Downloaded 09/28/21 09:00 AM UTC JANUARY,1916

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8 ., ; ;. , JANUARY,1916 MONTHLY WEATH,ER.. <','- REVIEW. -i 1 " 9 ..i ....i TABLE3.nohr radiation in.tensities ut Liiwh, Nebr. (State Uni- SOL-& RADIATION MEASUREMENTS AT BUDISON, versity furrn)-Continued. WIS., 1913-1016. [Grmealories per minute per square centlmeter of normal surfwe.] 15)' HERBEH'I' H. KIMBALL.Professor of Meteorologv, and ERICR. -- -_ . .- MILLER,Local Forecaster. Suds zenith distance. [Dated: Wnshington, D. C'., Feb. 15,1916.1 0.0' 148.3' 160.0° 166.5' 170.7' I73.0' 175.7" 17.4' I Xi" 179.S' I 80.7' The radiation measurements summarized in Table 3 Date. below nre in continuation of those for the period July, Air ms. 1910, to June, 1912, inclusive, published in t,he Bulletin - I of tlic Mount Weather Observatory, 1912? 5 : 177-181. 1.0 1.5 2.0 2.5 4.0 Thse hitter are included on the monthly nieans of --- - . ._ Talde 3, which are the arithmeticd means of all the 1915. Gr.- Or.- Or.- Or.- Or.- A. or P. AX. published measurements at the respective P. Y. eel. cd. cat. cl. tal. ax. Sept. 16 ...... 0.97 0.87 .._._n. 71; air nizisses for iiiontlis of the same name. 1s...... 1.43 1.33 1.24 1. 15 1.07 1.W (1. 94 19...... 1.10 ..... 0 .s4 0.75 0. I:i .... Tho ix(mis liere given arc gcnsrlly lower than those 3...... 1.40 1.32 1.24 ...... suninimim:l in the 12iilletin above referred to, p. 182, 21.. -.-. . 1.80 1.2s 1.17 i.ns 1) q9 n. D? 22...... 1.3 1.13 1.01 I). 91 I 0: sa n. 71; Table 3, aiicl especial!p duiinp t,he early months of tho 27...... l.2G 1.15 1.05 n. 97 t 0.91 0. s4 29...... ::::::I 1.27 1.13 ...... year. Tliia is no tlouht clua in part to the innrked de- ...... I..... pression in radiation int.ensities dr:ring the latter part of Means...... 1.31 1.27 1.15 1.06 0.93 ' 0 88 0.83 i !. 1913 and iiinst of 1913, following the eru Ition of hutmai A. ?A. ! Oct. 2 ...... _.___1.22 i.in ._...... ,! ...... volcano in Alaskn in June, 1013.1 TTn aoubtedly, how- 5...... 1.4.1 l.3? 1.21 ...... ! 1.02 .... ever, tlie oc.crt.iions are ram wlieii such high vdues as I ...... 1.25 ' 1.16 1. 111 s ...... ___1.51 1.44 1.37 1.3:) : 1.23 1.15 those of the early months of 1911 aiid 1913 will he meas- 9...... 1.36 1.2s 1.10 , 1.12 1.06 10...... 1.Bi 1.32 ..-. 1.13 1.____ .... ured at Mlndison, since t,he atmosphere at that place is 13...... 1.34 1.32 1.18 ...... I n.w n. sn n.es ...... apt to be more or less smokj-, especially during the 17...... _.__.1.3 1.27 1.19 1.13 j 1.07 1.00 0.N ...... !:::::. IS...... 1.27 1.19 ...... ' 1.06 ...... 0.iP ...... ~ ...... winter moil tlis. 21...... 1.9 1.21 1.14 n. 93 n.ss ...... '...... 22...... 1. 51:I 1. 25 1.14 11. s: 0. $0 ...... : ...... 21...... ____.1.37 1.30 1.22 1.02 0.94 n.87 ...... j ...... Tnnm l.--Pon~p~~risrmqf rrtdiatioii. .intensities mtwsurrd ut d[ferent 27...... 1.35 ...... I ...... slaliortr with c.rccp&ionullyelmr skies. 29...... 1.43 1.3s 1. 2i 1.13 I 1.00 0.94 n.si n.ig ...... I ...... Meaus...... ____.1.36 1.U 1.23 1.16 i 1.08 om 0.91 0.78 ...... [Gram-calories per minute per square centimeter of normal surface.] P. Y. ~~ Oct. 2 ...... 1.11 1.03 0.94 I..... _._. _____.0.04 0.13) Air mass. 3...... l.M 1.01 0.97 0.92 ...... I 5...... 1.44 1.35 1.27 1.19 I 1.12 1.05 n.99 c.9~ILS~ .__._. Station. Date. 8. 1.51 1.43 1.54 1.28 1.21 1.16 1.11 ...... 1.06 1.02'._.._ 3.5 4.0 9...... ___.1.P6 1.26 .._...... , ...... !: ..... 3.0 1 I 13...... 1.34 ..... 1.15 1.0s 1.01 0.96 0.90 n.u __.___i .._.._ ...... __...... 17...... 1.B ...... ,...... 21...... 1.21 1.13 1.04 I 0.99 0.92 0. s.5 0.91 ...... : Gr.- I-LI-Gi- Z!...... 1.21 1.13 1.04 10.9s 0.93 0.88 0.u ...... I :::::: I mi. I cui. I ai. 26...... 1.22 1. a3 ...... Yadlson.Wis...... Sept. 4,1914 ...... 1.0s I...... I...... 2;...... 1.24 1.10 ...... I...... ! ...... Mount Weather, \'a ... .I Sept. 28,1914 ...... 1.20 I 3...... 1.29 1. P 1. 14 ~ 1.01 1.90 3bdlson Wis...... 1.47 Meslm...... 1.41 1.25 1. i5 1.10 i 1.08 1.00 Warhh&on, D. C.. ...

