DECEMBER, 1920. lMONTHLY WEATHER REVIEW. 697
the cloud which the balloon entered was the same as
that observed in the nephos:ope, and whilo it is not certain that the cloud entered was part of the lowest layer of strato-cumulus, the circumstances seem to justif.y tho assumption that the nephoscope observation is applicable to the plaze where the balloon disappeared. In the first place the diro:t.ion of motion of tlie cloud as observed was from 123' and that of the balloon during the last minute of fight was from 120'. Above this lowest (?I
series of strato-cumulus bands were two others; the nest higher (?) one was from 130 to 135' at R s eed of 5.9 to
6.4 m/s for each kiloiiieter of elerat.ion, arid t f ie highest ( '!)
was from 130' a t a speed of 3.7 ni/s for encli kiloineter of
elevation. It was estimated a t the t,ime that the highest layer was a t about 3 kilometers. Assuming that the balloon eliteked the lowest laycr of
strato-cumulus, wliirh were nioving a t tlie rato of '7 mls for every thousand feet of elention, it should have hem moving a t the rate of 12.G m/s a t the 1,800 nieter l e d (the assumed altitude). If it had been moving a t t.hat
rate, however, during the last minute of flight., i t would have been carried out to a point 756 nietors l~ej-oncl where it was a t the elid of the eighth minute, or to n point
7,416 meters from the station. At that point, wit.li tin
elevation anule of 1 4 .3 O as observed, the height of tlie balloon woufd have been l,S90 iiicters, w1iit:h in turn would give us a velocity of 13.2 m/s, as the nonliosr.opc: readings indicated a velocity of 7 ni/s for every 6.1 \i onieter of elevation. Assuming a velocity of 13.3 m/s we carry the npprosi- mation one step farther, and obtain a clista.nce out of
7,458 meters, an altitude of 1,900 meters, and a velocity of 13.3 m/s. Further approsimations do iiot niatoriidlg alter this result. Since the balloon was so inflatocl RS to ren~-.li 1,Sl)O
meters in 9 minutes under 0rcliuar.y conditions. i t :q)poars
to have gained 100 nioters during the last, minute of its flight on account of ascensional an' currentmu.
A CONTRIBUTION TO THE METEOROLOGY OF THE ENGLISH CHANNEL.
By FIUG€ I I). (;RANT.
[Notd from The dmoniutical Josrnzl, January, 1921, pp. 25-38.]
Owing to the notorious capriciousness of the weather of blie bnglish Channel, and to the vast dependence of transcliannel navigation, both marine and aerial, upon thcse mga.ries, tliis study lins been matlo. It is an ttttcmpt to ~nulyze t,he twometric disturbslices which give rise to t,lie channel weather, and the relation of the topogrttplig to the sucltlon changes which occur. Winds, in mid-chii.nne1 and along the eotlst, were studied; the ltitt.cr w-erc irivestigat,ecl by nieaiis of pilot balloons which were filled so as to be in equilibrium in the surface air, ~n d hy this nieans n very good idea of the turbulence and gusts along the steep cliffs hetween Dover and Folkestone
\VAS ob tninerl. Fogs, thunderstorms, gales, and squalls
a.ra nlso consitlered. I t is pointred out that the number of wall-equipped observatories and dense population on both sides of the channel afford unusual advantages to t,he investigator, owing to tlie large number of voluntary observers.-C! L. Ji.
PILOT-BALLOON WORK IN CANADA.
Ry J. PATTERSON.
[ P r r .~ t d Irlorc the American Metcnrnlogiiral Poriety, Chiengo, Der. ZS, 19W]
[hothor's Abstract..)
The Meteorological Senice of Canada in conjunction with the Air Board of Cnnnda has established a series of pilot-balloon stations across the country. Last year st.atii>ns were openotl a t Vancouver, British Columbia, Morley Alta (near Calgary), Cani Borton, Toronto, and Ottawa, Ontario, and ltoherval (Lake St. John), Quebec. It is ths int.ent.ion to open stations this spring a t Peace River C!rossing and Fort Good Hope on the MacKenzie River. Thc! one theotlolito method was used and results plotted in the usual way.
