JULT, 1916. MONTHLY WEATHER REVIEW. 385
SECTmN II-GENERAL METEOROLOGY.
CLASSIFICATION OF TEE HYDBOYETEOBS. I
By nr. GUSTAV HELLMANN, Director.
[Iiiinlgl. preuss. Yeteorologische InStitut, 1915.1
(Translated for the MONTIILY WEATEEB REVIEW.-C. A. Jr.)
INTRODUCTION.
The present work endeavors t.o erect nnd establish a eomylrft system of the hydromet.oora [i. e., of the at.nios- pheric phenomena which owe their origin to t.he presence of aqueous va )or in tho atmosphere.] It is renia.r I able thnt, such an aatmtsmptm hns not, been preriously ninde, since t,he xecipltntions of a.t.nios iheric
formed an import,ant chapt.er in meteorology. Arist.ot.lo
and his successors discussed nll t.liose chief forms of con-
delisation of n uenus vapor which rccur in Greece or in
(Reif), mid Hail. They did not, discuss the clouds, which did not, entcr into scientific discussions until 2,OOO years lat,er. Yet. as the teacliinp of Greek nioteorolngy becmie
known throu h u t . central nnd northern Euro )e, tho
drometeois to those just. mentionad, nlthou-11 G1:tt.t.eis [i. e., the ice coating called ulazed frost, by &e Englisli] md rime (R d u e i f ) must Envs been often obseryedin im ressive and dist.urbing forms. frobably the retwon for t.his omission-aside from t.he pest aut.horit.ative influence &ill enjoyed by the Aristot.el-
itin system-lay in t.he fact. that t.he st.udents (-if those clays wrote, almost. without e.ucept.ion, in Lntin and PO l i d no espressions for hydroniet.eors not nlrendy nieriticined in the In classic tinies 9s woll as during
A es, interest! in these niatt,ers was fsr too slight- t.o evofe the iiivent,ion of new words to na.me phenomena t.hat, in nng case, wore rare. The phenomena
probably were known, but one and the same word was applied to relttt,ed processes. Thus  pruina  (Reif, frost) may also oft.en mean rime (Rnuhreifj, which occurs not
so rarely in northern Itdv.? Similnrly the word grnndo 
(hail) ,robnbl,ly serwd dso t,o designnte our snow pellets (Gfr. dr;iupeln, B i g 7 . soft hail), just ns t.o-(hy t,he Eng- lish lmgiage m&es no distinction between the two forms of the precipit,nte hail. Wo find hail and graupelJ
fist clearly differentiated and dist.inguishec1 by ,Ubort,us Msgnus, who drew at,tent,ion to the differences during his residence in Cologne where grau le1  is of frequeI?t occur-
rence ns it is throughout Low hermany. In his paper
water Tapor in the liquid nn h the solid fornis hare a !I ways
the eastern Me x iterre.ne:m-viz, Rain, Snow, Dew, Frost.
rnetaorologicnf treatises are not. found to add ot. 1 ier hy-
of t.he ancient,s.
IHrlZmann Q. 6 stem der Hydrometeore. Berlln 1915. 27 p. 1. (Yerijffentl.
2 This is the sense In which is t o he taken, e. g.. VirgWs cirmmfusa pniiuis rorpora d. k. preuss. heteorny. Institut. Nr. 2S5.; Abhdlgn. Rd. 5. Nr. 2.)
magnq bourn. Sirmlarly in the oldest weather journal preserved tous that of W. Merle at Drihy near oxforrl (1337-1344;, pruina** must often mean rime (R ~U ~~I I I when it reads as lor Deeernber S . 1340, pmina magnn et nebula magna et gelu temperatum; bera;Se in a heavy fog it ?rime, notfrost. that forms. The word pniina is stlllpr~.ser\-ed in1talian.and C:erosa( Elementidi meteorologia. Livorno 1cJoB. So. 167) gives it the significance of rinw.
8 In %fkrle*s journaPibere often occur? the eutry veutus magnus rum nive pluvis et grsndine multoties in die: The E n g l ~~h translatlon wrompanying the jour~h, SpenkS
oIhai1; but it Is evldent that Nerle here menut squally weather with Ireqiiriit alterns- tions of raiu, snow, aull graiip?l (snow pelletu). The English meteorologistg have recently devised the spec/al nameso1t hail  to iudi- rate graupel: but that name IS not known to the general puhllc and has not always lound mrirtancr ho the snnrialists. Thus Mosxmnn. in his ohservers ioiirnnlfrom the IVeddel
whethar hail means hail or graupel.
De pnssionibus ai&, written ahout, 1 5 0 A. D., after writing on hail, Nbert.us Mt~gnus clevc-itcs i-.lirea rlinpters
t.o graupel  De gr:tnulis cnclent ibus in Martio vel Aprili. In substqucnt. -cars wc smiet.inios find t.he eiicpc*hlwclic nrtirlas of the fourteenth :xiid fifteentli centuries i ~s well
as t,he testbookt of tho sist,eenth cent.ury, t.reilting t f tbcse  granulti cnnge1nt.n  in nddit.ion t.0 tho five hpdro-
niotoors discussed by h i s t.0 tle. Addi t.iond hy%wnt?teoi s
a.re not nientionecl, but on the other liaiid several nonrdated phenomena, such as nuldew (hicddt au 1,
 nitinnn,J etc., me classed here. Spcific t,ernis for wen the rarer hydromrt.cnrs WTC
developed mwh earlier in the 1anpirrgc.a of the twniiiinn
JWO des. but t,lillese teriiis did not. find pl:i.ccs in puhliahed
w o l l s l>e.causo the Itit trr were writt,en iillliost esclusivrly in Lnt.in unt.il the miildle of the sistcentli centmy j i i
France iiiicl It.aly, :uid until t.he end of that. perid in Germ t1.11 y .4
This is the reiison why some of t,he hydromczteora iiot treated of by Arist.ot,lo reccive no 11leii tion until quitc In t e in 1iiist:ory-rcally iirst, in t.he iiirt,ec?rologir;il t,cst,- books of the second htrlf of t.hc eight,cciit.li ct-iit,iiry-- slid d i y confusions of fwt, ii,~irl of iia.iiies orcur. Ind~t~cl we luck pwise drjititioiis nnd CI. strict tarwiimlogy. A beginiiii!g d o n g t,heap hies 1b-ii.S iirvt, macle in 1873 by t.he Secoiid liiternationnl Meteorolc~gical Congress st Vienna, w1iic.h introduced international syliihols for abhreviut,ing the rntries of observed 1iyclroinetroi.s and other niet,eoro- logicid phenclllle11ti atld also dct~rrniincd ~01iie of the concepts; t.o 11il sure the lattrr prc~vecl soniewhntm too brief 111 iiinny cases. The rcsults of this a.greenient. werc t,hnt t,he b L Instmctkms t.o Ohserrrrs J J of the vtwious
rount,ries were fit,ted to t h iifiw tlefinitioiis and s~-mhols. whereby again all kinds of errors crept. in, eit.hcr hcmnsc!
(as w2i.s the cnse with t .1 ~ southrrn ~~untries) ninl-!.v of
the solid fornis of coiidciisation were hut: li t.t,lr known i w
because the respect.ive 1nngn;igrs cont,iiinrd 110 ivord f(Jr
a phciionieiion of rarc occurrence in those count;rics. Thcw has result,rd nii ~xclinngr i-)f itle::.s t,hroughoii t. the
hst decennia., coiictlrning t.hr i*oiicept.s of t,hr hgtlro- met,eors, taken piirt in not.nbly l>g Sc.hoiiroc*k. KOJ)~X*I~,
Yernt,er, Schiytschinsky, Jdituiswii, A. Wt~gcn er, ii11 il (lnt,cly) Ciro Clhist.oni.6
4 Jn theventher o u m l kopt, by the prior Kilim Lelh 3t; Rehilorl/NiirnLerg. from 15!3 on (see Brhottenlohnefs mntrihiitioii t.ii 1~iezlr~-FesIsrhhl.111. 1913). Ihe joum:rlisI some- times had recourse to German espresshns,e. g.,pruina, quai11 vulcusrlulit ai~pelst. This expression to-dny mmmon in soulherii Germany and Aostris. alntm liacli to the Middle Ages. in Heynes \V6rterbnc.h I find n ritatiou frola the Ihlinndncers tl2l.h to 13th cent.) which shows that the pwple a t that time distinpilished hetween honrfrcst (1;eif) and rime (Rauhreif) or Duft (tiill), viz,
Srvaere tnge und srhnrfer luft macheut is, SUP, rifen, tuft.
