Evening star. [volume] (Washington, D.C.) 1854-1972, 1892-08-27
SOME WIND VELOCITIES,
Some Anomalies Which Provoke Inquiry as
to Their Causes.

Some Anomalies Which Provoke Inquiry as
to Their Causes.
From the New York Tribune
Charts have recently been published by the
United States weather bureau showing the mean
direction and velocity of the wind at large
number Of stations in this country during the
different months. They are valuable. both to
those persons who wish to study in detail the
meteorological conditions of any particular To-
cality and to students Of the general laws that
govern winds. While a majority of the results
herein embodied harmonic finely with each
other and with observations in other lands,
there are some curious exceptions which pro-
woke inquiry as to the causes to which they are
attributable
Two Of these apparent anomalies are to be
found on the Pacific coast. In most regions
lying at low levels and in temperate ATTITUDES
the wind attains its maximum velocity at the
warmest hours Of the day, that is, between
and O'Clock in the afternoon. The minimum
occurs at the coolest hours, or Just before
dawn. But Prof. Harrington's new wind charts
show that in portions of Oregon California and
Arizona, and at points even further inland, the
maximum usually occurs between 8 and d M
The cause Of this retardation may, perhaps, be
some influence exerted by the Sierras and
Rocky mountains. The system of diurnal
changes in velocity at great elevations, as upon
Pixies Peak, Is exactly the reverse of that pre-
vailing on adjacent plains. Even at the top of
the Eiffel tower. scarcely 1000 feet high, the
highest velocity Is not usually attained until 10
or III O'Clock at night, or about nine hours be-
hind the climax at the central weather office in
Paris, only sixty feet above sea level.
Another notable fact is that this same average
daily maximum exceeds the mean minimum to
a greater degree on and near the Pacific coast
than 1t does elsewhere in the United States
especially in summer. At st. Paul, Omaha
Galveston, Louisville. Buffalo, Boston and
Charleston, for instance, the highest daily
speed in winter is from IS to 70 per cent greater
than the lowest; in summer from 80 to 1876 per
cent. But at Portland, Roseburg (Oregon)
San Francisco, San Diego, Yuma (Arizona),
Boise City (Idaho) and Salt Lake City the in
crease in winter is nearly or quite 100 per cent,
while in July it ranges from $50 to $50 per cent
in most cases; at Roseburg it averages 900.
That the geographical features Of the western
part OF the continent in a measure account for
this difference is clearer than their share in
producing retardation of maxima. 1t has
been pointed out by Laughton that the phenom-
enon known az the 'sea breeZe'-a light wind
often observed in summer setting inshore in
the warmer part of the day-prevals to q
greater extent where the coast thus visited has
mountain range for its background. The
unequal effects OF solar heat upon land and sea
surfaces. to which is due this atmospheric in
flow, appears to be more conspicuous with
highlands than lowlands. The usual sum-
mer wind on the Pacific coast is q true
sea breeze and the conditions mentioned
by Laughton as promoting it are
there admirably afforded. What is true
of the effect of mountains upon a breeze which,
If it could be separated from all other atmos-
pheric motions, would last only few hours at
a time, is also true of that continuous, though
gentle, monsoon-like wind which in summer
flows night and day from the permanent areas
of high barOmetric pressure lying over the
ocean toward the great stationary continental
low areas. The Coast range, Sierras and Rock
les and no doubt the vast mountain plateau,
thus operates with double effect at the warmer
period of the year. 1t will be remembered,
moreover, that in our ATTITUDES there is a broad,
deep, permanent air stream flowing around the
world almost due eastward. Over the oceans it
dips to the surface of the water most Of the
time, and even over the continents its under
side is rarely more than q mile or two from the
earth. The tendency of this great current
would be to accelerate by friction any atmos-
pheric movement going on underneath it in the
same direction. such as the monsoon and sea
breeze Of the Pacific coast, but to retard such
as proceeded in n nearly contrary direction, the
southeasterly winds that favor the Atlantic sea-
board in summer, for instance.
These and some other peculiarities Of Ameri-
can winds revealed by the charts in question
deserve, and will no doubt receive, careful ex-
animation.