OmoBlq 1924 MONTHLY WEATHER REVIEW 493
Percantage of trees- --__________I-_
Trees struck _______________________ Relative frequency. _______________
Results of 15 years of observations published in the Revue des Faux et Forets:
Oak Beech I Epruce Pine Others
----___-_
1.8 lf81 41.6 30.8 15.1 61 155 131 __________ 1 6 7 - - -- - - -- - - I
52
Penrentage of trees ________________ Trese &truck _________ ______________ Relative frequency ________________
Observations in the Bavarian State forests, 1887-1890:
on the ounger trees, but less so on the older treee, which cban e
but d e from year to year and are robabl the most valuabqe and largest of a group and to be roddexin preLrence to the others. It ia our conviction, however, that the additional protedion of both trees and adjacent building often makes the trouble and expense worth while.
SOME FEATURES OF THE CLIMATE OF ALASKA 1
gg/- sg ( 71c2 MELVIN B. SUMMERS
[Weather Bureau, Seattle, Wa9h.J
Less than a generation ago the popular conce tion of Alaska was that of a land of per etual iceang snow infested with polar bears, and in l abited by a race 01 beings who dwelt in snow and ice houses and subsisted on the blubber and flesh of walrus, seal, and other animals native to a frigid climate. So fixed had thisideabecome that even to-da after considerabl more than a billion dollars of weal& has been wreste B from the Territory throu h mine, forest, field, and sea, there are those who find difficulty in divorcing these preconceived opinions from their minds. It is a surprise to many people to learn that tropical daytime temperatures are recorded in Alaska every summer, and that there are parts of the Territory, notably in trhe Aleutian Islands and alon the southern coast, where zero readings have never % een observed. Lying, as it does, north of the Pacific Ocean, with the vast expanse of British America to the east, and se arated only by Berin Strait from the la er land mass o P Siberia
during the winter by relatively high atmos hericprcssure. Over the immediate water surface on t % e south there usually exists a trough of low pressure with a wat-east trend, commonl known as the Aleutian LOW. Through this pressure va 5 ey, so to s eak, ass a great man of the cyclonic disturbances o f the gorthern Hemisp<ere in their west-to-east movement. Other disturbancss originate in it and alto ether it exercises a great influence
Canadian Provinces to the east and the northern,half
of the United States to the southeast. The mountains of British Columbia, with their south- east-northwest trend, present somewhat of a barrier to the eastward movement of these barometric depressions, many of which sta nate in the Gulf of Alaska for days
lying to the south manifests a tendency to move north- eastward over Oregon and Washin ton. In fact, after reaching the Gulf of Alaska a cyc onic storm ma be forced to ursue a retrograde movement and actua y to move nort R westward. ressure in the Arctic slope of Alaska, or from the nort%ward thrust of the Pacific High, these Aleutian LOWS occasionall take
toward Seward Peninsula and the Kobut Valley of Alaska, or they may take a similar direction of movement farther east over the Yukon Valley. So long as the LOWS
ursue their normal track over the north Pacific and the
B ulf of Alaska, fair and cold weather obtains over the interior valleys of the Territory, with warm and rainy conditions over the southeastern panhandle. When, however, they take a northeastward movement, the temperature of the interior moderates under the influence of southerly winds, and precipitation to a greater or less