The French word grPsil (Graupel) illustrates how slo\vly :qmlar i I r s i ~?t ions ?re arlol&d into the langun~e of tha stutlents. .\ccordinp to 1:odcfroys LDiCCtiomiir? de iunpien langue franqttise  the word (crezil) occurs already in tho Chmt de Rolu~~do of the 11th century. The oldest Meteorulogy in l.rench (A. hlizanl!l .Ire miruuer ale Inir, larjs 1 s . So) adopts the term. t a t hmrtollngl?., lor the rsptlon re:irls De la gunem tinn de Gresle. & drngetfisglwez: 011 si voolez gresil. Further on in his test the Grm- peln are descrilied as petitz r6deletz Ael;Set6s. The won1 dr;izetons I did not find in the French dirtionnry nleuti?nwl; it is prohsbly deriwd Iron1 dragCe; which also slp~ities a mfsture of snlall grums. * Brhonrock, Repertor. I. Yeteoml., 8t. Iet.erslmrg, SI. Kl. Mil,. iii. fiopprn, Ifeteprol. Ztsrhr I?%, 4:[iO] ; 1 4 S . S:[i.<l. IcrnM L Schr~&chzn8kfi.~l, imcht iiber diu meteorol. I~lrekto~~iI~onleron~ in 11111s-
Jeliansaon, Neteorol. Ztsphr.. 2228. litgrrirr in his  Thermodynamili der Atmosphhe. cltistoni, is now stntiaiied at yapis to
brurk 19K. p. M ffg.
wrr: \,ut his former long resirieme in northern lkily niadn him arqilsliit~d with nlany hv~lrometrors that are rarer in thc south. He his pnl.lished the followin J runtrilmtiuiis in the Rendiconti d. r. accad. 4. a.1 fis e nidernat d Nayoli 1910 auf 5011: Ruggind:r I guarm  Brina, gala\-erua e &al;rosa  d~r:elicidlo I S h a formazione dell? hrinn, Sopr;l\inn IIotkh del Dott. W . Knochi rigusrdantd lo formazione del Ghttcls.
386 MONTHLY WEATHER REVIEW. JULY, 1916
I hnd to consider this i uest.ioii in sonic ilct.ai1 while editing the 1nt.erna tionnl \kt.eorologiml Codes, and I found t.liat> heretofore sonie fornis of r:queous conilriisn-
tion have not been coi>;idered at, d l and thnt even t.he most coniprchensive metcoro1ogi:ir:i.l test.s are c-lcficien t, in this respect.. I t$erefore resolvcd t.11:: t sometime I would endeavor to dram up RII eshaust,ivclg coniplel-o systmi of t,hc hydroine t,eoi.u. Tlic presnit c.c,iInuunicnt,ion lins
t1in.t for ita object,. Of coursc we here littve to endemor t.n cletcr~~iine t.he niut,u::l 1iniit.s of t,he individud f0r11~ of ]~rccipit~:~t.inn of at.nuxpheric wat,er vc. or-in so far as Ntrt.urc lierself knows any such slir!.rp c 7 cliniitri ticins, fiw t.licw foriiin,tiws
&j have t.ransit.iclnnl forms-ril.t,lic.r th:m t.r) dcrdnp t.lie still very inronip1et.e t.lieory of the )I ~(~I I o I I ~P I !~I ~. NWW- t,lieless, tlic genc.t.ic p i n t ci Tiew wih 1w 1ic.111 t.cp as fnr as
possible, beci;llsc oiiiy in this ~1 .y c:u\ oiie WCIIPC R fised concept, in sonie cases. The discussion mill lw rrry hricf, for such wcll-known hydrometeors :IS r:i.in, dcw. l i d , which a .1 ~ not, likely to 110 cc-tnfust:tl lvit.11 r d i c w , iilitl I shall t.rent, in de ody t.hc llr~~t-ly p~~p~seerl fc .I I ~~S :L I ~
some t.liat n.re less shxrplp deIinrc1. 111 t.lw l:itt,c*r C ~P H it, will somehies l>e aclvi~xhlc t.0 d t l sc-iiiwt.l:ing :hmt. tlic
tenipord rind mml distribii t,ion of the p11~111~111~11~. Tho
nomenclature will also be considcred. The fnllowiiig schcnin.t.ic sunim:rry con t aiii:: t,li;.se f(:~iiis
of condensat.ion of tit niospheric wilt cr v :r p which repre- sent independeiitr plic~nomrn:~. They nre :rrraiigrtl in t.he three nntural groups : (1) Direct, c.c-~iiil:~ilx:it.ioiis at. or
dose to the enrt.lis sui-fnce : r2 1 direct coiidensitt.icins in tho free air (bhc cloucls~ ; (3) indircc.i. condcnscit,ions in the free uir (precipit,ntes ailing from chids). Under
each group the corresponding fi~rnis of fluid nncl solid
ag egiitos are set, in pitr:~llel columns. Rndly, before pa.ssing t.0 t.he discussion of the indi- vidual hydrometeois, I would say that we s1i:tll here concern ourselves with only the hydrome t eois in t.hc narrow sense of the word-viz, t.liose forms of conde~nsa-
t.ion that bring directly t.0 tho e:i,rt.li water in it,s liquid or solid forni-so t .h t t.he clouds (forming ti clinptcr by
themselves) m e not, considerd nt all.
SYSTEM OF HYDROMETEORS,
(1) Direct condensations of water vapor at or near the earths surface.
Liy i r id. Solid.
Sweat  . - . . . . - . . iBeschhggi. Dew - - . - . . . - - - - - - (Tau ).
Mist maters. -. -. -. . (Nehelwasser).
i Frost.ljetjc*hlag I.
lirost,. Iirrarfrost. - - (Rcif ).
Mist ice.. . -. -. . . ( Yebeleisl.
(1) DlnECT CONDENSATION OF WATEU VAPOU AT THE SUUFACE.
Satumiing, Sweat (Beschlng; ITIassriger Bcschlag).
The watery coating liere referred to is of two kinds. A . During the afternoons of wnm, clear Fnll dam, when tho at~iiosplieric content of water vapor is still rahhw high-in Berlin it nniounts on the average to 7.1 mm. in Oct,ober ns conipnrecl with 5.7 nini. in April and 4.8 mm. in M:ircli-tlie st.reet paveinent,s tliat lie wholly in the sli:i,cle, as on t;ho north sides of houses, become coated with
:i t>hin film of wat.er. This moisture does not gat.11er into drops, but, one can clearly perceive that the paving on the sli;idv sitle of tlie stmet, is cln.rkenec1 by tlie moisture and stnntls out in contrast with tale dry and t,lierefore brighter pi.ving :ic.ross t:lie way. St,regts running nortli-south into which t.he sun slijixs, a,nd large open squares, do not show this nioist.ure, while in RII c?sst,-west street it mny pcwist OH tlie sh:i.dy side h .y ani1 night. Of coiirse this ilepcisit is not the unevnporrtted remains of a. previous rain but is a procipitntion of the water
~:tpor of t.he lowest air 1ayc.r~ whose teniperature hns been brought, hclow the lmil dewpnint by reason of the ccnist8ut clny and night radiation of the underlying stone surface. The rocess is, therefore, similar to the forma- t.ion of dew ( nu) which also not rarely be ins before sunset.. If, nevertheless, I do not clws t,liis p enonienon with dew (Tau) i t is because in the latter cam botsh soil niid air furnish t.he iiioistiire for condensation, while the
air nlone supplies the moisture condensed 8s sweat (Beschlng), (I). The soil moisture can not rise through thick st.oi1e.s or asphalt paving.
R. In t,lie colder half of t,he year when a wnrni and very nioist, ilir c.nrrent sets in snddenly after :t rather long but only nio(lerate1y severe cold period, stone walls, marble and granite house faciiias etc., develop a nioist coating. In popular language ?die stones sweat (Die Steine scliwitzen). The stoiie has not been able to keep pace
with the rapid change in temperature of the outsde air, tlie nioist air c,oliiiivg in contact with the stone is cooled below t,he ilewpoint untl compelled to give up some of ita moisture . In this kind of swenting, which in contrast to that
discussed under A rtff ects vertical ing weather is generally cloudy. nota continue for lon , but is ninre vn.riaty first inentione $ . (2).
R; 4
The
Frost besehlag?
Wlieii such a sudden change of wetither as has just been desc.ribed, occurs after a long period of seyere cold then t,he house walls, stones, etc., are so chilled t,liat, the dew point. of tlie warm nioist air direct41y in contact with them is depressed below OC., and a solid deposit siniilar in ap mimiice to frost forms on them. This deposit is also w e \ 1 seen on smooth-barked tree trunks siich as the beech,
In q d u r language the cold is coniing out (Die Kiilte scli I iigt nus).
SThe author is uunhle to deride whether there ocrnrs an ice coatin (Eisbeschlag) cor. respondinc to the first kind of sweal.ing(Wlsriper Besclilnr,A).anBresulting fromtha Ireeeinc 01 tho Irrttcr: Iic hlinscli his never ohscrverl siich P phenomenon. Such a tmnsforniation would. however. prolmlilv be possible st elevated points in the mom. tgingwhere the temperature often rapidly falls to 1)clow 0C. after flue clear days In the lq.:ill. Here rrkrenre may IF made to an ire formatlon rcyeatedly observed hy Ratzel but n1 which he could find no pubilshed dtscrl Ilou (Lhs Wetter, I&% p. 216). Perhaps
I i r w nlso lielonrs an Ire formation ohserved\y Knoche in Chile and by him classed-I think iucorrectly-as Oiabteis (Metcorol. Zt.schr.. 1911, 28:93).
