JANUARY,1914. MONTHLY WEATHER REVIEW. 29 tmstworthiness there can nat be the slightest doubt,” is that report, it as audible at the time tlie liglits are most d great interest. He purports to have heard tlie sound active and vivid, for it, requires a certain time in which three times in all and says that he is sure it could not to trtivrrse t.hc dist,anc.eto the observer. On the ot,her hand it is not always when the aurora 0. J. Dalile drops down moderately near the earth that it can be dated March 30, 1910, heard. There are nunierous accounts of the polar lights was furnished me through the courtesy of Prof. St.ormer: which, judging froin the observers’ descriptions, have been JGght or nine ears ago I witneased from the steamship Erling Jar1 very near t,he surface of t,he enrt,h aad which according an extraordinar& interesting aurora. While our shill was crossing to t.liese descript,ions have not been acconipanierl by any Vaaga Bay, a little north of Harstad, a brilliant aurora in rapid motion sountI. WBB seen 80 low down in the‘air that it barely cleared the tops uf the In a work on t,he height, of the aurora Clevehnd haeta. It flamed forth in all the colors of the rainbow and was fol- by lowed by s eculiar sound, precisel such a sound m would be pro- Alhc in Terrest.rid MR netism, 1895,. are cited a great duced by rsbing together a weldied skin in the hands. It was nuniher of rep0rt.s of suc5 i displays which have been seen nation nor t,he mistaking of any sound 011 board, but un- against. the ninuntains and hence very near the earth, as Et:L?%e result of the movement of the aurora. I have not.ired for instance, t.hat.of the well-known polar explorer, Parry. also on o&er occasions that auroras in rapid motion hanging low in bhe atmo here have emitted sounds similar to those mentioned above. Sir William Hooker saw t.he smie phenomenon at Ben In%e above-named display it seemed that the auroral rays had x Nevis, Scot,land. General Sabine observed tin aurora that horizontal poition and appeared as separate layers, one above the wns so low that. it lay like a foe over the ground, through other: But the probability is t.hat it was a vertical ra which, by rea wliicli lie walked. Ga.lle, the Tanlous astronomer, saw a 8on of ita nearness and ita position directly over the dip, appeared to to IIE to be horizontal and that the higher layers mere the movements cloud growth following an aurorn. nnd also R display very of the meray wen through this identical ray from below. siiiii1a.r to t.liat which I observed in Finland, and I cite The Finnish liysicist, Lemstrom, has written a work Gnlle’s ohservnt,ions here because t,he account of such a entitled “The I! olar Lights.’? Here also are several nc- iii~iisurely ought, to be given great weight. It seems therefore inci:int.rovert.il>let.1in.t the aurora, under certain counts, one by a miner from Got,eborg wlio was in La 1- land in 1853. He describes an aurora obstvved at. nig1 it conditions, may reach down into t,he atmosphere at least inmidwinter in a temperature of - GoC!. A hand of rays t.o the nltit,ude of t.he cirrus level, cipprosiinat,ely 6,000 streamed u~ froni the plateau betwt.cn him ancl ndjacciit niet.ers. peaks and a rushing sound could at t,hc sam~tirnc I)(* EDITOR’S NOTE.-^ a letter froni the author, dated plainly heard.” (.!hristisnia, November 37, 19 13, he adds : The well-known Freiicli httlloonist, Rollithr, wlio with * * * It will perhaps interest. VOll to hear that the only Norwegian an attendant ascended froin Paris in 1S70 during thc nirniber of the Pcot,t.Antarctic Ekpedition. Mr. Trygve Gran, once siege and cam(’ down in Lifjrld , Tcleniarken, riqm%s heard a peculiar noise att.ending an -4urora Borealis [i. e., Aurora that he observed polar light rays throud t.lie liglit. fog Australis] ancl Mr. Gran also told me that the party of Lielit. Campbell and, “presently a peculiar rushing souii8 was heard. A had repeat.edlyheard 8uch a noise. short tune after, stron alniost suffncating fumcs of NIL phur were encountere f;,. Lemstrom himself, accxdjng to his own rc nrt, has THE mTEOROLOGICAL ASPECT OF TmSMOKE never heard tlie auroral sound, but lie specifica\ ly states PROBLEM.’ that he is convinced of its esistrnce, and this nssertinn is repeated several times. He s ,enlcs of t.lie Lap1andri.s’ By HERBERTH. KIMBALL. hbelief in tlie sound in the Iollowing languagc: THE ATMOSPHERE AND ITS CONTENTS. They my that B rumblin sound can often be heard and since it haa frequently been observed %y skilled observers. their belief t.liat it dtmospllerie pws.-The t.errestria1 atniosphere con- actually exists in connection wit,h strong, energet.ic auroras at low sist.s of a iiiisture of gases t,liat ning be divided into two is absolute. temperatures quit,e dist.inct, classes: (1) The denientnry gases, such as In a work by Prof. Hermaiin Fritz of Zurich, in 1Y81, nit.rogen, hydrogen, osygen, and t,he ga.ses of the argon concerning tlie polar lights, there is also collected from group; (3) t,he compound g;itses, such a.s vapor of water, all sources a great iiuniher of accounts of the auroral aininonia, ozone, carbonic acid gas, et.c. sound. Upon esaminiiig these we come across. many The gases of the first group are practically fixed in well-known men, even eminent. scientists, who believc in amount w4t.h res ,ect to one anot.her at any given level (l), the existence of this sound, for instance, Prof. Hansteen. while t.hose of t.i e second group are constantly varyin We find also in this book various old Norwegian reports. not only with respect to t.he atniospheric conditions, suc One would think since so many well-known and highly as t.einperat~ure,pressure, and huniidit.y, but, also witha esteemed men have given suc.11 ids utahle evidence of respect, to place. This is especia.lly t.rue of gases gener- having heard the sound that all doug t would gradually ated in the processes of conibust,ion, which niay be be dispelled. But this is so far from being true that, on almost unknown in thinly inhabited districts, but which the contrary, many scientific men, for instance, the have to be taken into account in the ntniospheres of large famms explorers, Leopold von B~chand Slesander von cities (2). Humboldt, assert un ualifiedly t.hat it is iiotliin but The ases of the atmos liere hold in suspension con- imagination. HuniboP dt says the native popuP ation siderabP e yuantit.ies of sor id and liquid particles. The knows nothing of the auroral sound and that it is the latter consist irinci ,ally of condensed water vapor, transients who have brought tlie belief with tolieni. But forming fog pcIdclou s, which may hold in solut,ion sub- this iq a singular niisapprelieiisioii of tlic facts, for the stances of various kinds, including some acids, as has belief is especially widespread among the natives. Ii The been shown by nunierous analyses of rain water and Rolar lights have .grown more taciturn,” says Huniboldt, snow. The soh particles niay be divided into several since we have learned to observe them more closcly,” and that is quite possible, for there arc piobnhly numrr- 1 Condeenssd. with additions and revision. from Smoke Investcytion Bulletin No. 5 MelIon Institute of Industrial Reseamh and School of Speclac ndustrms. Universitj! ous false reports .of tlie auroral sound, especially thosr of Plttsburgh, 1913.

