SEPTEMBBB 1936 MONTHLY WEATHER REVIEW 291
Wenchow ________________________________ Pelyushan ____________________________^___
Dlfferenoe ________________._________
Pagoda Anchorage __________________._____
Dlfferenm __________________________
Amoy ______________._.___________________
Tung Yung ______________________________
Chapel Island _______._________.__________,
TABLE 4.-Comparison of wind force at continental and irisiilar stations (Beaufort scale)-Continued
----___-___-_____________
1.4 .9 .9 2.4 2.0 .7 1.4 1.3 1.0 1.2 1.0 1.1 1.4 4.2 3.9 3.2 2.6 2.0 2.3 2.8 2.7 3.1 3.5 3.3 3.7 3.2 __~~_________________________--
-2.8 -3.0 -2.3 -
.I -.6 -1.6 -1.4 -1.4 -2.1 -2.3 -2.3 -2.6 -1.8
1.4 1.4 1.4 1.2 1.4 1.3 1.0 1.0 1.0 1.8 1.8 1.7 1.5
3.5 4.0 3.8 3.5 3.4 3.1 3.2 3.7 3.4 3.5
-2.6 -2.4 -2.1 -2.2 -1.7 -1.9 -2.1 -1.8 -1.9 -2.2 -2.1 -2.1 -2.0
2.8 2.6 2.0 2.4 2.5 2.6 2.6 2.5 2. G 2.9 2.7 2.0 2.6
4.2 4.0 3.6 2.8 2.9 2.8 2.4 2.4 3.3 4.5 4.2 4.0 3.5
............................ ............................
4.0 3.9 3.8 ~~~~___~_--_-___---
~~~~___~__c
___~~~~~_________~~~~
I January IFebruaryI March 1 April 1 May 1 June 1 July I August I 1 October 1 Ny:m’ 1 DiyF 1 Year
Winter
m m 110
133
143
150
150
153
Spring
mm 90 122
124
114
128
147
Dlfferenm ____.___._._._._._._______ -1.4 -1.4 -1.0 -.4 -.4 -.2 +.2 +.I -.7 -1.6 -1.5 -1.4 -. 0
3.4 1.8
---------=---
8watow ____________________---.------...
I
1.‘91 2.11 3.7 1.81 3.1 1.81 2.8 1.81 2.0 1.81 2.3 1 .8 1 2.3 1.81 2.01 3.3
Lamocks __________._._______.-----.-..--. 4.0 3.8 4.4 I .@/ 4.1 1.81 3. 1.81 8
Summer
m m 147
180 178
164
192
190
TABLE 5
Autumn Year
~--
m m mm! 188 541
22i 662
228 673 215 043
249 719
247 743
Stations Distance
1 frog:he 1
tude
m 7 1
7
8 17
20
CLIMATE OF THE ROGUE RIVER VALLEY, OREG.
By WILLIS B. MERRIAM
[Department of Qeography, Unlversity of Washington, Seattle, Wash., September 19361
The Ro e River Valley represents an area of about 300
western Oregon by the Rogue River and its major tribu-
taries. The elevation of the arable valley floor ranges from slightly under 1,000 feet a t Grants Pass t,o 2,000 feet in the upper Bear Creek Valley, southeast of Ashland.
The region is surrounded on all sides by mountains thst
rise to elevations of from 4,000 to 7,000 feet. The economic basis of the Rogue River vnlley consists largely of general farming of a rather intensive nature,
some mining, and an increasing health resort and tourist
business. Its agricultural specialization consists of pears;
it is one of the largest three commercial pear-produc.ing regions in the United States.