JULY, 1916. MONTHLY WEATHER REVIEW. 387
By mmns of a magnif-yin glass one can see that tlie ice film t-hus formed k m?. d e up of crysta-.Uine columns standing close together perpendicubr to t.he surftrcc md
Unitormly 1 or 2 mm. high, somewhat like hoarfrost (Reif) that forms on a bench during n clear night. Olio can write and draw patt.erns in the deposit,. Amorphous forms also occur, however, articularly when the filni
Thi$ frost coating (Irost.besclilng) tmlures relntiwly
a long time whon in the shade, and may last as long its
14 days if the preccvling cold was very severe.
In some of the older textbooks, and even in tho niore recent ones,  Frostleschlng, if nientioned :kt all, is f d d y described as rime (Rnuhreif). As will bo shown below, r h o is nlbogether different in nabure and origin.
is very thin can one see close P y crowded ice points.
Dao (Tau).
Dew is so well I i n o ~~, by reason of its widcspre.c?d oc- currence, ancl is a hydrometeor of such definite form that there is scarcely any difference of opinion as to its definition. Christoiii draws at tention to nn observn- tion by Iusiniwi that even under the t-recta a certain amount of clewinrss is sometmimes present on the gmss
when the sky is cloudy. This kind of light clew will usually escape the attention of the orrlinnry observer,
who, indeed, will not,e tho dew drops linnc4ng on grnse- blades and lenves, but does not esnniine txcr. griiss more dosely for moisture. We distinguish between evening clew and morning dew according to tlie time of dny when it is observed. The morning dew, which has formed during the long night, is naturnlly more frequent and more copious thnii the former. The Romance languages have n sopnrate word for evening dew or evciiing mokturc, viz, sorein
(Fr.), sereno (It& Span.., Port.).8
Hoarj?ost, Frost. (Reif).
Frost is frozrn dew, so runs the stnert.otyped ex- phnntion of most textbooks and instructions. It is a
very anc.ient statement, obviously dating hack into an- ti uity, perhaps coming from Chr-pippos or from Pliny (&st: Nat. 61) or from the pseudo-Aristotelian work
rep1 K~UWIJ; while Aristotle himself explicitly says that when frost is formed the water vapor solidities directly.
The Stoic Chrysippos lived in the third century, B. C., and accord- ing to the statements of Stobam, taught- that r b x ~~u 81 I51~15uou u e q -
yuiav (cf. Diels, Doxographi Graeci, p. 468, 5). In thework Hfpi dupoi~, whichXeller (Philm. d.Griechen, IIIa, p. 645)
thinka probably dates from the first century before or after Christ. Ohere occurs a remarkable paasage referring to frost which, I think, has not been properly intexpreted. After having again remarked of frost mixvq hi:
~psror zcur)yvia, it. pes on to say: iipouor&xuq 6;. ljlrraayds 6pbaos. 80 that dew-frost is a half frozen dew. BarthBlem Saint-Hilaire (M86orologie dAri8tot.e. Paris, 1883, p. 3743 transetes the word
i p o ~o ~a ~~q , which seems not to occur agmn in Greek literature, some- what boldly by the word rime (Rauhreif), which is actually incorrect. This translation is also in contradiction to t,he translators wuiiiphon
that Apuleius of Madaura is the author of the manuscript; for how &ould an author from Africa come to mention rime when, from his own experience, he could scarce know what frost IS?
-
1 During the 30s and 40s 01 last century the Itsllnn. Inwstlcntors Fiisinieri, Zsntedeschi bielloni and Bellnni carried on a lively dlscussion concerning lht. laws of radiation aid the thdory 01 dew formtlon. whereby sonie new details were l~rought to Ilght Quite recentlv Button 01 Kimherlv baa made some interesting communicstions concerning the Iormitlon of dew under aclondy sky (hieteorol. Ztschr.. 1915, 3232).
8 See tho remarks helow, under Rain without clouds Ior a 1alscsigniRc.ancc 01 tile French semn. The use of sereno In Itallan Is found in Pac1sSagglo dl meteorologis (Nnpoli, 1634 So 431;). I cite this niithority cxpressl): because the groat Itallnu dictionaries 01 P&oe)e&. Rigutini,snd otlyrs. do not grve thisniesnlng for sereno. A somewhat diflerent slgniflcnmre-riz. mist over the yadows In the evening-Is Ioi~nd in A. Bellnnis Della mglada. della hrlna. . . . (1S31). In Spanish sereno means In general the moisture of the evening or the night (Dlcclonarlo de Is Lcnya Castellma por Is Acndemia Espafiola). and llkewise in Portugucse.
Tho old idea that hoarfrost is frozen clew, t.0 which idea Cliisboiii rlist,inc.tly adheres, is not correct. in this general
sc!iise. I t is t.rue that, ofteii tmough it, happcns that dew first fornis and t,lint., if tlie tciii jernture cont.inucs to full,
wintr:rt.ime the clewpoint is initially below 0 C. the water
vapor imst ptws directly int,o hoarfrost.. Were lioaifrost nlw-ags frozen dew, thcn one should freque~itly find tile iJidivic!unl cle~vdrops which lie in the leaves to linvo been conmrt,ed iiit,o icc balls. Tlic writ.er can rrcnU but, fc?w occ~sions, niid tliosc wore ill tho Fnll, whon 110 olmrved such a phenoinenon.g If t,he clewpoiiita lies close to 0C. it, inny hnppen tlint, according t.o tlie rnrlint,ive power of t.he objoct,, dew ancl
hoarfrost ma form side by side.IO In this case t,he honr-
over ice is lowor than it is over w a h , and t. larefore t,he w n ter vapor condoiises iiiorc readily upon tflie frost.. Chistoni fivther clitinis that frost foriiia tion does not estond beyond n level of 3 niet.ers above the ground and that the frost-like phenomena observed a t orenter heights is rime (Raulireif). This, however, is ahogetlier c.oii- tmdictory to exporiencc in our nortliern countries. Her0 frost fornis both on the round niid on high roofs over 25 metcrs in height, whi ? e at the s8nio tiinn t.he twigs and brnnchca of equdp lofty trcos relvniii quite free of it. This would not be thc case were the formnt.ion rime (Rnuhrcif 1. The formation of hoarfrost requires intense radiation outward toward the sky, nnd as t,his can procmcl unhindered from n roof it np ears quite naturn.1 that hoai-frost fornis on niore or less Koriaontnl surfaces a t greater heights above tlie vound when there is suffi- oimt water vapor resent. aimo on the other hand, is
precipitated from t e clenieiits of fog blowin past ter- rostrial objects and thnrcfore its delicate o m s coat ohects hnvin nn upright position. hoarfrost d oes not always possess a crystalline s t.ruc-
ture even though its macroscopic appearance sugges t.s it, and Assmnnn showed this in 1SS5. Since t,hat t.iiiie Prinz, Grosniann, Lomm , [n.nd B ~i i t.lcj-I, I2 have revcdetl to us such a quantity of crystalline fornis of homfrost, (Reif) that I am inclinccl to regnrd it,s amorphous form
as the esception. This subject requires, however, fur- t,h(?r nnd niore long-cont,inued iiiv~tst.irrnt.ions. The niost bcnutiful frost fiuures I kave seeii-on only one occnssion, to be sure-lid foriiied in a sheltered spot. and under moderate cold diiiniiiium n~ns - 5C., 33F.).
They were snidl hollow six-sided p rnniids st.nncling on
nel. [See also Bent,leys photcgra hs, loc. cit.. P1ii.t.e V,
Grossniann LE: Lomns mere able to study t.Eese foniis niore in t.ensivply during Christmos, 1892, in northern Englmd,
n.nd they showed at that t,inic the coniplate similarity t o
the funnel c.rysta1s which form in ice c n v ~s l 3 where they
n.re able t u develop 1vit.h sptcinl rcgu1nrit.y 1mc1 to n great
tlio dow passes into tlio solid 1 o m . However, when in
I;
frost. is usul~ IY y more copious because the v:t or prcssure
B
?I
their point,s witrh the opening turne d: upwards like a fun-
fig. 37; Plate! xIV,fig. 116; Phte XLrV,fiw. Y 335.--C. A. jT.1
9 It is rcliably reported that this frozen state 01 or1 inlllv liquid rlewVdrops bas Imn Irec~iientlv ohserred diulng ?Liigiist I n the Korky $ountdins s t altitudes 01 li.000 or I.~X~feetibove sea level. Cox mentionsit but once. spprentlv. in his mnnogrilph nnfra?t.conliitlonsin TVisron- sin cranberry marshes nud regards it i s s periiliilr phenomenon. (Woither Bureau hullelin T Wasllington 1910. p. S9L-C. A. jr.
10 Fedr& the above-drnlloned ilea frost * (d p o r o s r i ~v ~) refcrs to this ghenomenou.
11 9t the nbscrvntorv of Potsdsm (Berlin I there Dre. on tho averxe. 60 (la s with hoar- Irosi (Reif) per yesr.whllr at Palermo (accrailin!! to ChLtoui) thore are gut flve surh days. It would appear Irom this that observors 111 norlhrru Europe hsve ~niich mom freipont oppnrti1uit.y to ohscrve hoarlrmt than do thuse nl soiitliern Italy.
Ilciitley in Mrmthly \\cather Review, Nor.. l ~w ., A Ann. Slim. 1Joi. 35.