Unauthenticated | Downloaded 09/24/21 07:29 AM UTC 30 MONTHLY WEATHER REWEW. JANUARY,1914 classes, such as cosniictll or meteoric dust, finely divicled amounts are equivalent to YO0 pounds of soot over each mineral matter or soil from the surface of the earth, square mile of area in a layer of air about 410 feet and ollen from plants, niicroscopic organisms such as 320 feet, thick, respectively. gacteria and molds, and the soot and other residues of days about twice as much soot was found in combustion. t,heoll-fogv air o Pittsburgh as on clear days. Atmospheric d~~st.-IvI~chof the dust consists of par- Deposit of soot in city aid coun.tvy driStricts.-By means ticles so fine that, as Barus (3) states, it niay be con- of soot gages, and from the analysis of rainfall and snow- sidered "an inte rant part of the atmosphere." hlete- fall, fairly accurat>edet,erminations have been made of oric dust is of tks character, and Young (4) has esti- bhe rate of deposit of soot, at different points on the British mated that the amount received by the entire atnios- Isles and elsewhere. The following are some of the phere probably can not exceed 100 tons per day, which results : would produce a covering an inch thick on the surface of the earth only after the lapse of 1,000,000,000 years. Rate of deposit qf soot ,in fmm per annitni per square mile. Humphreys (6) has suggest.ed that certain observed Brit,iah Isles: Tons. sudden changes in the positions of the neut,ral points of Industrial center of Lee+ (7) ...... 539 sky polarization a few niinutes after sunset or before Suburban residence sect,ionof Leeds (7j. -.- -.-. - - - - -.-. . - -.- 26 Center of London (sj...... 426 sunnse may be attributed t.0 the exist.ence of well- Sutton, Surrey, just outside the metropolitan area (8). - - - - -.- 58 defined dust layers in t.he atmosphere. The first. of (;lasgo\v (9)...... 820 these is the dense dust layer that is oftZenobserved from 13o'ness (9) ...... 72 mountain to s to cover t,he valleys and dains below. It consists oP comparatively coarse parbicr es caught up If the rate of de osit is nearly pro ortional to the by the turbulent surface wind, and is usually less t,lian R density of the dust Payer, as seems pro f able, it appears lulometer in thickness. Above. this, estending t.o n that the dust or smoke cloud over the central sections of height of about 4 kiloniet,ers, is the second layer, Leeds, London, and Glasgow, must be from t,en to twenty throu hout which some of the finer particles of the first times as dense as in the nearby suburbs. layer lave been distributed by means of diurnal conver- Measurements of the monthly rate of soot de osit were tion currents,P which are especially st,rong in suninier. macle at 13 different points in l%tsburgh, Pa., &wing the The third layer estends from the top of t,he second t,o year ending with March, 1913. At the point of maximum the region of the u ,per inversion, or to a height of about. deposit. the annual rate was 1,950 tons per square mile; 11 kilometers, an d throughout it, some of't.he finer dust at t,hepoint of mininiuni deposit it, was 595 tons per square particles of the lower lnyers are clist4ributedby means of mile, while the mean annual rate for all 12 points was the convective action of cyclones. Above the region 1,031 tons per square nde. of the uppe~inversion, wliich is also above the upper Li.mib o t&ibil,Lty.-Ait,ken (10) found a great variation linlit of convection, what little dust is present must he wit.11 wincf direcbion in the limit. of visibility in miles of the mostly of meteoric origin, ewe it that, volcanic. clust is air at Falkirk, which is so situated that west to north sonietimes t,hrown int.0 these high levels. This was winds come froni re ions havin less than 50 inhabitants shown to be the case after the great Krakatoit eruption per square mile, wdef winds !irom all other directions come from regions having a PO ulation averaging from of 1883, by the brilliant twilight-- phenomena of the two succeeding years. 100 t,o 1,200 pc?r square niile. I;r able 1 summarizes his The sur a.ce daust Znyo..--Nearly all human act,ivit.ies resu Its. are Carried on in the lowest dust laver. which is therefore TABLE l.-Mt*an hiit of i!i.?ibilitf~in ?wiles of &r at Falkirk, for wid of primary importance. Its den6tT; depends upon the .from difltwat dircetiow and icvth djfermt depresswtm of the ulehbulb relat!ion between the rate of supply and the rapidity theraionielcr. with which the particles can be carried away, or distiibu- ted throu hout the, atmosphere. The least- dust, is found in t5 inly inhabited re om covered with dense vegetat.ion. In arid regions t le surface wind takes up Direction 01 wind. great uantities of dust, whichT is distributed with con- ---_I - siderabf e rapidity by means of ache convection cur- rents. It is in great cities, however, and especially West to north ...... 50 100 132 132 198 193 191 1\11 other directlons...... 1 8 11 11118.5 16.1 19 2G where bituminous coal is burned, that tmhedischarge of _. .