A. Y. i Xadison. Wia...... I 1.45 1.40 I 1.32 1.X NUV. 1...... i ...... 1. nl 0. 91.; .!1.50 11.88 1.32 8 ...... 1 ...... 1.39 1.35 1.26 1. 19 1.12 ...... 1.43 1.35 1.30 ...... I.--.-. 12 ...... I ...... 1.40 1. 'sn 1. 1.1 ..... 1. (If ...... I...... I 14 ...... 1 ...... 1.54 1.45 1. :{!I 1.2.t 1.11 i.ni ...... 21 ...... -1...... 1.47 1.41 1.34 1.2s 1. 22 ...... 33...... 1.43 1.33 1.31 1. lfi 1.m i.n? _.__._!~~~~~~ On December 30, 1914, and December 28, 1915, the 29 ...... ~ ...... 1.45 1.36 1.30 1.22 1.li 1.12 _____.!:::::: highest Deceniber rudistion intensiticv of record at Mad- Meaus ...... i ...... 1.44 1.41 1.31 1.22 1.13 I ison were obtained, and on September 4, 1914, the high- P. M. I est Septernlm intensities. It is of interest to compare NOV. 1...... 1.30 1.3 1.11 1.0 0.91 11...... I-...... 1. .I2 1. :;6 1.23 1.1s 1.13 these with intensities at other stations at about the same 12 ...... 1.37 1.29 1. ?2 1.14 .._. 19 ...... 1.43 1.3 1.30 1..J .... time, as has been done in Ttible 1. The int.ensities meas- 21 ...... 1.5? 1.44 1.3: 1. :m 1.3 urecl at Mount \Veat,lier, Va., on September 28, 1914, are 28 ...... 1.m 1.29 1.16 1.07 1.01 8 ...... 1.49 ...... the highest September intensities ever measured at the 29 ...... 1.54 1.45 1.37 1.31 1.2: station. Likewise, those for Wnshington on Deceniber Means...... 1.45 1.31 1.25 1.1s 1.11 26, 1914, are the highest intensities for corresponding air ninsses measured at Washington in any month. This is Dec.AiM: _.___1___.__ i ______i 1.80 1. ??. 1.1.1 1. [YJ 1.03 also true of the measurements at Lincoln, Nebr., on De 8 ...... 1.41 .... 1.29 1.21 .__...._.! ...... ! ...... I 1J ...... 1.36 ...... I cernber 28, 1915, while those ohtnined at Ssnta Fe on 17 ...... 1.3s 1.31 1.3 1.17 1.10 1.E 1:::::: ::::::;:::::: 20...... 1.42 1.34 1.24 1.13 0.99 ...... December 24, 1915, are the highest December radiation 31...... 1.36 1.32 1.24 1.12 .....I ...... 2s...... 1.54 1.41 1.22 .... 1.17 :::::: i :::::: intensities yet measured at that station. I...... Marvin pyrheliometer No. 5. of the spiral-ribbon Means...... 1.38 1.86 1.89 1.20 1.09 1.02 I...... I type, which became tlie station instrument at Madison P. u. I nec. 3 ...... I ...... I ...... I ...... 1.30 1. ?S ' 1.17 '1.11 on November 34, 1911, has been in continuous use since 4 ...... 1.21 1. io I 1. nz 0. I that dnte. It was reconipared with Smitshsonisn silver- 8...... 1.35 .....I ...... 17 ...... 1.5 I 1.10 .... disk pyrlinliometer No. 1 during March and April, 1912, 21...... 1.35 1.3 i 1.24 1.19 28...... 1.3s 1.3'3 .... and ngsiii in March, 1915. The results are given below in Means...... 1.30 1.14 1.16 i(1. 10$0.86)/(0.D8) 1 Ste Bulletin of the Mount Weather Observatory, 1914,6 :208, figure 1, lor a graphia I-----'- - presentstion of thfs depression.

