216 MONTHLY WEATHER REVIEW APRIL, 1925
eastward of an area of high pressure and lower tempera- ture over the Rocky Mountain States on the 24th-26th, which, occurring simultaneously with the develo inient of
the Ontario EIQH, had the effect of segre ating t !l e nort,h-
observed on the 26th.
ern portion of the low-presmre into t i e P configuration
FIQ. 2.-Prwaum distributlon, 8 a. m., 75th meridian time. April 24, 192.4
FrQ. 3.-Pressure distributlon, Sa. m., 75th meridian time, April 25. 1924
An observation of SSE. wind aloft at 4,000 meters over Drexel on the 25th and at 4,500 meters over EIleii- dale on the 27th leacis to the inference that a norinnl west-to-east movement of the detached LOW was pre- vented by the persistency of the Ontario HIGH, of which
the SSE. winds aloft were a
nation of the isobars on the 24th to p. m. of retardation of the northern limb of the low-pressure
trough in the re ion of the Dakotas and Minnesota dur- ing this period t % at amounted actually to a slight retro- gression on the 2Gth. FurtheT confirmation of this is given b the surface-wind record at Ellendale, where the wind c &y ed from southerly to northerly on the 24th, and veere back to southeasterly on the 26th. I't is
noteworthy that precipitation did not occur at Ellendale uiitil t,he wind veered from northwest to directions rang- ing from north through east to southeast, and that at Jlresel precipitation was delayed nearly 20 hours after the wind had changed from south to northwest., and about 8 hours after it had begun at Ellendale. The significance of this is that the recipitation that occurred in the rear of the trough on t !it e 25th and 26th can not all be attributed to the under-running effect of the cold liigh-pressure area from the northwest. Over southern sections only was it plausibly due to this cause. Over mast of the Dakot,as and Nebraska it. seems more rea- sonable, from the foregoing facts, that precipitation was due to processes connected with t.he transport of air from around in front of the LOW.^ The distinction between the two types of preci itation is often evident by a gap
on the a. m. weather map of the 25th. In connection with the precipitation that occurred east of the low-pressure area, it IS interesting t.0 note the changes in temperature t.hat occurred with chmging confi ration of isobars and, consequently, source8 of
was 14.1' C. at 2,000 meters in a SSW. wind; and at Ellendale 15.2' C. at 2,000 meters in a southeast wind, and 6.8' C. at 3,000 meters in a south wind. At Royal Center the temperature was 7.2' C. at 2,000 meters in an east wind on the 26th; and on the 27th, 6.2" C. at 3,000 meteix in a SSE. wind, and 1.0' C. at 3,000 meters in R southwest wind. The lower temperatures at Royal Center than at corres onding levels at, stations to the
edl due t.0 t-he difference in the source of air. On tho 24tg tshe air aloft over Drexel and Ellendale was supplied by t,he drainage estending far to t,he south and south- west, hi pat.hs approximati the course taken hv the balloons. At Royal Centerxe winds in t,he lower levels on t,he 26th and 27tah had their origin in the HIGH to the east,, while t,he southwest wind observed at 3,000 meters on t,he 27t.h m n hc t,race,d hack in a curved path
to the cnld HIGH that appeared in t.he northwest on the 24th. Ra.iii began nt Royal Cent,er on the 37th n,s soon
RS t.he wind iiem t,lie groimd chmged from eastply to a
more sout~herly component, indicating the buildin up of
rents near t,lie ground end the cold southwest wind aloft."
in the shaded area in t !i e rear of the LOW, as is apparent
suppy F of a.ir. On t,he 24tli at Drexel the temperature
west and northwest a P ew days previously were undoubtr
a.n a.dia.batic gradient between the wa.rm souther F y cur-
.L - . ._I
59/. 5 5
N E W STANDARDS OF ANEMOMETRY
8. P. FEItCiFSSON and R. N. COVERT
With the approval of the Chief of the Weather Bureau, the authors, in 1931, began B redetermination of the rate
of the standard anemometer estending to lugher velocities than any attained in earlier tests of the instrument. This work was made possible by the enerous coo eration of the aerodpamicd laborator of t % e Bureau o P Standards in providmg and operating ts i!L e two wind tunnels in which