------soot from numerous chimneys procluces the densest' dust or smoke layer. Aitken (11) has also shown that the product of thenuni- Qua.n.iit of soot in the air of eiii.rs.--illeasureiiient,s brr ot particles ier unit of space by the limit of visibilit made in Keeds, England, indicate t.hat factories and is a constant b for e unl depressions of the wet-bul t domestsic chinineys annually introduce int.0 t,he atmos- thernionietcr. Some oY his results follow in Table 3. phere of that city 35,000 tons of soot, and into the TABLE3.-JkHu of C. .Vu proditct of the limit of Visibility in miles by atmosphere of the United Kingdoni 2,420,000 tons. the auniber of particles per cubic cmtiineter. The measurenients also show that' there is 300 pounds of .- soot suspended in the air over each square mile of Leeds; Depression of the wet-bulb thermometer. that about 11 per cent of this falls in the immediate I e- region where it is generated, and that t,he remainder is 3"-4" y ...... 17,535 carried to consideSable dist.ances before it is deposited(6). J"-i' E ...... 105,923 -0 -10' ...... 140,6% An anal sis of air collected 'ust outside a second-st.ory F... window o9 the University of Attsburgh, in the residence h, Pa., gave for the mont,h of May, of soolmpel 1,000 cubic 1913, 0.0149 grams. These

Unauthenticated | Downloaded 09/24/21 07:29 AM UTC JANUABY,1914. MONTHLY WEATHER REVIEW. 31 of large objectv like mountains at ti tlistance of 100 ot.lirr inipiirities in the titnioiphere of cities can not have miles, while 100,000 would produce complete obscurnt.ion an appreciahle effect upon tjhe amount of ,precipitation. at a distance of 1 mile, and 1,c)@O,OOO at a distance of one- Oif!i and cownfry -fop.-The c.oolhig of the atmosphere tenth mile. . Tables 1 and 2 are in accord with numerous to it.s sat .imt.inn bemperat ire is usually brought! about observations, which inclicate that the iiuniber of particles by the mixture of warm and cold iiioist air currents, or per cubic centinieter in lnrge cities niay esceecl 300,,000, by noct.urna.1 cooling &her by iiieaiis of radiation out- even in fine weather, as compared with only n few hun- ward nr hy ra.cliat,ion and conduction to the cold ground. dred in the countr$ (12). In London in wint,er t,he These processes a.re operat.ive in t.he countrv as well as in average limit of visibdity in the clear put of the thy does t,he cit.y, except t.liat. the carbon particles in smoke, not exceed one-half mile (13), a limit, of visibility which which a.re good radiators of heat, will cool below. t,he corresponds to 300,000 particles per cubic centhet:er. In t,eiiiperature of t,he air in which they are suspended, Pittsburgh, Pa., the limit, a.t 7:45 a. ni. averages 1.1 niiles thereby ha.stenin0 the condensation of moisture u on and at 12:30 . ni., 1.7 niiles. This is less than one-tenth t,lieir surfaces an^ t.he forniat.ion of fo . Carpenter 53, the limit at bount Wea.t.her, Ya., which has a climat,~ has pointed out. t.hat. t.he . prhicipal I5 iff erence between similar to that of Pittsburgh, escept that it is free from city and cr)unt,ry fogs is t,hat tlie foimier beconie nihed local smoke. with smoke t.o such an ext.ent that their color is changed These figures, however, fail to inclicate the relat.ion from white to brown, or even to black, and their density between the dust or smoke cloud in t.!ii.nly inha.bit.eddis- is so increased t.1ia.t t,liey are ahiiost, opac ue to sunlight. tricts and in the cent,ers of large cit.ies when for any They at,t,aint,lieh geat.est density when ti e surface wind reason the smoke over the latter instead of being carried is eit.lier very light or else has a direct,iono posite to that away at a reasonably rapid rate, accumulat,es for a coil- of the wind a short, distmicc above? so t.r iltt t,he smoke siderable t,inie. uist.erttl of being blown away is brought back over the cit.y. The accumulat.innof sniolre in fog is al5o faqiitated METEOROLOGICAL EFFECTS OF THE IMPURE dIR OF CITIES. 1.))- reason id the :thsorpt.ion by t>he .mot artdes of nii iist.iire from t.he fog, therehv SO increasing tieir wei ht It is the pur ose of this piiper to set fort,li our present t,liat. instend of rising t.0 their accustomed heights tf ey knowledge of tR e effect of the sinoke and ot,her impurities quicklv set.t.le ti) t.he lower atnm heric levels. in the atmos here of hrge cit>iesupon the meteorologicnl While there is abmidant proof or t.he increased density conditions. X-roni the preceding paragrnplis it is tip- of fog in cities 8,s compared with connt,r-y fogs, the evi- parent that these effect,s depend not alone upon t,he size dence is not conclusive that fngs n.re inore frequent in the of the cities a.nd the rate of dischtirgc of inipurities int,o city than in t,he country. Howver, Brodie (18) thought their atmospheres, but nlso upon tlie rat,e zit which the lie w-as able to tlctect an increare in fog frernency at vitiated atmosphere is cnrrietl n.wil-y. It follows that Rrixton, R sii1)urb c.,f London, with increased d ensity of the nieteorologcal effect.svary wit,li geograplGcn1 position populatit in in that section, ~ndAibken (19) has shown and with the season of the yens; that cit,ics in regions t,liat dense Imze nr fo frequently fornis after suyjse in having high average wind velocitks art? affect.ec1 less the iinpure sir of Fa7 kirk. when there is no hazlng or than cities located in regions of: light wind; niicl t,littt t,hr fogging in the pure n.ir of t,he surrounding country. effectsare less in suiiimer than in wiiit,er,,becnuse in suni- There is also sonic\ cvitlence that fog frequency in London mer convection is active and helps t.o lift the inipurc air to 11 as decreased ancl the hours of sunshine have increased levels where the stronger air current,s will niore quickly siiicc 1880. 