M~RCH, 1921. MONTHLY WEATHER REVIEW. la
1$72-18111_____ ._ ____.... _____...._ ______ ___ ___ __ _..... _.. 18821881 ____.._____..___..__...__________________......_ 18%%1901 ._._..____....___._..._____________._.._._._____ 1m-1911 ..__...__._...___ __._.... __. __. __ __ ___ _._ .. ...__ 1912-1921 ................................................
The average date for the whole period is April 8, but the chief interest lies in the averages for lo-year periods. For convenience'these were taken for the 50 years from 1872 to 1921, inclusive, and show for the decades in Table 2. For com arison Table 2 also shows the tem-
and March, a t Oswego, N. Y., which were averaged for each year and then 10-year averages worked out. These resulted as follows:
perature means of t 1 e three months, January, February,
TABLE 2.-.iWean dates of optwing and feniperatures at Oswego, N. Y.
Apr. 13 __._ ___..._. 27.4 Apr. 10 ..._______._ 24.8
Apr. 9 .._____..____ 25.0
Apr. 4 ._____ __ __ ___ 26.0 Apr. 5 ._...._.._.__ 25.5
PWiOd.
.-
I I Temoera- turi at
The Oswego station is about 30 miles from the lake. With the exception of the first decade the results con- form to the theory that the lake is an indicator of the intensity of the winter cold and the earliness of spring combined. One factor which may in art be responsible
shine. Central New York has an excessive amount of cloudiness in winter but the amount, especially in March, is very variable, and it is possible that in some cases
for discrepancies is that of relative c f oudiness and sun-
where the temperatures were mild the excessive cloudi- ness prevented the melting of the ice as rapidly as would have occured with normal sunshine. The reverse
also have been the case in some instances, but gener y s eaking, the melting of the ice seems to be a function of
thus to indicate, in a way, the weather character. .
This would seem to indicate that although the lake opened this spring earlier than in m y ear since 1880,.
there is a tendency shown in the last 10 years toward a
return toward average conditions. Incidentally, it may be noted that in the record- breaking mild winter of 1889-90 the ice in the lake broke up several times, the last date being March 27. The two years when the lake made its record for late 1873 and 1885, both had hard winters previ-
Openin% ously, ut in 1918 and 1920, when the winters were equally severe, the lake o ened little if any later than
The real effect can on1 be seen by averaging a period at
The lake records are now ke t by Fred Beebe, of Con- stantia, to whom, and to Miss J! M. Smith, of that village, who has the early records in her possession, the author's thanks are due, as the are also to Mr. Julius G. Linsley,
Bureau, who Aorded him ready access to the climato- logical records of the office.
Xht
t K e temperature durmg the winter and early spring and
and more than three weeks earlier than t E e average date,
the average, due to unusua P warm periods late in March.
least a decade in lengt K .
official in char e of t x e Oswego station of the Weather
REGISTRATION OF THE INTENSITY OF SUN AND DIFFUSED SKY RADIATION.'
By A. ~N O S T R ~M and C. DORNO.
[Storkholm, Sweden, and Davos, Switzerland, December, 1920.1
[Translated by C. LeRoy Meidnger.1
SYNOPSIS.
The yranometer of A. Anptr6m has been combined, at the observ- atory o! Prof. Dorno, at Davos, wlth a recording device consisting of lamp, galvanometer, and a rotating photogvphic film, u on which the galvanometer deflection is recorded. In ths way m o r 2 are obtained of the total heat radmhon from sun and sky upon a horizontal surface at all times of day, and from this record the daily sums are easily com- puted. In the present paper the recording method is described, the ~~urces of error am &museed, and finally the results from the records at Davoa are presented and compared with results of measurements at Washington and with the recorda of the brightness previously obtained by Prof. Dorno.