Unauthenticated | Downloaded 09/28/21 09:00 AM UTC JANUARY,1916. MONTHLY WEATHER REVIEW. 9 able 2, and do not indicate any change in tlie constants TABLE3.40lar radiation intensities at ilfdson, wis., 1915 to 1915, of the instrument. .inclwive-Continued. [Oram-calariaper minute per square centimeter of normal surface.] TABLE2.-Cmparison oj pyrheliometers ot Mudison, JVix -- Son's zenith distance. Smith- Ratio: Data. ' ...... - , No. 1. 0.0' 1 48.3' 160.0' 166.5" 1 70.7' I 73.6' 1 78.7" 117.4' I 78.7O I 79.8*I80.7' I- I- I_--/_____

1911. i Gr.4a7. / G~.-MI. i Air mpys. Nov. U...... 1.369 1.361 I n. 994 24 ...... I 1.3iSI 1.350; 1.001 __. .- I 1.0 1.5 2.0 2.5 3.0 3.5 4.0 1912. I 1 I 1 yIu.28 ...... I 1.3fi11 1.349; 0.991 -_-I_ _- - -I-I- 29 ...... I 1.w 1.509 ' 1.019 29 ...... i 1.5191 1.503' 0.9s9 A. M. Qr.- Gr.- Or.- Gr.- [ Gr.- 1?14. Cd. Cd. cut. Ed. cul. Apr. 5 ...... ; 1.251 1.243 0.935 Feb. 1 ...... 1.33 ...... I ..... 5 ...... \ 1.252 1.258 I 0.9n: 2...... 1.21 1.0; 0 96 ...... 0.1 5 ...... 1 1.016 1.002 [ 0.91 1.1...... 1.25 1.09 699 0.91 I . 18...... 1.47 1.3; 1.2; 1.li ...... 1::::. 1915. I 21...... 1. %1 1.19 ...... 1.05 11.01 MU. !B ...... 1.419 1.486 1.0% ...... 1.500 1.529 1.019 1915. [ i Feh. 1.48 1.37 27 ...... i 1.393 1.425 4 1.030 S...... +n ! 1.404 "1.417 ~ l.OIJ!! 2ti...... 1.52 1.43 1.31 ...... I:: ...... 07 30 ...... i 1.394 1.391 I 0.Y9Y - ...... 1.45 ..-. 1.x 1.18 ...... I ..... 30 ...... 1 1.W 1.373 ! 0. !r3" I Means I1911- 1915)...... __..1.5~ 1.35 1. w 1. eo 1.19 1.14 *IItrr resooting surfnee of tire Marvin inslrumeat. P. M. IY13. For more detailed information relative to csposiirc of Feh. 1 ...... 1.15 ...... 0.01 ..... instruments and niethocls of ohsei~ntionthe render is 8...... 1.27 1. lti ...... I ...... I...... 1. u5 .._...... referred to t81iisnumber of tho pzge 2. 4 ...... 1.2'1 1.11 1.00 ...... 1: .... REVIEW, 8...... 1.03 ...... 11...... 1.2s 1. I4 1.04 ...... 1 ..... TABLE3.-Solur rodintion intcnsitia ut ,Udt'son. IT%., 191.9 to 1912, 12...... 1.3 1.24 1.16 1.08 ..... i)2clusiw. 3I ...... 1.1s 1.07 0.97 _____.1 .__._ 1914. I [Gramcalories per mtnute per square centimetar of irormal surhee.] FdJ. 7 ...... 1.22 1.14 1.03 ..... 14...... 1.25 ...... 19...... 1.94 1. lti 1.06 ...... Sun's zenith distnnce. 1915. ,. ,I., t'eb. $ ...... 1.3s ..-...... 1 i0.7' 173.6' 1 Xi"i 77.4" I7S.i' 1;Y.S" M.i0 h: ...... 1.50 ...... Date. I 17...... 1.119 ...... __ --- 21;...... 1.45 1.34 1.25 1.17 1.11 ;' _.- ...... 1. a5 1. ?ti ir mass...... -,i ..... I...... leans (1011- 19151...... 1.36 1.20 1.18 1.14 i ...... i l.o j 1.5 1 2.0 2.5 1 3.0 3.5 I 4.0 I 1.3 i 5.0 I 8.6 ! 0.0 I: I--- -I-- . .--I- ...... -1 A.M. .I 1913. I A. 1. Gr.- \ Gr.- Gr.- GI..- , G1.- Mar. 4 ...... 1.31 1.2s 1.14 1913. 1 cal. I ca1. eal. w:. , cd. ti...... __..1.31 1. lti .... Jnu. 8 ...... I ...... I 1.3 ...... ,.,11; ...... 24 ...... I ...... I...... 1.2 ...... I--.... I-...... 1.19 _..- as ...... 1.23 ...... 2'7...... 1.22 1.03 ...... 29 ...... 1 ...... 1 ...... 0.99 ...... I ...... -.----I----'. 29...... __.1.07 .._...... 