1)erliq~stlne tn it mitigation of the smoke carry it away. Generally speaking. 11. city in H ynllcy nuisa.ncr through inil)roveineiit,s in niet,liods of heating suffers more than n city in nn open plain: tind n city in and 1iglit.iiig (18, 20). It. is generally believed that the high latitudes suffers more in .c\int,crt,han a. city in lower same was t.iiie of Pit.t.shurgli,Pa., l>et,ween18% and 1895, latitudes. on account of talie.pole\\mrd clecreasv in the when the use of natural gas for 1)ot.h maiiufacturin heatsingeffect of the sun atat,liis season. cloiiiesbic purposes wxs quit,e general; but this wvi; Efect of smoke u, on. conJoieai~io~i.--rlit~ke~i(14) ancl referred t,o again in a lat.er section. others have shown tl? at nnp consiclernble conclensat.inn of I$kcis qf impiiw air qf cities upon-fogcl.i.ssipa.tion,.-In the atmospheric nioisture takes place only when the s-'1 t ,111'R- case of cheiiiical union, gs where sulphur diosicle unites tion temperature hns been nearly renched, and then only wit.11 wnt er vapor froni t,he air t.o forni sulphuroiu acid, uponfree ta@a,ces, such as the surfaces of sus ,ended ilud or where it. is first osyclizetl a,nd then unites with the part,icles. Once conclensiltinn has set in, inwercr, it water vnpor tn forni sullhiric acid, the eva oration of can cont,inue upon the surfaces of the fog ilrt,icles the fog prticles is retarded. Smoke from tituininous already formed. In fact, by a process which Ait,f -en dls wtil nlso contabis oily or tarry substances (hydrocarbons) d@erentiation the smaller fop ~~artirlestend to con1rsc.e which fnrin a cnating 011 the fog particles .and retard wt.h the lnrgcr particles. until t.he lat,t.er hrwme t,oo evitporat ion. heavy to be suppoTtet1 by t.he at,iiio~split.rt.,and fall tn Furthrriiiore, blie incTcusecl opncity of black city fogs the ground. In this way ti fog mtiy rain it.self out, (151. ns compared with wlute country fogs prevents the heat The analysis of the air of cit.ies slinws cnnsiderahle rays €ram the sun penetra.ting bo my considerable depth sul hiir clioside in t,he residue from burning cnal . (161, into tlie former. so t.lint,in R great, city like London the an8 its presence is believed t,o hicrease the prohabilit,y of fog frequenbly persists throughout the day. while in the the formation and maint.eiianceof fog in two ways (17) : (1) suburbs it is dissipated by the micldsp heat. In the presence of sunshine imclei are formed which have Dwation. qf s.u.nshi:ne .in.citits.-It is principal1 because such an affinity for wat.er t.liat coiidensa,tioii sets in a.t. of this persistencc of city fogs t,liat the observecT hours of than t,he sat,uration tempera6ure : sunshine in large cities are less thnn in the suburbs. soon arrests t.he process of differ- Thus, R~ssell(21) has showw that a st.ation in tlie.heart above, so t.1ia.t t,he fog rarticles of London enjoys but seven-tenths RS much sunshine as maintain a small size and may he supportec in t,he Kew, which is 'ust outside the city? while for the months atmosphere for a long perincl. Sovrniber t.o kehruary . when die vertical component Since there are always sufficient, nuclei present in the of the solar rays is very small, it may have less than one- atmosphere for p~ii-posesof contIensat.ion, t.he smoke aid third RS much. Coheri (22) has shown that the duration Unauthenticated | Downloaded 09/24/21 07:29 AM UTC 32 MONTHLY WEATHER REVIEW. ,JANUARY, 1914 of sunshine at the center of Leeds is 17 per cent less than QmJity oj. daylight .in. cities.-Pyrheliometric observa- at Adel 4 niiles distant; and Rubner (23) concludes t.ions (24) made at different places indicate a very con- that the duration in Berlin is less than it, would be if thc siderable decrease in the int,ensity of direct insolation after smoke cloud were not present. violent volcanic c!rupt.ions, tlue without doubt to the Intensity oj- szc.nd.Ge .in eiti.es.