So much of the economic development of the valley depends upon its distinctive climatic conditions t,hnt a
resume of the climatological environment is prerequisite to
an understanding of the region.
square mi F es, carved out of the Klamath Plateau of south-
RAINFALL
Climatically the Rogue River Valley is located in the southern part of the north Pacific climatic province; that
is, it represents the more arid phase of the Maiine Tem-
perate or West Coast Cyclonic type. The American Mediterranean lies to the south in central and southern California and the Arid Continental lies to the east in the lee of the Cascade Mountains. Because it is situated
some 60 to 100 miles inland, with a mountain interval
between the valley and the coast, certain characteristics of both a subtropical and a continental nature are in
evidence. Many of the older homes in Medford and
Ashland have palm trees in their yards. They are not
too vigorous in appearance, to be sure, nevertheless
palm and pine meet in the Rogue River Valley, and at
least tw-o pomegranate trees have weathered some 30 or
40 years in the town of Jacksonville.
The maximum rainfall occurii in winter when the mild, moisture-laden winds from the Pacific blow across the
cooler lands. The annual precipitation may be as heavy as 40 to 80 inches in the surrounding niountnins; but the
fact that the agricultural sections in the valleys lie from
2,000 to 6,000 feet lower than the surrounding territory, places the entire region within the rain-shadow of the
ranges, definitely reducing the amount of precipitation
that might otherwise be expected, and resulting, in fact, in a dry valley island within the Klamath Plateau. Down in the vnlley proper the avernge annual rainfn.11 runs
from 25 to 30 inches near Grants Pass where a considerable orographic precipitation carried over from the coastal
mountains is still in evidence, to around 15 a t hledford,
the center of the “island.” Except for
occasional light conrec tional showers July and August are
practically rainless. There are several reasons for the
summer drought conditions. During the summer months
a dominant anticyclonic area, the Cape hlendocino HIGH,
lies off trhe coast in the north Pacific. Winds blowing
outward on the eastern side of this HIGH have little oppor- tunity to take up moisture before reaching the coast. Furthermore, during the summer the land becomes warmer
than the ocean. The winds tend to warm up as they
progress over the land, increasing the vapor capacity,
and hence they are drying winds rather than moisture-
giving winds. This tendency is further aggravated by
the fact that the valley areas receive a great deal of inso-
lation as the sun blazes down through cloudless skies,
causing temperature to soar during the day. The result
The minimum rainfall occurs in summer.
292 . MONTHLY WEATHER REVIEW SEPT~MBEB 1936
is that the winds unduly increase in temperature as they
progress through the valley. Although local convection must be great, thunderstorms are not common, as the
Rogue River Valley appears to be dominated by thegreater convectional low pressure of the central California valleys and the permanent summer LOW that lies over the arid
southwest. The valley winds, in other words, are drawn southward and southeastward instead of being allowed to
amend over the area; furthermore, because of the relative dryness of the air, the convection that does occur does not
carry it high enough to reach condensation temperatures.
TEMPERATURES
According to Ellsworth Huntington, a month is cooler
than is ideal if its average temperature falls below 32’ F.; and warmer than ideal if the temperature averages above
70’. The Rogue River Valley fits well into this optimum temperature range. The mean annual temperature for the valley proper ranges between 52’ and 53O, with
extremes a t Medford, 110’ and -loo, respectively. Zero
temperatures are rare; and the mean for January, the coldest month of the year, is between 37’ and 39’.
The means for July and August range between G9O and il”. However, the hottest spells
usually last but a week or so; and although general high
temperature prevails, the humidity is low and the sensible temperature is not excessive. It is only with the passing
of a cyclonic storm, resulting in nn increased humidity, that
the temperature becomes in the least oppressive, and that condition lasts but a few hours. Because of the cloudless skies, which facilitate rapid radiation, and the nocturnal
drainage of cooler mountain air into the valley basins,
nights in summer are always cool. This coolness lasts
well into the morning, until the regular winds spring up and solar heat warms up the passing air.
The combination of mild winters, frequent temperature
changes, warm to hot days in summer, but delightfully cool evenings and nights, is undoubtedly conducive to a
maximum of human energy, and the Rogue River Valley may be safely referred to as one of the most energizing
geographic regions in North America.
