674 MONTHLY WEATHER REVIEW. DECEMBER, 1916
SECTION 11.-GENERAL METEOROLOGY.
CUBRENT EVAPOEATXON OBSERVATIONS BY THE WEATHER BUREAU.
By B. C. KADEL and C!. ABBE, Jr.
[Dated Teather Bureau, Washington, Jan. IS, 1917.l
INTRODUCTOlt I-.
The Weather Bureau has been enga.ged for the pnst two yeais in gradutilly instnllin a t carious points in the
for the inensurement of evnporrctioii losses froin water
confined in iiietnl nns. Friendly cooper;it.ion on the
ests, Weat,her Bureau officisls, and others lxs perniit.te4 the work t.0 rogress to Q degree that wirr;ints tho belief
to engineers, cliniatologists, botanists? plii11t~ physiologists, foresters, and others ; and LLS arr~igeiiwii ts lii~lrc, breii iiiade
to publish the obssrrntiontil iiinteiinl i.:!onthly, it seeixs proper to record here t,he stations R t which evn.pornt.ion observations are now bcing made as well RS to give son^
account of their equipment, their operation, and the places of publication. X list of these stations. known ;is
TABLE I.--Cluss A eL-aporatim stations o the Tentlier Bureau ia
United Stn.tes n chain of uni B orni1-y equipped st.at,ions
psrt of State agricu f t.ura1 colleges, private irrig,.a.tion inter-
that the resu r ts being secured will be of c*onsidcmihle vnlue
.- -
operafion Jan. I , 1917. (See a G o j g w e 1.)
. . .
I - .
I ,O I 0 ,
Arizona:
Colifornra: Roosevelt ................ * ........... i 33 40 i 111 09
...
Tahoe ............................... ! 39 10 i 1XI MI
Dbtrict of Columbh:
~~
AmerhnUnivereity ................ i I 56 Idaho: Arrowrock Rewrsation.. ............ 43 36 Deer Plat Reservation.. ............ .: 43 35 liaonsas: Lawrence.. ....................... .._I Tribune.. ......................... ._I
MahK: I Gardiner ,I ...........................
Columbia (University of bfissouri ! cam us) ........................... I
~olumRia (university of XiJsouri golf links) ......................... .:
Bozeman. ........................... vauer.. ............................ .I
Elephant Butte ..................... _i Santa Fe.. .......................... Tucumcari .......................... ,
MIsn Springs.. ................... .:
Missouri:
Montana:
X e u Merico:
Newdc
Lamolle.. ............................ kfarlette Lakn.. ..................... Ohio:
\Voost?r. ............................ Port0 Rim. I
San Iuan. ........................... I S d h Dakola: I Rapld City. ........................ .i Trcor: Austin (Hills ranch land pan) ..... 1
Austin (Hills ranch: floatlng pan ) . .>i Wmhi ton. \v% Ala.. ....................... j
I
3s 58 3s as
44 11
3% 57
3s 57
45 40 4s 25
33 10
35 41 35 10
36 31 40 27 39 10
40 47
1s 20
44 04
30 14
46 02
57 05
115 55 116 43
95 15 101 46
69 46
93 20
Y2 20
111 03
1U7 10 1075 57 103 48
115 43 11s 25 119 55
81 56
6 6 0 7
1 w 12
!37 41
11s a0
iia 20
__ ._-
pprosi- j mate ,Ititude  l?ate of first of pan observation. ahTe 
eslevel. I
FCEI.
2,375
ti. 230
393
3 230 2: 510
1,018 926
1303
73s
........
4.754
4,475 6 975 4:2(1l
3,136 6.100
........
7,900
1,030
48
3, a0
4775
1,000
..
Nov. 55,101s
J u !~ l,l$lb
-4pr. IS, 1915
June 17 1015 Mar. 13:1910
Aug. 7,191ti Aug. 16,1916
June 4,1916
hpr. 1,19113
Apr. 15,1018
July 1 lWi July 1:1b16
Apr. 14.1916 May 18 1916 JUIY 1: 191ti
Jiue 25,1916 July 1 1916 Sept. 15:191lj
June 11,1916
May 29,lYlti
Yay l.llll(i
Mar. 9,1916
May 16,1916
...