-Rubner (23) further scattering of the solar rays in pmsing through the dust calls attention to tm fact that a comparison of the hours or 'smoke that has been thrown t.o peat heights by the of.sunshine in cities and their siibu bs is not a fair cri- eruption. Spec.trobolonietric measurenients made under terion of the actual deficiency of daylight in cities. He t>hc direction of t.he Astrophysical Observatory of the cites the fact that while overcast skies are the rule in Sniithsonian Inst,itution (.25) show that lidit of short Berlin in winter, and smoke CR~not, therefore, greatly wave lengt,hssuffers ti greater deplrtion than@iight of loni diminish the hours of sunshine, measurenieiit,s with ti wave lengths in passing through a clear atmosphere, an Weber photometer have shown that on an except,ionally that the furt,lierdepletion in passing through a hazy atmos- dark day, such as might be attributed to the accumula- )here is relat.ively greater for short wave lengths than for tion of smoke over the city, the light was only one five- long wave lengths. Furtheriiiorc. bolometric measure- hundredth what it was on an ordinary overcast day, tind ments made on Mount R'ilson (26) in 1905 and 1906 in- only one three-thousandth to one four4housandth what dicste that the ratio of blue to rod in diffuse skylight is it would have been on a day with an entirely clear sky. six times tho ratio of blue to red in direc.t,sunlight. Also, Cohen (22) has found that. the intensit,y of the The above accurat,e inst,runient,alniensurenients coii- light in the center of Leeds is only 40 per cent of it.s inten- firm what we are able t.o observc with the unaided eye, sity at Adel, a much greater loss than was indicat,ed by viz. that both the direct, and t,he diffuse solar radiation the comparison of duration of sunshine ~t these t.wo which filters t,lirougli tlie smoke cloud hanging over cities places, which is given above. is relatively poor in the blue light? or light of short, wave In Table 3 are summarized observat,ions niade at longtlis. Pittsburgh, Pa., between November, 1912, and May, 1913, Although bolometric nieasureiiieiits of solar spectrum inclusive. The observa.tions have been arranged in two energies at. the bot,t.omof a smoke cloud are not available, oups, the first including days on which t,he presence of it is safe to say that. when the sun is ncar t,he horizon the %g or smoke was not recorded, and the second including snioke cloud over great cities alniost, completely extin- days on which light. or dense fog or smoke was recorded. guishes the blue light rays. It will be noted that although the hours of sunshine are &feet qf the smoke eio1i.d OIL city tem.ptra.twes.-The practically tlie same in each group, on days inclucled in presence of dust or snioke prt,icles in the atmosphere, the seconcl grou fog or smoke. ha.s a parently decreased by tlecreasing its t,raiisiiiissibilityfor light and heat waves the limit of visitility 20 per cent, ans the decom osition as has just been shown, affects atmosphere temperatures of oxalic acid 25 per cent, below the averages for tP ie clear in three ways : days included in group one. Furthermore, on the smoky (1)Thore is an increasnd scat.tcring of the incoming heat or Ioggg days of the second group? with an average limit, rays, which are also partly absorbed by the dust or smoke of visibility of 0.9 mile the decomposition of oxalic acid particles, thereby raising tlie temperat,urt?of tlie atmos- was only 76 per cent of what it was under appa.rently ~~lierr,in which the lat.ter we suspended. similar atmospheric conditions, except that the limit, of . c2) The rays reaching the surfitce of the earth are much visibility was 1.5 miles. In ot,her words, a decrease of 40 weaker than they would have been if they had not been per cent in the limit of visibility wa.s accompsnieil by a scat,tered and absorbed. In fact, in the case of dense fog decrease of 24 per cent! in the choniposition of oxalic or smoke almost no heat penetrates to the surface of the acid. It is presumed that the decomposition of oxalic earth, but tlie upper boundary of the fog or smoke cloud acid is proportional t,o the intellsitmyof daylight. becomes in eflect thc absorbing surfacc. In such cmes A corn arison between observa.t,ions made in Pitts- tlie temperature above tlie cloud becomes much higher burgh an K in Sewickley, a small suburba.n t,own about 12 thnn t.he t,eniperat,urein the cloud. Carpenter (27) men- miles northwest of Pittsburgh, shows that tlie oxalic acicl tions an inst.anco in Tlondon where the surface tempera- decomposition under the smoke cloud of the' city is only ture was 44' F., while on the roof, nearly vertically above 60 er cent of what it is in the count.ry. and 59 foot higher, the t,eniperaturt? was 51.5', or 7.5' both cases tsheglass vial containing the acid has been higher, although generally the t,eniperature was found to ex osed outside tlie window in a sniall box wit.11 t,he open decrease wit,li altit,ucli?at. the mt,c of 0.52' F. per 100 feet,. siR e facing accurately east. On this particular occasion the surface temperature rose from 36.5' to 44' between 9 a. 111. and 3 11. ni., or a range TABLE3.-RelaCion between sky mditioiur and the deconi ositwn of of temperature of 7.5', while on the roof above it rose oxal,ic acid when qpospd to daylight, at Piffsbrogh, A. from 35' to 51.5', or a range of 16.5'. At Kew, on the same date, the range was from 32.5' to 54'. or 21.5' F. GROUP 1.