Summers are hot.
WINDS
There are no really destructive winds or storms through-
out the valley. However, strong steady winds along the Bear Creek Valley sometimes present minor problems.
The prevailing winds are westerly. In winter they are dominantly cyclonic in nature; they impart a southerly
component to the westerly winds during the cool season.
Anticyclonic and solar cont’rols are dominant during the
summer. At this season of the year, the winds may gain considerable impetus as they blow outward from the
Pacific anticyclone. In general they follow the direction
of the valley, due largely to conditions of local topography.
As they leave Ashland they proceed definitely soutli- southeast, drawn by the summer LOW of the arid southwest
and by Sacramento Valley convection; this is evidenced by the fact that the hotter the day, the more steady and
firm are the winds. In fact on a hot afternoon the winds are drawn southward from the Rogue River Valley with such force that they tax the capacity of a powerful car in
pulling up the Siskiyou Mountains northbound. These
summer afternoon winds are so important a factor locally that drivers and truckers who are familiar with conditions
schedule their trips so that they will be southbound over
the Siskiyous in the afternoons and northbound either in the evening or morning, to escape the strong head
winds that must otherwise be encountered.
Grants Pass, lying in what might be termed the “wind shadow” of the coastal mountains, has the second lowest
average wind velocity of any station in the United States. As one progresses eastward through the valley, however,
the winds increa.se considerably in velocity. This increase,
and a prevailing northwesterly direction, mean that young
orchards need to be especially pruned and sometimes propped to prevent leeward leaning and excessive lee-
ward development of the trees. The practice of establish-
ing orchards in the lee of poplor or eucalyptus whdbreaks,
as is done in many prairie areas and in parts of California., offers a possible solution but as yet has not been utilized
in the valley.
FROST HAZARD AND THE GROWING SEASON
In the spring of the year there is considerable frost haz- ard in many parts of the basin. During nights favorable
for frosts, the winds die down altogether and the colder air from the highlands drains down into the valley bottoms.
If the winds are associated with a passing cyclonic area,
the humidity has a tendency to be somewhat higher and
frost is not likely; but if the winds emanate from anti- cyclonic areas, the humidity is lowered and damaging
frosts may occur.
As a rule it is only on the valley floor that serious injury may be caused by the low temperatures during the bloom-
ing period. Where there are slight elevations no frosts may occur, while serious injury may result only a few feet
below. The hillsides surrounding the valley usually es-
cape frosts altogether, once the normal spring season has arrived. The average variation in temperature in favor
of the lands lying above the valley floor is from 5’ to Go,
due to a marked inversion of the temperature gradient
when cold dense air creeps in and lies in stagnant pools
underneath the warmer air. P. J. O’Gara, a special
weather observer, who studied the frost problem of the Rogue River Valley a number of years ago, recorded
temperatures ranging as low as 23’ to 2 5 O on the ground and 32” to 35’ 50 feet above. “There is a t times”, he
reports, “a difference of 12 degrees or more between ground
temperatures and 50 feet above the valley floor.”
Because of this frost danger on the valley floor, most of the more recently established fruit orchards have been in
along the detrital slopes where air drainage is better. Here
is located the greatest orchard acreage a t the present time, although several fine old orchards are still found in the
lowlands. Eternal vigilance against spring frost is the price paid for these orchards, however. Without art5cial
protection the danger of injury by frost is greater in the
lowlands of the Rogue River Valley than in most frult growing sections of the country. This fact has caused the
development of one of the best systems of orchard heating
in use among fruit growers anywhere in the United States.
In spite of the early season frost hazard in certa-h well- spotted sections of the valley, the growing season 1s favly
long. The Umpqua mountains north of Grants Pass pro-
tect the region from cold north winds, and the Cascade Range stops cold easterly winds to a large extent. Ash-
land, Grants Pass, Jacksonville, Medford, and Talent all range from 160 to slightly in excess of 200 frost-free days.
