Cooperation
between the Weather Bureau Flight Advisory Weather Service and the
Army Flight Service was maintained at a high level throughout the
period. Civil Aeronautics Administration also cooperated in providing
space in Air Traffic Control quarters for the Flight Advisory Weather
Service units. During the early part of the period the methods of
operation and the efficiency of the system were largely dependent
upon arrangements worked out locally by the individuals of each unit.
The Flight
Advisory Weather Service staff was recruited largely from Weather
Bureau personnel with several years of experience in airway weather
work. A limited number of those assigned to Flight Advisory Weather
Service had previous airway forecasting experience. The emergency
nature of the inauguration of this program made it necessary to draw
personnel from these sources, and for the most part results were satisfactory.
Ideally, however, each Flight Advisory Weather Service forecaster
should come to his position with some previous experience at an airway
forecast center.
Research
projects directed towards the solution of local airway forecast problems
and a better understanding of short range forecast techniques will
be mutually helpful to Flight Advisory Weather Service and to the
airway forecast program.
The amount
of traffic reached such proportions by the end of the war that it
was difficult to provide individual attention for each clearance and
flight plan. If traffic should again approach these proportions the
method of operation might well be improved by the introduction of
some form of route forecasts to handle the bulk of the traffic. This
procedure would free the forecaster of much of the routine load and
would permit him to devote more time to the individual problems of
pilots who plan flights which are out of the ordinary. Consideration
should also be given to means of providing the Flight Advisory Weather
Service forecaster with completed weather maps and charts in order
to permit him to devote his full time to answering the questions and
solving the problems brought to him. The most promising solution appears
to be some form of facsimile transmission from the forecast center.
Protection
for International Aviation.-United States international aviation
activity prior to 1942, consisted of two flights weekly by Pan American
Airways to Ireland, one flight weekly to Ireland by American Export
Airlines, and service for British Overseas Airways Corporation, making
two flights weekly to the United States. Pan American Airways also
made flights to and from Mexico and the Carribean, but provided its
own communications and weather service. As a party to the Transatlantic
Air Service Safety Organization (TASSO) the United States was providing
weather service at New your (La Guardia Field) for transatlantic operations.
The transatlantic forecast unit at La Guardia made route and terminal
forecasts, briefed pilots, and exchanged reports, analyses and forecasts
with Canadian and Irish forecast offices.
The vessel
weather stations that had been established in the North Atlantic supplied
surface, pilot balloon and radiosonde reports on a regular schedule
to New York for use in forecasting. Commercial ships also furnished
surface weather reports. International exchanges of weather information
were received currently from Canada, Greenland, Iceland, the British
Isles, Europe and the Atlantic Islands. By teletype, the La Guardia
office received United States weather reports.
Before
the United States entered the war, it was difficult to obtain sufficient
weather information to make reliable maps from which to furnish forecasts.
Radio silence by ships at sea, to protect themselves from detection
by submarines, and enciphering of weather information by the belligerents
reduced very seriously the amount available.
After
we entered the war all of the weather information available came to
hand through arrangements with the Allied meteorological services.
Since all weather information fell under security regulations, it
was necessary to provide increased staff to encipher and decipher
weather messages. It was also necessary to revise the TASSO arrangements
as weather information supplied by radio to aircraft in fligh had
to be transmitted in a secure form and yet not be subject to misinterpretation.
The participation of Ireland, a neutral nation, in the TASSO service,
also led to difficulties in the matter of exchanging restricted weather
information, which was necessary for the protection of flights of
commercial aircraft.
A meeting
of representatives of the United Kingdom, Canada, Ireland, and the
United States was held in Dublin in April 1942 to discuss these problems.
It was called on short notice and no United States technical or military
representatives attended. Accordingly, at the request of Canada, another
meeting was held in Ottawa, Canada, in September of 1942. The Weather
Bureau was strongly represented, and military and State Department
representatives were also there. Considerable progress was made with
regard to the procedures, under wartime conditions, for furbishing
meteorological communications and air traffic control services to
the commercial air lines which were operating wholly in furtherance
of the war effort.
