General Meteorology. Tbe Melting of Snow

DECEMBER,1915. MONTHLY m'EATHER REVIEW. 500

.*> I, 1, ,I * f, 2, SECTION 11.-GENERAL METEOROLOGY. TBE MELTING OF SNOW. that snow under suit.able conditions behaves like By ROBERTE. HORTON,M. Am. SOC. C. E. other permeable medium, such as a porous soil, as regar Bs the percolation of water through it and its capillary reten- IDated: 57 North Pine Avenue, Albany, N. Y., Jan. 14,1916.] tion in the iiiterstices of the medium. In the experiments It is a familiar fact that if there is deep snow on the above described the snow prisms were placed on a solid ground streams do not rise as rapidly after a rain tis they surface. If the snow risin was placed on a capillary would if the ound were bare. On the other hand, when surface, such for esanip!i? e as a mass of blottin paper or a there is a falF of light snow followed by a warn1 heavy rain layer of nioist nonsaturated soil, then the cap1% axy lifting which removes the snow the intensit.ies of resultiii floocls power of the snow column would be balanced not by are sometimes greatly augmented. In general, t? iere is gravit.y alone but by gravity plus the capillary downward a marked 1 between tlie melting of snow and tlie ap- pull of the underlying medium, and a portion of the pearance of 5t e resulting water as run-off in the streani.~. capillary water hehl in t,he snow column would be re- As an aid to L better understanding of the relation of moved. snow accumulation to the flow of streams and to floods, Duriw t*he last three winters there have been un- the writer undertook L number of smple esperiments. usually geavy 1a& of snow at Albany, and on each such Several cylinders with open ends were filled wit.11 snow, occasion tehewrit,er has kept a record of the progressive the average depth being 53 inches. The cylinders were decrease in depth and increase in density of snow on the each 2.45 inches in diameter and they were placed on ground, and has performed various esperiments to de- end in air at a temperature of from 30" to 35OF. The terniine the rate of melti of the snow and the disposi- snow in the cylindeis had an average density of 0.333. tion of the water producz thereby.' These experiments

Water at temperature 4S0 was poured on the snow in the were performed in a yard nearly level but with a very c linders in varying depths from 0.16 inch to 1.46 inches. slight slope toward the center from all sides, so that no &e cylinders stood in tin dishes intended to catch any surface run-off takes place. The soil is a he-textured ercolation through the snow which might. take place. uniform sand into which water percolates veq readilz. fn no case was there any percolation whatever through Experiments show that water will percolate mto thw the snow after the cylinders had stood for one hour's material even when the ground is frozen. as hard as brick, time in this test. On removing the cylinders from the owing apparently to the fact that the soil surface is never prisms of snow it was found that the water added had all fully saturated at the time when it freezes. percolated to the bottom of the prism and was held in a The accompanying Table 1 presents the resulk of snow- capillary column of a height proportional to the quantity density tests during February and March, 1914. This of water added. It was necessary, therefore, to make a series of tests begm immediately after a very heavy fall further test in order to determine the height to which of snow. The dept3h in the miter's yard was 27.75 water would be held in capillary suspension in the bottom inches, as determined from a mean of four samples taken of a column of snow before any percolation would take in a galvanized raingage can. The water equivalent lace. By adding increased quantities of water it was was 2.04 inches. This was somewhat greater than the found that for the new sample, having density of 0.448, recorded catch at the U. S. Weather Bureau station about a capillary column 3 inches in height was su ported by 23 miles distant. Owing to t,lie local surroundings, it the snow. This was e uivalent to a depth oP 1.1 inches appears that the depth of snow which fell at this imme- of water. It was foun8 , however, that 1.57 inches of the diate locality was considerably greater than that which water added to the snow remained therein, indicat,ing fell hi otslierparts of the citv more exposed to the wind. that part of the water added remained in the unsaturated There was little drifting of the snow in the writer's ard. prism of snow above the capillary cdumn. From these The results of this series of observations are Jown and other experiments described hereafter it appears graphically in figure 1, from which it appears that the Unauthenticated | Downloaded 09/29/21 06:22 PM UTC 600 MONTHLY WEATHER REVIEW. DECEMBER, 1915 temperature was uniformly below freezing for sis days each of these tests a prism of snow was carefully cut out after the heavy fall of snow. There was but little wind, with t,he galvanized-iron cylinder of the raingage and the snow did not drift but the depth decreased uniformly was set undisturbed upon n perforated pan to permit and the water equivalent and density increased quite drainage, the drainage being caught and weighed in a cu uniformly. Similar progressive decrease in depth and underneath. The dra.iiiing and weighing apparatus used increase rn densit prevailed escept when the depth wns is shown in figure 2. The successive forms of the rism augmented and tx e density reduced b additional falls RS melt,ing progressed in the two tests are shown in Pgures of snow, until the entire snow cover %ad disap eared. 3 and 4, respectively. The object of t,hese esperirnents From February 26 on, tvhe temperature generalyP rose was t,o determine, first', t,lie aniount, of lag in time be- above freezipg during trhe daytime, and during the period t.ween a partial melting of the snow sild the appearance TABLEI.-S;no.w densityItests, Albniy, N.Y., February-Narch, 1914.