THE MAKING OF UPPER-AIR PRESSURE MAPS FROM OBSERVED WIND VELOCITIES.'
By C . LEROY MEISJIXVQER.
[Weather Burem, W\'aah~ngloii, D. V., Nor. 27, lCJ20.l
SYNOPS1S.
If the equation which expremes the relation hetween the sp~ed of
t.he wind and the distrihution of barometric pressure be solved for the gradient in t.erms of the observed speed. density of the air, radius of
curvature of the MFind th. and latitude. it is possible to work out a
fairly accurate ma of dist,ribut,ion of barometric rewne at. upper levels. This has teen done for the ohsewations marye &oui. 8 q.. m.,
March 97,1920. at most of the aerological stations of the Weiither Hureau and the Signal Corps. The pressures observed by liitea. when used in
connection with the computed gradients. give t.nr clue to the values of the absolute presures at, the level in quedon. Slaps of t.hr 1, 4, and
3 kilometer levels sere tilug con3trurted.
The gradienl wi.nd.--If it is assumed, as is usunlly justi- fiable, that the effect of the friction of the carth's surface
is ne li ible a t about, 500 meters above the sur€~~c'e, i t shod% %e possible to use observed wind velorit.ies 8s a
basis for determining the distrihution of pressure nloft..
The gradient wind equation is frequently used ti) deter- mine the speed of the wind, using us a hasis the soa-level distrihution of pressure, but it is obvious that, by solving the equat.ion for the gradient, in ttlrnis of the speed, t,hc density of the air, the radius of curvat.ure of tho wiritl path, and the latitutle, an nccurata uppcr-ir ninp ought to result i€ based upon sufficient ohserrit t.ii)ns. Pilot-
balloon observations give only mind spcod m c l dirw:t.ion at Tarious heights; and wit.h t,liesc! data slime it, is possi-
ble to tlet.ermine t,lie gradient hut not the absolute pres-
sure. This deficiency nia be supplied by kite ohserva- tions which, when recluceJ give the ahsolute value of the pressure a t rnrious le~-els. Since wind direction is an index to t.he direction of t.he isoha.r and, therefore, the gradiunt,, (the h t t e r ?wing normal to the former) ww are cnahled to determine uite accurately the radius of curvature of the path. %he densit-v may he determined from kite dnta also. Thus we liavo all the necessary values to suhst.itut.e in the ocption. If we t,nlie t,he tBree equnt.ions for the velocitp of the gradient wind, n s given hy Dr. W. J . Hiiniphreysla ntmiely :
~
1 Presented herore the American Meteorologi?r.l Swicty nt Vhira:q Der.. 23, 1951. I Thf I'lipeirr of thf .4 ir, Franliliii Institute, 1920, pp. 139-140.
698 MONTHLY WE.ATHER REVIEW. DECEMBER, 192U
_. .- -. ... -. . .- - ... __ .
Altitudo (km.).
dP p (4) ... z- =--(v* + 2zrl.w sin 4) for cyclones,
- - ...