-DAYS WITHOUT (3) There is less radiation from tlie ground and out- SMOKE OR FOG. ward from the lower pnrt of the atmosphere and from particles suspended in it,. This tends t.0 give higher minimum tmiperat,ures in cities than in tbeir suburbs. In fact, this principle is est.c?nsivelyemployed in pro- l--l- l--l- I tecting sniall fruits and garden truck from injury by 4.11 Milfa.;:;I Per13.7i! cent I frosts. A snioke cover is formed, which acts as a blanket 4.0 14.43 I to prevent tlie loss of surface heatt by radiation. I I On the whole, t.lien, t,lic cffect. of a smoke cloud is to GROUP 2.-DAYS WITH raise the minimum temperatures, decrease the diurnal SMOKE OR FOG. I range of t.emperature, and, in case of a very dense cloud, I I I 'to lower the maximuin temperatures. It is possible to 4.11 0.91 9.06 conceive of a smoke cloud of such depth and density 4.2 I j , that the maximum temperatures will be raised. ,

Unauthenticated | Downloaded 09/24/21 07:29 AM UTC JANUARY, 1914. MONTRLY WEATHER REVIEW. 33 Hammon and Duenckel (28) found that the niinimuni While in each of these cnses the temperature shifts are temperatures at Forest Park, a suburb of St. Louis, Mo.. in the direct,ion in which we would ex ect them to occur were sonietinies 30' F. lower than at the Weather Bureau as the result of the locnl conclitions a.B ove described, we officein the heart of the city. The differences were great? can not state with certainty that they are entirely the est in September when the air at the Park wras clear. result of changes in the elevation of the instruments, or while light winds allowed the smoke to accuniulatc. ovcr of vrtria.tions in the smokiness of the atmosphere. It the city in a dense cloud of Feat thickness. The differ- inn. be that changes in the chnracter of the instrument ences were least in the cloudiest months-Deccmber ani1 she9 ter, as from a window to a roof shelter, and in the March. The thermometers at the Weather Bureau office chnrncter of surrounding buildings, may also have es- were 110 feet above ground, and at Forest Park 10 feet. erted nn influence, the estent of which it is impossible Smith (29) has found a similar, though less marked, to est,imate. difference between the teniperatures recorded at the In Table 5 are sunmarized comparisons between the Weather Bureau office, Columbus, Ohio, and the Ohio minimum temperature and the range of temperature at State University, located about 3 miles north of thc center the Weather Bureau office in St. Louis and the suburban of the city. At the Weather Bureau office the t,lirr- stat.ion in Forest Park; at the Wenther Bureau office in rnometers have been esposed in a shelter on the roofs of C'olunibus, Ohio, and the suburban station at the State several different office buildings. and at present are 1'70 Univeisity; and at the Weather Bureau offices in Pitts- feet above the ground. At the University the sheltcr is burgh, Pa., Phihdelphia, Pa., Williams ort, Pa., and 6 feet above the sod. His conclusions arc hwcl on n Harrisburg, Pa., and at stations surrounhg these cen- summary of the obse'mations for the 28 years, 1SY3 to teis, but in some cnses several des distant, and at a 1911, inclusive. considerably different elevation above sea level. Tlie conditions at Pittsburgh, Pa., tire of cslwcial The comparisons for St. Louis include observations for interest. According t,o the statement of Mr. IIenry 1 year, those for Columbus 39 years, and those for the Pennpitt, in charge of the Weather Bureau office at four remainingstations the 10 years 1902-1911, inclusive. Pithburgh ,- TABLE5.-Excas of iirini~/iiiiiiitaiiperatures, and dqtic-kny of range of F'reviors to 1885, when soft coal was almost exclwively used for teiiipo.ntiire in n'tb ns miiiparcd with the surroimdiding county. fuel for both domestic and man:.facti.ring pi rposes, the air was orcli- .. .-. .- narily filled with smoke and mot, and many dark days were the res It.. _ About 1855 natwal gas became very plentif: 1 and cheap, largely Bt. Louis Colum- Pltts- Philadel- iVilliams- Harris- supplanting soft coal as a fi.el. and the air 1;ecame comparatively bus. burgh. phia. port. burg. .------free from smoke. The price of gas was increaeed abo:.t 1595. and Month. the use of soft coal was again rewrted to, with t.he res;.lt that the air %i 6 !+i & d E' WBB ain filled with smoke. In the venrs 190.51907 mnny days 2 d .s' B B .g B c" : 2 z -v 5 Pis !x withyense smoke were recorded; hit the panic of 1907-8 res lted .- - - - .... - -- - in a diminished 1;se of coal in mamifactones, and there has I.ieen an OF. 'F. OF. OF. OF. F. 'F. OF. OF. OF. improvement in domestic furnaces nncl methods of stoking, SKI t.liat Janimv...... 2.5 1.1; 3.1 2. n 3.0 3.0 3.0 2.8 2.6 3. 'I the vol: me of smoke has again been greatly diminished. However, FebrlVdry...... 2. Y 3.8 1.2 1.3 2.6 3.5 2.6 3.3 2.6 4.3 the air in the vicinity of Pittsburgh is never free from smoke. except Yarch...... 1. 6 0.2 2. i 3.3 3. i 3. x 2. S 2.9 1.2 4.7 .lpril...... 4.4 3.1 3.2 3. 8 3. s 5. R 3.0 2.9 3.6 5.9 after a rain or snow storm, and with high westerly winds. Mlny ...... 