(.;rossmslm B l,nnnsin lroc., ~o y a l sw., IN*, 55; rle!ails iu ksiuri, Lonilon, Oct.
brinz i j b tiel c t Lcrrr, ISM. Coni xire also tlie cmitribution hy E. Budde on !<iskrystnlle in PoggeudorEs Annslkn, ,150: 5ii.
13 Sc!i/7g11zlureit. Neuo Uiitersuchuingen iibor d. phys. pogr. d. Alpn. 11. 4G9.
Assmnrm im Nrt.eoro1. Ztsrhr., lW, 2 :W i .
18 lS94, p. .
388 MONTHLY mATHER REVIEW. J a y , 1916
size b reason of the prevailingly quiet air. They are
The frost figures, so-called ice flowers, t,hat forni on the surfaces of glacieis often show beautiful forms. Finally, I woulcl refer t,o a rernarkrihle ice growt,h in the soil, which must not) be confused with frost,. In the
late fall or early winter, when t.he upper layer of soil is quit,e moist, one iiiay at times see in the emly niorning, after a frosty night, lit,tle colunins and tmhes of ice lit.er- ally powiiig up out, of the s1iglit.l.v frozcn ground niid ushmg t.he surrounding soil i1it.o little clnnies and rolls. $he: +e m e t,he ice columns or ice fi1ai:ients (Eisfiltmeiit,e) .I4
Mist wuter, Wetting fng. (Nebclwsser; ATG8.wnt7fr NiJbd).
Wat,er sepn.rates froni a wetbing fog (nassender Nehel)
in A. two (N t war: eI!m).-On c1ea.r calm evonings in suninier atid
fall, less frequent,ly in the spring, nbout, sunset, or perhnps
a 1it.tle before, a li .ht radiation or ground fog (Bodon- nebcl. Sbrnhlungsne fl el) forme oyer nioist. nieuclows of ton to B height of but, one-hdf nieter. In the rciurse of the
night, the fog may incrensa t.o a depth of n nims height or more. It,s white color mnbs tho fog visihlo at. coli-
siderable dist.anres and throws it into such contrn.st. with t,he dark surroundin that one can t.race its cspmso long after sunset.. 8 fteii men.dows of niaiiy 1iect.nres extent are unifornily covered by the fog, more frequent.ly, however, there are fog-freo spots hero and thnrc which are usudy soniem.hat higher and drier. If the sky re-
mains dear t.hrou h t,he night the fog grows denser with the markedly fal f ing teniperat,ure and wirtor sep:mrt.es out: the meadow becomes moist.. Chistoni properly p0int.s out, that t.his conclensstion may not be classed with dew. If the observer finds t.he fog st,ill present at the morning observation he can read- ily different.iat.e between t.ho fog moisture and t.he dew moisture, but, if the fog lias nlready disappeared then it, is more difficult, t.o dist.mguish theni. I t,hink, however, that my own ohservat.ioiis justify 1.he statement t.hat the dew is readily hou-n by its well-formed droplets
while the fog moistens the lenves and grnses more
uniformly. In tropical locslities where the wntcr-content of the air is specifically high, dense ground fog (Bvdennebel forms precisely during the dry semm and refreshes the plant, world with a generous morning moisture. The cacimbo of Portuguese most Africa is n frtmous ox- ample of t.his phenomenon. B. Wctfog (Ncba~~c,,jSsni).--Ofteii t,he ground is cov- ered by ti fog denser than the meadow fog (Wiesennebel which hns just been described, and thon i t is a mntt.er of indifference hcnv tdie fog originated. As long i1.P
t-he mist droplets are very mid1 t,heir surface tension is so peat that. when t,heg strike nn object they rebnund without bursting (clry fog). When t.lio fog particks become larger, however, cont.twt. ~ausos tlieni t.0 split up
or burst into the finest, droplets (wet. fog, niissendcr Nebel). One says the f c g is burstingJ (der Neld
 reisst.  ) . The aniount of wntm that, sepnr:it.es out or is precipi- tated in consequence of t.he fog hurating is, of cmirse, slight, and it becoiliris coiisiderahls only if the ~~rtwrss
cont.inues for so~ue tinw. Siicli is not.fib1.v t.he case whrn
even 9 ound occurring in t,he cooling rooms of breweries.
(3)
~~
14 Readers of the I:ETIEW will find this pheiiomciicm. which Is not. a hvdmmrteor in the striat sense. descrihcd. illiistratcd, nnal rlisriiwt! in thc YONTSLY WEATHER REVIEW 1598 26217 (bihliographyr: IW5, April, 33:IX-8. and Uec.. 3 3 :X (illustr.). A datdl&? study r i f thc related ,henon~ni~m of ice fringvs fJn plants will hr Inunl in the August, 1914, issue, 42:4WLd.-c. A., jr.
brisk air c.uTents chive large iiiasses of met fogJJ (nassenden3Nehels) a sinst proecting objects; that is,
siniulbnnoously. In t,he free air t,he fog ptrrticles can
st.rike only a ninst one another, so t.hnt but few droplet8 rcrsult. from t f e breaking up, hut in forosts t,here develops mi actual rain undcr t,he t.rees. Leaves, bushcs, and twigs mtch the fog dro lets, wliirh run t,owt,her into larger drops rind tlicn fa1 r to t.lic grouncl, so &at the forest soil becomes thortsu 1 ~y wet wliilo t,he soil out,side tho woocls is hut. nioist,ene$. This capture of water by t.he foresb,
which I woulcl call fog drip (Ncheltmufe), is of importance in forest, econoiiiy arid oft.rn has been w olly uvcrlooked in studies 011 t,he iiiflucnce of forests on pre- cipitnt.ion. If t,hese st.uclics consist essentdly of a coni-
)srisoii between t.he procipi t.ation iiicasured out,side t,he ~o r w t :i.ncl t.lint. iiieasured in a clcaring within the forest, t,hrn the process just described is nlt,oget,her MaturJlg fog dri yicltls t.he greatest. ninoiint of wa.ter
on thc lee side of a P orest., so tlint niriuiit,:i.iii forest,s on t,he
 wcnther side or 011 t.he suniiiiit.s of mountain rmgm oc.cupy t,he inore fnvorcd posit.ions in this respec,t,. A C1:iwir esmiplo of t.his feature is furnished by Marloths
nirnsurcnimt,s l8 on Table Mt-)un t.trin i i ~n r C a p Town, whrre tho veget,nt,ioii capt,ures much wntcr from the driving clouds of t.he Sout,heast Tradcs during the dry siiniiiwr senson. The higher part, of t.he dry island of Ascension also securcs inoist,urs in this nin~incr.~~ In t.he 1owl:inds of dry regions it is also frequcntaly the case
that met fogs are the only source of the litt,le water recrivcd by the vegetat.ion. Typical esaniples of this are t,he gnrtia.s on the c0ast.s of Chili and Peru, driving 1:tndward from tho sen in t,he Winter and Spring they iuoiatm t,he soil; sirnilnrlp t.he frequent fogs along the
coast of German Sout.hwest. Africn (Ywalcopniund has 149
clays with fog per annum) have produced a fog-fed vegct.ntion (Nehe1vcgetat)ion) of t,heir
when wet fog ancf driving / og (Nebeltreibed occur
rt
Mist ,ice (Nt~bcZciu 1.
Ice separates out from fog either directly by suhlima- t.ioii or inclirect41y froni subcoolccl fog droplets.
A. I c c -j b g jrosf-s~nnke. (Ei.sn.ebeZ).-Truc rndiation fo corrcuponding to the nicnclow fog or niist (Wiesennebef of Suninier, can not. forni in Wint,cr when it is cold; but
a fog due to niisture (Mi~c1iuii~~iiehe.l) can forni over
wttriii spots. Many hoclics of wntcr (e. s., the Norwegian fjords, mid particularly ice- rec spots in the polar seas)
form such warn s water is at once ice ptutic.1e.s , which nisy even he beautifully foniied snow cryst&, slowly sink tao t.lie onrt.11. This ice-fog or froat-
sniokc (Eisnold, Frostnebol, Frost,rirctuch, = Noru~. Froatrog) was first described, I belicve, by the Hamburg wlialing niaster Friedrich bfart,ens 2o mid later iiiore aecu-
The wat.er vapor rising from the in tho cold air and the rt?sulting
15 It may not be out of place to here state again that the problem which hss recent@ attracted renewed attent.ion in the United States and in the Weather Bureau. is a purely mcteorologicnl one. It ilom not deal with forest econom a d is: Can the existence d
forests induce or further rainfall. properly sn ralled? die answer must he bawd upon oomIimsons of mmwrements wholly free from swh unrelated and disturhlng phenomena as fog drip-c. A. jr.
16 Meteorol. Ztschr.. Memher. 1%, 23 : 517-5.53.
11 Gee MONTHLY WEATHER RRVIEW. Octolner. 18R. 26: 466.4. A. IT.
18 Much for IS not.hinR eke than low-Iomq cloud therefore manv might prefer to class wet fop (Nebelreisen) and its intensified form. :<fog drip. with precipltstjon falling from the clnids. Transition staxes of course exist. I have not so clssed these two forms h~eause rertnin fn.es form only at. the earths surface and hecause a mountah rlwllcr does not. much care whether the mist (Nelel) t.hat inwraps him is fop or cloud (Nebel aIs solchrn d e r als Wolke).