31...... ___1.17 1.04 0. Y2 ...... 1!114. .... Mar. Y ...... 1.45 1.30 1. 21 1.13 .... 11 .._..-. ..__.1.42 1.2i ...... I...... lli...... 1.39 1.24 ..-...... 17 ...... _.1.07 I 241...... 1.u 1.32 1.19 ...... Jan. 18 ...... I ...... 21.. IY15. 1.43 lhr. 1 ...... 1.40 1.23 0.91 0.87 ...... Y...... 1.Lq 1.36 ...... Means (1011- 11; ...... _..1.47 1.35 ...... lola)...... 1.33 23-...... 1.43 1.35 ...... 2'1;...... 1.50 1.44 ._...... I: 27...... 1.43 1.35 _.._ 29...... Jan. 8...... 311...... _I 1.41 1.32 ._...... 24 ...... 31...... 1.36 1.28 ...... 25 ...... !.._ ...... z:29 ...... 1i:::I:: ...... leans (1911- ' 1 1015)...... 1.43 1.33 1. e6 ...... Jan. 22 ' ...... P. Y. ::I ,,i* 1513. I Msr. 4 ...... 1.32 1.25 1. I4 ..-.I ...... E.:...... li...... I ...... 1.27 1.14 .... I...... 11 ...... l.?.l 1.12 .... Means(l911- 2s ...... 1.07 ...... _.. 1016)...... I 1 I 29 ...... 1.02 ...... A. Y. 1914. 1 1913. Mar. 11 ...... 1.45 1.33 .-...... I.. ... Feb. 1...... 1.27 ...... 14...... -1...... 1.20 ...... i ...... 3 ...... 1.21 ...... 20 ...... 1.36 ...... I.__.-...... 0 ...... 1.23 1.11 7 ...... 1.1 1.16 ...... I 8...... Mar. 1G ...... 1.48 ...... 11 ...... 1.21 ...... 26 ...... 1.51 ..... 1.28 1.18 12 ...... 1.2: .... 1915-30 ...... 1.46 I. 36 .._...... 0.97 ...... I9 _._.____,.__.__.._._.0.u I I 2-4 ...... 1.28 1.19 ...... Means (I911- 2.8 ...... 1.16 Ul6j ...... i ...... /1.30 1.34 1. SI 1.81 ......

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TABLE3.--60t!ar radiutiqn intF'tice at Madison, Tis., 1915 to 1915, TABLE3.-8olat ladiae Ctena'tka a? dlodison, JF48., 1913 lo 1915, anclusw-Continued. ancltcsivt-Contmued.

[Qram*alorfas per minute per square centimeter of normal surface.] [Gramcalories per minute per quare centime& of normal surface.]

Sun's zenith distance. Sun's zenith distance. -- I 0.0' 48.3' 60.0' 66.5' 70.7' 73.6' 55.7' 77.4' 78.7' %.So 80.7' O.Oo I 4S.3O I 60.0° 166.5O 1 70.T 173.6' 1 Xi' 1 i7.4' 1 iS.7" 179.8" I P0.7. Date. I I I I I IIIl I Date. Air mass. -_ - - - ._ ----- 1.0 1.5 I 2.0 2.5 1.0 1.5 2.0 2.5 3.0 ' 3.5 4.0 4.5 ------_ 5.0 I 5.5 I 6-o A. M- Gr.- Ur.- P. Y. Or.- Gr.- Or.- Gr. Gr.- 01.- UT.- Gr., Or.- UT.- Gr.- 1013. eat. ed. 1913. eal. cal. cal. cat. cal. cal. cal. cal. eal. eal. eal. Apr. 1 ...... _._ 1.12 JUM 9 ...... 1.12 ...... 5...... _._ 0.93 10...... 1.14 ...... 13...... I. 26 1.01 13...... I._.. 1.09 ...... 14...... I. 42 1. os n ...... 1.0s 0.99 Q. 91 0.83 ...... 15...... 1.36 0.99 It)...... 1.31 0. S? Yean8 (1911- 18...... 1916)...... 1.11 ..-...... 19...... 1.23 1.03 26...... __. A. Y. as...... 1.41 1. 08 1912. 29. .+. ... 1.36 0.92 July 5 ...... 1.04 ...... I ...... 38...... I. 31 .... 14...... 16...... 1.13 3.7: ...... 1914. 17...... 1.21 ...... I ...... ::::.. ::...... Apr. 8...... _.._ 25...... 1.1G 9.4: ...... I ...... 9...... 1.47 1.41 1.32 .... 26...... 1.17 1.78 ...... 1915. 1913. -4pr. 29 ...... _. 1.31 1.21 1.13 1.04 ...... ! ...... July 2 ...... 1.03 ...... 20...... 1.10 0.97 ._...... Moms (1911- I----- 23...... 1.31 ...... 1016)...... 1.35 1.31 1.19 1.11 1.09 ...... ----_.