~ ~
6 Mo. WEATEER REV Januery 1924 52: 21 (pa.. (e)).
6 Mo. WEATHER REV:: Januar){ 1924; 52: 20 (ad par., 2d. column).
b, 1M4. MONTHLY WEATHER REVIEW 217
Diameter of cups. ____________ Length of arms _______________ Original factor ................ Factor for average veloeitim- Value of 1 rotation: Factor 3 .................. Factor 2.65 ............... Factor 2.50
the instruments were tested. During the stud of the standard anemometer, Dr. J. Patterson, of the 8 anadian Meteorological Office, published an investigation showing that a Robinson anemometer having three cups is better than one with four or more; trials of two instruments of this type confirming Patterson's conc.luaions, our investi- gation was extended to include the develo ment of a new standard, the design or plan of whic f should be based upon the most recent studies and accumulated experience. Between April, 1922, and June, 1923, 38
anemometers of different kinds, proportions, and dimen- sions were tested in the tunnels and on a whirlin machine and compared in the natural wind; many of t f ese were modified temporarily to ascertain differences of rate, in stead and variable winds or due to variable friction, etc. In a{ including a large number recently studied b Patterson and by Brazier, of France, there are now ava2 able measurements and rates of about 100 anemometers, including probably all patterns likely to be needed. From these there has been selected a new standard whose pro ortions and dimensions were decided upon after
during which was considered the desirability of a uniform international standard. The same type of anemometer with the same ratin has been approved for use in Canada. In advance of pu lication of the com lete investigation, which will occur at an early date, an in order that the new standards of measurement may come into use as
soon as possible, the authors present herein a table of correct values for velocities indicated by the old standard throughout the range of the natural wind, and com ari-
new instruments.
TABLE 1.-Correct or true velocities corresponding to velocities indi- eated by the standard four-cup Robinson anemometer of the Weather
con r erences with Doctor Patterson and others interested,
B l!
sons of old and new values of the rate and of the 01 a and
4 inches (102 mm.) __________ 5 inchw (127 mm.). 6.72 inches (170.3 mm.) ______ 6.29 inches (159.7 mm.). 3 ............................ 2.60. 2.65 ......................... 2.M).
10.56 feet (3.B meters) ....... 9.84 feet (3 meters). 8.92 feet (2.72 meters) ........ ............................................. 8.20 feet (2.60 meted.
machines, but a comparison with the table of true veloc- ities published in 1890' shows that the differences between the two are small.
TABLE 2.--Cnmpamfiz~e dimensions and proportions of old and new anemometers
45.6 5 2 9 60.1 67.6 75.0 82.3 $9.7 97. 1 104.7 112: 119.I 127.1 134.5 141.8 149.2
~-
I Old standard (1&30(?)-1924) I New standard (19.24)
46.3
5 3 .i
60.9
68.3 75.7
83.1 90.5
97.9
1oj.4
113.0 1200.5 1P7.R 135.2 142.5 149.9
...............
87.5 95.0
102.6
117.4 124.8
110.1
8 8 3 95.8 103.3
118.2 125.5
1io.n
5a5.
642.
333.
400.
The mechanisms of the old and new instruments are so nearly alike that the former can be altered to indicate true velocities by equipping it with the cups, spindle, and one gear of the new pattern, at a smaller cost than that of an entirely new anemometer. The dimensions and proportions of the new pattern are such that registra- tion in an scale desired-kilometers, meters, miles, feet, or sixtietL of miles-an be accomplished by simple changes in the wheel work.
TABLE 3.-Trzie or correct tielocities corresponding to velocities indi- cated bg new standard
In meters a second In d e s an hour
Bu.rea; [In miles an hour] -
1
-
10.2 18.1 25. 7 33. 1 40. 5 4i. 8 55.1 A2 4 69.8 i7. 2 EL 5 9 2 0 99.5 107.0 114.5 122.0 129. a 136.6 144.0
, - . - - -.
.-
-
3
-
7
Average in Amerioe
Qale.
Av- In America.
Ode.
Hurricane.
I I
I :
4 1 5 1 6 Indi- cated velocltj
0 2
-
4. 2 12.8
28.0 35.2 42. 7 50.0 57.2
64.5
72. 1
79.4 86.7 91.2 101.8 109.3 118.6 124.1 131.5 138. 9 1.46. 2
m. 5
-
liurrlarne.