Concmiw th instrument.-A. Angstrom's pyrano- meter has been described in an earlier number of the REVIEW.^ ' The J. L. Rose Co., of Upsala, has, since that time, furnished a somewhat smaller ty e of this instru-
screw, level, or the screen mechanism for cuttin off the
manufacturers, may be quite accurately checked, by first exposing the stri s to the sun and sky, and then to
simultaneously made pyrheliometric determination of the solar radiation intensity, I, and the solar altitude, h, enable-one to determine the constant by means of the fundamental formula R=cia, (where R is the radiation intensity, i the strength of the heating current, and c
the constant), and the known relation, c =%-, (2 and 2
being the two heating currents in the two exposures men- tioned above).
ment in a slightly simpler form,. wit 1 out the leveling
sun. The constant of the instrument, furnishe f by the
the sky alone. #l ese observations combined with a
I sin h
1 2
1 ublished simultaneously in the Mdeorolcgiache ZrUscluift Feb. 192l. : trom Anders: A new instrumont for measuring siy rabiation. Mo. WEA-
L. iovember, 1919,47: m5-m.
Small variations of this constant are to be expected since the absorptive power of the black platinum stnp and the reflective power of the magnesium oxide are not abso-
The constant evaluated in lutely uniform for the entire length of the sun and sky. Davos instrument, 12.93, compares similar measurements on the lar er t
instrument proves to be very reliable and uniform neglecting a few very easil removed deficiencies.
tory and a 10-day comparison was made between t h two
s ecimen instruments under very favorable conditions. $lis comparison was made during the period of November
8 to 17, 1920, the registering instrument proving very practicable. In con unction with these comparison
and two December decades. The registration ap aratua
Zeitschrijif. With its application the compensation pro- cedure will naturally be neglected, only the swing of very sensitive galvanometers will register photographically; auxiliary tension and damping resistance will not be con- sidered. Both poles of the thermoelement are grounded, but between one of these and the earth the galvanometer is placed and the necessary resistance introduced to diminish the current. On this meter throw of 1 mm. a very small correction may possibly value, while the constant, e, as has tioned, awaits a more absolute
which, in another manner, was P I oun
Numerous trials have been ma L9 e a t the Davos Observa-
measurements, recor d s were taken over two November
is described in the January, 1931, Meteoro 7 o+he
further, the relations with lar er solar altitudes will be more reliable, and because, fnally, the quality of the
138 M~NTHLY'WEATHER REVIEW. MARCH, 1921
belt-gass leaves something to be desired. Even with winter solar altitudes, the width of the photographic piper upon which the galvanometer deflection is recorded, 14.6 cm., does not sufEce, and the am litude of the throw
1000 ohms resistance, and, occasionally, at the beginning of registration about the middle of November, it is necessary to insert 2000 ohms; the corresponding readings must then be multiplied by the factor 3.05. The zero line is determined in the morning, a t noon, and in the evening, by breaking the circuit for ten minutes. If the instrument is screened off from the sun and sky, the record is only slightly influenced by small variations (only up to 1 mm.) due to the long-wave radiation of the bell- lass and cap, and it appears that warming elevates the Fine, and cooling lowers it. The evaluation of the curves is managed in the same manner as the evaluation of brightness curves. The small remaini residuals have three causes: (1,
not satisfactorily homogeneous and it even has bubbles of such size that they can be seen readily b the shadows they cast.' By exposing the bell-glass an8 the strips in exactly the same orientation to the solar beam, one obtains quite similar alvanometer swin ; but t-his is no8
changed. During the daily registration, errors originate if the instrument remains in a fixed position, and these errors can amount to as much as 4.5 per cent. This error can be reduced to a minimum. (2) With a horizontal exposure of the strips and a very low sun, whic.11, of course, causes the rays to fall in a ver slanting manner, there is some radiation which falls E etween the strips on or in the vicinity of the thermoelements. This also needs improvement, even though a perfect remedy may not be ossible. (3) The instrument possesses a certain
The cause of %is is found in the heat capacity of the receiving surface and in the fact that the heat is not transferred instanta- neously to the thermo-elements. When one makes use of the chief su eriority of this instrument, its registering
uence of the relatively large induction forces opposing %e small electromotive force of the t,hermoelement. By means of alternate shading and esposing, it is discovered that in less than the galvanometer's period (scarcely ten seconds) at least 63 per cent of the intensity will be regis- tered, the difference between t.he incident radiation and the pyranometer reading will be reduced in less than 10
which has been applied by Eric R. Miller to his testing o 7
seconds to at least the e-lth part-a definition of the la
the Callendar recorded and which seems very adequate.'