~.--.-.24...... 1.37 ...... 28.. 1.00 ...... P. Y...... 1913. 1914. Apr. 14...... _. 1.27 1.14 ...... 1.30 1.20 1.10 1.01 ...... 16. 1.02 July -&...... _...... 17...... ,.._. 1.25 1.17 ...... 28...... 1.23 1.09 ...... 20. 1.23 1.15 ...... 1:::::...... 29...... 1.19 ..---.._...... 1.1s 29. - - - -.. 1.39 ..... I...... 1914. 1915. Apr. 11...... _.. 1.44 1.3 -.._ July 3 ...... 1.11 ...... 17...... ,.... 1.19 1.11 1.02 ...... Yemr (lBl1- 21...... 1. -23 1.13 1.04 ...... 1916)...... 1.34 1.27 1.19 22...... 1.18 1.07 1.w ...... A. 16. Hean8 (U10 1913. 1916)...... 1.84 1.14 1.1 ._...... ?&y 6 ...... 1.37 1.22 1.11 ...... I ...... I...... 7...... 1.32 ...... I...... 9...... 1.32 ...... P. 16. 10...... 1.23 1.17 1.03 ...... I...... 1912. 16...... 1.25 ...... !...... July 16...... I._.. 0.99 0.74 ._...... 1914. 1913. May 6 ...... I. 48 1.?8 ..... 0.94 ...... July 24 ...... _...... 1.01) ...... 9...: .... ._-.1.29 1.1s ...... _...... as...... 1.11 ...... _...... 15...... 1.23 ...... I...... m...... a w 0. &a ...... _._..I ...... 18...... I. 1s 1.05 ...... _...... I...... 30...... 0.95 .__...... 23...... 1.23 1.05 ...... 25...... 1. 19 1.m ...... 1914. %...... 1. ?6 1.18 ...... _._...... July 21 ...... 1.08 0.91 ...... 30...... 1.42 1.25 1.19 1.11 ...... I ...... 29...... 1.23 ...... __...... Yeani (1010- 191s. I May 10...... I. 15 1.03 ...... _._...... I...... IOU)...... 1.06 0.89 .._...... 1 ...... xeulr (1911- i A. Y. 1916)...... I. ai 1.19 1.10 0. 99 ...... I ...... 1912. I ---- Aug 2 ...... 0.64 .... 0.1 ...... P. Y. I 19x3. 1913. Yay 9...... 1.14 0.91 ._...... i Aug. 1...... 1.30 1.18 1.09 1.01 ...... 23...... 1.17 1.13 1. in ...... 1914. 2.5. - -.-. . 1.16 ...... lay 6 ...... _..1.29 ...... __ 26...... 1.35 1.19 ...... 1.91 ...... 18...... -__.a 9s 0.84 .... 27 ...... _.1.14 ...... 29...... 1.08 ...... MOE~~(1911- 1916)...... 1.16 0.88 ...... I ...... 1914. Aug. 3 ...... 1.21 D.97 ...... A. Y. 21...... 1.35 1.22 ...... _...... 1913. I June 2 ...... 1.06 ...... I 1915. 4...... I. 21 0.83 ...... Aug. 18 ...... 1.33 ..-...... 8...... 19...... 1.33 ...... 10...... 1.20 ..__...... 11...... I.21 _.__...... Mean# (1910 la...... I. 24 ...... 1016)...... 1. ai 1.20 1.11 1.01 0.89 0.93 0.86 0.71 ...... 13...... I. 20 ...... 27. .... P. Y. 6,i ...... 1913. 1914. A=. 1...... 1.01 ...... June 15...... -. 1.25 1.11 .... 1s...... 0.86 0.75 ...... 25...... 0.w ..-...... 0.45 ...... 1915. 26...... _._.1.24 1.13 .__...... June 17 ...... -- 1.21 1.17 ...... 38. - -.. -...... 1.23 1.08 ..-...... Y.mr (NU- 1911. 1 1.1 11 .lug. 3 1.04 .... I ...... uls)...... 1.24 1.17 1.07 ...... I.....

Unauthenticated | Downloaded 09/28/21 09:00 AM UTC JANUARY,1916. MONTHLY WEATHER REVIEW. 11

TIplr 3.-8olat diution inteities at ,&dison, Tis., 1913 lo 1915, TABLE3.-sotcrr m&twn intensifies at itfadidon, TVk, 1913 to 1915, #tclusiiie-Continuec. inclusiue-Continued. .[thuu-cdoriespex minute per square centimeter of normal surface.) [Gram-caloriespex minute per squsre cmt~meterof nwdsurface.) --- __ Sun's zenith distance. Sun's renlth dlstanca.

