Arizona republican., 1922-01-01
the other stations considered, were
the determining factor.
inversion LAYER

the other stations considered, were
the determining factor.
inversion Layer
The inversion layer appears to
have it's base some 40 feet above the
lowest elevation shown in the sec
tion. at least on the north side of
the valley. In a general way this
layer may be thought of as made up
of superimposed, approximately hor-
izontal air strata in which the tenn
perature rises with the increase In
elevation. The positions of the strata
within the layer are subject to con-
stant change from the moment the
condition of inxersion begins, uSu-
ally late in the afternoon, until the
condition is ended by the rising tenn
peratures of the following morning.
We are more particularly interested
in conditions within the layer at the
time of minimum temperature as
that is at the time at which almost
invariably the differences in tenn
perature of the upper and lower
strata will be greatest. Mean tenn
peratures at the same elevations on
the north and south sides OF the val
ley agree pretty closely at this time
though for individual nights the diff
ference will often be considerable. A
south wind will check drainage on
the north side Of the valley and ac-
celerate it on the south side, or a
cross wind will break up drainage
lines on one slope while the other
may be calm. Even where a single
slope is considered there is a con-
stant variation in the inversion lay
| er from night to night The sec
| In hn Y-raf "a
of vertical change is greatest shifts
up and down, the depth of the layer
almost certainly changes. No two
nights show identical records.
Study Of Temperatures
1t is in relation to study of inver-
| sion on a single slope comparatively
free from complicating topographic
features that most of the graphs and
thermograph tracings were made up.
| The Indian school, being at the foot
! Of the slope drained, is taken as a
| base and five other stations on an
unbroken slope rising 635 feet above
1t offer excellent opportunity for a
| study of temperatures within the
layer. The thermograph tracings
show the development Of the inver-
sion condition, as does one set OF
graphs, from the time of maximum
! temperature on the preceding day to
the time Of minimLm and the rise
of temperature the following morn
! ing. Other graphs show simply the
| temperature gradient within the law
er at the time Of minimum tempera-
ture and represent the mean OF q
number of days.
Relative humidity appears to be
q factor in determining the contrasts
of temperature within the inversion
layer. Where a number of consac-
utive mornings ara considered tha.
one with the highest humidity the
preceding evening almost invarsao.y
shows the smallest contrasts of tenn
peratuie in the Inversion layer. The
| Erarhs show the decrease in tenn
nerature contrasts through Nove.n-
Der. Tecem5er, January and Fe5ru-
a~y while in Mar Ii there was 9
| sharp increase. Records show thai
the mean 6 pm. ralltivc humidity
| increased II ON November and lher
dropped sharply in March. 1t also
| suggested that the cooling of the
earth itself, the gradual loss of ac-
cumulated heat with the advance Of
| winter, may partly explain the pro-
gressive decreases in temperature
contrast shown by the gradients o.
December, January and February and
the increase with the higher day
temperatures of March. in othel
words, there is less heat radiatet
from the earth itself to influence
the temperature of the upper strata
of the inversion layer