The result follows the form of a ver steep exponential curve, only about the last seventc of the intensity remaining after about l+ minutes after screening the instrument. Thou h this lag, with continuous auto- matic registration, t ere originates a small smoothing out
of the curve which is hard a parent on the normal scale (16 mm. to 1 hour) but w&c%is shown b a comparison with the hotoelectric record. This thirf small residual
must be reduced by about one-half 73 y the insertion of
the bell-glass as it has Y een furnished up to the present is
exactly the case if t a e orientation of t 7 e instrument is
lag, an B does not follow the variations of intensity so
capability, t R en the lag becomes important in conse-
uicMy as does the photoelectric method.
error can R ardly be eliminated or corrected.
J Le* theZeksCo. hasfurnbhedforuse with theinstrument bellglansep whirb havo
4 YO. Wm"KEB REV., June, 1920, I: 358. proved ofmart entirely free from the disadvantages mentioned above.-d, A.
Results.--ks an example of a day's radiation of sun and sky received on a horizontal surface, the curve of Novem- ber 26, 1920, is offered. On this day there wm delicate bright cirro-stratus (cloudiness 3-6), the bri htness of the
a. m., the sun rose over the mountain, and a t 3:12 p. m., disappeared behind the mountain: between 9:48 a. m. and 2% p. m., 1,000 ohms were inserted in the circuit, and the circuit broken from 7:57 a. m. to 8:03 a. m., 1 :31
p. m. to 1:37 p. m. and 5 2 0 p. m. to 5:35 p. m. In figure 1 it .is seen that on the one hand from 8:OO to 9:28
sun varying between bright to very brig f t. At 9:28
I 1.- Y
Ti Fro. l.-?tad13tiOn of sun and sQ received on a horkontol surfseo recorded at Davw, Switzerland. on Nov. 28,1920.
a. m. and from 3:OO to 3:12 p. m., when the resistance
WRS not in, there are scarcely any vibrations in the line; and, on the other hand, durin the day, with the 1,000
ohms in, there are sharp1 mar a ed variations corres ond-
facts indicate the trustworthiness of the instrument. In Table 1 are given, in gram calories per s uare centimeter for the two last decades of November an ?I the two first decades of December, the mean hourly totals (true solar time), the daily sums, as well as the absolute and mean intensity maxima, and for noon, the mean, mnsimum, and minimum intensity. All of these data are given (1) for all da-ys, and (3) for clear or nearly clear (la s.
i e t us compare next the observations of radiation of a horizontal surface from the sun alone made during the years 1908-1910 on absolutely clear days with the daily
For example, compare F g e L .e r 17, 1920 (ne@ec.ting the time the sun was behind the mountain) with the mean of November 15
from 1908 to 1910 (Table 4 of "Studie" 6), increasing the dail sum by 3.5 er cent in order to bring them to.the
calories per square centimeter per minute for the dffuse
sky radiation with a mean solar altitude of 10'. Then one obtains for the pyranometer mea.surement 185 calories and for the com uted values for 1905-1910, 175 calories,
which is about the same amount as the sun radiation in November, 1920, was in excess of that in 1908-1910.
For a similar comparison for December, the result is somewhat different, but is satisfactory. The bright snow cover after December 1, on the mountain heights, increased the diffused radiation by over 60 per cent.
ing to the temporary o t scurations of the sun. Fhese
the present method.
heig 3; t of the Smit K sonian scale, and calculating 0.04 g a m
the former case Yl eing 4 per cent greater than the latter,
d "B@dic i i b a Lichl ur#d Luf6 &a Hoc~ebirgea,'' Vieseg, 1911.
MONTHLY WEATHER REVIEW. ,:!a7 %CH, 1921.
TABLE 1 .-Hourly and daily totals, mazinia and minima of sun ard aky d t w n on a hmkonhl surjace, in gram calorie per pcr min.
1920.
~~.,l s t d d e ____.___. m .,~d e a a d e _____._..
NovZddmde _._._.... Nw:: Bddeurde. ._..._..