0.0' 45.3' 60.0' 68.5' 70.7' 73.6' 78.7' 77.4O 78.7' 19.8' 80.7' Dab. Bate. IllIIIIIII Air Alr mass. - - -- .- ___ _- . -. - _- __-- - 1.0 1.5 2.0 2.5 3.0 I 3.5 4.0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 -- - - .------I-- P. M. Qr.- GI.- Gr.- 01.- Gr.- Gr.- Gr.- P. 31. Gr.- Gr.- Gr.. 07.- Cr.- Or.. QT.' 01.- Or.- Qr.- Or.- 1915.~~ cd. cal. cal. cal. cat. I ccl. ml. 1912. CUI. cal. cal. Cd. cal. Ed. CUI. ed. cal. cd. cal. Aug. 18 ...... 1.1s ...... 0.S j ...... ovt. 1...... 1. CY 0.95 ..... 0. ii ...... _._...... 19...... 1.25 1.12 ...... Q.S 0.i.j 5...... 0. s4 ...... 30...... 1.11 ...... _...... I ...... , ...... 1.04 0.92 0.82 .... 0.6: ...... 13 ...... 1. 0i ..___...... _.. Yema (1810- 14...... 1.0; ..... 0.81 ...... _...... 1U)...... 1.12 0.99 0.86 0.70 1.5...... _...... 1B...... 1. Oi ...... A. Y. 17...... 0.91 ...... I._., 0.51 0.45 ...... Illli?. I IS...... _.. 0. .% ...... __. ..-.- ...... &pt. 21) ...... 1.03 0. s9 0.77 0.69;...... _...... , ...... I!)...... 1 ..... 1. li 1.08 1. n2 ...... -,...... 30...... 0.93 -..- 0.i3 I ...... ,...... Ii ...... !...... z...... -.. 0.91 ._..._.. ..-...... 2c. 1.1: 1.03 0.91 I I ...... I ::::: ...... 1913. I I 30 ...... 1.01 0.94 ...... _...--...... *t. 4 ...... 1.01 ..... 0.84 ...... ! ...... I...... 0...... 1.25 1.18 1.04 ...... I ...... 'I.----- 1813. 12...... 1.25 1.?1 ...... : ...... Oct. 2 ...... _.1.11 ...... _...... 13...... 1.23 ...... 1.00 ...... I ...... I---... 3...... U. ss ...... -...... aa...... 1.23 1.20 1.08 ...... IS...... 1.1; ...... 27...... 1.25 ...... 0.62 .....i ...... I ...... 34...... 1.u ...... dl...... 0.9G ...... _...... 1914. ! Ikpt. 2 ...... _..__1.27 ...... i...... i ...... 1814. 3...... 1.29 ...... _..0.9s _..__...... 1 ...... OCt. 30...... 1. "2 .__..I 1. w .._...... 4...... _____I1.37 1.29 1.1s 1. os ...... I ...... _.._I ...... 8...... 1.03 ...... i ...... I ...... 1915. n ...... 0. s5 ...... j ...... ! ...... Oct. 2s ...... 1. 2i I._...... _.. ._.I ...... 24...... 1.24 ._.. __.._1.m ...... I ...... I ...... Means (1910- 1915. 1911)...... 1. I? 1.09 0. 98 0. 0i 0.8: 0.m 0.64 0.69 .._._. sqlt. 21 ...... 1.29 1.22 1.17 1.13 _____...... I! :...... i: ..... 22.. 1. 27 1.16 1.04 1 I A. P...... 0.98 ...... , ..... l...... 1!112. Ma=# (1910- Nor. 2...... 0.60 .-...... 0.55 ...... lslb)...... 1.85 1.24 1. ca 1.12 0.96 0.91 0.85 0.80 j ...... f;.- ...... 0. RL ...... 0.s ._-.- ...... I i 14...... n. 9s ...... -...... 0.48 ...... P. l4. 15...... 1.?1 1.08 0.95 ...... I 1912. I 18...... 1.u ...... _...... 0.68 0.61 ...... tlept. 26 ...... 0.65 ..... 0.42 ...... ,...... I ...... I...... 19...... ,._...... -...... 0.78 0.70 _.__.__.____ 30...... 1.62 ...... i.._._...... ?1...... 1.Si 1.07 ...... 0.81 0.76 ___.._ 1913. 1!113. No\-. 1 1.1: 1.12 1.05 0.85 sept. 4 ...... __.I 0.9s ..... 0.73 ...... ~ ...... 9...... _._._Iy; 1.10 ...... !...... I.. :::: I...... 1.12 ...... IO...... u. 95 ...... ,-.--.. 11 ...... 1.1; 1.11 .... ._.. 0.95 ...... 12...... _.___I1.27 ..... 1. 0; ...... 13...... __...... 0.77 ...... 21) ...... I 1.22 ..... 1.09 ...... 23 ...... 1.3C 1.19 1.11 .... __.. 0.98 ...... 24...... 1.5 1.22 ...... 1.11 ...... 1914. 1914. 8ept. 4 ...... _._..1.3 ._..I ...... 18...... _.-1.12 ...... _...... _.. Kov. 10...... 1.32 1.26 ...... 21 ...... 1. of ...... xeans~1910- 1911)...... 1.19 1.08 0. 98 0.95 I 0. 0.76 1915. ___._I z Nov. 2 ...... 1.20 ...... 1.00 ...... A. II. I 8...... 1.31 _.._...... -...... 1912. Oct. 1...... 0.98 0.92 0.9s n.ig 0.70 0.63 Means (1910. 4...... ___1.20 1.09 0.95 0..W 0.S? n. 7.1 1915). ._-...... 1.3c 1.20 1.12 1. I1 1. c 0.97 0.80 0.45 ______5...... 1.03 0.94 0. 82 0.69 0.61 0.55 7. -.-. -. . , ..... 1.1s ..... -.._...... i .... P. n. 12...... __.__1 17 ...... I :: ...... 1012. 13...... 0.88 0. XI ...... Nw. 14 ...... 1.05 0.95 .._. .... __...... 14...... 1.10 ...... 15...... 1.10 1.00 0 91 ...... 15...... 1. ne ._._ ...... ,...... 10...... _...... 0.W .... 0.42 ...... 16: ...... 1. n7 .... 0. 65 ...... I...... 21...... 1.07 ...... 