I New mow. I Water equivdeut. Ratio. - - -I Data. i No. Water snoa loss. Tohl. Depth. and nint. I tents. slush i ___ (9) (IO) (l6j (17) -.,- __ - .- H~urs.1 Inch. irlrea. Inches. 'IlCh.?S. Znrhcs. lnrhe8. I?lchc.s. IneAcs. 5p.m...... 0 i27.75 0 2i.75 0 ...... IJ u. 0011 U.WlX ...... Sa.m...... 3Y 23 0 1.00 I1 ...... U .123 .m -0.76 0.p2 ...... I.. ..:...... 01 12 m...... 52 ~ 11.6 0 21.m IJ ...... 0. i5 0.w . 2.9s , n 1--2:9i- .130 .13U - .lS ...... m 123011'. m... Js.5 m.0 II 20.00 n ...... ?. i5 .154 .164 - .31 ...... 3p.m...... 146.51 14.W 0.25 14.31 n ...... 0 .2m .m .148 ...... 11 a. m _.__._44 I 12.ii .?s 18.05 u ...... 0 I1 1 8. 146 ! I) S. 141; .3 in .910 -.a04 ...... I ...... 1.10 4p. m ...... I ii l..ii:k' .xi is.40 0 ...... 6.00 ~ 1.10 4.86 I) 4.s .B5 .si5 - .714 ...... 119a. m.. . .13.6 ' 15.34 1.w 16.40 0 ...... 11 I 0 , 4.411 : 0 1.411 .258 .w> .4Q ...... I ...... : ...... )...... 16 i...... 4 n 16.90 0. r* 17. 41) ,284 .ll 8 ...... 4 . li) 15.50 .a11 ...... 11...... 4 .. .i5 14. R2 .xi5 ...... 13...... 4 0 13.45 .iB 14.20 .3M ...... U...... 4 0 9.75 .i5 10.3 .JO1 ...... 17...... I ...... 12 1s ...... 4 ...... I1 9.m .50 10.11 .318 .M 1 .Si .3r a0 ...... Noon ...... 0 8.7i .i5 9.52 .812 .3G6 ! .31 ...... a3 ...... Noon...... 0 K 77 . i5 9.00 .301 .so j .% .02 24 ...... I"'is...l ...... , ...... 01 !xi...... Noon ...... I 6.70 S. ii 1.00 6.70 .35) .4i2 .33 ...... - - - - 1 For precipitation 24 hours,U. 8. Weather Bumau. with thawing days and freezing nights a layer of slush of the resulting water as run-off; second, to determine the ice accumulated underneath the snow as indicated rate of melting ner unit surface esposed at given tem- and C. L of in Table 1, columns 6 and 8. The quantity of slush and ice where the measurements were being taken was prob- ably greater than the avera e over the entire yard, owing to the slight depression wit8f resulting drainage from the surroundmg snow to the lower parts of the de ression. This accounts for the total water equivalent geing at times greater than the total precipitation as measured by the U. S. Weather Bureau station.

of the winter to an avera e density of 0.30 to 0.40. When. however, the laver of slush and ice at the bottom of .the snow is taken. ihto account, the density may become much greater, being oftentimes nearly unity when the snow has become reduced by successive thawings and to a nearly solid mass of ice. f*e=in!On ebruary 20 and a ain on March 18, 1914, labora- tory teats were made to determine the rate of disappear- FIG.2.-Apparatns for the snow-melting test. ance of a nsm of snow under constant temperature conditions. heresults of the test of February 30 are perature. Owing to t-he fact that the snow prisms be- shown in Table 2 and those of March 18 in Table 3. In came very irregular in form RS melting proceeded and

Unauthenticated | Downloaded 09/29/21 06:22 PM UTC DECEXBEB,1915. MONTHLY WEATHER REVIEW. 601 further owing to the great difficulty of determining accu- melting during the earlier sta ea of the experiments rately the height of the capillary column of water re- From these figures it ap ears tB at each degree of tem- tained at the base of the risrn, the results given in perature above 32' is a?I le to melt a depth of snow Table 2, column 28, and in $able 3, column 25, can only equivalent to from 0.04 to 0.06 inch of water per 24 be utilized for the purpose of determining the rate of hours.

