Evening star. [volume] (Washington, D.C.) 1854-1972, 1930-09-14

1.-The second way to get the warm air up is to
have a mountain chain, up the sides of which
it must travel In order TO flow to the other side.
Cooling takes place near the mountain tops.
The Sierras, in California, the highest noun
tains in the United States, are responsible for a
great deal of rainfall in the Summer and for
heavy falls of snow in the Winter, the drifts
sometimes piling as high 40 feet But there
are no very high mountain chains in the East
ern or Central portions of the country to aid the
process of precipitation
The third way and that which is most eff
fective in causing rainfall throughout the Gen.
trail and Eastern parts of the United States, is
brought about by air circulation The warm,
moist air from the tropics more directly from
the vicinity of the Gulf of Mexico and the
Caribbean. moves along the line of least
sistance up the broad Mississippi Valley region
to meet the cooled air from the Arctic, which
IS moving southwark down the central part of
the country.
Naturally, where the two come together the
warm, moist air rises as the cooler air sinks and
circulation is produced. This tendency is
greatly increased by the rapid movement of the
air caused by the rotation of the earth from
is lighter, would more easily be thrown to the
east while the cool, heavier air tends to TOW
to the west
SPTNHESE air currents behave much as you
and I might we tried to maintain our
balance a swiftly rotating turntable. They
tumble over themselves and get In tangle.
The warm air slides up to the top where it
becomes cold and releases its vapor rainfall.
In this Interchange Of air currents, storms both
general and widespread develop Local condi-
tions make the circulation of the current more
vigorous in ono place than in another, which
in a measure determines the local character of
certain rains.
During the average year Central United
States and Canada are the happy hunting
ground OF the air currents that travel down
the Mackenzie Basin and Hudson Bay regions
of Canada to the mississippi Basin and of the
warm moisture-laden air from the equatorial
region. But this year the interchange of cold
and equatorial air has been limited over the
Central United States. The cold air has
drained down from the Arctic over other parts
of the world-over Europe, East China, Korea
and the rainfall has been exceptionally heavy
in those places. The usual circulation of air
around the United States has been absent.
The stagnation best explains both the preva-
Ience and the persistence of the drought
why it happened that way we do not know.
Why those countries got the rainfall and we
failed to receive our normal supply may not
be known for many years to come, when our
knowledge of meteorology, weather conditions,
air currents from the Arctic and Antarctic is
much more comprehensive than it is today.
1.-THE heat we have had during the Summer
of 1890 is result of the drought The drought
IS not the result of the heat When a region
has not been rained on, it heats up. As long as
water is there the evaporation tends to cool
it of, but If it is already dry it simply gets
hotter. If you put q wooden bucket of water
and ball of metal out in the sunshine, the
water irP the bucket will remain fairly cool
because of the evaporation, but the metal gets
hotter the longer the shines upon it. So
it is with the surface of the earth.
THAT in a measure explains why it has
been almost as hot in the Northern sections
of the great central valley of the United States
as it has been in the Southern parts. Where
there have been local conditions which might
cause some evaporation and cooling of the
air. the showers have been local in character.
If you bring large block of ice into warm
room, some circulation of air is created in the
immediate vicinity of the block of ice. The
warm air from the far corners of the room
does not rush toward the ice block, how
ever. The same principle holds true with the
circulation OF air in the immediate vicinity OF