A further
conference on the same subject followed immediately afterward in Washington,
under the guidance of the Combined Meteorological Committee of the
Combined Chiefs of Staff. At this conference, the necessary coordination
between the military, commercial, and civil activities with regard
to transatlantic flying was achieved.
During
the war years, the Weather Bureau participated in arrangements for
and furnishing of service for international civil aeronautics, and
, in addition, furnished material assistance in the operation of Army
and navy air transport. The map, Figure 17 shows the routes and places
from which service was furnished.
Research
in Meteorology.-A list of the research projects conducted in
the fields of Short-Range and Local Forecasting, Rainfall and River
Forecasting, Verification and Error Analysis, Climatology, Analysis,
Observations and Instruments, Meteorological Physics, and Dynamical
Meteorology as well as the field of Extended and Long-Range Forecasting
is in the Archives. Only the most important of the projects will be
discussed here.
Under
joint support and direction by the Army, Navy, and Weather Bureau,
an extensive study was made of the formation of stratus clouds along
the coast of southern California. It was expected that the results
of this study would be of considerable value in forecasting stratus
cloud formation on the coasts of pacific Islands and at other coastal
areas where stratus ceiling conditions are an important factor in
planning military aircraft operations. Many observations were made
in connection with this study that had been almost entirely lacking
in previous work. The Army and Navy furnished personnel as well as
airplanes, blimps, and captive balloons for reconnaissance, and other
special observational equipment. The Weather Bureau furnished radiosondes
for frequent soundings. The project was operated by the University
of California at Los Angeles, and the results were published jointly
by the Army, Navy and Weather Bureau.
Another
joint project was carried out by the Massachusetts Institute of Technology,
with the object of studying the development and movement of pressure
and flow patterns at the 10,000-foot level in order to derive more
reliable forecasting techniques. Study of the influence of various
disturbing factors on the movement of pressure patterns led to the
conclusion that thermodynamical factors are as important as dynamical
factors in controlling atmospheric flow at the 10,000-foot level,
and that temperature measurements aloft are as necessary as pressure
measurements for forecasting.
Only
a beginning was made during the war on a project to provide more detailed
and specific information on the movement and development of cyclonic
and anti-cyclonic pressure centers for the Northern Hemisphere. The
location, direction and speed of movement and other pertinent information
about Lows and Highs were tabulated from the 40 ½ years of Historical
Northern Hemisphere Sea Level Maps, and frequency summaries were prepared
from part of this material for the Pacific and European theaters of
war. This project had the joint support of the Army, Navy and Weather
Bureau, and was carried out in part at New York University, as described
hereafter.
Another
group of projects was of especial importance for furnishing weather
information for war purposes. A discussion appears elsewhere on the
preparation of synoptics daily weather maps for use in connection
with the war. This discussion refers to the preparation of normal
values and frequency distributions of some of the weather elements.
A set
of maps was prepared and published, showing for each month the normal
isobars and isotherms for the levels of 10,000 and 20,000 feet and
10, 13, 16 and 19 kilometers above sea level. The charts covered as
much of the Northern Hemisphere as could be represented by observed
data or by reasonable extrapolations from observed data. Most of the
work was carried on at New York University with joint support by the
Army, Navy and Weather Bureau. The title of the publication is "Normal
Weather maps, Northern Hemisphere Upper Level," published by the U.
S. Weather Bureau in October 1944.
This
project was extended to provide maps of normal values of wind speed
and wind direction for the same levels and for practically the entire
Northern Hemisphere, and to provide vertical cross-sections, from
the surface to 19 kilometers along every 20th meridian,
showing monthly normal values of temperature, density, west-east,
and southnorth components of the wind velocity, and altimeter correction
over the Northern Hemisphere. These charts were not published.