1 ...... 17 , 1.15 0.98 0.57 _.._._.. .__._ ...... n.49 j ...... ! ...... w13. 19...... 1.20 1. 00 ...... u. 53 0.51 1 c.4~ 0.44 I . 23...... 1.35 1.3 ...... 11.~1 0.i.i _..___j:::::. Snv. 21 ...... _.. ._...._.-. ._...... 0.3 ...... 28 ...... 1.33 1.17 1.04 0.04 .... 0.82 lo.7i ...... 1914. soo. 10 ...... 1.29 ,..-.. ._...... 1913...... i I 21...... _..1.22 I.._...... _.._...... Oct. 1...... 0.98 0.87 ...... j ...... ::'". I ...... 2...... 1.31 ..... 1.13 ...... _._...... I ...... I ....I ...... 3.. 1.19 (1. Mean8 (1910- ...... I ...... _...... so ....., ...... 1911). 1. e5 1.17 0.93 0.48 13. -.-. -. ., .._..I 1.17 ...... _.1.03 ...... n.x ...... _...... IS...... __..I 1.30 1. 18 1.07 ...... __...... A. M. 23...... 1.15 1. n3 0.B? ...... 19l.2. 24...... 1. 21 1. nA 0.97 0.Si .._. Dec. 9 ...... __..1.113 1.03 ...... 0.72 ...... 31.. - -.- -., ...... 1.22 1.16 ...... 1.00 0.92 21 ...... -.._n. RB 0. 85 0.62 ...... 0.59 0.54 __.__. 22 ...... 0.92 ...... 1914. 2s...... __.1.23 i..ii- 1.03 ...... 0.82 ...... OCt. 27 ...... 1. M ...... 30...... 1.23 .... 1.QO ...... 1913. 31...... 1.18 1. OY .... Dee. 4 ...... _.1.16 1.05 .... ._...... 3.78 0.72 ...... 11 ...... 1.20 ..... 1.07 .... 0.94 1.88 ...... 1915. 17...... 1.12 _.._._...... OCt. 9 ...... -.,-.._ ._._ 18...... __..... 1.16 .-.. ..-. 0.98 ...... 21...... 1.21 .... .-.. 1814. 29...... 1.17 ...... Der. 11 ...... 1.29 1.17 ...... -, 3.94 ...... 16...... -_1.13 ,...... Means 11910- 21 ...... -..., ._..1.14 ...... lUl1)L.. - ...... 141 1.14 1. OI 0.98 l am a 81 0.6Oio.U 0.w ...... a-...... 1.47 i.3' ...... -......

Unauthenticated | Downloaded 09/28/21 09:00 AM UTC 12 MONTHLY WEATHER REVIEW. JANUARY,1916 TABLE2.4olor radiation in&nsiticS at Mndison, Wk,1915 to 1915, apparent path is inclined 49O to the pkne of the prime imlusiue-Concluded. vertical, at the equinoxes it takes 1 hour and 52 minutes [Oramcalories per minute per squtue centimeter of normal surfnce.] for the sun to pass from the horizon to a point 1s' below. At the time of the winter solstice it takes 2 hours and 3 minutes, while at the time of the suinfiicr solstico the sun does not reach 18' below the horizon. In fnct, there is a period of 23 days, €rom June 10 to July 2, inclusive, dur- mg which 011 the clearest nights tl19 twilight niay con- tinue from sunset to sunrise. Soon after sunset on verv clear eveiiing there fre- I 1.0 I 1.5 2.0 I 2.5 3.0 quently appears in the western sky a rosy or purple low, I - in the form of an arc about 30' to 25' in diameter wit!?l the Or.- eal. sun at ita center. It disappears when the sun is about, 6" Dee. 2 ...... I ...... ,...... -- ...... below the horizon, indicating that it, comes from atmos- 14...... 1.37 __-...... !a ...... 1:::::l:::::: ::: ... l.M 1.39 1.32: 1.25 ...... pheric layers not more than 5 or 6 niiles (8 to 10 kilome- I., ters) above the surfacc of the enrth. It is in these layers MO~M(1810- 1.25 1.17 that convective action yrincipdly occurs, and they are P. m. therefore the dusty layers, as well as the layers that con- 1912. tain niost of the atmospheric moisture. Drc. 21...... 0. s3 ...... 22 0.53 is attributed to the diffraction of light byThe the "le ust and 28 ...... 1.01 ...... water particles in these layers. Dunng the day the same roduces the whitish glow t1in.t is seen about,t,he Dea. 1913.11...... -1.. !/I ... -1...... !...... -...... sunprocess in c f ear wextlier...... 1.21 1.16 With the disappearance of this glow tahe intensity of ...... _.. 1.12 .... 1.31 ...... twilight becomes iiisuffic.ient for the continuance of out- door occupations. Hence it is the duration of this por- .I ...... 1.29 j ...... I ...... tion of the twilight,, which Europeans term civil twilzght, ...... 1.40 1.22 11.3 ...... I ...... I...... that is of pra.ctica1interest and especially to those eng ed in pursuits having to do with tr;msporta.tion, or any ot"a er ...... 1 ...... i ...... 1 ...... I -- line of out-door work that recluircs artificial lighting after ni htfall, either for illuminixtlo1i or for signal purposes. 