4 Observcs at 7 a. m. and at 6 p. m.. all other stations observn but once 8 day 81
about 7 8. m. loca; time.
1 clws .A evaporation stations, now. in operation is iven in Table 1 tmd their locations indicated on fi we 6.
!heir equip iiient and operation are briefly descri B ed in the following paragraphs. The observations at each of these 24 stations are limited to one daily measurement of the loss due to evaporntion froin cl pan of water, the daily wind movemenb across the pan, md such other meteoro- logical ohservritions as will serve to identify the general c:linI:ite of the region.
e g UIPMENT.
I11 t Iidcr t u insure coinpurn.hle observational results from ninny different portitjns of our country t,he entire rquipnirnt lias been wilrked nut. with n view t,o securing
thc grc.nt.cst. prnctic.nl)le unifc irinit,y of esposure conditions
:m1 t:;C equipinent,. Ewh station prcsents esscnt.ially the npjmir:ince of t.he o w illustmt,ed in t.hc ncconipany-
ing iigurr 1 : ti plun is slrnmn in fi ure 3.
Ihch :;ttition is quipped as Io K ows:
1 evnpor:ttic.m pail, 4 lcet by 10 inches, witli ita
Sll]q)(Jrt,. !See iig. 6 .)
1 still-well, with H 4-inch carpent,ers bench level.
L hook-gage. (Sec iig. 4.1
i fence.
1 supply taiil.; (covcrd i . where re uireil.
1 mi1i-a-e Wetttlitnr Ilureti1.1 S-inc P 1, wit.h wooden
1 she f a  t,cr, TVtwt.her 13urtmi cotton-region pattern.
1 pair ~nnsiniiini cnll nririiniuni thernioniet,ers, with their support.
1 itiienioniet,er, Wcatli~r Burenu Robinson. with
:t qwcid support..
1h p m .--The st niiclrrrcl ewl)cmit~ioii pan is cylindrical
i l l !ornil 10 ilic.lic!s decp, 4s iiiclies ill dinmt)t.er, inside tliincnsions. It is iiiatle of 23 B. IT. G . iron, galvanized
h l fim the pan is nidi. up. IJie bot.tnm is t,zirned up and
rketetl to t.lw siclcs. Thv t.op, or rim! is fit.t.ed wit.11 n Q by
I inch gdvanized iroli 1ii-)op sc.cUrely rivetcci t.0 the pan.
271:- ei,:~Z-.z/iaZE.----l?le st nnclard st,ill-well, clesignrd by i3. C. kadt.1 and u t l o ,trtl liy thr Wentlier Burmu, con-
wch side by + inch tliit-!i with n le~-elling screw 3 inches loiig :Lt. c d 1 coriicr. n i ~l t.lw wcll proper Y iiiches high and 33 inches outside cli;imct.er, nia.tlc3 of seaniless brass tuhing rigidly niountetl i~ii this triungu1a.r base. The water is admitted to the w.ell by metins of it short length of st.cind:ml $-inch brass pipe est.eiiding t-hrough the vnst.-iron base. (See fig. 3.)
A $-inch c.arpent,ers bench level is provided for test- ing thr licirizont,alitg of t,he top of the still-well. T h 7~oo7i-~~-lyt,.---TIi~i niicrometcr evaporation hook-
gage s1mv1-n in acconqmigiii figure 4 wns specially de-
tsce fig. 3.)
sup mrt. snd measuring stick.
(Yrv fig. 1 .)
sist.s uf triangular ga 1 nnizcd cast-iron base, 12 inches on
signctl by Prof. Charles F. 2 amin for evaporation work.
1 More complete details are p e n In: Weafiier Burau. Instructlous for the installa. tionandoperation of class A evaporatIon.statlon. By Bmj. C. Kadel. Wash&gkm. 1916. 28p. ill-. 8. (I n s t s ~t D l v i s l o n .~L .)