TABLEZ.-Experinmta on svww melting, Albany, N. 17, Febnrary 20, 1914. I Cplindri- Total SIU- sur- :apillary HOW. Helght. Perimeter. esl sur- End area. Mean d,zer face. face. face. &e. --I -I-- (1) (9) (8) IN (7) (8) 19) (10) (11) (19) (18) --- . -- ___- P. m. Ides. Inchrs. Inches. Sq. inches. 9q. inchea. Inches. Inclea. Inchts. R. inches. a.inChG6. ao . 25.13 552.0 8.0 0 0 0 12:4s a0.w 537. L' 50.26 0 1:00 19.80 7.65 24.02 475.6 I 45.96 BPI. 6 8.0 50.26 0 0 0 500.2 + 9.6 1 a0 19.00 7.32 23.99 436.8 42. Os 478.8 7.s 47.18 0.25 11.94 9. 0 444.9 +%.O 2:oo 17.70 6.75 21.20 375.2 35. 7s 411.0 7.7 45.57 .95 13.28 34.1 0 394.4 f 1.8 200 16.80 6.80 m. n 343.6 34.21 377.8 7.4 43.00 1.05 45.16 36.: 12. Q 352.3 - 3.6 3m 19.16 297.6 29.22 2-3.8 7.2 40.72 1.00 40.72 321 ar I 30% 6 - 7.77 330 17.91 364.9 35.52 ?go. 4 6.9 37.39 .I33 31.04 24.1 34. i 30.9 -12.73 4:30 15.40 192.5 ia 86 211.4 6.2 30.20 .50 15.10 12. 4% : 195.1 + 2.1 &40 14.78 163.3 17.35 179.0 5.5 23.76 .75 17. Sa ld.! 85. I 156.7 - 4.76 6:30 13.35 1'20.2 14.19 134.4 5.0 19.63 .€a 11.78 9. ' '76. I 90.1 - 6.35 Sd7 s. 64 5.93 5i. 8 9.65 ' .40 3.86 3. I 94. i 28. 9 - 3.08 = - 51.8 I - - 3.5 I __- Melting. Melting per To$d delting pa depth of Diflewnre r21ting,pa squaffloot Surface Drainage Drainage. remyera- I legree per Per d$%i. meltmg. 24 hours. water per ture. , from 32'. 24 hours. degree per exposed. 24 hours. i 24 hours. I ~ (18) (S) (94) (35) (17) ___

OU9eS. k. inches. 91. inche8. %. iiir1ie.s. Inrhes. OF. CU. hChf8. 76.0 0 0 I 75.75 43.75 3.73 75.5 [ 0 0 48.0 9.6 m. 8 71.5 425 10.8 8.11 3.47 73.5 0 0 48.0 25.0 1,200 2.70 73.5 41.5 2s. 9 9. 31 3.10 73.5 12. I 22.36 1,075 2. 78 73.25 41.25 ?fJ. 1 D. 53 2.74 73.0 12. I 18.02 864 2.46 72.5 40.5 21.3 S. 70 2.45 .oBoI 74.98 72.0 10. I 9.53 457 1.58 71.5 39.5 11.6 5.42 2.14 .a378 84.61 71.0 16. I 13. ?2 817 I. ?6 70. ?5 3s. 25 s. 81 4.76 1.74 .0332 87.71 89.5 15.1 28.81 590 3.03 89. 25 37.25 15.9 11.7 1.36 .W1 lZ64 13. I 17.73 510 3.2s 37.5 13.6 12.5 1.09 .os67 144.21

18. I ??. 19 231 2.40 BR. 6 I 5.98 8.97 a. 87 .oBa2 166.46 I 166.46 i 1 Original weight, 97.44 ounces. 9 Overflow estimated at 10 ounces, pMbably more.