5 '* . j ,/'..< .* - DURATION OB TWILIGHT.' heintensit of twilieht is not entirely dependent upon the position o the sun,howevcr. The state of the sky is By twilight we mean the light experienced after sun- a modifying factor.9 Clouds on t,he western horizon, or a set and before sunrise, and due to the reflection, hazy condition of the atmosphere that niay be due to diffraction, or diffusion of sunlight by the pis niole- either dust or moisture, noticeably diminish the twilight cules, the water particles, and the dust of the ntnios- intensity, and in the case OIvery dense clouds may almost here. The greater thc distance of the sun below the com let.ely obliterate it. It is believed, however, that gorizon the higher and less dense. :we the atmospheric Tab% 1, which gives the duration of v.id twilight or the layers from whlch the light is received at the shaded sur- time re uired for the sun to pass froni the horizon to a face of the earth. Observztio:: h:is shown that uiider the oint 62 below or vice versa, will 1x fouiid useful to most favorable stinos heric coiiclitiolis the last trace of b elither 13uresu officids and others. Hut it must be twilight disappears 11-'F, en the swi is from 16' to lSo undeistood that the duration a.s .given upplies to clear sky below the horizox, iiidicating t.hntsabove it height of 40 conditions only and is too long for cloudy or hay condi- to 50 miles, or 60 to SO kilometers, the air is too rare to tions. Furthermore, high niountnins and buildings, or reflect or diffuse an appreciable amount of sunli5ht. any objects that obstruct the liorizon?ienr whefe the sun The duration of twilight map be computed from the rises or sets, will diminish t.lie durntion of tmhght. It equation : will be noted that at the Equator civil twilight only varies coy Ib = siii a - sin t$ sin6 in duration from 24 minutes at the equinoxes to 26 min- cos t$ cos 6 ' Utes at the solstices, while at latitude AS', near the northern boundary of the United States, it varies in duration where a is the sun's altitude, considered minus below the froni 3G nlinutes at the equinoses t,o 43 minutes.at the horizon, 6 is the solar declination or distance from the winter solstice and 4s minutes at the summer solstice. celestial e uator, t$ is the latitude of the place of observa- At Cleveland the variat8ion is from 32 minutes at the tion, arid 2 is the sun's hour angle from the meridian. equinoses to 37 minutes at the winter sobt,ice and 39 min- From the above equatiori it will be fourid that at the utes at tho summer solstice. equator, at the time of the equinoxes, when tho apparent Table 1 'ves the difference between the time when path of the sun is along tho prime vertical, it takes the the center o!? the sun reaclirs t,he true horizon and the time sun 1 hour and 12 minutes to pass from t.lie horizon to a it reaches :t point 6' below, or vice versa. Without mate- point 18' below it, or vice versa. At the solstices, wheii rial error, we iuay add this interval to the time of sunset the sun ap ears to describe n sinctll circle about the earth's given in the Weather Bureau Suns'liine Tables, or subtract axis 23i0 Prom the prime vertknl, the time is 1 hour and it froiii the time of sunrise, t.0 obtain the time of ending 19 minutes. At lntitnde 49'. or t,he lnthde of the of civil twili lit in the evening. or its beginning in the northern boundary of the LTLiited States. where t,he suzi's monling. detime thus determined will be that at which -__ .. -. - - .-.------the upper limb of the sun is 6' lower than it was at the inied rom ulc pzp "Davli.Tht illunlinatim and the intmsits and durntiou o~~~htI) H. €I.himball.~Ph: Il pwrupd lo the I'ittslnugh Section of Ihe time It appemed to rise or sft on a true horizon, Fuming Illaminat& nghearhg Sociew, (levei'&d, C~IIU. $'el). IS, 1916, and pmtd by the modoty fn its Transactions. iiormal atmospheric refractmion,and mean solar diameter.

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