Evening star., 1941-03-22
Of Stors, Men
And Atoms
Notebook Of Science Progress
In Laboratory, Field
And Study
BIZ Thomas r. Henrv.


The North is getting dryer and the
South wetter.
This has been evident in weather maps
for the past 20 years, says DR.. j. B.
Kincer, chief of the Genealogical divi-
sion of the United States Weather
Bureau.
In this period, for example, the annual
rainfall in Minnesota has declined 20
per cent and in Iowa and Missouri about
II per cent. In Arkansas and Louisiana
it has risen slightly less than one per cent.
If this trend continues for another
two or three decades, says Mr.. Kincer,
it may become a serious factor in Amer
ican agriculture. 1t manifests itself in
both wet and dry years. The marked
difference between the two sections of
the country, he points out, shows the
fallacy of trying to predict rainfall cycles
for the country as whole.
Particularly surprising, he says, is the
record for Minnesota. 1T brings to
mind" he stresses, numerous sugges-
tions that have been made in recent
years that the construction of ponds
or small lakes in relatively dry areas
would, through evaporation, replenish
atmospheric moisture and result in in
creased rainfall. Minnesota is the pre-
mier lake State, but we find it showing
the greatest decrease in precipitation
during the recent drought period. If it's
10000 lakes were not effective, why con-
struct ponds in other areas? They might
have value for other purposes, but they
would not change the climate materially.
Again, much has been written re-
Gently with regard to the relation of lake
levels and Sedimentations in distant
countries, such as Africa and Scandi-
navia, to tree rings in the Western
United States. Responsible investigators
realize that such records could apply
only TO the particular area in which
they are found, but unfortunately many
have gained the impression that records
of lake levels in Africa or tree levels in
Arizona are valuable as climate indica-
tors for other and distant areas If so,
to which State would such cycles apply,
Minnesota or Arizona?
The United States, says Mr.. Kincer,
can be divided roughly into three rain
fall districts:
l. All States from the Rocky Noun
tainS westward
2. All States between the Rockies and
the Mississippi, including Montana.
3. All States east of the Mississippi.
The average rainfall for district one
is 179 inches, for district two e inches
and for the Eastern division 43.5 inches.
Analysis of these year by year shows
striking changes, he points out.
In area one the period l889-l897 had
mostly above normal rainfall, followed
by six years deficiency. Then, starting
with 1904, the general tendency was
markedly above normal up to 1916. 1t
remained above normal until 1928. when
an extremely dry period started. lasting
until 1885. All but one of the past five
years had above normal precipitation.
Area two showed mostly below normal
rainfall from 1889 to 1904, followed bv
abundant moisture, except for a few drv
years, until 1925. The wetteSt year was
1915, with 25 per cent above normal,
and the dryest was 1917, with 25 per cent
below. West of the Rockies the wettest
year was 1906 and the dryest 1924.
The area east of the Mississippi is
characterized by small variations from
year to year, and relative absence of
prolonged drought periods The wettest
year was 1929. with IA per cent above
normal, and the dryest 1880, with 20
per cent below normal. Thus, the maxi
mum amplitude of the wet-dry shifts
has been IS per cent compared with so
per cent in area two and So per cent
in area three.
On the whole, Mr.. Kincer SAYS. the
shifts in area two correspond most
closely to those of the United States as
a unit.
The newly discovered North-South
variation, however, seems to affect all
three areas alike. Meteorologists can
find no physical reason for it, but it is
shown clearly in the accommodating statis-
tics and seems to grow more pronounced
from year to year.