Intensity maxi-
mum. Intemitp at 12 d c ~m ~ (nom) Nm-
Lmrd Total nor- Yaxi- Minl- mal 8 0 10 11 Noon. 1 9 3 Abolute Mean. Mean. mlllIl. mum. -.
1.34 187.5 1.001 a7m 0.m 0.713 0.135 ___._. 149.1 0.686 0.598 a637 0.648 0.410 ___... 1.10 3.87 10.m 10.99 2 6 .~ 25.71 20.23 ixga 128.0 n754 a m 0.4% 0.748 0.181 _._... 0.86 4.07 13.1 27.55 51.30 33.6 25.11 16.05 158.9 0.m a702 0.584 a838 am ......
1.22 3.61 19.12 31.80 36.48 31.W 29.66 19.56 1.55 4.16 16.41 20.72 3.90 28.73 22.75 24.50
(True solar t h e ) hours ending at-
------- --___-__-- ~----
Under the influence of cloudiness, the radiation re- ceived on a horizontal surface was diminished during the two November decades from 389.5 calories to 366.6
calories, or a decrease of 13.6 per cent. (This represents observations during 71 er cent of the total possible
featurea around Davos.) Table 6 of the "Studie" shows that the direct solar radiation a on a horizontal surface was decreased by cloudiness in November in the avera e by 59.4 per cent. The calculation of this table is base 9 , however, upon the 10-year means (1899-1908) of records of the Campbell-Stokes sunshine recorder, but the sunny November of 1920 surpassed these means by fully 22 per cent (130 hours as compared with 107 hours). In view of this rather crude calculation, it appears that the radiation value as determined by the solar intensity measured in a clear sky and from the duration of sunshine 'as measured b the Campbell-Stokes instrument does
total of radiation from clouds is nearly compensated by the diminished brightness of the sun as recorded by the sunshine recorder. This previous experience, which @ended only to low solar angles and mnter cloudiness, demonstrates that for radiation we can count with similar conditions as for bri htness. The total brightr ness is less dependent upon &e brightness of the sun a t low solar an les than at high; with low and bright sun,
the radiation by 10 to 20 per cent. Clouds are most effective when near the sun with high altitude angles. Ibfaxima (an increase u to 65 per cent) occur when the
the values are quite simi ar to the normal; with very hazy sun it reaches about four-fifths of normal; with ver
two-thirds, with average snowfall from nimbus, the value is one-half to one-third of the normal. The value
is thus less with low clouds than with the high ones, and
the are not identical with other conditions under the h$ valley conditions of Switzerland. xcludin the sun and the bright sk immediately
on a homontal surface amounts to 0.09 with the solar altitude 25'; to 0.08 a t 20'; to 0.04 a t 10'; and to 0.02
ut O', all values bein gram calories per square centi-
meter per minute. &en after sunset, the diffuse sky radiation is of measurable intensity. With the appear-
ance of white cumuli or bri ht stratus at bri ht or medium
duration of sunshine, as a etermined by the topographical
not disagree wi B ely with the real one; that even the mean
the effect o B clouds goes in the direction of increasing
gun suddenl breaks t %r ough an o enin in high white
9
stratus clou K s. With haz sun (Ss andbright stratus,
. hazy sun in a valley filled with low, light gra clou 6v s at an altitude of about 100 meters, the value g ecomes
adjoining t % e sun, the radiation receivezfrom the sky
bright sun an increase to % ouble or three-fo 9 d the normal
value is measured, while with very hazy sun, it amomta to only 15 to 30 per cent. With a clear sky, the nocturnal long-wave radiation of the earth a t Davos imounts to-
Oct.
1
Nov.
1
De.
1
Jan.
I
Feb.
1
Mar.
1
Apr.
1
May.
-~-~~---
aim 0.17s 0.163 aim am 0.216 ai& . ai=
these being mean values from twilight to twilight in gram calones per square centimeter per minute. The assumption that these values of the long;-wave earth radiation are also applicable to the day h e is hardly to be doubted, as waa shown by the observations of A. An triim a t Avike, in Sweden, during the solar eclipse
length of the clear day sky in .the high mountains in winter is only a small per cent of the, long-wave outgoing heat radiation, there is a continuous stream of heat movin from the earth to the sky, and this effect L
time. ?he reflection from freshly fallen snow on the mountain slopes amounts, at a solar elevation of 20,
to 69 er cent of the normal sky radiation with a clear sky; tks value was determined photometrically in the years 1908-1910 to be about 50 per cent on the average.