1: I Front smoke is given by the Venturv IXctionarp RS the nr?nie of t8e fog of ice nwdei that forins nwr l,orlies of water during severe CrJ\ll.-c. A. jr.
20 Martcn8, Fridrrirh. Rpitzl-bergisrho oder c:ronlandbcIie Reiss-T3ewhreibung, &=than in1 3:Ilire 1071. IIm~Biirg, 1675. 4. p. 39.
J~LY, 1916. MONTHLY WEATHER REVIEW. 389
rately by W. Scoresbp time that when tlic wind drives i frost-rime  or who pointed out at the smic frost-
smoke against the ship tlie . frost-rho  dcyosits rime
(Rauhreif) on t h o ship. B. Rimt (Raw7irci.f. Ba~dz~kj.-Rini~ (Rculircif) is the rough (radio) fro<t-lih do losit of tlclicnt,o st,ruct,iirt?,
at moclcrrrtmc to sercre coli1 t,eiiipcr:.twi :s, oi: tK 1)r:Lwlies arid leaves of t,roc?s, 011 all corritw, joints, ant1 c!dgca of upright objccf,s. It forms i:ot$ a t nll, or in i!isiyiiianiit aiuouiits, on liorizoii t .d surfncss. Siiirro it is brii! t, of t.lw fog particles clrivoii 1 9 7 tlio wind, it, prows iiioat, rapidly
011 tho winclwnrcl sitli? of objects, i. c?., it grows ngtiiust the wind. R h o dircs not form unifonii1.v on ~1 1 ohjwts rt t.1io siuiii? Iil?i$t: t>lic siiicllcst. t#-i*-; iiw,v 1.w so lnnil~~d with it t,liat t,lio,v swin t,o 1.w iiicriiPti.3. wi!h nt, tlic smic
titnt? the hranc~h~s imd s ;f .~~I i of t.lw p h i t rmi:ti!i free from
it. Tlim H bush wliitc. wjt,li riiiin m:3y st.ri.ntl out in st.rik- inu b cnn .- tmst. to t.lie i l d i st.cn1 of :I, riciglilwrii~g t.rw. If tho trec! t,ru~li prcwn ts :i,ngiilrw, piiintc-vl yr~~,ic~~~ti~~iis, how-
ever, such :is would wise froin previous c l nniiige t.o t.lw bark, t,licli riim foriw o1> those projec t.io:is. Iho l (~:i ~~(~~
of evorgreens aritl Il(!cdi(!-l~:iYedl t.rr!w liar-n rii M form priuciipally dong tlicir cdgcs : sindnrly t.ho mlgw of qundrangulnr posts, lmw(ls, ctc,, arc niorc! heavily ro:i,t.c?d wit,li rime thnii are t .1 ~ ::vrf:wes htx-tv11.~~ Tt. tliwcdorc
seems that those portioiw of tlw. o1,jcc.t which (*no1 iiiost
rrapirlly and in t,cm:iply, :1 ,~ t h 1iior:t f:lvoril,l)l1? pxtioiis for
the deposithi of rimn. ;i p i i i , rinic foriiis Iiinri? phiti-
fully B t high levols bt?ciiunc t.liero t.lie. tLir iiioveiiim t. is faster so t,hntr thc! supply of fos pnrticlas (Nchololr!mcn ton) is Kine has cryst.nlline stmcture when suhliniat,ioni occurs; it is iimorphous when unrlercnoled fog droplets solidify to ice upon staiking the su ,porting object.
fornis which :ire readily recognizable as belonging t,o the Hesagonill Syst,em [of crys t,als] : t8he seciind inet.hod, wliirli was first, 1)rnuglit t.o public nt$ent,ion by Assniniin on the Brockcn in 1SX9, yields more coiiipnct icc! i1eposit.s which are really Rauhcis. Lnt.er Dobrownlski 23 ma.de
detailed studies of the structure of rime (Rrtuhreif) during the Belgian ant,a.rct,io esprdibion and mblished numerous drawings of t,he forins it, ~~s i ~n i c s . Le fount1 many more cr-ys talliiie forins t h m niiiorphous ones ; alii1
even these latter, which nrise from a succession of solidi- fied droplets, seeiii to obey the laws of t,lie H e s a p ~d Systrni to a certain degree. This probably signifies t,liat
the sublimation of t,he wn.ter vapor, taking plnce nlter- nately or simult.nneous1-y with the other process, induces somewhn t of nii hexagonal-system chnrart.er in t.he whole pattern. As Assinann had dreacly point cd out,, t,he aniorphous variet,y of rime gives the iiiiprcssion, to the naked eye, of bein ice crystds. The 11su:i.l met,eorologi- cnl observcr woult 7 be unlikely, t.liorcfnre, t,o nccurn t elv report the st.ruct,ure of the rinie lie ohserws: so thnt. how- ever t,heoretica.Uy correct. iiiay be Pern ters proposit.ion to clist,inguish lwtween the cr>rst,nlluic? :tnd the al~iorphous forins, it. would not be possible to put, it. ii1t.n prnct,ice. Penit,er proposes t,he iia~ne  Rnuhreif  for the first or cryst,a.Uine forin mil  Rnulifrost, for t,lic secontl or mnorplious form of rime. Since these tw:) terns liare
heret-ofore generillly been rcgnrclccl its s~11o11y1iious, tdie
so. \.Ill. 1. I>. 4?A.
which iiiay l)t% deposit,otl at. 21 I lioiirs (hiring fovrrv v.w~i.lic~r
eater tlinn a t low &viitioiis.
The first niannm of foriiintion gives c I elirii.te, fcathery
.-
:I Scnrtsby, 1 i -f i l l i :z t n l . An a~roilnt of the :ireti.- rrgions. ::di:il;i:r.gn. 1431. 2 v.
~1 P. Ililsott 1::ld o1,scrved this krt nr; early 3s 1i:-I1 in I ;!n<go\v. See ..An ncmulit. of B
mmt e~traordi~mryde~reeol cold Pi-~il.trans..l;;il.70: X.1-47d: [:~lJr.c~l.,l.W, 14; 704-11.1 n Assinrnn In Mcteorol. Zt.sq&., 1?3S9,6: 339.
Dobrorrobd. Laneige et legirre. dnvers, 1503. 4. (Rth1llsts fliivoywe de S. Y. BeMiw en 1997-1W)g.)
\Yrit.er would prefer the nnnie Rauheis for the ainor- phous variety. This nnnie n t 6he same tiiiie shows the rchtion i t bears to t.lie ice coating known in England as
 ghzecl frost, (B(T. Glatt.eis, Anwr. glaze) .2.1 In fact thcre imst be n close relat,ionship between the two dcposit,s, for if Raulicis is foriiicd froin undercoolecl fog drop1et.s while glaze lGlat.t.cis), as will be shown lat,er, results from undercoolc~l raindrops, then the mode of origin of hot.li coat.iiiw is essentiiilly the saiiie, although in t,lic rase of ghze &lat.tc.ie! the ilrops of undercooled w i t er s!iread out over horizoiit,al surfaces at8 the same
t.imc they H ~C solidifying int,o ice. If Raulieis and glnzo (Gint.t.ris) neocrt.lieless 1-10 not, present the saine
appea.rnnce, Rnuheiu giving rat.!isr a crys t d i n e effect, t.lirn t.liis must he due-ns remarked befora-t,o tshe cir- cumst,nnce t81iat two processes are 1i.t work simultmeously in t,lie Litter c:we-t,lie freezing of unrlerroolcd fog particles
a.liil thr sub!i~nat.ioii of water ~:tpiw. Accordnig as t.lie
one pri:)cess or the othcr prtri1oniiiint.c.s t,he st>ruct.ure seeiiis to he 11i01-e n.mcwpiious or ni(m cryst.alliiie; tind i t is con-
ccirn?~le t,ha t. ihr frozcn dropli1t.s iiiay so predominate
over thc auhlij1i:l.t.e t.1i:i.t the rcsult.iug Rauhols is scarcely t.o 11v i1ist.inguisliec-1 froin glnz~ (Glnt.t.cis). Riine (Rnuhreif) I w l o i i ~~ lnrgelv t.o the 1owl.niitl phe-
1iCliliCI1t1, Raiilieir ritt.her t.o t.hc high J i ~~>U l l ~~~l I l loCali- tics; bc?cn:ise t.lw wiiit.rr fop of t.iic lowlancls rarely has untlercoolecl tlroplets, whilc t.licse latter frequently occur
in t,lw cloucls wliirli cii\\;r:i.p the ~iiouiit~nin sum1iit.s where thcy sppcwr ns fog (4). Of course riiiie deposits are not l;i:*lring on the i1iouiitiii1is; under very low t,eniperat.ures tlirv arc thc so!c f m i i that occurs. h i i t ,e r s stnt,rwirnt,,   Riiiie iltnuhreif 1 foriiis in calm, foggy wca.t.hcr during ciuit,e low tcinlierntmm, when great, climiit,it.irs of ice crystds tire deposited from the ice fog (Eiuiic~bc.l), ~p o i i o1)jocl.t.s (trees, bushes,
c?t.c.) . . . , is iii nocd of soiiie c.orrect,ion. Firs!, to t,hr writ.cr it, seciiis supcdluous t.o rquire t81int, the ice c.rgst,nls shall form in coiisidernl?lc nnimints. There are
:111 possihle wi tln tions in t,he clcvelopinent of tlie rime R:iiilirc.ifl,il~ii,i~) from t.~icA most. c1clicate ire feather hnrclg visihlc to t.he nnlied t y , up t.o t.hs mighty ice han- n c ~~ (Eisfnhncn) . StwntZ, cnlm w-eti.t,lier is not necessmy for tho forniat,iou of rime. If a cnlm prevails then,
n t ,l i ~r things reiiininiiig t,he snnie, t,he de Josit of rime will
ing rlriving fog or Nt?beltrciben) that, riiiir foiiiis in larger c!unntit.ies, because then more fog ptirt,icles (Nebdele-
iiicii te) are driven against t,errest,rin.l objects. Th:ird, * r1uit.e low t~cniperntmes dso are not, a requisite. The
obsorvntions at. Potsdaiii from 1 M 3 t,o 1913 tench that rime frec uently fornied n t air t,oniperatures of - 1 t.0
- YC., a\t,liougli the deposit, was then slight. Heavy de )osit,s of rinie, on the &her hand, occur undcr.grentm coh. Finnbly, the Potsdnni observations make it, clues-
tionahle whether foggy wcat.lier a.lma.ys is present wlieii rinie forms. Thus, of t,lie 144 days wit,li rinie rec.orc1ecl
during t!ie 31 years, t,lierc were some :lays 011 which no fog (Nebel) occurred: a clear sky (heiterer Hininiel) or
low degree of cloudiness preva.iled. hut on onch owasion it. w:is very r d t l (- IOo t,o - W C .). If t,lierc. wns no
confusion wit.li hoarfrost, (Reif )-itnd t.liis cn.11 scarcely
he clc terniincd suhscqii~n t.lv, but app~nrs improbable in
son^ cases--me must, conchde that such n suhliinat,ion niny t.ake plti.c?a wi t,liout, n n t,ec,cdent, coiiilsnsttt.ioii of the wnkr rapor int.0 fog (Nebel). Since actual fog (Nebel)
..