Unauthenticated | Downloaded 09/29/21 06:22 PM UTC 602 MONTHLY WEATHER REVIEW. DECEMBER,1915 TABLE3.-Snow-melting teak at Albany, N. Y.,second am'ea, March 18,1914. - TOP. Prism. Is I I I I 0- 6." I 4 d E E; P -a 3 Mae : )I: & -E --- -w -SI (90) (21) (E) (98) (24: lW ------k. in. In. OF. OF. In...... ?& ...... 74 42 ...... 1. ((2: 74 42 ...... 564 3.94 ...... 0.m 1. i7i 394 2.73 71 39 .om 1.70; 264 1.63 71 39 .Me9 1.6i: 458 3.18 71 39 .os16 1.65; 232 1.61 72 40 .04M 11:40...... 8.00 7 14 40.49 1. MI 332 2.30 72 40 .0575 lam...... S.W ilOl~.~i.l5!4U. 15 t. 12 39. $1 22.36 2S2.5 .W23.W 15.35 - 1.61 6.92 5.31 f 3823219.4 1.5% 31 1.74 73 41 .M25 12:ZOp.m.. 7.85 6.9037.39 R. %i33.70 6.73 35. ti 21.11 245.6 .5018.i 12.W - 3.29 3.65 5.36 4 3S5.91QQ.I 1.3Pl 2% 1.94 73. 41. .0467 l2:Q ...... 7.50 6.9037.39 6.35131.07 6.62 33.42 20. is 23i. 3 .5ols.7 12.w 0 12.11 12.11 f 8il.9 187.7 1.304 p71 4.65 74 42 .I110 1:OO ...... 7.20 6.6434.21 6.05 21 75 1.32 31.3; 19. S5 2007.2 .5U 17. 1 11.02 - 1.04 6.92 5.W f 423.4 171.3 1.13 dW 247 74. 42. .05m 1:aO ...... 7.00 6.4532.57 5 95 27. So ti. 30.19 19.47 194. S .El) lH.B 10.51 - 0.51 6.92 li.41 $ 481.5 163.6 1.13s 406 2.82 75 43 .om ~40...... 6.90 6.35 31.67 5: B 3.8; I ti. 111 9.22 19.16 1%. 4 .4n I!!. i A. 19 - 2.32 ti 92 4. 60 331 9 159 3 1.m 301 409 75 43 .0488 2:00...... 6.70 6.32 31.35 !id3.60 I 6.07 2% 93 19.07 lS2. ti .Lfl.15. i 10.12 + 1.99 R.92 8.S5 1 637:!154:5 1.07: 590 4.09 75 43 .IN51 2:aO ...... 6.70 6.2.030.19 5.65 25.07 1 5.92 27.52 1s. 59 170.5 .~0'15.1 id - 0.39 6.92 6.53 f 470.2 149.7 1.011 451 3.13 74 42 .0745 2:40 ...... 6.50 6.052S.3 5.40 zz. 90 s. ;A ni. 24 is. 15 15s. 5 .XO 9.61 5.55 - 4.18 9.155 4.47 4 321.8141.2 0.92 3'29 2.28 7i 45 .0507 3:00 ...... 6.20 5.'9027.34 5.20 21.23 5.55 24. 19 17.43 142.7 .X.i 9.55 fi.10 + U.61 R.YZ i.53 4 543.0 129.0 .s9,- tux 4.21 76 44 .w5: 3% ...... 5.W 5.7525% 4.95 19.24 I 5.35 2.4s 11:. SI 1129.3 .40 io. :$tj ti. in + 11.54 s. ti5 9.19 4 Ml.2 116.0 .Rlt 5.70 75 43 .om 3:m ...... 5.40 5.352144 .3il B.75 4.38 - 2.35 5.19 2. M 1 114.2 104.9 .i2s 25;l 1.95 73 41 .0476 4:00 ...... 5.3s 5.2321.9 .411 N. ;ti 5.65 + 1.30 3.46 4.75 343. I161.2 .721 475 3.311 75 43 .076S k20 ...... 4.50 5.0520.uz .40 8.01 5. li - 0.4h 10.3s 9.MI 1 712.R s3.1 .5ii 1,235 R.57 74 42 .xu k40 ...... 4.00 4.851S.47 .BI 5.53 3. M - 1. lil 5.19 3.5s f 257.S i4.2 .51: 501 3.48 75 43 .om 5:OO ...... 3.90 4.4015.20 .3lI 4.54 3.94 - 0.62 S.65 S.03 4 5iS.2 M.9 .448 1.303 9.09 75 13 .211 5:aO ...... 3.60 4.1013.20 .-IO 5.28 :5 40 + 0. :G S. 19 5.1% 406.8 59.6 .114 9% 1;. !4 75 43 .159 5:40 ...... 8.20 3.6410.1S .:in 3.w i:~l- 1.43 5.19 %.io j 270.7 44.3 .30i 882 6.12 76 44 .r* 6:OO...... 6aO...... I..:...... ' ...... B:40...... 2.10 2.27 4.05 2.25 3.9s q. 3; 4.01 i.10 9.1 .XI 1.62 1.04 -0.93 3.4li .131 1,390 9.64 74 42 .m 7:OO...... 1.W 1.95 2.9s 1.8s 3.75 1.91 2.31: KIM 5.5; .30 .SI4 U.5* - 0.46 3.46 .n94 2,300 15.96 75 43 .3n p...... 1.20 1.31.23 1.2Sl.29 1.5 1.3L3.95 1.3 :m .a46 .lti - 11.42 3.48 .04l 5,341 37.06 75 43 .859 ~40...... 0.60 1.15 1.04 1.100.95 1.13 0.~3.ii 1.1: .%I .M8 .I3 - 0.W O..%t .OB 2,Lw IS.% 74 42 .434 s:00...... 30 0.50 0.1% 0.45 0.159 0.4s 0.1s o..m o.o! ...... I._...... k05...... a ...... 0 ...... 0 0 ...... I ::::...... 1::::::1::::::::1:...... - - -.-. - - - In figure 5 an effort has been niacle to determine the after nielting began before any percolation took place. relation between the total amount of melting ex ressed In t,he nieaiitiiiie snow equivalent to something more than as a depth of wat'er in inches, n.nd tlie amount oP perco- 34 cubic, inches of water had been melted. lation taking place from a snow prism Tlie line marked As tfhetotal weight of percolation finall obtained from "total rneltmg, cubic inches,'? figure 6, has been ob- t,he ineltina of the prism was but slightT y less than the tained by addmg together the percolation and tfhe quan- weight of he original volume of water contained in the tity of water accumulated or stored in the base of the c?sperimental prism, it appears that the loss from surface snow column,in -the form of slush. Later esperiments evaporation during these tests was comparative1 sli ht. on the percolat~o~iof water throiigh snow indicat,e, "lie niore rapid melting of the less dense, new$ faflen snow lying on the siwface is clearly illustrated by gure 3.