Const ant
p (kghna). ( !!*p_)
S.164
- .- -. .. -
(5) ... $,=2ivup sin 4 for straight, isobars;
(6) ... - =-(22rlw sin +--v?) for antdcyc.1ones; a p P
dn T
dP in which II is the velocity, is tlie difference in pressure
per unit horizontal distancc normal to t,he isohtm
9 -=~, sec a, where T, is the radius of curvature of the wind path, and a is the angular radius of the circle upon
which the air is moving measured from the ceiider of the eaIth; p is the density of the air; w the an le through which t.he earth turns in a second; and 4 is t 5 e lntitiicle
1 .............................................................. 1.101
3 ............................................................... 0.896
9 .............................................................. 0.w
of the place. Since the differcnce between T and T, is usually small, and, in this case, the value is only an approsiniation, it is possible to regard them as equal. I t is noticed further
161 x 10 6
145s 10-6 131 x 10*
cl p that the three equations which have been solved for tii
contain the term 2wp. For a given level, t,his may he
considered as a const.ant, since we may assunir? t,lw value of t,lie density constnnt for a givcii level. Thc
value of the density used was that given by Dr. H. H. Kimball tis The angular velocitg of the
2r
58,164 earth's rotation is, of course, -- These fnc.t.013
when multi lied to ether give a constant for the level in question. gor it k e following values of this const.ant 11 w e been conipu ted :
77re complta.twns.-Owing to t,he difftculty in obtaining an accurate estimate of the radius of curvature of the wind path, and the fact that, in eneral, such radii are
isobar equation be employed in this connection. his would have the advantage ol inalring tlie computat,ion somewhat sim ler. It is doubtful, however, whether this
pressure gradient,. Reference to figure 40, page 143, in the "Physics of the Air" shows what the error would amount 'to in meters per second when the velocity is determined bv equations (11, O!, or (3). The diagram
is comput.ed tor latitude 40' and a pressure gradient of
1 millimeter of mercury per 100 kilometers. I t is seen
that when the radius of curvature is very large, greater than 1,200 kilometers, the agreement between equn-
very large, it has been suggested t % at only the strai ht-
equation sliou P d be used universally in determining tlie
8 Kimball Herbert H.: On rclations of atmospheric pressure, temprraturo, and density to ahltude. MONTRLY WEATnER REVIEW, March, 1919, 47:lW-158.
tions (1) and (2) and between (8) and (2, is within 2
meters per second. With radii less than 1,200 meters, however, tlie discrepancy becomes rapidly larger, espe- cially in the case of the anticyclone where, under these conditions, the radius of the critical isobar is about
600 kilometers; at this radius the difference between equations (3) and (2 ) amounts to slightlv over 7 meters per second. Between equations (1) and (2) the differ- ence at 600-kilometer radius is about 2 meters per second, and at 100-kilometer radius the difference amounts to about 8 meters er second. These discrepancies seem
and anticyclone equat>ions where. the radii are she$ The quest.ion of which equation to use in solving for t,he gradient was answered by inspection of the -
from the wind directions as observed. I t is possiblo with these data to procede to the solution. The follow- ing table gives the observed data as to wind direction mid speed at, the 1, 2, and 3 kilometer levels from pilot balloons and kites:
to be suffic.iently P arge to demand the use of the cyclone
liminarv charts of wind stream lines which were sketc re ed
TABLE l.-Obsrrrwl rrii,itd clirci.1ion.s. und spveda.
~
. - .
3 kihmetrrs. I kilmw!w. 2 kilxueters.
...... Stali,xi.
...
Denver. Cvlo.. ............................. Fort Sill. Okls ......... ASW.
Ellendnle.. NE. Drcsel .................. H R W . BrukienArrow BBW. Kcllv Pirld.. ........... S9W. 19
Madip m... ............. R. 1" wsw. 8
22
18 L~nsiiit. Royal wlrr I WNw. 16 WNW. NN I\'.
.......... 12 WkW. 11
............ 4 wsw. 14 Camg Ky.. WSW. Lees iirlr.. NW. Mitchel r icltl.. ......... Ahcrdren.. .............
............. la .......... ........... ......
............... 20 NW. ...........
.................... ~n s ~i i i i p t m i .. ..........I ...... ............ (h i p \ail .............. Fort Monroc W N W . ............ ............ ........
... -~
In Trihle 2 arz aiven the data froni which it. is lossihle t.0 draw t,he isogaric maps of the upper levels. For each level the data include the value of the gradient in millibars per 100 km. horizontal distance, the distancc between isobars in kilometers for pressure intervals of
2.5 millibars, the actual pressure observed with kites in millibars, ancl the estimated pressure at several of the kite stations, where the kites did not quite attain the desired altitude. This extrapolation was effected by use of the hy sometric formula, using the greatest
desired altit,ude as the upper level, and using as the moan temprature of the air column thab value of tem- perature which would have been attained at the middle of the intervcning air column had tho vertical gradient continued at the rate observed at t,he highest point in the fliuht. This gives a value of t.he pressure at the upper yevel which is probably very nearly correct. This operation was performed in the case of Ellendale and Broken h r o w for the 2-kilometer level, and for Ellen- dale, Drexcl, and Broken A4rrow for tlie %kilometer level.
altitude attaine s by the kite as t,lie lower level and the
DECEMBER, 1920. 1MONTHLY WEATHER REVIEW. 699
-
Btation.
