Arizona republican., 1922-01-01

find with the climate. One is the
great diurnal range in temperature
and the other is the comparatively
high humidity which accompanies
the chill of the early morning. The
climate OF the hillsides overlooking
The valley is free from these faults
The temperature range will average
from to 10 degrees less than on
The floor of the valley and this de-
crease in range comes mostly at the
cold end of the day. The chill Of
the early morning is missing and
with it the Objectionable high hu-
midity. Few places in the world
can offer a more nearly ideal winter
climate than these little hillsides
with the abundant healing sunshine
and warm days OF the desert, but
without it's great temperature range
and chill mornings.
May Lines Explained
The position of the temperature
lines on the map in their relation to
the contours of elevation establishes
the fact of temperature inversion
over the Salt River valley. But the
lines also establish the fact that this
condition of inversion Is not with
out complications. The area Of low
temperature lying midway down the
slope from the northern hills to the
river Is the most self-evident in
consistency while the relatively high
temperature shown at Phoenix and
Riverside nursery. further down the
slope, call for explanation.
TO permit q more detailed study OF
this inversion layer nine stations
were established in the spring OF
1919, crossing the valley from north
to south. Starting in the north OF
Squaw Peak No A. 1850 feet eleva-
tion, the line dips down to Riverside
nursery at 1,075 feet, on the north
bank Of the Salt river and rises
again to 1,400 feet at Tarr's sanita-
rum. The total length of the line is
IA miles
A graph showing temperature cross
section of the valley is based on
mean minimum temperatures for De-
cember and January, shown at the
stations with correction, given by
the long Phoenix record, necessary
to reduce them to a true mean. Along
this particular line it is apparent
that q considerable mass of air at the
lower levels fails to show the con-
dition of inversion. The lowest tenn
perature lis shown at the Indian
school. which is 25 feet higher than
Phoenix and 40 feet higher than R1v-
erside nursery. The map offers an
explanation for this seeming incon-
sistency.
Cold Air Channel
1t will be observed that the canals
north of Phoenix show a wide curve
convex toward the mountains. The
depression or secondary valley Sc
indicated crosses the slope OF the
valley proper diagonally from north
east to southwest 1t is so slight q
depression as to escape entirely the
notice of one passing over the
ground, with a depth of only about
% feet and a width Of more than
four miles. but 1t offers a channel
for the cold air streams draining
down from the slopes to the north
minimum temperature Of 80 degrees
and east. This area with a mean
or lower, shown on the map, IS IN
this flat valley and gets the full
benefit of this cold air stream. Land
on the south is warmer because OF
this diversion OF the cold air to the
southwest, even though of lower ell
ovation than the floor of the SUBJ
valley.
The relatively high temperatures
SHOWN Dy the EnOSLllA SIdIlon ~ lily
weather bureau, while probably due
in considerable measure to the city
influence almost certainly are high
er because protected from the cold
air draining down from the north
Riverside nursery is protected o.
the north both by diversion Of the
cold air stream and by the city o.
Phoenix itself with its warming in
fluence. Protection on the south Il
afforded by the broad bed of thu
Salt river, which diverts cold al
draining from hills on the south t
the west. Riverside nursery is 3 o.
degrees warmer than might be ex'
pected If elevation. in relation t