3.2 3.3 5.2 6.9 3.2 3.3 4.2 8.9 JUIIe...... 5.23. I ". 2. s 3.9 4.5 5. s 3.i 3.0 2.8 3.2 3.3 5.9 In Table 4 the average masiniuiii and iiiinimuni t.im- Julr ...... 5.5 4. 0 3.2 3.4 4. Y 6.2 4.5 4.4 3.2 4.3 4.3 6. 4 Auiust...... 4.s 4.2 3.4 4.1 5.0 6.6 4.4 4.4 2.2 3.8 3.5 6.1 eratures and the rance of tenipcrnture, in PittsiJurgh, Peptnm1)ar...... 9.0 9.0 3.5 4.3 4.4 7. R 4.i 4.2 ?. 5 3.4 3.5 5.3 I 5. (I 2. r gave been arranged in four groups : (1) 1%-5 - 1 SS4, corrc- October...... 5.8 5. 9 3. s 4.5 4.4 5.6 5.; ?.S 3.! 5.6 2.2 2.9 3.2 4.5 4.1; 2.4 3.c 3. I 5.0 s onding to a period of dense smoke, a.ccoriling to tlic 1.5 1.9 2.0 3.0 3.1 2.7 2.r 3.1 4.3 a ------_ - \ ove statenient: (2) lSS5-1X94, to a period of coni1~ara- 3.5 2. 8 3.1 4.1 5.1 5.8 3.1 3.6 5. 4 tively light smoke; (3) lS05-June, l!lO4, to a pcriod of - __ .-.- - - - - dense smoke; and (4) July, 1904-Dec., 1811, to a period of dewensing sniokiness. At the outlvinc stations. and also at Willia.msDort. t,he t1ieriiioiiie~eYe;lohavebeeii esposed in a shelter 6u t a TABLE4.-Average annztal niaxin~i.naaid wiii~iniziin ten1 pt-ratiirc and few feet above t,he ground. At Pittsburgh they are now range of tenlpcrraturt! at Pittsburgh, Pa. 353 feet a.bove the ground, at Philadelphia 153 feet, and at Harrisburg 94 feet; but the elevation at Pittsburgh has been changed during the period of conipai'ison, as has a.lready been shown. - ... - ...... I ;.. From Ta.ble 5, it is seen that the minimum tempera- 'F. e F. F. 0 1.: Maximum...... 62.7 81.9 til. 9 lil. 0 ture at t.he sis stat.ions under consideratmionaverages Minimum...... 43.4 44.0 44.6 ' 43. ti about 3.6' F. higher, and the range of temperature 4O Range...... 19.3 17.9 17.3 ' 1;. 5 _I - less than tmhecorresponding data for surrounding sta- tions. The maximum temperature must t,herefore aver- The elevation of t,he thermome teis above groun cl was age about 0.4' lower. The differences have a mtvsimum about SS feet during t,he first, period, about 120 feet dur- in the warm months of the year. ing the second and third periods, and 336 feet during Tlie ma-uinium teniperatures in the city are generally low most of t,he fourth period. The increase in elevnt.ion at during the warm months by approsimately the amount the end of the first, period tippeais t,o have decreased the that may be attributed to the greater elevation of the diurnal range of temperatmureabout 1.4' F., while the thermometers above the ground, or by about 0.5' F. per further increase in elevat.ion atr the elid of t,he t.liirc1 100 feet. Only a art of the minimum tern erature excess period appears to have decreased bot.11 maximum and can be attribute(P to this cause, the rest geing undoubt- mininiuni teniperatures by about 1' F. Duii~~pthe eclly due to some city influence. smoky third period the minimum temperatures averaged Bolton (30) has computed that the tota.1 heat emitted about 0.6' F. higher than during the comparatively clear from all sources in the city of New Tork, but principally second period. froin the combustion of fuel in average winter temper- 53181--14--3

Unauthenticated | Downloaded 09/24/21 07:29 AM UTC 84 MONTHLY WEATHER REVIEW. JANUARY, 1914 ature of 40' F., would add 2' F. to tahetemperature over I ani indebted to Mr. George SI. Bliss, section director, an area of 326 square miles to a height of 1 mile. This United States Weather Bureiiu, in charge of the Peiinsyl- could only be true when there was no movement of tlie vaiiia section, for the data for Philadelphia, Williams- atmosphere, a condition that only occasionally prevails; port, and Harrisburg, aiid for information relative to and the effects of the heating would be more marked in conditions prevailing at these stations. winter than in sunmier. Evidently some other influ- ence also has a part in modiffiiig the minimum teniper- SUMMARY. atures of cities. Table 6 shows that in cities t.he ininimum temperature 1. Citv fogs are more persistent than country fogs, excess is more pronounced on clays when dense smoke priucipdly because of their increased clensity on account prevails. We a.re therefore justified in attributing a part of the smoke that accumulates in them. of the excess in the niont,hly mean nlinirnuni tern erature 3. In consequence of the above there are fewer hours of cities to the general sniokiness of their atniospR eres. of sunshine in cities than in the country. 3. 111 the clear part of the day in winter inLoiirloii the TABLE6.--Depurtures oj tlat! ntn;L.iim?tt and siin.iinum tmiperatrire a?id the range o teniper'aticre in cities, itden smoke or fog 'uwa dense,froni the averlige liniit of visibility does not esceed one-half mile. rorrespon ding averages at surroiinding stations. In Pittsburgh it averages about 1+ miles. This latter is less than one-tenth the average limit of visibility in the open country about Pittsburgh. Station. Maximum. ' Miuimum. j Range. 4. The chemical actioi? of light in smoky cities has been 40 IF. "F. found to be per cent less than in the open couiitry, mid Pittsburgh.. .. . -. .. -...... -. .. . . - -.. . . . -. .