1 Mometer. 2 kilometers. 3 kilometers.
dp Distance observed Estl- Distance 0-d 2::L Distance oben7ed Esti-
dn
I
between
1
pressure
1
mated 2 between
I
p ~s s u ~
I 2 I
between
1
pressure
1
mated (mb/100 isobars (mb.). pressure (mb/100 isobars (mb.). Pressure (mb/lM) isobars (mb.). TbUr.e b.). (km.). (mb.). Inn.). (km.). (mb.). Inn.). (km.).
................................................... I I-' Denver.. Fort Sill .................................................... EIlendde .................................................. Drexel.. .................................................... Broken Arrow.. ........................................... Kelly Flrld ................................................ M a d m .. .................................................. Lonsint.. ................................................. Royal 'enter ............................................... Cam&Ky.. .............................................. Lec*1 rg.. ................................................ Mitchel t wid. ............................................. Aberdeen. ................................................. Washington.. .............................................. Camp \ail.. ............................................... Fort Monroe.. ............................................. Camp Bragg.. .............................................
.......... 2 5 0. 8 2.8 2.0 0.5
1.3
0.8
1.6 2.2 2.5 2.1 1.1 0. 8
au
as
a 3
102 352 92 121 431 273 1m 2i3 352
159 113 102 121 240
352
a:!
............................ 0.) 641 .......................................................... ................................................................................................ .......... wl.O 0.5 481 ' 77s.2 1.1 240 6 6 6
s s .0 .......... 2.5 1112 7 s .5 ...................................... 6W.i
893.4 ...................................... 793.6 ............................ 702.5
.................... 1.9 213 .................... 1.2 213 .................... .................... 1.3 192 .................... 0.7 38s .................... .................... 2.4 105 .................... 1.3 192 .................... 898.8 .......... 1.2 213 796.2 .......... 1.2 213 703.0 ..........
.......... ..........
.......... i .......... 0.8 3% .................... 0.9 273 .................... ..........; .......... a 3 wi? .................... 0.9 273 ....................
.......... ' .......... 1.8 I36 I .......................................................... ......... _I_. ..................................................................................... ......... .:. ..................................................................................... .......... 1 .......... 1.6 1% ' .................... 2 0 121 .................... ..........I... ....... I 0.8 3521 ..........................................................
..................................................................................................
AUXILIARY CHARTS.
I n order to facilitate the drawing of the maps, ausiliar? charts (figs. 1 ,2 , and 3). were drawn. These figures show the distance between isobars in eastern United States where the interval of pressure is 2.5 mb. The lines of
e ual distance between isobars are drawn for every 100
dometers from the data contained in Table 2. By means of these figures, one can tell a t any point in the
lower layers with a lower pressure a t upper levels. The effect of the HIGH in the southeastern part of the United States, while still strong a t the %kilometer level has dis- appeared a t the 3-kilometer level. This is shown also
b the slight winds a t Leesbur up to 2 kilometers which
In one or two cases i t will be seen that the station arrow does not exactly coincide with the .direction of the isobar nearest the place. This may be due to one of
c T iange to strong from the WS 6 . a t the 3-kilometer level.
3km: v
Ftoa. I, a, and 3.-AuxiUary mapsshowingdistance betweenisobarsineastern United States at the 1,2, and 3 kilometer levels, Mar. 27, leaO,8 a. m., 75th merldian time.
re 'on in question what the distance is between the
UPPER-AIR PRESSURE MAPS.
is0 % ars.