.___-_ 9.3 17.3 24.9
39.7 47.0 54.4 R1.7 R9. 1 76.5 83.8 91.3 98.7 106.2 133.8 121.3
135.9 143.3 150.7
a 4 3
im. 5
-
2.2 11.2 18. 9 2c. 4 33.8 41.3 48. fi
55.8 63.1 70.5 78.0 85.2 92.7 loo. 2 107. 8
115.2 1 Z 7 129.9 13;. 3 144.7 . ._ - - -
-
3.2 I?. 0 19.7 2i. 2 34.5 42.0 49.2 59.5 63.8
71.3
85.9 93. 5 101.0
115.9 123.4 130.7 136.1 145.5
78 7
108. n
-
. 6.9
22 I
30.2 37.5 44.9 52.2 59.4
66.9 74.3 81.6 89.0 Q6.4 101.0 111.5 119.0 126.3 133.8 141.1 148.4
15. ,o
0
1 10
30 '40 50
60
80 J90
100
4 110 120 130 140 150 160
170
b 180 190 200
a0
m
Hlghwt recorded.
Hlghest recorded.
TABLE 4.-Trrte tielocities corresponding to velocities indicated by old and ?iew standards when the instruments are adjusted to record correctly at average velocities
IN ENQLIGH UNITS
I MUes an hour
Indicatedvdocity ____________________ Oldstandard. factor2.65 _____________ Kewstandard.factor2.50 ____________
I Average velocity in the United States. : Average standard of gale.
a Average standard of hurricane.
Highest standard velocity by whirling machine la 1890.
Highest velnrlty hy whirling mschlne in 1913. 67 35 miles an hour. IN INTERNATIONAL UNITS
~
Meters a tmmd
I I I I I I I I I I I
mUes an hour.
ington January. 19713. second; or 137 mlles an hour.
4 Highest velocity usually recorded at exposed stations.
5 Highest wind at the earth's srwface. 186 miles an hour (Indlcated) on Mount Wash- Highest standard velocity in wind tunnel, 1922, 61 meters a Indicated velocity ____________
~
_______ Old standard. lactor 2.65 _____________ Newstandard.factor2.50 ____________ Tenths of miles or meters in this and the tables following are used only to obtain smooth values and are of no importance in correcting velocities for the reason that two similar instruments exposed near each other will sometimes disagree 5 to 10 per cent or more. These new values indicate that the rate of the old standard determined in wind tunnels is nearer constant than the rate ascertained previously by means of whirling
I I I I J I I I I I I
The preceding comparisons show that differences between the old and new standards areaunimportant or incons icuous .at low or average velocities, but increase
miles an hour or higher indicated by the old standard are at hig I? velocities. When the factor 3 is used, galea of 25
7 Circular D, smnd edition, p. 16.
218 MONTHLS WEATHER REVIEW APRIL, 19224
about 22 per cent too high, and when the instrument is adjusted to record correctly at the most frequent or
average velocities, by changing the factor to 2.65, it,s rate is still 6 er cent too hi h at 25 miles an hour and 9
per cent too %igh a t 100 m' I f es an hour. Velocit.ies indi- cated by the new standard are about 2 cent too high at 25 miles an hour and 5 per cent too h at 100 miles
is properly adjusted and indicates a velocity of 50, the true velocity is 46; when the new standard indicates 50
miles an hour, the true velocity is 48, e.tc. It is expected that the new standard will be adopted as
soon as instruments now in use can be inodiiied and replaced. A description, including plans of the new anemometer, is in preparation for use by anyone interest,ed in the operation or manufacture of these inst,ruments.
WHY HARDWOODS DO NOT GROW NATURALLY I N THE WEST
By J. A. LABHEN, Forest. Esuiiiiiirr
[Excerpts from Thr Idaho d'orfslrr, anniml. 1922, 4: 2&34
an hour; as indicated in the Table4, when t fl e old standard
Unfortunate1 the beaut.ifu1 lit~rclwootl trees wliich are
the West. We have here only t1.6 en, cottonwood, sni:ill
coast are oak and maple, but, limited laigely to lower moist sites such as st,renms bed and canyons. 'l'lie geii- era1 absence of broad leaf trees in the West is most. likely due to the difference in prwi itatioii iiiicl temperature between the East and West. 'fo be sure, there we other factors which limit the distribution of t,rees, such as soil
acidity, alkalinity, soil and atmospheric. moisture, as well as inherent qualities in t,he lltnts themselves. Soil acicl-
native to the j5 astern States do not grvw nat,urally in
birch, hawthorns, cherry, and ti P der. 0 1 1 the I'ucitic-
soil moisture or qua s it of the soil can at hest be
only within a {imited area, and since it except for areas near the sea, t.list tit,- mospheric moisture varies according to tlie precipit,,zt.ion, it is only a result and, as such, not a controlling fact.or. Internal structure of leaves and stems, tlhilit,y to t,ransport much water, injuries by frost,, etc., must he looked u on
as direct results of the plant.'s environment rather t 1 RJI
factors which control their distribution. There remains, therefore, the factors of temperature and precipitnbion and the variation and estremes of these worthy of con-
siderat.ion . Air temperature, thou h it may not in a11 ctises he L
either by too short, too cold summer weather sild fr0st.s during the growing season, or by too great. est,remes. Esperiments have shown that t.he leaves of trees do not become reen in tem erabures above 104' F. a~id do not
cause root killing, bark and wood split.t,ing, and killing
of buds and stems of hardwood. If the rowing season is t,oo short, the spevies ivliidi
in the spring, or have no time t.o f o r i suflicimt. wood i t 1
the new st,ems to withstand frost injuries in t,he fall. If the ni hts are too cold throughout. the summer mont,hs,
freezing, has not had time to form before tlie cold weather sets in. The plant food is therefore chiefly in t,he form of starch, which is damaged by frost,. From the standpoint of water requirement of trees, i t is well to note that the structure of the leaves, stenis, and wood of trees may render some entirelv unsuit.able
for certain climates, es ecially in r 'ons cliaract.erized by dry summer air an: low r a i n f a r Deciduous trees
cont.rolling factor, oft.en 5 h i t s the distribution of t,rees
function % elow 40' 3 Unusually low- temperat.ures nin.?
