aslong, or

400

^months,

which

is near the

Bruckner

period, 25

months

is one-sixteenth, 21

months

closely one-nineteenth, 11

months

closely one-thirty-sixth,

8 months

^isone-fiftieth,

and

7

months

one-fifty-seventh of itsduration.

If

we

admit provisionally (subject to the findings of subsequent years) that the solar variation is

made up

of the seven periodicities

^See SmithsonianMisc.Coll., vol. 85, no. i, fig. 3, I, 1931.

'J.\Ul

NO. 9 PERIODICITY IN

SOLAR VARIATION ABBOT AND BOND

named,

^it

becomes

of interest to see it these

same

periodicities are traceable in temperature departures of the weather.

We

have inves- tigatedthis question for threewidely separatedUnited Statesstations,

8

SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL. 87

mean monthly

temperatures 1918-1930,

and

have subtracted

them from

the observed, thus giving

monthly

departures exactly suited to theepochstudied. Lestthe influences of shorter-periodchanges should obscure the general

march

of events,

we

have

smoothed

the

monthly

temperature departures

by

taking five-month consecutive

means

of the

form

ai

+

^a2

+

^ao

+

^ai

+

05 . a-i

+

Oz

+

^ai

+

^{o-^}

+

^{C'^.} _^^^

5 5

With

the data thus prepared,

we

have sought

and

evaluated with theperiodometer all theperiodicities

which

thecurves disclosed.

Our

procedure, as in the case of solar variation, is to subtract

from

the data theeffect of each periodicity as soon as determined, before pro- ceeding to evaluate in the residual curve another periodicity.

We

continued the search

and

evaluation until

no more

periodicities could be perceived.

The

result obtained for Clantonis

shown

in Figure 4. Periodicities of 8, _9-I, 18, 21, 25, 34, 39, 45,

and

68

months were

evaluated.

These

periodicities

and

their partial determining curves are indicated

by

letters C,

D,

E, F, G,

H,

I, J of Figure 4.

The

residual

shown

in curve

B

plainly indicates the ii^-year period.

We

also note the large positivedeparture

shown

in the residual curve

B

for theyear 1930, a year remarkable for the extraordinary drought and

accompanying

cloudlessness.

A

similar extraordinary positive departure for 1930 ^is

shown

in Figure 5,curveB, for

Washington, and

also in Figure 6 ^for Williston. Itwillbenotedthatstrongperiodicitiesof8,21, 25,45,

and

68

months

foundin Clanton temperatures are

found

also in solar vari- ation.

The

¹¹

-month

solarperiodisindistinct in Clantontemperatures.

The 135-month

period isdoubtless ofsolar origin,although ^it doesnot appear conspicuously in the solar variation

between

1918

and

1930.

The

other Clanton temperature periodicities of _9^, 18, 34,

and

₃₉

months were

not

found

in the sun, but nevertheless34

months

is one- half of 68 months,

which

is conspicuously

found

as a periodicity in the sun.

The

results for

Washington

are

shown

in Figure5. Periodicitiesof 8,9^, 13^, ^18,25, 45,

and

68

months

arefound asindicatedat C,D, E, F, G,

H,

I.

The

residual curve

B shows

clearly the

135-month

peri- odicity in practically the

same

phase, though lesser amplitude, than Clanton.

The

extraordinarydrought of 1930 produces ^itsstrong posi- tive departure.

Here

again the strong periodicities of 8, 25, 45,

and

68

months seem

toreflect solar-radiation changes.

The

periodicities of

NO.

9

PERIODICITY IN SOLAR

VARIATION ABBOT AND BOND

₉

9^ and

ⁱ⁸

months

are foundalso at Clanton.

The i3|-month

periodi- cityis new.

No

appreciable influence of the 1¹

-month

solarperiodicity

is found.

The

results for Williston,

N.

Dak., are

shown

in Figure 6.

Much

wider rangeofdeparturesis

shown by

curve

A

than

by

thecorrespond-

lO

SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL.

8/

'-T T T 7 T Y

NO. 9 PERIODICITY IN

SOLAR VARIATION ABBOT AND BOND

II

curve B,

and

has a very differentphase

from

corresponding curvesat Clanton

and Washington.

In ordertofixourideasof therelationsbetweensolar

and

terrestrial periodicities

which we have

discovered,

we

giveinTable i a

summary

of them.

We

invite attention to the fact that a majority of the peri- odicities in terrestrial temperatures

which we

have

found

are identical in length with periodicities in solar variation.

The sum

of the

maxi-

Table I

Periodsof

12

SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL. 8/

We

do not venture to claim this important conclusion as yet.

We

intend to carry

on

the research

much

longer.

But

at least the inves- tigation has decided promise.

We have

been es^^ecially interested to

compare among

themselves thecurves

marked A

^{inthefour figures}3, 4, 5,

and

6, giving thesolar variation

and

the temperature departures at the three stations.

We

havealso wishedto

compare

thecurves giving periodicities of 25

and

45

months

ⁱⁿ solar radiation with thecorresponding temperature peri- odicities at the three stations.

These

comparisons are

shown

in Fig- ure 7.

Itappearsatsightthatpartsof thecurvesoftemperature departures forA\^illiston

and Washington

^{arevery similar,but that the similarity}

is slight as between Williston

and

Clanton.

On

the other hand, there are

many

points of similarity between the temperature departures of

Washington and

Clanton.

The

largedeparturesof similar

form found

atWilliston

and Washington

^intheyears 1918to 1921 occur

from

one to

two months

later at

Washington

than atWilliston.

Finally,

we

have

made

an experiment at long-range weather pre- diction. Instead of

making

our readers wait several years to test it,

we

have

made

ourprediction

backwards from

1918instead of forwards

from

1930, sothat

we

couldimmediately

compare

expectancy withob- servation. Figure 8

shows

the predicted

and

observed temperature departures

from March,

1918,

backward

to September, 1916, for Clanton,

Washington, and

^Williston.

The

agreement is not perfect, yet thereis ineach case atendency to a correspondence inthe trends.

But

^it

must

be recalled that the periodicities found represent the average

march

of weather

from

1918 to 1930,

and

therefore are to be regarded as of the epoch 1924.

None

of the periodicities fits this entire long interval of 13 years ^perfectly.

Hence

in predicting back-

ward

to191 7

we

arereallyattemptingaseven-year forecast

from

1924.

It is perhaps extraordinarythat thecorrespondence isas

good

as it is.

If our

method

should be used for serious long-range forecasting, it

must

be perfected so as to pass

from

the last year or tivo of

known

valuesto the

unknown,

not seven yearsas hereattempted.

NO.

9

PERIODICITY IN

SOLAR VARIATION ABBOT AND BOND

I3

1918 1919 1920 I9?r 192? 1923 1924 1925 1926 1937 1923 (929 1930

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SMITHSONIAN MISCELLANEOUS COLLECTIONS

VOL. 87

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