The average growing season for the valley is about 190
days.
S~PTSMBES 1936 MONTHLY WEATHER REVIEW 293
RAINFALL VARIABILITY
One characteristic of the precipitation of this complex climatic region, and one which has played an important
rainfall in the history of the station occurred, with a total
of 28.87 inches. Two years previous to that record, the lowest amount was recorded, when but 11.99 inches fell during the entire year. Following the dryest year, 24.25
FIGURE 1.-Isohyetal map of Rogue River region, Oregon.
part in shaping the economic history of the Rogue River Valley, is its variability in amount, monthly and annually.
In illustrating this time distribution, the precipitation
record for Ashland has been used for the reason that Ash-
inches fell, more than double the amount of the previous
year. The monthly rainfall likewise shows this variability.
In January of 1881 a total of 12.29 inches fell-more in 1
FIOURE 1.-Annual precipitation record, Ashland, Oreg.
land has the longest record, some 54 years, plus a l?-year unofficial private record, and conditions here are typical of
the entire valley. There is a noticeable difference rn total
month than in the entire diy year previously mentiqned. The driest January on record received but 0.47 inch.
Au ust, ordinarily a rainless month, has had up to 2.71 precipitation from year to year. In 1907 the heaviest inc fl es of rain. The November amounts range from a
294 MONTHLY WEATHER REVIEW SEPTEMBBR 1936
trace to 8.10 inches. Such fluctuations mean that the rainfall is not dependable for ordinary types of agriculture. Under natural conditions the Rogue River Valley would be
rn area of agricultural risk. With this variability of rain- fall, together with a low average total and an unfavorable seasonal distribution, it is easy to see why the agricultural
specialization of the valley has awaited the development of irrigation.
A third type of rainfall variability may also be demon- strated from the Ashland records. Examination of the
yearly precipitation curve since 1879, and the fragmentary private record from 1854 to 1865, shows considerable
oscillation. It is also noticeable that these oscillations
rise to definite crests. One such crest seems to be indi-
cated around 1864, another between 1880 and 1885, and still another from 1905 to 1910. The average time lapse
between these peaks is roughly 23 or 23 gears. Appar- ently this represents a rough pulsation of rainfall. Clima-
tolo ‘sts are inclined to discredit claims of fixed and defi-
frequently evident. While these pulsations do not occur with mathematical frequency, they may form the basis for
a certain amount of prediction or expectation. It is
evident that a drought period reached its trough about
1930. Since 1930 the trend has been somewhat upward,
with slight drops in 1933 and 1935 as is to be expected because of the high annual oscillation characteristic of the
valley. During the past two decades, 14 years have been definitely below the mean and only 2 have been defi-
nitely above. Hence it may perhaps be expected that the
next 5 to 10 years will average an inch or two more rainfall than the last 10 years have. As it stands now, the mean
nite ff y recurring climatic cycles, but a pulsatory tendency is
for the official 44-year record for Ashland ending in 1922,
and contained in the old section 17 of the Summary of Climatological Data for the United States, is indicated as
20.35. In 1935 that mean stood lowered to 19.75 inches
of rain.
If such an increase occurs, it may aid in bringing on
generally improved economic conditions for the valley, as
it was probably no accident of history that the upswing of
the last rainfall crest, 1905 to 1910, saw the greatest increase in population in the history of the valley. This
will not mean that irrigation will be less depended upon, as extreme oscillations in annual amount are likely still to take place during a series of heavier rainfall years. The
greatest benefit will accrue through a lessened cost for
irrigation water on an average, an increase in good pasture land and a restoration of ground-water supplies both for
dry and subirrigated farming in the lowlands and in the natural water-s torage reservoirs in the uplands.