(" Studie, " p. 47.)
For more than 10 years at W d i g t o n means of the sun and sky radiation falling on a honziontal surface^, as recorded by the Callendar pyrheliometer, have been measured.* These values in comparison with those at Davos show good agreement. For instance, with 27'
solar altitude the value of 0.6s gram calories er square
December 22 and at Davos on November 10. And at
Madison, Wis., which lies in latitude 43' 5' as compared with Davos at latitude 46' 48', and a t an elevation of
300 meters as compared with 1,600 meters a t Davos, the
November mean of eight years of observation s m l y departs from that observed at Davos in the second November decade, so far as the sun at Davos is not obscured morning and evening by mountains. The result is unexpected. Since the solar intensity in high mountains is usually in excess of that of lower elevations (in the foregoing exam le the solar intensity at Wash-
of f ugust 21, 1914.' While the radiation of shortrwave
probaby 5 also in the average the same in the summer
centimeter per minute was obtained at W a& ngton on
ington was 1.18 and t Yl at a t Dnvos 1.38), it must be
____ ~
eMo WEATEEB REV June 18ao )8: 34% Thls Is an extended comporlsan b tween 'the Tulipan instrzment And &meter whlch shows that the slmple Tulipan instrument can be put to the use of &termlning h e nocturnal radletlon and at the SBIM
time the conditions of cloudiness during the nlght.
7 Meteorologische Zeitscbrllt 1916, p. 58. aMiIler, Eric R.: Some Charaeteastics of the Cellendar pyrheliometer. Mo. WEA~EB REV., June, leZo,4& ,344447.
138 MONTHLY WEATHER REVIEW. &WH, 1ml
concluded either that the diffuse sky radiation a t a given place is extremely important (ratio of vertical com- ponent of solar radiatlon to that from sun plus sky wtw
m Washington 0.80, in Davos 0.92) or that the differ- ence lies in instrumental errors,. of which a clue mi ht be found in , the above-mentioned investigation %y Eric R. Miller of the Callendar recorder. A comparison between the curves of heat radiatiori and the brightness curves iven in the January, 1821,
might expect, that the former has a smaller aniplitudc than the latter. As a rough approximation, to illus- trate, the brightness intensity incrcases in. the ratio 1 :1.5 :2 with solar altitudes of 15, 20, and 25O, while the heat radiation increases in the ratio 1 : 1.35 : 1.6. This point will be discussed later. In spite of the three small residual .errors discussed above, tho instrument has proved itself to be a great advance and will probably gain general use. It will
issue of the MetsoroZogkc a e! Zeitschrift shows, as one
serve R useful purpose in man investi ations which aro
depend upon the interc.hange of %eat between the earth, sun, atmosphere, and space. This will depend also upon a correct understanding of the relations of nocturnal radiation to temperature and huniidity and to the type nncl amount of clouds. Furthemore, the instrument will serve to give Dhe values of vorderlicht and unter- licht  (vertical surface, and horizontal surface exposed downward) in colorie measurements; it will give data ou the relations betwean altitude and optical purity and rrtdiatioii; and if a suitable bell-glass is perfected it will estrud iiiveatigations 011 single p:wtss of the spectrum. The results obtained with this instrument may also be
nt valurtblr! check on tlw resultts obtained with other differently constructed instruments; in order that we may be sure of an espcrimeiital result, it seems impor- t,mt tahhat it should appear on the basis of different methods agreeing with one another.
of great importance to meteoro T - oaical a R vances and which
NOCTURNAL TEMPERATURE INVERSIONS IN OREQON AND CALIFORNIA.
BT1oomJ.