c: 0 c3 El al 3 40 RM. 5:40PM. 7:bObM.

SCALE Fro. ~.-SMW prism during melting, March 123,1914...... J 12:48 RM. 2:05 RM. 3:30PM. 6:30 P.M. 8:45 6M. It was noted in the ex eriments that the hei ht of the FIO.8.-Snow prism during melting Feb. 2IJ 1914. Experiment started nt 1248 p, m.; capillary column at the gas, of the prism gra% ually in- drain& started at 205 p. m. creased to a maximum before percolation be an. however, that this line does not represent the total amount After percolation began the process seeme2 to be very of melting. Meltin takes place at tlie surface and the re- irregular, the water flushin out at times ra idly, then sulting water ercof ates downward though the risni of again there would be but 'ttle percolation ror a time. snow, part oft% e water reniainingin the portion of t1 e prism Some of the snow crystals were apparently melted by the above the saturated column as a ca illary film. The esperi- percolating water so that the porosity of the base of the ment does, however, illustrate strif ingly the lag in time be- column was increased and its capillary power decreased, tween the melting and the appearance of run-off, since in thus the height of tslie capillary column decreased as the the experinients illustrated m figure 5 two hours elapsed melting of the prism progressed.

Unauthenticated | Downloaded 09/29/21 06:22 PM UTC DECEMBER,1915. MONTHLY WEATHER REVIEW. 603 TABLE4.-snow density tests, Albany, N. Y., December, 1915-Janu- On December 25, 1915, an ex eriment was made to m'y, 1916. deterniiue the maximum rate o Ppercolation through a prism of this snow, treating it as a porous medium. For this purpose a prism of snow of 4.71 squars inches cross sect.ion was used, its temperature being about 30' and its average density 0.64, the snow being packed into the t.ube as uniformly as possible. The depth of the .- prism was 21 inches. When the surface of tlm prism of __:-- snow. was kept. covered with water at 32O, the water flowed through the snow prism by percolation at a (6) (6) velocity correspondipg to a depth of 2.28 inches '(0.19 -I--- ?itches. i Inches. Inchrs. ! Inchfr. OF. foot) on the surface per minute. This may be taken Dw.13 ...... 1.9SS...... i...... 32 to represciit thc trausmission constant analogous to ...... 0.358. I...... I .....i.. 32 d.4ti.5 the transmission c.onstoaiitfor flow of ground-water for 3.465 I 0.110 ...... "1+3.465 2i ...... I ...... i ...... 30 snow having n porosity of per cent and at the given 3.345 i .l41 n.zm. 3.in -0.s 3s 36 3.4?uJ I .MI 1.12R.I 4.S 1-1.32 39 trm lcrrtture...... I ...... I 3i I4I here snow lying 011 the ground contains a saturated 3.4,s 1 .241 ...... 1:: ...... I ...... St ...... : ...... I 32 layer or lager of slush at the bottom, the water will tend ...... I:::::. ..I: :...... I I 3339 23 U.OSR./ 4.S ...... to flow along the ground surface from higher to lower ...... I ...... j :: .. ".. j I:! 25'...... I...... 0.01R 4.s~...... _.._.. 45 levels apparently in accorclance with the ordinary laws I 6.72 I...... 23 ...... I ...... '."E'l} ...... 46 governing the flow of pound-waters. Using the trans- It 2i ...... I ...... I 35 inission constant. deterniined as above for snow of the 28 111.25 Q ...... 214 ...... I ...... given density and takin the hei ht of the capillary ...... -234 colunin as D, the rate of orizontn flow of water along ...... 20 a f Jan. 1 ...... the ground surface woulcl he .... '0...... as ...... I q= 0.19sn, A fall of 298 inches of snow occurred at Albany Decem- where = the quantity of flow in cubic feet per minute per ber 13-14, 1915. The results of density tests of this foot oP width, measured at right an leu to the direction snow layer and of subsequent falls of snow are slioww in of slope; S=slope of the ground suIf ace. Table 4. At the time this snow fell the ground was not saturated nnd was but little frozen. Snow temperature