he insignificant,. It. is prccisely in win( I j r \veat,her (dur-
.-
94 Oln7.e (Ohtteis) is n recently adopted .\mericzn terhnical name preferred lw the U. P. Wenther Bureau over the English term ghzcd frost. Ssc? this REYIEW.lI~,
1916,44:1S5-8.
390 MONTHLY WEATHER REVIEW. JULY, 1918
Redured water- equivs lent of rime.
rime ought to be measured and added thereto. At my suguestion the observer there madn such measurements nnzas follows: Every morning he scraped off the rime and ice which had formed on the 36-centinieter-high, cylindrical jacket of the gage, melted i t and determined its water equivalen tm (Schmelzwassermonge) . On reduc- ing these equivalents to the area of the gage aperture so that they niay be compared with the tnic precipitation, t h e result the Iollowing figures for 1 ~8 1 :
Rain and snow.
........ - .
~
-. . . - .
Jnniinry 7-31 ...................................................... Felrruary ......................................................... 3Iarrh ............................................................ Al~ril.. ........................................................... May .............................................................. Xovemher ........................................................ llecemlm..
Total.. .....................................................
......................................................
Month.
--
A h . Mm. 1% 3 33.9 19.6 64.8 2-4.4 98.9 9.6 3.6 5.0 101.9
1.2 40.3
35.1
simultaneously prevailed in 96 per cent of all cases, I also have accepted its presence as n prerequisite (Becl- ingung) and included it in the above statement of the concept of rime (Raidireif), The fog is indeed oft,en very insignificant, bein thin and shallow (nicht hochj , so
ing hut a delicate hnzc (Duft). This word Duft robably meant originally the ali lit haziness of thc stir
from which the rinie deposite.d nnc 5 later was trsusferrctl to the product itself (cf. foot,iiot,e 4, p. 3Sfi).25
The following results, conqdeci froni t,lw Potsdim observations, will serve to illust.r.ate the ocr.uiwnces of rime in lowlands. Tho nienu runinn1 numhc?r of days with rime at Potsclnni k 6.8: in 1895 thcre vi7cre 30 such
days, in 1912 only 1 clay. Distributed among tlie months the nieaiis are:. Jrtnunrp, 2; February, 1.3 ; hhrcli,
0.6; April, 0.05 (once 111 21 yenrs]; Noveiiiher, 0.6; Do- cemhor, 2.2. The iiinsimum in any iilont,li w i s S
da-ys. I t is not rare to find rime forming OII severs1 r1;~j-s
in succession; the estrenie case w:is n series of B c1nj-s
(Dec. 9 to 14, 1S94). This occurred in t,hu winttv hying the largcs t rccorclctl numhcr of dibys with rime : From December, 1S94, t,o 1lnrc.h~ 1895, there werc 24 cl:iys with rime, of which 14 dnya cmie in D mher nnd Jaiiunry.
In Potsdam tho ina ority of rases sliow but slight or
very hetivg deposits, and of those ~c~urrences Dcoeniber and January enoh hnd 4 and Fsbrucry had 1. On five of these occnsioi!s of heavy rime it is wry cold
(- 16 to - 2-L0C!.j ; OIL mother dnte t.ho teml~t~r~~burc
fell but to -3OC., hut on this occasion there wns :L lisiivy fog (starker Nebel) and the hygrometer stood c,ontinu- ously a t 100 per cent, which is not Llie rule. h h i y ilsys
when rime forms, show relative liumiditos of 90 per cent or even lower. Rinie (RauhreX) and Rauheis form niost frequently and most heavily in tlie polar regions and on isolated mountain peaks which lie in the thvemge levcl of t h o winter cloucls and are not far froin the sen or from tlie paths of LOWS. Ben Ncvis, Scotlad,2e hits B ccrtiLi1l amount of fame in this respect, as abo Iiavo t.lic? Broclim (Harz), the Sclineekoppe (Riasangc+birge), nncl the BielaSnioa (Bosnia). Rauheis starts to form 011 objects in a nianiier siniiliar to that of rime, showing R preference for all corners :uid edges. If the process continues days, or even weeks,
then the intervening surfaces also reccire a deposit of ice (Eisansatz), and soon all upright walls nre uniformly covered and appcar to be wholly inc.rusted. By reason
of its loosely knit joints Rauheis, like rime, readily breaks off under the action of stronger and it, also niekq
awa rapidly in the sunshine. Tie writer first made the acquaintance of the grotesque forms which the coating of rime gives to objects, while visiting the meteorological observato on the Scl~cre-
coatings which convert, e. g., a telegraph pole into a heavy plank 50 to 70 centimetels wide, I formed the opinion that in addition to the amounts of precipitation caught in the rain- and the snowgages, the quantity of
that the blue sky s K iows through. Often tho fog is no&
moderate amounts o I rime: only iiiiie t.init.2; wore thero
koppe in January, 1851. Inipressed 7 y the heavy ice
s The term Duftanhtinr was also used. hnn:evcr. In Orimrns Deutsrh. IV6rter-
huch, v. 2, 1500. I flnd the Cilhwiug 0151 pswge cited: daher man don tult nobel nennel, die den loft oud nehcl im wiuter an dic hituma blasen Itlist is the m w n whr we ciill tho frosting (tuft) by the name of fog (nebel) which the air and fog blow i i on the trees in riste!]. %The Bon Nelis meteor$o.eists ha!-e ra119d r i m (Rarihreif) by the name fog crystals. The occurrence 01 hrol~n b c rrystsls there is most remarlishle and they have not explsined it; often, indeed, lho nlwr\-ers journni records dark-lnrown log crysta1s;while thenert day perhaps white fnc crysla1sis e!itered. Is this discolnr3- tiou due to some dust and smoke Irom the Anglo-Scottish industrid district, or to vol- canic dust horn distant rwionnt-U. I.
2, For the sake of brevity the word rime (RaulueiI) alone will be used hereafter. although meaning both Rsubreif and Rauhels.-G. If.