to the west, t E e main portion of Tl t e Territory is covered
on the weather of the fk erritory as well as on that of the
a t a time, eapecia K y if the Pacific high-pressure area
19 f
Whether from a breaking down of
a northeastward movement over Berin Sea and a 1 vance
1 Hasd bclore tho mating of the American Metmrologiml Society, Leland Atanford ITniver::ity, Jiinc 3;. 192.1.
494 MONTHLY WEATHER REVIEW OCTOBER, 1924
extent ensues. Occasionally, from some cause, the Arctic High builds up to an exce tional extent, and then
weather, prevail over practically the entire Territory, including the usually warm and rainy south-southeastern section. In the summer season, with the building u of pressure
of the land surface of the interior uncler the influenre of the lon days of high latitudes, the interior pressure
With these meteorological conditions in mind as the major weather controls of the Territory, modified greatly by its diveivified relief, a few of t le climatic features will be briefly considered. The south- eastern or anhandle section will be taken up first. It shoul B be understood a t the outset that this part of
Alaska is of unusually strong relief. Mountainous in the extreme, the land areas are cut by innumerable tidewater bays, sounds, inlets, and fiords. Peaks 3,000 feet in height are common, while scores have elevations above 5,000 feet, and a number rise to 10,000 feet or more. Because of its strong relief and also because of its peculiar position with respect to the north Pacific storm track and its close proximity to the ocean itself, this southeastern portion of the Territor receives very heavy precipita-
States'proper is the, annual precipitation as great as is
recorded at several stations at or near sea level in the Panhandle and Prince William Sound districts. Ketcli- ikm, one of the most important commercial centers of the Territory, receives 157 inches annual1 , including the water equivalent of 40 inches of snowfYal1. Fortmann Hatchery, near by, receives 148 inches, and Cordova and Latouche, at the entrance of Prince William Sound, 131 and 147 inches, respectively. At Jumbo Mine, at an elevation of 1,500 feet, the total is about 193 inches a
year, including ap roximately 450 inches of snowfall,
The effect of increase of altitude on precipitation is indicated clearly in a comparison of the records of Juneau and Perseverance Camp. Although only 3 miles distant from each other, Juneau, at sea level, receives 80 inches a year, while Perseverance Camp, at 1,400 feet and in the lee of a recipitous and narrow moun- tain ran e 3,800 feet higl and running athwart the
inches. Juneau receives these same winds, but not the full effect of t;he adiabatic cooling incident to the ascent of the mountain. Clouds from which heavy rain is falling on the crest are erceired to continue their
distance in their honzontal movement across the T-alley in which Perseverance Camp is located. Southeastern Alaska can lay claim to a heavier monthly precipitation than any on record in the United States, exce t for a few places in the mountains of California. ketchikan had a total of 53.85 inches and Jumbo Mine, 61.46 inches, in November, 1917.* Because of being so frequently in the eastern quadrant of the north Pacific c clonic area, the fre uency of
gtates. Whereas the rainiest ortions of Washington,
receive measurable precipitation on from 175 to 300 days a year, a large portion of southeastern Alaska has from
200 to 240 such days.
northerly winds, attended by ? air and unusually cold
over the cooler waters of the north Pacific an a the heating
is relative B y low and is attended by occasional rains.
a1 thouK1l
tion. In fact, at no o is serration station in the United
as indicated by a t % ee-year record:
moisture- ei aden southerly winds, receives about 150
precipitation with apparent P y the same intensity for some
recipitation also, excee B s that of any part of t B e United
on the seaward slopoy of the B lympics and Cascades,
:In January. lW, at Helen mine, Calilornis, 71.54 inches were recorded, and other polnts recdved more than 68.86 inches.
Despit.0 the phenomenally large monthly and annual t,otals, t,here occur no intense downpours of short dura- t,ion, such as are common in the central valle s of the
convectional thunderstorms. At Juneau, with its annual precipitation of 80 inches and a maximum 24-hour fall of 5.54 inches, the maximum 15-minute fall is 0.28 inch, and the maximum hourly fall, 0.56 inch. Thc economic importance of t,he heavy precipitation
of southeustern Alaska may well be mentioned here. The extremely rugged t,opography of tfhe coiintry lends it,self readily to the creation of storage reservoirs whereby the abundant precipitation can be utilized in the develop- ment of hydroelectric power. Already every town of
iiii ortance is deriving light a.nd power fTom this source,
limdling 8,000 tons of rock a. clap. Numerous other sites, some of them of lar e possibilities, have been
nnd mineral resources with which the count is endowed.
;ind quantity of.rainfal1 in the panhandle of Alaska that the air is always moisture laden, for, with a ressure dis-
the comparat,ivelv dry interior of British America, there comes a marked decrease in both the absolute and relative humidity, the latter being reduced still further by the adiabatic heat,ing incident t,o the descent of the air from the mountain crests. 9 relat,ive humidity of 12 per cent has been recorded at Juneau under such conditions. While these cases of ext.reme dryness are com aratively
in cut-over lands when they do occur, especially in the spring of the year, when t8he precedin year's growth .of
and kept damp by the new growth. As a corollary of the heavy precipitation may be men- tioned t.he moderate temperatures that prevail in that re ion. At Juneau, with a January mean of 2 7 O and a
year with freezing temperatures and at Sitza only 106,
tis against 186 days at Bismarck and 109 a t Chicago. Zero readings occur less than twice a year at Juneau, on t.he arerage, and less than once a year at Sitka. In the int.erior of the Territory, as exemplified b the great Yukon Valley, t,he out,standing features o f the climate are the reat annual range in temperature and
the Guzof -4laska by the higl! mountain barriers of the Alaska range, the climate here, especidl
the Arctic Circle, tmhe ran e between the January an!
at gembina, N. Dak., which is enerally considered as bei
Fairbanks, 164'; and at Pembina, 155'. The summer temperatures of the interior are deli ht-
light, vegetation makes rapid gro.wth. Temperatures of
70' and above occur on an avera e of only 13 da
ing influence of Bering Sea is manifest to some extent, but at Fairbanks the number of such days is increased to 61. In tho Tanana and upper Yukon Vafieys temperaturw in excess of 90 are occasionally recorded. While freezing may occur in any of the summer months, except where t.here is good air drainage, such temperatures are usually of short duration and do little or no damage.