/,----

TIME- eH. CCbZO, IoI4. FIG B.--Vertical temperature gradients in snow, at Albany, N. Y. FIG.5.-Illustrating time lag in rum-& from melting snow. (Experiment of Feb. 2n. 1914.) Under t.hc conditions given, with a ground-surface gradients havo been taken in this snow as shown oafigure 6. slope of 1 in 50 or 100 feet per mile, and with a depth of The tenipcraturo at the ground surface remained nearly slush of 0.10 foot, the rate of flow through a layer of constant from December 15, 1015, to January 1, 1916, slush would be 1.G cubic feet per day per linear foot. ILt 30" to 33'. The temperature within the nixss of snow This IS cqiiivabnt to nhout. 0.1 c.ubic foot per second er oradually decreased from the bottom to the surface as mile and illmt.rates the estremcly slow rate at whit% B rong as the t.enipernturo \\-as low. On Jmunry 1, 1916, stream may he fed from the nieltin of snow where the with an air temperature of 30°, the minimum tempera- water must flow through the layer oB snow itself. ture of the preceding day having been -2"F., there was Since the transmission constant for a porous medium a sharp inversion of temperature 5 inches below t.he increases much more rapidly than the porosit it ie surface in the snow layer. probable that the rate of flow through snow of tzk ordi-