Figure 4 shows the distribution of pressure and tem- perature on the mornin of March 27? 1920. The isobars are for sea-level in milfibav, and the isotherms are for the surface in degrees, centigrade. Figures 5, 6, and 7
show the distribution of pressure a t the 1, 2, and 3 kilo- meter levels, respectively.
' The 3-kilometer ma shows the tendency for tlie low center to ahift westwar8, which is what would be expwted, since the inflow of cold dense air in the rear of the cyclone would tend to concentrate a great weight of air in the
two reasons: either the winds were so entle that tho indicated direction was of little signgcance, or the legitimate smoothing of the isobar necessitated makin
tions are iven onlv in 16 compass points and for this reason suca slight d i s c r e y i e s can not be avoided. It will be seen that at t e 3-kilometer level the radient
figure 7. This is believed to be 'ustified by the fact that
Ellendale for that elevation, hence it is fair to su pose
it pass the station a t an angle sli htly a t variance wit E the (LITOW. It should be remem B ered that the direc-
as drawn in figure 3 is somewhat less than that s 5 own in
the estimated ressure a t Ellen dl ale is more reliable than the value of t R e gradient. There is no wind record at.
that figure 3 is less trustworthy than the extrapo P ated
700 :MOKTHLE’ WEATHER REVIEW. DECEMBER, 10%)
FIG. 4.-Weatber map far Mor. 2 i , laa0, S 8. m., 75th meridian t h e . (Pressures in millibars and temperature in degree8 centigrade.)
FIG. 5.-Pressure at the I-kilometer level, in millibars, Mar. 97, 1999, 8 a. m., 75th
meridlan time.
I
FIG. ii.-Premre ot the %kilometer level, in millibara. Mar. 27, l9!X4 8 a. m.. 75th meridian time.
DECEMBER, 1920. MOKTHLT WEATHER REVIEW. 701
ressure, and for that reason, the pressure slope has
L e n represented somewhat steeper than the gradient uld indicate.
CONCLUSION.
This short study is an esam le of tahe application of the theory of the gradient win$. In spite of the ninny
observational errors that may Cree into ilot-balloon
method, there is a striking congruity in the figurcs obtained. I t is true that a t present4he making of such map3 by this method is impracticable, not only because of the considerable computation involved, but nlso be,cause of the nuniher of aerolo4xl stations is too sninll to furnish as much data as wouh be recuired. Never- theless, the difticulties of the proposition he more largely with external circunistances than with t.he scientific reasoning. We must improve our methods of forecast- ing for aviation. and to do it we niust have first-hand knowled e of what is going on aloft--not in n desultory and fitfu 7 nianner, but in a solid, consistent net-work of aerological stations. Those the Weather Bureau is operating a t present are doing rsc.ellcnt work, and the assistance of the Signal Corps is extremely uscful, but still this is only a beginning and espansion in the neroiopi-
cal work is one of the mentest needs of the Weabhor
data, especially when obtained by t P P le sing e theoclolite
Bureau. Such a methocluof drawing chnrts of the upptxr air may prove to be useful in prepitring wind cliarts for
aviators.
m ~~;i ~g ~s i i r c at the 3-kilometcr level, in rniilibars, Mar. 21, 1920, Sa. m., 75th
THE WEATHER FACTOR IN AERONAUTICS.’
By c‘. LEROY ~I E I S I V G E ~.
[Weather Bureau, WashingLon, D. C., Jan. 20, 1921.1
LL8colt and C’ooke speiid nitieh time at the chart table. inensuring ccnqles o j dr$ a d ctr2odati~ig lhe COUTSC. Aei-ial ?tatligation is more conipli- enled than iravigation on the .w:facc? ?f tht sea. hiit t h m i s ?io rensoii why, ruhrt, uic h o u ~ more tibout the a i r and its ~~c c i ~l i c w i t i ~s , it shorild ?rot be
made just as accurate.”-Brig. Go&. Maitlamf, in the log of the R. -3.1.
SYNOPSI9.