States. This fact can be explnined by the a % sence of
inc P d i n g a large gold-mining operation at Juneau,
surveyed and await the deve P opnient of the vast timber
However, it should not be inferred from 7l t e frequency
tribution that induces northeasterly winds, b P owing from
few, they nevert.heless may create a forest L e-hazard
ferns and other vegetation has not yet 5) een covered over
J u 7 y mean of 57O, there is an average of onl 108 days (t
t.he com arativey P light preci itation. Separated from
valley, is cont,inental in the extreme. At 6 ort in Yukon, the upper on
Jul means is 89O and at IF airbanks, 76O, as agamst 71
one of the coldest places in t B e United States. The abso Y Ute range in temperature a t Fort Yukon is 170, at
fully pleasant, and, under the effect of the prolonged f ay-
summer in the lower Kuskokwim 57 alley, where t IT e cool- each
OCTOBER, 1924 MONTHLY WEATHER REVIEW 495
While the number of days a year with zero tempera- tures range from 61 in the Matanuska Valley to 123 a t Fairbanks and 159 a t Fort Yukon, such low readings do not ersist throu hout the winter, as is popularly sup-
ever, is evidenced by the fact that in the winter of 1917- 18 zero tem eratures revailed continuously in the up er
mean temperature for December at Eagle of -45.8' and
a departure from the normal of -34.6'. At Dawson, Yukon Territory, the mean for December was -51.3'. Subnormal temperatures prevailed throu hout the Ter-
under the influence of pressure that was half an inch above normal along the sixty-fifth parallel. In contrast to this abnormally cold December may be cited the same month three years previous, when the mean at Eagle was 7.8', or 19.0 above normal, thus making a range in mean temperature for the month of 53.6', as against a similar maximum range of the monthly means a t Bis- marck, N. Dak., of 33.6'. The recipitation ranges from about 19 inches in the lower mp ukon to about 12 inches in the middle Yukon and lower Tanana Valleys, but this shades off with recession from the sea until at Fort Yukon the total is less than 5:
inches. The four months from June to September re- ceive over half the year's precipitatioii-a condition most propitious for agriculture and placer mining. Thunder- storms are common during the sunimer months, but they are usual1 mild in character and are seldom attended by heavy hai1 As an illustration of the possibilities of agriculture in some of the interior vdleys, i t may be said that in the Fairbanks district, where sprin wheat, oats, potatoes and other vegetables, and smai fruits are successfully grown, there has been only one serious crop failure in the 19 years since farming was begun in that district. This was in 1922, when a killing frost on August 29 destroyed practical1 all crops. These had been unusual1 late in
and wet summer. The variability of the climate of the Territory from year to year is msclosed in a study of the records of five representative stations: Sitka and Fortmann Hatchery, in the southeast; Eagle and Fairbanks, in the interior; and Nome, on the northern Bering Sea coast. For the pu ose of this study the calendar ear was disregarded,
warmest eriods of 12 consecutive months. Grouping the montL in this way, it is found that at Eagle thc coldest year had a mean that was 5.6' below normal, and the warmest ear, 6.4' above. This does not differ
imum departures are -5.2' and +5.5". The conipara-
tive uniformity of the coastal climate is exemplified by the Sitka record, which shows the coldest year to have been 2.4' below normal and the warmest, 3.7' above. At Seattle the maximum departures are - 2.1' and + 2.5". During the last 20 years, the calendar years 1905, 1912, 1914, 1915, and 1923 were decidedly above normal in temperature throughout the Territory froni the Arctic Circle southward, while the ye- 1909, 1910, and 1917 were decidedly below normal. These de artures Irom
Seatt B e, though rn lesser degree, and, w t h two exceptionH, a t Bismarck.