The totnl amount of rime thus determined, accordingly smounts to 21 per cent of the other precipitation measured in the same months. (5)
Subsequent winter visits to inountnin stations soon convinced me, however, that such measurements of riine have buta a relative value and that even were it possible to determine absolute values the latter should not be added to the other precipitation. The grounds for this conclusion are as follows: By reason of the matutinal scraping ofl of the rime [and ice] the forniation of new rime is furtlicred and more of the icy deposit is collected tlinn would have hcen the case had the deposit heen left undisturbed until it fell of itself from time to time. Furtlierniore, tlie wind direction is of considerable importance here. If the wind is from such a direction that the raingngo stands in the lee of buildings, which would not nffect tho measurement of fdiiig precipitation but would partidy or completely screen the gage from the liorizontd cmrents which brin the fog particles,
stands on the weather side. The principal reason, however, is tlint the heavy rime de osits on the mountain
on upri lit objects, i. e., on objects set up by man. The
larger t B ie number of such objects the greater the quantity of ice taken from the clouds. If they did not exist at all while. the summit retained its natural character, then the slight natural ine ualities of the surface would soon be smoothed out by t 1 le winter snow and the deposit of rime on tlie snowy ently inclined surface would be estreniely slight. T o f e sure rime is deposited on snow, indeed it, there nftcn assunies a beautiful, large-leafed form, but such deposit,s nre infinitely snidl c,ompared with those on hoiisw, telegra h poles and other objects that project freely out into t i e air. when a mountain
peak has steep rock groups that t e formation of rime (and ice rime) would be favored in a natural way. It seems to me that this consideration has a rather brond hearing. It is precisely the heavy rime deposits
on momitSnin summits t,hat have led to the frequently expressed opinion that in the polar regions of deficient pwcipitntioii the snow is chiefly supplemented by hoar-
then tlie deposit is much slighter t a an when the gage
peaks of the Brocken, the Sclinee R -oppe, etc., form only
It is on1
z P
3 On tho other hmd the rime [and ice! which forms in the mountam forests ja a natural iiicrement of the molsture that re$~?s the ground. The rime falls oft melts and increases the amount 01 water seepmg mto the soil. It is a fog drip (!NeehelthW) iu the solid form.
JULY, 1916. MONTHLY WEATHER REVIEW. 391
Brocken (1,112 m.l. 1898-1913.
i
frost (Reif) and rime (Rauhreif). Certainly both con- densations contribute soniething to the preservation and increase of the snow cover, but their copiousness niust not be overestimated. This is shown by the long series
of measurements on the sumniit of the Brocken, of which
I submit some of the results.
Rbiie ?tiC(isii,rmenbs on tiile RrncX.Pn.
The frequent do osidion of rinio on the Broc.ken mntlc it necessary t.o &vise sonie nit! t,liocl of tie tforniiuing possibln n(!w fornint.ioas of this rln]>o+ For this pur-
poso we om doyotl tho fwdy e s p o d iron iiinst, support!- mg tho winA vmo on t.liu plntrfnrni of thc tower. At each
obsnrvat,ion hour (7, 2 P , !PI tho tml?ic:lsnese of the rimc that, had formed was ii~casmetl in c,eiitimetors nnd then the deposit M-RS knocked off. It snldoni liaplxmnd tliat, the deposit. had fdlon ofT prciiiat>urely. In this
way was eecurid t,ho nunihnr. of tlnys cui which riiiio
formed, mid nlso zi. rnlzi tive niwsiir(? of t,l LE! niiioiint,. The obscrvations from 1SW to 191.3 show t.lint on t,he Brookmi suniniit t.he tivmige niiniial nnmbt~r of days wit:h rinic is 137.4. The estrenics :i.nio~ig tho inclivic1u:i.l
yews were 179 niicl 10s cltiys. The rlistrihut.ion by months is shown in Tnblo I .
TABLE 1.-Statistics of rime on the BTocken and the Brlmeekoppe.
~-~_-_____ I I
Schnec-
(ItOOm.) 1W2-1913.
k0l~W.
Dags. Days. Cin. Cm. Days. 23.3 29 423 k10 20.1 32.8 29 365 716 2. B
22.7 27 307 532 21.0
1s 43 134 G. i
1 0.3 5 1.4 0 0.2 0 0.5 0.4 14 6.1 9.8 0.1 17.9 2s 276 564 23.8 1 29 3% 640 22.2
14.5 I 25 153 407 16.0
459 19.2
Months.
.......... Year .............................. I 137.4 1 liD
I P ~y s with rime. 1 Thlrknessofrime. I--
..........I 145.8
Janu a. ........................... Feiir wry... ....................... W h ............................. A ril .............................
lune ............................... July.. ............................. August ............................ &p m b r . ....................... oc OM.. ......................... November.. ....................... December.. .......................
akay .I.. ...........................
21 Ifdlmann, G. Die Niederschliige in deu norddeotschen Stromgehieten. Berlin, 1806. P. 1, p. 218.
wort.hy of mention t,liat in 1912 even September hnd 22
days 1vit.h rime. The amount of the rime deposit on the Sirhneel<o lpe seeiiis to be sornewhztt less thnii t,liilt on
t.lie rocka an, w1iicli lies nearer the ma. 0hs~i~nt.ions fr?r 6 to 10 years show that. t.hc annual number of days wit.h riiiir on the Ficht,elberg (1213 in.) in tht? Erzgehirge is 140, on the Inscbbcrg (314 in.) in the Tliuringer Wdcl is SS, m d on t,he Grossen Winterberg
(55.7 111.) in t,hr Siichsische Schwia it. is 65. On the highest. elmitt ions of thv Grrninii Mit,tcl- gi.lJirpc thcrc :i r ~ hut, t.wo t.ypos of wint.er weather-riz, in the iiiidst. of ii clond or freo of cloud. The first. coiidition niny mdure for weeks aiicl even ~:ioiit,lis, and rime is
nliiinst. nlwnys forming t,lien. IItwcc t.hc mnsiinuni iiuiiihrr of sucwssiw d;i,ve on which new riiiio fornied
niny mount. very himh. Durin- t,hc 17 hi cars, 1897 to 1 OI:.:. t,he ninsiiiiuiii Lis nevcr Keen lees t,han 10 on t,he Urockeii: in sis ycnrs it, ~s w d e d 30, and in 130s even
:;iiinunt ed t.o 56, riim foriiiiiig ercry clttg throughouta the S succrssire wct:lis from Ja~iusr~- 26 to March 31
~
inclusive. Alt Iiough the iiit~:isurc.meub of t,lic t.hickness of the riiitc (Ipposit, (xi the windviinc. support. litis but a relative rduii, it is, ~icvert.lirlcss, worth while t.c> give t.hc average
tind liuisimuni iiiont,hly v:i.luc~a fsec Table 1, columns 3 :i.ncl 4 ), and p:irtirulnrly so sinw it is probahlc t.hnt. they
X ~P t,Iic only systc.iiictt.ic niea.silrciiicnts of t,heir 6ind. M1ic.h iiiore intcrcst,ing them t,liese monthly smns nre the individunl iiietisIirciiinit.8, fur t.1ie.v show what great qu:int.it,ies of riiiic can deposit in n short, t,iiiie. Froiii
w e observntion to thtr iiext, in 7 and 10 hours res ec-
nniounted to 80 or 30 ciii., in one c .~e even totding 35
cm.-i. e. 35 m:i. pcr liour. The lienviest. deposit4 in one day, froni 7 t,o 7 wiis 7Y mi. 011 March 26, 1911. To invrst,im.t,e t,hc effect of rinie cleposit.ion in iiicrens- ing t,lie t.liic%ness of tlic snow cover me must select a
wriocl when no t,ruo precipit,n.t,ion (snow, min, grau el)
pt~riotl. During ccmtinuoi~s fng, storniy cast wind, and t,ci!npc.rat.urcs 1itlf.werii - 1 .Oo tind - 10.1 C., rime de- posit.s of t,he following t,hicknesses were measured :
tivrlg, t.he t,hic.kncss of the newly forniecl rime o F ten
ldls. The int,errtal, Mnrcl1 19 t,o 33, 1901, was SUC Y 1 A
Date.
1901. Unr. 19.
211 .............................................. 21 .............................................. 2.2. 5 23 .............................................. ................ ............................................. 5
In spitme of thcse t,reiiiendous rinie dcposits the dept,h of the snow cover was increased ?)ut, 1 centimeter. Even
udniitting that, thcre is considerable uncertainty involved in the liieasureiileli t of siiow clep t.h , 11 evertlieless these and :dl other nva5iblo esani des show wit,h sufficient
is vanishingly siiisll in coniparison wit>h it.s deposition on upright w d s , post.s, et,c.
The terms used to designate rime (Rauhreif) deserve a few remarks. No other hydrometeor lins 80 many different names in German aa this rime (Rmhrdf!.3U I know the following: Raiilireif (Rauchreif),
ccrtnint,g that t.he depsitaion o / rinic on the snow surface
3jOno of Chistonis routriiiutions, mentioned abos-e under footnote 5. shows that althniigh the solid hvdrometeors do not often wnir In Italy the Italian language ron- tains a lor mestar niumber of names for these phenomena thaii on0 would eximt.. Most 01 these naiiies however seem not to helm t o tho en1 written x-ocsbulsr 7 ; mt of tho 15 words n;o?ltioned there were S I coud not iinl5e;n the great Italian dlctibnary of Petrocchi. Riptml Fanfani. Among thew words are galamma and *mIal~ma,~ which Chistoni a pIm as shown 1,s his context to rime (Rauhreif) and Rauhels respectively. Ferkbp he will be intarestad to lead1 a designation for frost (Reif) whicli ha did not mention. In the work by Rao I metemi (Vcnetia, 1582. 4) I found the chapter heading De la brha communemente chiamata gelame [On frost, commonly called 6rgelame].