How may these precipitation variations be accounted for? It would appear t’hat they are closely related to migrations of the prevailing paths of cyclonic and anti- cyclonic storms. The winter cyclonic path ordinarily
passes just north of the Rogue River region. However,
cyclonic and anticyclonic storms seldom follow one another in identical paths. Oscillation is much more character-
istic of their behavior. I n plains areas it is probnble that deviations may make little difference; but in a narrow
valley embedded 2,000 to 3,000 feet below the surrounding
country, the very hearts of these storms must pass through, or else the meteorological effect may be almost
entirely nullified, as t,here are mountain barriers casting a
rain shadow from any direction.
GALL’S PROJECTION FOR WORLD MAPS
By I. R. TANNEHILL and EDGAR W. WOOLARD
Weather Bureau, Washington, September 19381
The properties of the projection on whkh any given map
is constructed are often of c,onsiderable interest and ini- portance in connection with the purposes for which the map is to be used; it is always clesirnble, and ia many
cases essential, that these properties be known. Hence the particular projection that, has been employed should
be specifically stated on the ma.p, as it may be difficult or impossible of identification wit-h c.ertainty from mere
inspection. It is a somewhat cmious fact that one of the most widely used of map projections, particularly in meteorology, and the one that has long been t>he. principal world base used by the United States Weather BurewJ-
viz, Gall’s projection for world maps, figure 1-has seldom
been thus explicitly designated, and must often have been mistaken for Mercator’s projection, figure 3, to which it is superficially very simila.r.
Gall’s projection was devised by the Reverend James Gall, of Edinburgh, and first presented by him in 1855,
before the British Associa.tion for the Advancement. of
Science. It has received litt,le recognition in forma.1
treatises on map projections, probably for reasons indi- cated by the following comments of Deetz and Adams, who mention the projection but do not describe or
figure it:
Two projections of t.he sphere that are found in some atlases, as giving a fair re resentation of the world, are the Van der Grinten projection and &all’s projection. These two projections are neiiher conformal nor equal-area and may be classed as intermediates, having no properties of definite scientific value. They present a fair uniformity in the configuration of the world, avoiding the
1 C. H. Deetz and 0. 8. Adams, Elements of Map Projection, U. 8. Coast and Cleo-
detlc Burvey, 8p. Pub. 138, 4 ed.. p. 182. Washington, 1934.
excessive scale incremenBs of the Mercator in the higher latitudes and lessening the distortions of equal-area projections. Their utility nevertheless is pictorial and t.heir practical importance is limited.
A satisfa.ctory cartogra,phic re.presentation of the entire
globe presents even greate,r ciifficulties t,han that of only a more or less limited portion of the eart.h’s surfa.ce; and
it cannot be espected that any one projection can be found whkh will adequately serve all purposes. The choice of a projechion must depend in each case on the
pn.rt,icular needs a t hand. A cylindrical projection has many advantages for world maps, and this fact has led
to an extensive use of the hlercator projection for world
maps for all purposes; this projection, however, w?s designed primarily for use in navigation, and although it
is so perfectly adapted to naut,ical needs as to be indis- pensable to the mariner, it ha.s notable defects for many general purposes, even though it can never be entirely
displaced by any ot.her projections.a
Ga.11 was led to devise his projection while constructing
maps of the constellations for a celestial atlas. In his
own words:
Having occasion to publish an “Atlas of the Stars”, I was anxious to roduce a panoramic view of the equatorial heavens, extending as g r northward as possible; and my object was, of course, to con- serve the appearance of the constellations both in regard to form and comparative area. I first attempted Mercator’s projection, but the result was not satisfactory: the orientation, indeed, was perfect, but everything else was sacrificed. It then occurred to me that if, instead of rectifying the latitude to the longitude through-
: 0. Deetz and Adams, op. cit., pp. 1413-147, 101-104, and 34-35.
I James pall: On a new projection for a map of,the world,Proc. Roy. Geographical Boc., 15: 159,lBtO. This paper mcludes 8 plate showing the proiection.