Unauthenticated | Downloaded 09/29/21 06:22 PM UTC 604 MONTHLY WEATHER REVIEW. DECXMBER,1915 nary densities-say 0.30 t.0 0.4O-of an accuinulnted 1. With temperature below freezing, the snow settles snow layer would be four or five tinies as peat as through by gravity without change in its Crystalline structure. the sample tested, and freshly fallmi snow of clensit-y 2. If the snow mc4ts at t,he surface or if warm rain about 0.10 offers comparntivc.1y little resistance to the falls on it, most of the wat,er percolates down through flow of water over the surface of tlie ground. Further the body of the snow, provided the latter is at about 32' experiments are needed t.0 determine the transmission tempemturc? and a part of the water adheres t,o the snow constants for snow of various clensities. crystals as a capillary film. During the winter of 1914 the ground was tlioroudily 3. If alternate thawing and freezing occur or if the frozen wben the heavy snow ren. In the snowf:dl of interior of tlie body of the snow has a temperature well December 14. 1915, the ground was but little frozen and below freezing when rain ftds or when the surface is melt- fairly dry. During 1914 n layer of slush and ice ap- ing, the adhering films become frozen to the snow and ared at! the bottom of tlie snow, as shown in Table 1. increase the size and volume of the crystals, changing !?mce the snowfall of December 14, 1915, there has heen their crystalline form and increasing tshe density of the lit& accumulation of slush 01 ice at t.he bottoni of the mass. This is ap arently the cause of the snow becom- snow, although the temperature has hem above 33' ing coarse grainexwith age . !l'he infiltrated water melts much of the t.ime md a rain of 1.35 inches fell on Dccem- some crystals, especially t'he sninller ones. The size of ber 17-18, 1915. There was no apprecialde difference in the pores is thus increased and the capillary su porting t.he ap earance of the snow cover before aiict aftw this power of the snow decreased, as wa,s observe8 in the rain. heaccumulated wat-er on the grouiicl su1fac.e espcriments shown in figure 3. before Ohis rain was 3.34 inches, and following the rain its 4. There mag thus result from alternate tliawings rrnd was 3.49 inches. This was accompanied bjr a clecreasc freezings, or from rain, a further increase in density inde- in depth of the snow layer from 23.5 tmo14.5 inch~sand pendent of the decrease in dept,h of tho snow. by an increase in d0nsit.y from 0.141 to 0.341. As shown 5. Under suitable conditions of low snow temperature, by the above figures, praoticn.lly tione of the rainfir11 of rain may freeze at, the surface, forming a crust. December 17 or 1s remained in the body of tlic snow. 6. When a tqliawoccurs after a cold sna the snow at A marked rise in the ground-water lrvd und~~nirntlithe a lit,tIe depth below it,s surface beinu mucF: below freez- writer's yard took place? however, day or EO followinq ing temperatiwe, the mater resuhing from surface this rain, indic.thting that the rain hac1 siniply filt cred for melt,ing percolates t.0 n slight de th in the snow and the most part through the sncw ana piw.mln t,ed into tlic becomes &sed by the freezing of tie liquid filnis on the ground in very inuch thv smie innliner as if t.lwrr hl crystals, forniing st,mtificat,ionin the snow mrtss. been no snow covcr. 7. Iflien snow and mater nre in temperature equilib- To melt 1 pound of ice or snow at 33' requires the riuni (i. e., 38O), ercolation and capillary action though addition of 133.S h. t. ti. or at 7'77.5 ft,.-lbs. each, 11 1,504.5 the sii~rniiiiiy tili? ai? plece in the sitiiie iiitmIier ns the flow ft.-lbs., or roundly 3.4 h. p. for one niinute. of wnt.er through .a porous soil. Let, 1 8. Snow in this condibion will support a colurnn of T = depth of rainfall, inches; water n.gninst rnvit8yhaving a hei ht t,hree to five times Q = water ec uivalentmof nccumnlntmwlsnow on. D in indies, wP iere D is the snow Ansity (water = 1). groun ct in inches; 9. The t,ransniission constant for n.uked snow, density & =temperature of rain (OF.); 0.64?u-ns found to be about 2.2s incP ies dept,li per minute, tw.= temperatmureof air (OF.'). which equals 273.6 feet, per 34 hours for free downward percolation. We shall assume t,=ta=f, and tlhat 37.75 cu. ins. = 1 10. When snow stttnds on a. sloping inipervious sur- ound of water. For melting by rain n,lone, there will face, lnt,eral flow will be proportional to the product of !e !e required a rainfall such tsliat the depth of slush under tlie snow, t81ietransmission fac- tor, a.nd the slope of the surface, jointly. 'r (t-3Z0)-= 143.S- W 11. With thawing days and freezino nights, most of 27.75 27.72 the water resultiiiv from the melting or snow lying upon impervious grounx will percolate to the bottom of the layer and may there be held by capillary action until subsequent cold convert's it, into n layer of ice. renmin as ice until most of the snow above it is melteIt mx This esplains the layer of ice coninionly observed around the margin of a snow bank a.s it melts, even when the Thus to melt 1 inch of congealed water, or say 5 inches snow bank lies on a steep slope. compact snow, or 10 inches loose fresh snow, with rain 12. The run-off to streams from melting snow, will lag at 42' would re uire 14.4 inches of rain. The melting of behind tlie process of iiielting until, if melting tempera- snow by rain one is a very slow process. High teni- tures continue long enough, nearly the whole snow maas perature, especiallyP with direct solar raclintion, is much will be converted into slush. In the meantime the run- more effective. off will take place only through the slow processes of CONCLUSIONS. capillary flow. 13. After the reater ortion of the snow has been Some of the experiments described in this paper must converted into sushK' su% sequent heat-due to direct be considered as preliminmy and somewhat crude. Those insolation or to warm rain-may ra idly break down the relative to heat abso tion by snow will, in particular, remaining capillary structure, an% cause a relatively bear repeating in the 'pight of the experience gained, and rapid flushing of water into the streams with resulting with greater refinement. flood conditions. As snow melts ordinarily, the perco- The experiments and the writer's observations lead to latin water under the snow accumulates in low laces, the following conclusions which, it is believed, are cor- break thou h the obstructing barrier of slusg into mt : outlet channeK s and the actual rate of run-off is somewhat