pose $ . That proonged 7
Yukon Val P ey from {ovember 23 to January 3, wit P i a
ritory during that month, except in the A 4 eutian region,
extreme cold may occur, how-
maturing i ecause of a late spring and an unusual P y cloudy
anFannua1 means were compute d for the coldest and
materidy from t i e record a t Bismarck, where the m&x-
avera e temperatures are reflected in t Ill c records of
The variability of precipitation from year to year like- wise is greatest in the interior. Here, a t Fairbanks and Eagle, with normals of approximately 10 and 12 inches, their wettest consecutive 12 months show excesses of 99 and 53 er cent, respectively, and the driest ones defici-
extremity of continental Alaska, there has been an excess of 79 per cent and a cleficienc of 58 per cent on an annual normal of 17 inches. At alrthree of these stations the recipitation is a fattor in placer mining, and a t Fair- Ian, in a riculture as well. The records a t each sta-
below the normal to interfere with, although not neces- sarily to suspend, operations alon those lines. In the southeastern ortion of t 5l e Territory, as shown
12-month periods were 28 per cent above the normal in quantity a t both stations, although the normals M e r by 64 inches, being 148 and 81 inches, respectively, for the period under consideration The driest 12-month eriods show deficiencies of 28 per cent a t Fortmann hatcher and 29 per cent at Sitka. These figures show
power purposes, althoug marked defiaencies for several consecutive months indicate the wisdom of providing storage facilities when practicable.
A coni arison of these maximum and minimum de-
the States shows the Alaskan climate in a favorable light. At Bismarck, with a typical continental climate, the excess of the wettest 12-month period is 87 per cent, and the deficienc of the driest 55 per cent, with a
marine influence, the excess is 45 er cent and the defi- ciency 37 per cent, with a norma P of 34 inches. Much greater departures from normal conditions than any of those enumerated above are found in the records of many stations on the Pacific slope, articularly in California. In conclusion, it may be sai R that while the climate of Alaska presents great contrasts and in some sections is quite rigorous a t times, it is healthful and invigorating. The economic development that has already taken lace in the Territory has been ncliievetl largely througf the i d of cliniatic conditions, rather than in Y ite of them,
land trans ortation of supplies, machine , etc., for min-
a climate with winter temperatures above freezin with- out the building of expensive roads and bridges. hodern tractors now draw great loads across frozen streams, bogs, and tundra to remote districts, with but little previous preparation of roads and trds. The excessive pre- cipitation of southeastern Alaska has fostered the devel- opment of the vast mineral and timber resources of that district by making mailable nn abundance of cheap hydroelectric power. Even the great fur-seal industry
ot the Pribilof Islands is la ely de endent for its success on the excessive amount 'd.; cloucf and foggy weather that prevails there during the seactaking season, since the driving of the seals to slaughter can not be accom- plished durin periods of sunshine without an overheating
of the animtfs and a lowering of the qualityof thefur. Given the necessary resources and favorable ecbnomic conditions, there is nothing in the climate of Alaska that should prevent the Territor from ultimately becoming
encies o f 39 and 37 per cent. At Nome, near the western
tion show t % e minimum 12-month totals to be sufficiently
by the Fortmann Hatc 1 ery and Sitka records, the wettest
a proba t ility of a fair1 uniform supply.of water for
partures ! rom normal precipitation with similar data in
normal of 17 inc 5 es. At Seattie, under considerable
11s is sometimes contended. As an examp P e, the over-
ing and ot R er development work, would lg e impossible in
n mighty empire aniong the B tates of the Union.
496 MONTHLY WEATHER REVIEW Om-, 1924
E&...-...
F&-.. Nome-. ____
Sltka _._____
Fortmann Hatchery. Seattle ______
Bismarck-..
EzLremes of mean ternperdure jor periods of 18 consecutive months at representative Alaskan stations and at Seattle, Wash., and Bismarck, N . Dak.
-- -- -I-
17 23.8 July, 1917JUne, 1918- 18 2 -5.6 October, 1914-Sept8Dl- 30.2 4-6. 4
1% 5 July 1917-June 1918- 21.1 -4.4 _-_._do ___---------- ---- 31.0 +5.5
OF. OF. OF.
ber, 1oT6.
17 25.2 Jan&, 192O-&XU- 21.2 -4. 0 January, 1912-Decem- 29.5 +4.3
24 43.7 October, 1w)3-8ep 41.3 -2 4 Octohr, 1014-Septam- 47.4 +3.7
19 4!2 8 January.i!3O!+Decem- 3& 9 -3.9 Jan&', 1915-Decem- 46.6 +A 8
32 51.3 Jan&, 1916-Decem- 49.2 -2 1 Januky. 189!2-Deeem- 53.8 +25
49 UL 6 December, 1874-No- 35.3 -5.2 Deeember 1877-NP 46.3 t5.8
ber, 1m. ber 1912.
tember lwu. ber 1915.
ber 1908. ber 1915.
ber, 1916. ber, 1892.
vember, 1875. vember,'l878.
1-1 I Coldest Ismonth pwbd I Warmsst lsmonth pepid
Extremes of precipitation totals jor period8 of 12 consecutive monlhs at representative Alaskan stations and at Seattle, wash., and Bismarck, N . Dak.