Des ite the significant advances of commercial apronailtics since thc war, &ere remains a singular incliflerence of the pulJic t n the enter- prise. It is believed that a recngnition of the importailre of the westlicr factor will assist i n overcoming this inrlifference through the incrr;lse
of szfety and efficiency. Since lighter-than-air and heavier-than-air craft each have an important place in the scheme of atvial transport. their respective function8 niud be understood; the former is the prob- able carrier for long, non-stop flights, and the latter for the short fast flights. The effect of winds on aircraft may be summed up in an equation, which expresses the speed along the course:
I’= Fa cos e, - J; cos e
wherein V, is the still-air speed of the rrzft. JTw the wind speed, el tile
angle the craft must turn relative to its course to overcome the effect of drift and e the augb between the wind direction and the course. The experience of great Europesn coinmercirl aerial transpvrt entrr- prises hm indicated that the development of this form of transportation will naturally evolve a iield for the apronauticd meteorolGgist. whose work will consist esqentially in reducing for the benefit of his organiza- tion the detailed information for the individual pilots, a function too complex for any governmental agency to handle. A specific example of the effect of winds on flight is given which in- dicates the linea along which meteorological information may be or- g m i z d . In this connection, one reseerch problem of profound importance is that of thr reductiou of bamnietric pressure to levels in the free air. The success of this problem is largely dependent upon the amount OC
upperair obser vat ions collected.
INTRODUCTION.
Civil aviation in the Un&d Stcctrs.-The trend of opinion among thoso who are most conversant with the results of the first >‘ears’ efforts in commercial aero-
1 Prkented in art brfore the American Xeteorological Snriety at Chicago, Ill., Dec. 28,1820; and (he Ikildsophical Society of Washington, Feb. 12, 192;.
nwt.ics socnls t.o be t.lirtt, to tho present, these efforts must be rcgnrdecl as demonstmt,ions rather than as suc- cessful busincss cntcrprises. Sonic in Anierica, make it appcnr t,hnt \vo must. look to the other side of the Atlantic for our objcc t. lessons in comniercial acronnu tics, thereby iwglcct.iiig the oscellcub large-scde activities of aur own mail scrvicc and niimerous succcssful smaller enter-
f ~k c s . We nro likc.l>-. to forget that the route between
ani and Hnbana, wliilc perhaps not so difficult to fly, is nbtsut thc snnie lriigth ss t,he much heralded London- Pwis rout,c: and that everi- day the mail planes are suc- wssfully fl;:iiig owr laps of such lengths tlint the famed Europcan routes seem to diminish in im Iortance as es-
Eiiropcitn nntions with a considerable de pee of intorost
niitl our Aerial &hi1 rogarclecl by Maj. 8 en. Sir F. H. S;:kcs, comptroller general of civil aviation, 8s a “par- ticiilar\i. int,areatin csperimcnt.”a There are those who
leash nunicrous enterprises which stand red;\- to put into operation n large prograni of a e r d bransportation. The 1egri.l probleni involved is of considerihble magnitude and profound impnrtmi~c.~
Ycb with all blie interest and encouraging rospects of t.hc efforts, tlicre n years to be a sin 1ar in (P ifference on t,hn part. of tho pu \ >lit to commercia T I aeronautics. And
t,]lis ma:- bc att,ributod in n large measure to the lack of
>ublicit>- giwn the venture.’ In anir ewnt, the fact must Le rccogiiizecl that the confidence of the public, one of the
nniplc!s. Wc find tlint our nctivities are 1 ooked upon by
point out t,liat, n f ack of ndeaunte lnws is holding in
__
I Civil aviation abroad.
3 Paris, Maj. W. Jefferson: Laim of the J r . V. S. Air Sfrsies. December 1920, pp. 24-28.
U. 8. .hr Scrrire, Dwember, 1920, pp.
.-
0.1 I , .-;,.a.
4 Aerial mail as a promoter of ctnumerciolaeronautics. Editorial note. Aerial Ags TI’csk?#, Nov. 29,lWO, p. 311.