Unauthenticated | Downloaded 09/29/21 06:22 PM UTC DECEMBEB,1915. MONTHLP WEATHER REVIEW. 605 ater than would be the case for uniform capillary Dr. L. A. Bauer, C,arnegieInstitution, Waehington. gwalong the surface. E. A. Beals, U. S. Weather Bureau, Portland, Oreg. Prof. W. R. Blair. U. S. Weather Bureau, Washington. 14. The rate at which the snow is melted depends on E. 1%.Bowie. U. S. Weather Bureau, Washington. the rate at which heat can be absorbed by the snow sur- C. F. Brooks; Yale University, New Haven. face per unit area with air ut the given temperature. Prof. J. E. Church, jr., University of Nevada, Reno. ' The writer's esperinients indicate that the melting con- Dr. €1. H. Clayton. Oficina Meteorol6gica Argentina, Buenoa Aires. Dr. I. M. Cline, G. S. Weather Bureau, New Orleans. . stant is about 0.04 to 0.06 inch depth of water per 34 Prof. IT. J. Cos, U. 8. Weather Bureau, Chicago. hours per de ree of temperature above 33'F. Loose Prof. 0. I.. P'assig. IT. S. Weather Bureau, Baltimore. snow apparent9 y absorbs heat at about the same rate as Prof. 11. C. Frankenfield. IJ. S. Weather Bureau, Washington. packed snow, but as the water equivaleiit of the former Rev. A. (;akin. 8. J.. Woodstock College, Woodstock, Md. Rev. M. (iutierrez-Lanza, 8. J., B,elhn Colle e. Habana. is lower, its rate of disappearance is much more rapid. I'rof. A. J. Ifenrv. u. P. Weather Bureau, ifashisgton. 15. When snow overlies unfrozen ground, or frozen but Prof. R. 1%.€Iobhs, University of Michigan. Ann Arbor. porous and unsaturated soil, most of the water from Prof. W.J. Humphreys, U. S. Weather Bureau, Wuhington. Frof. X. Huntington, Sale University, Wew Haven. melting percolates to the bottom of the snow layer and Dr. 1'. A. Ja.ggar. Volcano Observatory, Hawaii. thence into the soil. The melting of snow or warni rain Prof. H. H. lunibail, U. 8. Weather Bureau, Washington. falling upon a snow cover under suitable conditions, is Ih. C. J. Gullnier. Syracuse University, Syracuse, K. Y. thus more favorable to the repleIiishnieii t of llr. I.. T.anda. director general of public instruction, Honduras. Dr. C. Imyuin, director, Observatorio Meteorol6giro del Instituto M6- water than would be nn equal volume of dico, Sucre, Bolivia. bare surface, since in t.he presence of mow, surface run- r'rof. (.!. t:. hlarvin. chieE, U. 8. Weather Bureau, Washington. off is great.ly retmardedand the opportunity for iiifiltratiou Ing. J. C. Millirs y IIernBndez, subdirector of the Notional Observatory increased. of Cuba, Hahana. 1)r. T.'. IC. Bipher, Washington University, St. Louis. 16. Under suitable conditions and especially in the W. G. Heed, OHke of Farm Management, Department of Agriculture, woods where the ground is least frozen, a deep layer of Waxhiugton . snow on level ground may wholly disappear by invisible Rev. 8. Sarasola. 8. J.. director, Observatorio del Colegio deMontserrtt, percolation wit.liout causing any suiface run-off what- Cieafuegos, C:ul)a. l'd. J. Warren Sniith. U. 5. Weather Bureau, Columhua. ever. Where there is opportunity for infiltration, the Ibr. W.F. 0. Swann, i'arnegie Institution, Washington. melting of snow contributes more to the grouncl water Prof. (!. 1'. Tahnan, I;. 8. Weather L(ureai1. Wmhington. and lese to the surface run-off than would an equal A. 1;. l'hiessun, U. S. Wedier Ihresu. Salt I.ske City. volume of rain on n bare surface, and by providing a Rev. 14'. A. Tondoif. S. J., Georget.onn University. Washington. .J. 1.'. Voorhrcs. 1.:. S. WaLther Hure:ui.Kno~ville.. high ground-water level, the effect of the nieltiiig of snow I'd. R. 1)eC. W?d. .lIarvard t7niversit.y. Cambridge, bluss. cover may be felt for a 1011 er time after t.he snow has J2. L. Wells. li. S. Weather Bureau, Boise. disappeared than if an equ 3 volume of ruin had fa.llen Dr. It. S. Woodward, president, Carnegie Institution, Washington. at the same time. f. Lj The attendance included, in addition to these persons, I. ' , several officials and employees of t.he Weather Bureau and others who were not members of t.he Congress. METEOROLOGY AND SEIMOLOGY AT TRE PAN AMERI- A brief account of the proceedings follows: CAN SCIENTIFIC CONGRESS. By C. FI~rzHmmTALIUAN, Professor of Meteorology. SECOND PAN AMERICAN SCIENTIFIO CONGRESS, WASHINQ- TON, DECENBER 27, 1915-JANUARY 8, 1916. [Datod: Weather Bmwdu, Washington, Jan. 20,1!316.] In the Second Pan Aiuerican Scientific Congress, which MIh'ZiTES OF SOHXECTIO?J IIB, ME'PEOXOLOOY AND SEISMOLOGY. met in Washington from December 27, 1915, to January First ses&

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