-. . . -0.9 +6.5 -7.4 over 30 per cent less on smoky days than on compara- Phlladelphh .-. .-. -. - -.. . . . -. - -...... -. -. . . . -0.4 F.+6.9 1 -7.3 tively clear days. 5. Minimum temperatures are markedly higher in Table 6 also shows that the masiniuni temperatures cities tlinii in the country, partly on account of city hent- are not affected to the same extent as the minimum ing, but principally because the snioke acts as a blanket to temperatures. This is because the smoke is densest prevent tlie escape of heat at night. duiing the morning hours, the convection of midday helpiiig to carry it away. At the same t,iine the more REFERENCE AND NOTES. thorough mixture of city aiid country air teiids to equalize (1) Hum hrevs. W J Distribution of gases in t.he atmosphere. temperatures over tho two regions, and it may also be Bull., Mt. g-eaiher obs., kashington. 1909, v. 3, 66. that the absorption of heat by the snioke part.icles tends (81 IIenriet, 11. (.'ontrihutioii 1'Ctude de pair atmosph6rique. ' to increase the niaximuni temperat.urss. hniiales. Observatoire muiiicipale (de Monteouris). Paris. 1906, t. 7, Williamsport, Pa., is a small city in which the effwts p. 3i. 257, 390. of city heating must be slight; aiid since the thernioniet,ers The soot fall of London. The Lancet., London, Jan. 6, have had ex osures similar to those at surroundin 1912. p. 47. (3) Barus, Carl. Condensation of atmospheric moisture. U. S. stations, naiiieY. y, in a shelter a few feet above the grounce Weather Bureau Bullet,in 12. Washington, 1895, p. 49. the only known reason why the minimum temperatm-e (4) Young, Charles A. General ast.ronomy. New York, 1898. should show the escess rerealed by Table 5 is the influence p. 476. of the smoke cloud, which quite dense at tinies owing (5) Huniphreys. W. J. Dust lay$rs in the atmosphere and changes is in t.he neut.ra1 points of sky polarization. Bulletin, Mt. Weather obsy., to the est.ensive use of bituininous coal for manufacturing n'ashington, 1!111, v. 4. p. 397. purposes. (6) (.'ohm, J. B. The air of towns. Smithsonian instit., Ann. rpt., Betweoii December, 1913, and May, 1913, inclusive, 18115. p. 360. (.'ohen, J. R., & Ruston. Arthur C. Soot: ita rharacter and compoai- temperature readings were obtained froni thermometers tion. Jour. mc. chem. ind., London, Dec. 15, 1911. esposed a few feet above the sod h a park in Allegheny, C'ohen, J. B., (I: Ruston, Arthur C. smoke: a study of town air. Pa., just across the river i'rom the Weather Bureau London. 1912. office in Pittsbur h, and froni thermometers similarly 171 C'ohen. J. B.. & Ruston. Arthur C. Smoke: a studv of town air. esposed at Sewickfeg Pa. The results, which are sum- Girlon. 19i~p. 16. (8) -The soot fall of London. The Lancet, London, Jan. 6. marized in Table 7 s ow rather small differences between 1912. the readings at Allegheny and the Weather Bureau office 19) -Soot. Nature (London). Feb. 29, 1912. v. 88, p. 598. in Pittsburgh, but differences between the readings at (10) Aitken. John. chi some observations made with a dust counter Alle heny and Sewvickley of about tho magnitude that on the hazing effectof atmospheric dust. Pror., Royalsoc. Edinl) rgh. 1S95. v. 20, p. 92; and v. 30, p. 548. wouf d be espected from the comparisons suiiiniaiized in (11I Aitken, John. Report on atniuspheric dust. Trans., Royal mv. Table 5. Edinburgh. 1902. v. 42. p. 485. Other conditions being equal, the diurnal range of (12) Aitken, John. On improvenients in the apparatus for counting the Royal 8oc. EcliiibuEh, t.emperature should be proportional to the amount, of dust Darticles in the atmosnhere. Proc..I" - lfi90. v. l%,p. 187. heat received during t.he day; but, as alreadv stated, it (13) C'arpenter, Alfred. London fog inquiry. 1901-1902. London. seoms probable that in the cases under considerat.ion t.he p. 8. diminished diurnal range of t.emperature is due princi- (14) Aitken, John. On dust, fog. and clourls. Trans., Royal mc. pally to retardation of nocturnal cooling by the smoke Edinburgh, v. 30. p. 337. (hi mme nuclei of cloudv ronde~isat~ion.Trans.. ,. Rovd EOC. Edin- cloud aver the cit,ies. burgh, v. 39, p. 15. The aun as a fog producer. Proc., 1Eoyal mc. Edinburgh, v. 33. p. 189. TABLEi'.-fij%Wlce8 bdween temperatures in PittsbiLlgh rind ;la subiirbs. (16) Aitken. John. On the particles in fog and clouds. Proc.. Royal

~ ~ ~ ~~ mc. Edinburgh, v. 19, p. '260. (161 6, Stations. Maximum. Ran@. -The soot fall of London. The Lancet (London'). Jan. Minimum. igiz i.47. ~~ -- (17) Aitken. John. Dust, fog, and clouds. Proc., Royal mc. Edin- F. F. OF burgh. v. 11. p. 1% Alleghmy-Weather Bureau, Pittsburgh.. .. ._. _. +0.8 -0.3 +l.1 The sun as a fog producer. Proc., Royal soc. Edinburgh,v. 32, p. 183. AUe@my-Bewickler.. -...... -...... I -0.1 +3.3 -3.4 Gewlckley-Weather'Bu, Pittsburgh.. ._... . _I +0.9 -3.6 +4.5 (18) Brodie. Frederick J. Decrease of fog in London in recent years. 1 Quart. jour., Royal metsorol. mc., 1905, v. 31, p. 15-28.

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