Not enough attention has been paid in the past to locatin cro e
subject to damage by frost on t.he more frost-free hillsides; andfiat t l e present day the phenomenon of nocturnal temperature inversion is not well understood by moa fruit growers. Orchards set out 20 years
sgo in some of the coldest sections in Beverd fruit districts on the pacific conat are still being opezated at a loss, while others have been =moved only during the last two or three yeare. Detailed records of nocturnal temperature differences on slopes, covering entire frost seaaone, are Bcsrce. Obeervationa of nocturnal temperature inversions, made at Pomona, CMif., and Medford, Oreg., during the froet seasons of 1918, 191.9, and 1920, are given in detail and d i s c u d in this paper. Inversions at Fomona during the winter are compared with those at Medford during
the spriug. Differences in minimum temperature as great as 2So F. were observed between stations at the baae and 225 feet above the baw,
on a hillmde at Pomona. lhe greatest inveraions occur on clear. calm nights, following warm days. The duration of the minimum temperature on the hillside is uaually much shorter than on the valley floor below, on account of large fluctuations in temperature during the night on the: hillside. On every hill where observat.ions were made, the data indicate that on clear, calm nighta the top of the hill is colderthan pointa on the hillaide mme distance below.
The temporary vertical distribution of temperature found in the atmosphere over a plain or a valley floor on clear, calm nights, wherein the air temperature increases from the ground up to a height of from 100 to 1,500 feet above the ground, is called nocturnal temperature in- ve.mion. The steps in the development of a nocturnal tempera- ture inversion may be summarized briefly as follows: Ihrring a clear, c h day the temperature of .the ground surface is raised through heat received by radiation from the sun, and the air in contact with the ground is warmed by conduction. This warmed air is forced upward and replaced by cooler and denser air from near by or above, and s circulation is established, which continues as long as the ground surface is warmer than the air in contact with it. Near sunset the air up to a height of a thou- sand feet or more is very nearly in adiabatic equilibrium. Aft& the sun goes down, the surface of the ground loses heat rapidly by radiation to the sky and its tem- gerst&re.aoon falls below that of the air in contact with it. The surface air cools through conduckion of heat into the colder round, and its density becomes increas- ingly greater. fts increased density tends to keep it in
oontact with the ground, where it continues to grow
colder a.nd colder throughout, t<he ni ht. As air is a
the a.ir n few hundred feet above the ground falls much more slowly, and by sunrise a considerable difference in temperatmure has develo ed between the air at the sur- face of the ground and t E at a few hundred feet above the ground. In the case of a va.lleg, with fairly steep slopes on either side, t.he minimum temperature on a frosty night is likely to be much lower on the v d e y floor than at points on h e hillside, the highest minimum t.ernpera ture oc-
curring at a height of froni 300 to 1,500 feet above the valle floor. A Lowled e of the average and extreme diflerences in temperature %ebween different portions of the hillsides and the nilley floor is of eat, practical value in deciding where certain crops mill Y e grown. If this information is availnble, crops most susceptible to damage by frost can be plrmted a t tahe level on the hillside where the highest miniinuni temperature is fiund most frequentlv, and the colder locations on the floor of the valley can he u tilizecl to grow more frost-resistant crops. A single seasons observations may be misleading, as
the nocturnd temperature inversion vanes from year to year in the same wa that one sensons weather differs
to occur, in which low tern eratures are accompanied by high winds, and crops on t. 1 e hillsides suffer as much, or even more, damage t,hm those on the valley floor. Temperature inversion also lays an important part
of the inversion and the amount of wind l q $y determine
A strong wind wi 1 prevent the develo ment of a mar Yht* ed what the efficienc of the heaters will be on a given
ten1 erature inversion by keeping t e air a t different
tures during the growing season usual1 occur with fittle air movement, orchard heating can l e practiced with greater success than in districts where low temperatures are often scconipanied by high winds. In most of the orchard dlstricts in the Pacific coast States, either through lack of knowledge or through dis-
poor conductor and radiator of heat, t % e temperature of
froni anothers. At s ong intends freezes are likely
in the protection of crops by orc i ard heatin ; the extent
leve f s thoroughly mixed; in localities where low tern era- % 9
* Sce Iiiunphmeys, W. J.; Frost Protation. Mo. WEA-M~EB RET.. October, 1914, 42:
5Ij&&L