1 To face P. 674.1 M. w. K., December, 1916.
FIQ. 1.-General view of a Weather Bureau standard Class A evaporation station. (American University, District of Columbia.) (See also a. 2.)
2
6,
1 To face P. 674.1 M. w. K., December, 1916.
FIQ. 1.-General view of a Weather Bureau standard Class A evaporation station. (American University, District of Columbia.) (See also a. 2.)
2
6,
DECEMBER, 1916. MONTHLY WE,iTHER REVIEW. 675
It is so constructed that. one complete revolution of its
micrometer screw head nioves t,hhe liook rert.icnl1.v
through esactly inch. The inches imtl tenths R ~C
graduat.ed on the casing or t'ube, and t.he huntlrdthe and thousandths are on the micrometer scrw 1ic:itl.
SuppZy 'U!U~CT ta,di.--Tliis is necdtvl only IVIILW tilt.
water supply is so far clist,ant that nn n. qmv:i~Ildt~ wror
would result, from t,he iung time require d to hrhg w:i!vr
to fill the pan. The tank, wlirn present,. is 1;ryt c.ii\'c1':d
to prevent its cont.ent,s influtwcing t.lic vnpw on'r I Iw
evaporation pan.
Instrumen.f sh,e.ltt?r.-Tliis is the staiiililrtl louvcwd Weather Bureau shelter issued t.ci coopemtivc. staticins.
INYTALLBTION OF EQUIPMENT.
/Z,yww/v..- -T! LP instrructions for selecting tlics sitr oI the vvaporntion station rratl as follows:
Sdcr:t R coniparalivdy lwei lovation, representative of the region ant1 open i o the Yonsliine all thy, if posdile. If hillF. trees, l>iiildinqe.
1-tv., #*an not 11v aroirled, the length of time the pan is shded morning m r l evcuing slioulrl Iir indicated in the rlcsc-ription uf the station. In nnbr to IIP frw frnm Imssihlp reflec*ted Iwat the pan slinuld kJC no nearer to m y trc(2.. huilrlinq. cliff, or ot1it.r olljec-t than t h ~ height or the ol$?t. Nr:inirse to 1JOndS imd sw;%m]~a. particurilarly when mch ponds
llr swamps are tempornry in character. should hr nvoided, as B rule. llut
it m:ry ut times be dcsirahlt. to erposl: )am near a I)odp of water or even
tsn a raft tloatinq in the water. Such rxpoaures should be carefullv described SO rliat the results may be vorrwtly interpreted when COG- pari,wn clf the revortls of onr station arc macle with those of another.
,OUTLINL OF PAN.
PLAN
It screens the maximum and niinimuin theniiomatrrs sup- plied to the station. Both the shelter and its support8
are painted white in all cases. R&gaga.-The standard Weather Bureau S-inch gagti consists of a funnel Y inches ip climieter, a brass nitwur- ing tube whose cross section is &J the arm of the funnc.1 receiver, and an overflow can of gdvanizccl iron. (See
Instrument Division Circular B and C, for accounts of
thermometers and raingage.) w n t outfit, this
pm mth a flange adapted to bemg fastened to tlic w i c ~t i t ~u
support of the evaporatlon pan.
The unemom.ett?r su.pport.-In the. suppo.rt is a simple brass castii?g wliic p" 1 combines a brass
Grass sud waeris in t.li+. immt.diate neighborhood of the atation Hhould Ile cut orcaionally .
Thc awangorlcnt qf f 7 ~ oyuipment for tbese standard st.ati0n.s is shown in figurcs 1 and 2. TE:> rectanylar
plot of open ground, 12 by 15 feet in size, is inclosed y a .Woo t fence of 1-inch mesh woven wire stretched taut 1)etwwn eight bractvl posts. Tlw scooda.n support for tho. c v a or&iotl, p 7 .t ~ is laid on the ground with the. low side bloc P -ecl up to ilialie it level, then it is fillrd up witJiii1 an indi of the to with ground 1)rouglit ~roni tt tlist,aiice, and this is wet tamped in. Thus drainage is assured, and a desirable slight circub tion of air undrrnenth the pan is permitted. (See fig. 5.)