are intro B uced from a warmer climat,e burl out. t o t -1 c ~r l y
one o B the plant foods, sugar, which is not injured by
nre able to trans ort, much more water than conifers. Dr. Franz R. von gohnel, of the Austrian Forest Experi- ment Station, determined by careful tests over a period
of 12 years that 1 acre of oak forest lost by transpiration from 2,227 to 2,672 gallons of water per day durin periods of growth. This is equal to 2.9 to 3.9 inches o
rainfall per month for the growing season-much more t,lian occurs over the western sections of the United States. Other broad-leaved trees are much like oak in respect, to evaporation of water. An examination of the distribution of hardwoods in the Eastern States shows t,hat their general northern limit follows tt line t.hrough St,. Paul, Minn., to Eau Claire and Shebo.ygan, Wis. * Grand Rapids, Lansing, and Detroit, Mich. North oi this line the forest is re- dominantly coniferous. From Detroit to central Bew York an inversion occurs in that the hardwoods are on t>he north and the conifers to t,he south. This is evi- dent,l due to low land and relatively warm air surround-
south. From central New York the line goes northeast t.hrough west,ern Massachusetts, through Concord, N. H., and August.a, Me., wit.li conifers on t.he n0rt.h and hard- woods to the south. The westward extension of the harclwootls is defined h the Mississi pi River from St.
Iowa, Kansas, and Oklahoma, irregularly, according to local variations in t.opo raphy. In conclusion it, may 5 e said that precipitation and at- mosplieric nioist.ure over the western United States are insufficient. for the east,ern hardwoods. Air temperature is suitrable in most t.owns and cities and over ext,ensive farming sections. This makes it, possible by irrigation or by plant.ing in certain very favorable sites such as
moist slopes and aspects sheltered from the driving summer winds, to raise eastern hardwoods in the Pacific Northwest. Escept for southern Idaho and the Pacific. coast cities, however, the frequent frost which occurs over most of t,he region during late sprin and earl fall
young trees and ret.ards growth on the mature trees. [Charts showing the mean air temperature and rain- fall for different eastern and western cities accompany the article showing t.he distinction spoken of in the test.]
TEMPERATURE SUMMATIONS WITH REFERENCE TO PLANT LIFE
5
ing t { e Lakes and the higher land with colder air to the
Paul to Rock Island, I l l , t.hence sout R westward through
are ti serious drawback, whkh stiints an d kills hac K trhe
c51. sa4 : 63 Z
By G . A. PE.4RION, Director
[Fort Vnllcy Forest Experimt'nt Station]
Plant invest.igat.ors are seeking an index which is espressire of the heat conditions re plants. The mean temperature enerally nieteorolo ists and too often by f iologists when app k led in the vegetable world. Plants are far less concerned with the relatively low night temperatures than wit.h tdie more effective temperatures prevailing during the hours of daylight. For this reason a mean which gives equal wieght to night and da temperatures is a poor inemure of the heat available ? or maintaining the physiological processes involved in plant life. The inadequacy of mean tem erature is very evident in the mountain forests of the ii outhwest, where an extremely high daily range is the rule and where the native ve e-
tnt.ion experiences little discomfort from low nig ph t temperatures even to the point of frost, but is exceedingly dependent upon heat energy for carrying on photo- synthesis.