Ins. In#. Ins. I Eagle _____ 17 9.87 July, 19lO-Jme, 1911. 6.18 163
F a 1 r - 18 11.88 Novembex 18oboc- 2S.b 197 bank8 t o h loin. Nome--'-- 17 17.37 Dfmmbr 192-No- 31.14 179 vember 'ls22. Sitka _____ 24 84.08 Febmard 19Wan- 107.S 128 w y , ldla
mann tober, I&. F o r t - 19 148.06 November looWe la 88 128
Hatch-
Se%&---[ 33.431 AfrU. 1893-March.
1
48.891 1 4 1 D ~r ,;;;p N o -
1
21.04 63
Blamd.49 l6.W Fehruary, 1876-Jan- 31.78 187 Jnne,dJuI~,lsW) 7.70; 46
ON THE APPLICATION OF THE FRONTAL THEORY TO CYCLONES IN THE SAHARA
1
~ary, 1877.
SS/. ~/~(6 6 /) BY M. L. PETITJEAN
(Comptea Rendus, 179, No. 1. July 7,1924, pp. 64-65)
[Translatea by B. M. Varney, Weather Bureau]
The thermal discontinuity between winds of Mediter- ranean and of tropical o r i p in northern Africa reveals the existence, especially in the warmer months, of a
s ecial front,I which seems to be related to that of the Aade Winds.' It delimits the warm and the cold sectors of depressions, the centers of which, at the time
of their appearance on the s noptic charts, occupy
ment of which is confined to either SW.-NE. or W.-E. The warm sector is at first limited on its western side by the Hi h Atlas of Morocco; it extends toward the
Atlas. On the emtern side its boundary is prolonged aa far as southern Tunis. The la er of southerly winds. * * * extends to a higher ahtude the greater is the heating in the tropical regions. It rises above the
extreme sourthern Morocco, an B the direction of move
north and f ollows in its course the Saharan chain of the
I Petitjean L Surfaces de discontinuit4 en A l g i e et au Sahara. (Cahlm du Servicw ~~r n i o e i i u d t d .~~~e ~l s i ~a a NO. 1, P. 13.)
1 Bjerkned, V., On the dyn&iar of the clrcular vortex. with a plications to the atmos- phere and at- heric vortex and wave motions. (Geo&e Publikationer Kris- tiania, 2, NO. 4, 111, pp. M.)
winds from the sea [these constituting the cold sector of the c clone.--Ed.], and its progrw northward can be tracdfrom one station b the radual lowering of its
ta meteorological stations in Algeria and the Sahara. b e maintainin itself in general parallel to the
lates, with variable amplitude and variable period, as a
result of the conflict between the tropical and Mediter- ranean winds. This is made clear by tracin the lines
periods which accompany the passage of depressions oiiginating in the Sahara. These lines give way, some- t,imes toward the north and sometimes toward the south,
under side, as shown by p i I Y ot bal oon soundings at mili-
orientation of the At T as, the front of discontinuity oscil-
of synchronous rainfall in connection with t B e stormy
heating due to compression, this heating acting in addi- tion to the gain of heat induced by condensation of water va or during the ascent. Gorth of the Atlas the warm airkagain forced up, this time above the ocean winds. ouble ascent is
revealed by the isochrones of rain occurring on the two sides of the mountainous massif. The warm sector of Saharan de ressions usually
the case with depressions in the Temperate Zone, he
'' cut off," either as a result of the arrival of colder air at its rear or of the weakening of the tropical flow. A
second depression is thus produced following the first and may in its turn be cut off. It is not rare to discover
on tho charts of the meteorological service of Algeria cyclone families made u of three of these depressions in
Stlas.
remains open toward the south side, g ut it may, as IS
a string, lying essentia E J parallel to the trend of the
SS/.S/S (2 6 2 .3 -
SECONDARY DEPRESSIONS IN THE ADRIATIC SEA
By FILIPPO EREDIA
(Comptes Rendus, 179, No. 1, July 7,1924, pp. 66.67)
[Translated by B. M. Varney, Weather Bureau1
Sometimes, over 'the Adriatic appear barometric de- pressions which, as soon as they are formed, move ra idly in a direction from Northeast to southwest, grad-
when they reach Sicily or Tripoli. Rarely do they take
a course toward the southeast, crossing the Ionian Sea to the Cyrenian Sea. These de ressions, believed by most scientists to ori inate over t e ljmhenian Sea, prepnt
ua fl y changing their come by turning toward the south
ver different c % aracters from those of other depressions inwt % e M edi t err aneanB asin.