392 MONTHLY WEATHER REVIEW. JULY, 1916
Rauhfmt, Hayfroat, Nebelreif, Duft, Duftanhang, Anhang, Abhang, Bihanp, Amam, Anraiim. In Austria. southern. Geman?. ani Thuringia the most common erpression is the anclent one (see above, p. 385), but the name Anhang is also ancient and is widely iised in foreet districts (Forstkrehen). (Pee Grimm, Deutsch. W6rterbuch, v. 1, E. 366. rlfe und anehmc). To-clay the most usual term in nort ern Germany and also among meteorolo sts is Rauhreif . In the Riesencebirge the phenomenon ie callec? An- raiim, tmbably derived from Anreim. which is the more usual form of t e word in Austria. This word ~o e s back to the (.)Id Norse
hrim, whence are also derived the Englhh rime and the Frenc4i
1 I frimas. 9 ,a1
(To be roafinzied.)
Duft
ON THE VABIABILITY OF TEMPERATURE.
By ALFRED ANGOT, Director.
[Dated: Bureau Central YBteorologique de France.]
Tlie meteorological character of a given duy clcpeilils, in soine degree, upon taliat of the prec,ecling day and per- haps even upon. t,hat of several previous iln;vs.? Ilie
question t.hus ames wliet,lier i t is possiblo t.0 go fiirtlicr and to forecast, e. g., the character of t i se:uon froiii t,liat of the preceding senson, or to say if after a series OF ~v m i i
winters the chances of a sewre winter we increased. A
very large number of siiiiilar questions can be raised. Teiiiperatures niay be used as a numerical esnmplc of the mswers t.0 such questions. The arit81inietical iiienn of the teinpert~tures of t,lie
same nioiitli for a large iiuniber of consecutive years is called the nornial tern of t.liat iiiontli. The noniial temperature for at Paris is 2.7c.
The temperature of a particular Dcceiiiber, for instance, December, 1914, was 6.3C. The departure of this temperature froiii tlie iio~mial December t.enipera.t,ure
+3.5C., that is the difference between 6 .2 O and 2.7.
If all these departures were t.he result of purely fort,ui- tous causes, the tlieory of irobnbility would .give clircctJy
probability is one-half, i. e., the  probable cleprwture, is 1.9C. I n 100 Deeeiiibers there would be 50 with
a temperature between 0.S (2.7- 1.9) and 4.6C.
(2.7+1.9). Likewise there woulcl be 1s in which the
departure froni the nornial would excecd twice t,he probable departure-that is, of which t.lie would be above 6 .5 O or below - 1.1 C!. artures may likewise of the tepiperatures 16 years tigo, observations made different sections of France and were discussed froin this point
the degree of robability o f a departure of a gven aniount,.
Thus it will R e found that the c1epart:ure of wluch tlic
- - . . - - _ __
nThe name silver thaw devised hy English meteorplogists fpr the henomei!on of
rime (Rauhreif), seems to de unable to maintain its footmg even in proI!ssioual rlrcles. Earlier good ohservers like Lukn Howard ScorealJy and others, nlwavs mwd t.he word rime for t% deposit. At present thek is great confnusion in thh b t t e r , for Moss man has a lled thename silver thawto the deposit known as glszed frost  i.Engl. ),
*gIme (f?S. h.) (Glatteis). Old French textbooks in meteorologv a plied tho term Irimas to hoarfrost I R P i f ) and to rime (Rauhreif). Only wlthin the k&t 50 years h38 there been a clesr discrinimn- Urn between gel@ blanche and *givre [i. e hetween hoarlrost and rime]: while Irim%j has disappeared lrum the scientific liter;;tore.-Aatlror. !lmnalntors note.-The m a p in the Vnited States witb regard to these terms has lrern discussed in some detail in the MONTHLY WEATRER REY~EW, May 1916, 44: ?S1-2%
notably p. 2 W , where the P. S. Weather nurenu offlcially adopts *hime* (R ~u l i i ~i f j and LG1azes (Glattfw!. The same artlcle also shows to what extent the term silver thaw . is known and used Is the lhlted States and Canada.-c. A., jr.
1 Ingot. [ Charlea] Arlfred]. Sur la varial?llitP des temperatures. Corn tes rendus, Acad agric de Fmes Paris dfc. 22 1915 l:7S9-792. Transl. by W. G . Reed.
1 In this &nectim he: Ncwham E. r. The persistence of wet and dry weather.
Quart our Roy. meteorol. sot., Lindun, July. 1916, 42153-162. Abatrsrted on p. Xi3 of thiiI!+sucof the REVIEW. a Anpot A . Etudes sur le climat de la France: Temperature 1h. Partie-Stations de com&ism. Annales Bur cent. m4t&rol. de Frnnee 1887 1. YCmoires, Paris, 1888, pp. BB3-BliO; iW., io00, i. M6moires, Paris, 1802, pp. b B l l 8 .
studies without, exception the results ii orousl con- foriiied to t,liose obtained froin the t,lieory o B proba is* ilities. The physicd causes t,liut determine one nioiith shall be w:~rni or cnlcl are so many and so c.oiiiplcx t<liat the net result is the mine 3.5 t h t from purely fortuitous causes. lt, is pcissildr to go a st.ep further and inquire if the!e causes haw it ccat.:iiii perninnence niicl cont.inue t.0 not in tho smie siwse during u c.onsiclcmh!o time, two iiioiit,lis,
:I serr.soii, or n l~iiigrr peririil; in ot.ii.c-r y d s , if the char-
r of tlie hqiiiiiiiig nf a seasm lust,ifies a forecast for
the entire senscin, or t.hat, of cine seakon n forecast for a 1:i.t.w scnsoii. If t,lie chrrracter of n nionbli (wnrni or
c*oldj is represcwted by -4 nntl the opposite chsracter by
U, t.wo consccut.ire iiiont,lis offer t,hc combinations A 4 ;uid AB. Likewise for t,lirec coiisecm t.iw iiioiitlis there will be t>he conibinnt,ions AJA, d d B , ARA, ABB. If tlicrc is R reln.tion bet.wecn the character of one nio1it.h
m t l t1ia.t. of t,he follo\\ing inont.li cme of these coliibinn- t.ions will appear iiiore frcqueii tly t,linn tlie others. Olmrvations of t,ni~pwnturs :~~ndc. in the vicinity of Inris during the 65 ycnra, IS51 to 1015;have been esmii- iiiecl to clotermine ivlict,Iier such a condit,ion esist.y. A s
:in example t,he results for soi~ie p u p s .of t h e e consecu- t.ive months are. giren below; the figires indicate the nuni- IJer of occurrcnccs of t.lic diflercnt combinn.tioiis :
dAA d d B ABA ABB
Nuveml?er- i:~c.i;elnber-Jan~i:~r~. . . . . . . . . - . . - - . . . 16 I~e~i.rn1~cr-.li11nuary-Febru:lr~. -. . . . . . - -. -. - -. . - IS 14 19 1.1
June-July-dufiast . . - - -. -. . -. . . -. . . - - . . . - . . - - . - - 13
Even for two nonsecut,ire months there is no systeni- atic relation. The iliiTerent. combinntions lime all the sttnie probrt1)ilit.y ns t.lint wliic4i appectrs in the succession of red and hl:ii*k t.111 t,hc roulrtke wheel. This is sliown even inore st.ron& wlieii successions of lon er clunit,ioiis iire esnniincd. No rchtion can bo
ilia% out het,t\-ettn t h t,rniper:i tnro of one 1 i m i t.h and that of t,he following niont.li, st.ill less bet.wrcn tlic tenipera- ture of a se~wii am1 thitt of the follotviiio season; a wanii suiiii-tier mill 1je succeci~cil iiitIiReren t41y E, n warm winter
or by n cold winter. Forecask iii:i.de froin the act,ions of animals or phnts
me in the smie cutegory. There is R belief that when the hech t,rees lose their leaves earlier than usud an esceptiondly eti.rly or severe winter will follow. The causes t,lint bring about the fdl of lcaves froni a tree are t o be founcl in the nieteorologicd characteristics of the suniiiirr or autunin. I t hats just been shown that t,liese chract,eristic,s baw 110 iniiueiic.e on t.hose of the following season. Anot.lier irejuc-lice not less frequent supposes that
within short peiiolls. Froni 1909 to 1914 the six consecu- tive I)ecembers 11-ere rtll wann. Therefore, if the short- ieriod coixpcns:tt.ion were ef ec.tive,, the chances that the lollowinn Uec.eniher, t,lint of 1915, will he cold would be incretiseQ. But, t.liis is not, the cnso; past seasons do not cont.ro1 future contlit,ions. Aft.er a series of very warm niont,lis the chalices that the following nionth will be wmi or colt1 renitin cc:lunl. which is the same as the chance t,hnt red or bhck will rtppear at roulet.te after a run of :my kind 11-hatever. In conclusion, the varirtbili t y of nionthly, seasonal, or annud t.rniperat.ures in Frrtnce follows exactly tlie same
law as if t.lie ouuscs were purely fortuitous, and i t is not possible t.0 forecast for nioiitlis, seasoiis, or yews by nieans of past phenomena.
(.)~t l ~~J l ~r -~~I ~~l l l ~J ~ ~-r ~~l ~l l .l ~~C  ~ _..........-...... 18 13 19 16
17 17 15
2 18 12
t.he iiiet.eoro I ogicnl phenomena t.enct to be complementary