676 MONTHLY WEATHER REVIEW. DECEMBER, 19M
I
MANNER OF OUYEBVLNG.
Tilr lime ?f o h s o .~~f i o ~z is uniforndg wit,liin half an hour
of 7 a. ni., local st,andurd t,iiue; aiid whate7er hour is fixed u on within this limita, is adhered t.0 at the st.atioii
Eiuporation meustimnent is made by placing the hook- gage (fif. 4) into the still-well with t.he honk near the center o t.hc we.U as shown in figure :-i ; then, v;it81i t-he hook standing slight.l;y below the level of t,he water, t.he find set,t,ing IS iiivariably made by cnusing the point, of the hodi to rise slowly until it :ust pierces the wnber surface,
enaoursged to test his readings by niakinc. 9eve.ral suc-
cessire set,tings, rexiloving the liooli-gage anX changing the position of the hook between each pair of settings. has been made, the gage is removed from the still-w e5 to read and the reding is at once re- corded on the blank form provided. The evaporatrion pan is kept, iilleil with clean fresh water t.o within 2 inches (5O.S mm.) of t.ho rim, nnd it is refilled nt, a regultir observat,ion when t.lie. w\t,er level has receded
1 inch (25.4 111111.). The dept.11 of water in the puli is thus niaiiit.itined at. l>etween 'i nnd S inclies at all stations, while space for n reasonably heavy ra.inf:i.ll is also available. OrerHow aiid result,ant; loss of record due to heavy rain, is to be foreseen and guarded against by the timely re-
in tho P uture.
making the sniallest possib ll e pricking. The observer is
After a settin
UECEMBER, 1916. MONTHLY WEhTI-IER R.EVIEW. (377
+
YYETEOROLO"ICAL CONDITiONfI.
Am T E ~u ~. PmamAnm.*
WIND. I EVAPORATION. I
Y
niovnl of a sufficient amount oi water, making hookgage readings before and after such removal. The pan IS
emptied and stored during t.he season of freezing t.ei11-
perabures. Tht a.neinomcte~ is read once daily at the observation hour, and the total wind movenient of the past 24 hours is recorded.
T7t.e prevailing dircctim of t7t.c uriiid is deteriniiied by means of frequent eye observat.ions on the iiiorc?ment of smoke, bending of tree twigs, etc., nncl tlie entry mnde at. the time of the evaporation observation refers to the pre- vailin direction since the last entry. When t,he wind
(var.) is made. The tempamt.ure obsemmtion.8 aro made in tlie usual Weather Bureau manner, by means of the niasiniuiu and niiniiiiuin theriiiometers esposed in the shelter shown in fiaure 1. Readings me ninde and entered at the regular ogservation hour (about 7 a. m.) and obviously give t.he air temperature only.
The recordingfm supplied and used is best understood by the sample extract shown in figure 7.
has b B own froni various directions the entry " rariable "
PUBLICATION OF OBSERVATIONS.
'' Climntologicd data by [State] sections " (not t,he SHI~L?
m anot.liw publication of dnta by sections beariw the
same title hut also known as Weather Bureau Baetin
'' TV ' I ). A11 evtiporation observations of this current series made under the direct supervision of t.he Weather Bureau during 1915 and 1916 will be phblished in t.he Annual Suniniary for 1916 of the "Climatological Dah by [State] Sections " for the appropriate State. A detailed description of each station will be published i n the respectire issues which contain the first data for the st>at,ion. These descriptions will not be repeated in subsequent8 issues unless changes in n station occur. The temperature, cloudiness, mid wind direction will appear in thc regular tables of climatological data as now pub- lished in these section reports, but. the daily evaporation niea,sureiiients and wind movenients, together with any other specid da,t,zx will be placed in a separate table of a
form similar to that now used for the daily temperature estremes.
SLOPE AND VALLEY AXE TEMPERATUEES.
1:y \V I I .L I .~ H. R ~A I B , ProfeRsor of hletrorology.