In addition
to data on average or normal values of wind, temperature, and pressure
at high altitudes, the Army and Navy found need for maps of the extreme
temperatures and extreme winds that might be expected. Extreme temperature
maps were prepared the basis of the highest and lowest temperatures
that had been recorded at observation points over the Northern Hemisphere,
plus a considerable degree of statistical smoothing and extrapolation.
These maps were published under the title "Extreme Temperature Maps,
Northern Hemisphere Upper Level," by the U. S. Weather Bureau in July
1945. This project also was carried on at New York University with
the joint support of the Army, Navy and Weather Bureau.
Frequency
distributions of winds at upper levels were computed from analyzed
maps at selected points over the Atlantic and pacific Oceans, and
published in two volumes, "Wind Frequency Distribution, North Atlantic
Ocean, 6 and 10 Kilometers," September 1945, and "Wind Frequency Distribution,
Northwest Pacific Ocean, 3, 6 and 10 Kilometers," July 1945. The Army
Air Forces provided partial support for the Pacific wind project.
Historical
Northern Hemisphere Weather Maps.-In October 1941, a project
was undertaken under joint sponsorship of the Army, Navy and Weather
Bureau to investigate the possibility of entering additional weather
data on manuscript daily weather charts of the Northern Hemisphere
which had been prepared currently for use by Weather Bureau forecasters.
The purpose was to obtain a series of daily charts with more information
than it had been possible to obtain currently, which could be analyzed
in greater detail, and thus provide a series of carefully and consistently
analyzed charts covering a considerable number of years which could
be used in extending the range of forecasting, both in time and in
area. The outbreak of war increased the need for the development of
extended range forecasting on a hemisphere-wide basis and accelerated
other weather research, much of which could be implemented by such
a series of past weather records.
Preliminary
investigations having shown that sufficient data were available to
justify the preparation of a series of charts, methods of preparation
were developed and a ten and a half year series was undertaken, from
January 1929 through June 1939. War conditions limiting the available
weather data for much of the Northern Hemisphere after June 1939 resulted
in the ending of the series with that month.
The great
variety found in methods of observing and recording and in units of
measurement of meteorological elements employed by various meteorological
services of the Northern Hemisphere necessitated conversion to standard
comparable values for entering on the charts. The average number of
individual weather reports on each daily charts was about 600, so
that for each year of maps more than two hundred thousand entries
were made, each involving five or more weather elements any or all
of which might require conversion. One of the most difficult problems
encountered was that of maintaining an efficient flow of work while
using sources of data which varied in form of presentation from a
few days observations for a large number of stations to a long period
of observations for a single station. This condition was aggravated
by the fact that sources of data for foreign regions were the only
copies available and were frequently required for other projects.
The charts
were analyzed by analysts under direction of Weather Bureau meteorologists
in cooperation with university meteorological staffs. The completed
charts were printed in booklet form by months for distribution to
various weather research groups and were used in projects by the Army,
Navy and Weather Bureau.
An additional
30-year period was planned in May 1943, for which a more rapid system
of preparation was necessary in order to meet time limits set by military
requirements. Accordingly, a system of using punch cards for handling
the large amount of data was developed.
In the
early part of 1942 plans were made and an organization set up to prepare
a set of upper air charts to parallel part of the period covered by
the sea-level series. This series begins with the International Polar
Year, October 1932, and extends through 1940. In order to obtain values
of temperature, pressure and humidity at 3000 dynamic meters, for
the many sources of data for which these values had not been computed,
a large amount of involved computation was necessary. Various aids
were developed to simplify computation, such as graphs, tables, and
slide rules. The use of such aids and the separation of the work into
functions assisted in solving the problem of adapting such technical
work to untrained clerical workers. The analyzed charts were used
in original form and in the form of microfilm copies by many research
groups during the time of preparation, and a limited number of copies
have been printed in the same form as the sea-level series.
At the
request of the Army, the Weather Bureau made arrangements to obtain
and forward to the Tropical Research Center, Army Air Forces Weather
Service at Albrook Field, Panama, complete series of weather maps
issued by the United States, Mexico, Brazil, and Argentina, from 1941
on.
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