Table Of ContentMETEOROLOGICAL MONOGRAPI-IS
Volume I AUGUST 1947 Number 1
WARTIME DEVELOPMENTS IN
APPLIED CLIMATOLOGY
CONTENTS
PAGE
Fore,vord. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Types of weather problems in staff planning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Climatological techniques for military problems with reference to civilian ap-
plication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Climatology for forecasters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 33
The accumulating, processing, and filing of basic climatological data. . . . . . .. 35
Bases for a "synoptic" or "synchronous" climatology. . . . . . . . . . . . . . . . . . . .. 38
Problems associated with the presentation of climatic information ........ " 44
Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 52
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 52
PUBLISHED BY THE AMERICAN METEOROLOGICAL SOCIETY
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FOREWORD
W
AR is a practical business. I t demands practical answers to practical
questions. In time of war a scientist or technologist may be deprived
of his peacetime heritage of scholarship for scholarship's sake. Accordingly,
it has been stated that during the recent war expediency retarded important
fundamental research. Perhaps this is true; but certainly in all technical
fields, and particularly in meteorology, much was achieved in the realm of
applied science. Those achievements so recently directed to the problem
of making war can now be redirected toward highly important uses in a
peacetime world.
Throughout the war, I was associated with the AAF Weather Service,
which was charged with the mission of providing weather intelligence for all
branches of the United States Army. Thus I had the opportunity to ob
serve the immense strides that were made in the preparation and utilization
of weather information. The weather intelligence that was put to immediate
practical use fell into two categories: weather forecasts for operations, and
special weather studies for strategic and planning purposes. This paper by
Dr. Woodrow C. Jacobs deals only with the latter. The special weather
study evolved under pressure of necessity as a standard factor in all military
plans. Its development was gradual and, at first, even uncertain. We were
asked to provide answers relating to a diversity of undertakings-under
takings as complex as a complete amphibious operation or as relatively
simple as the design of a microscope for use at a remote point on the globe.
Frequently the questions concerned areas on which little or no weather data
were available; sometimes they involved the solution to theoretical problems
that even today are challenging science. Always an answer, the best pos
sible, was required. Invariably some degree of improvisation was necessary.
Each of the many hundred special studies that we made was a problem in
itself, some phase of which demanded unique methods of solution.
iii
I can think of no one who is better qualified to present a comprehensive
picture of the advances made in applied meteorology as a planning aid than
Dr. Woodrow C. Jacobs. As head of the Special Studies Research Group
within the AAF Weather Service, Dr. Jacobs directed, and in many instances
personally participated in, the preparation of weather studies used by our
armed forces throughout the world. Close cooperation and coordination
with allied meteorologists and studies of intelligence on our enemy meteoro
logical achievements convince me that the weather study as a practical tool
was as highly developed and as widely used by our armed forces as by the
armed forces of any of the warring nations. Therefore there is no doubt in
my mind that Dr. Jacobs is indeed qualified to present the paper that fol
lows. As to its merit, I am certain it speaks for itself.
DONALD N. YATES
Brig. General, U.S.A.
Chief, A ir Weather Service
IN APPLIED CLIMATOLOGY
By Woodrow C. Jacobs*
Hq. Air Weather Service, Washington, D. C.
INTRODUCTION that meant climatology. But not the climatology
W he knew in 1941.
ORLD WAR II was the greatest "battle of
During the war the demands made on the
wits" of all time. To an extent never
Army Air Forces Weather Service for climato
before approached, it was a war of technician
logical information to be used in strategic and
versus technician. Particularly is this true of
tactical planning were exceedingly heavy and
the technical use of weather. Weather has al
the requirements exacting. Although they were
ways been a potent weapon jn warfare. History
of almost endless variety, the final need in all
tells us that battles and sometimes even wars
cases was the same-the effect of weather on
have been lost because weather aligned itself with
the military operation or activity. In no case
the enemy. In this war, the intelligent exploita
was there any real requirement for pure climatolog
tion of some single weather factor often supplied
ical information as such.
the slight technical advantage which meant the
The solutions of the more difficult problems
difference between success or failure of an oper
demanded very close coordination between the
ation or campaign. But the attainment of that
meteorologist-climatologist and the military plan
technical advantage meant continuous and de
ner or designer. Sometimes the climatological
tailed long-range planning which in turn meant
approach to a particular problem was entirely
that it was impossible for the military planner to
theoretical, sometimes it was completely em
wait for a short-range forecast before incorporating
pirical; most frequently elements of both ap
the important weather factor into his plans.
Weather planning on an equally long-range basis proaches were involved. However, in all cases,
was the only answer and, to the meteorologist, a thorough knowledge of the military require
ments and specifications was required.
• Now at the U. S. Weather Bureau.
1
2 METEOROLOGICAL MONOGRAPHS VOL. I, No.1
During the early part of the war there was a tion. If climatology is regarded as the historical
tendency for some of the operating units to aspect of meteorology, or simply as the study of
make requests simply for forecasts, climatological the normal state of the atmosphere, the neces
data, or general climatological studies. Follow sity for considering the individual atmospheric
ups by the AAF Weather Service indicated that processes in all their complexity is not removed.
in a large percentage of cases the information If, on the other hand, climatology is regarded as
supplied to various agencies was grossly misused. a study of weather and its effects on man and
Specifications for fuels, lubricants, clothing, etc., his environment, an entirely new system of
were outlined on the basis of mean temperature complex variables must be added.
data from scattered stations within large areas; As a result of the "weather naivete" of the
airfield runways were oriented as directed by military planner, the AAF Weather Service was
wind data scaled from locally fictitious mean placed in the difficult position of educating the
pressure charts which were originally prepared to military to the possibilities of the use of specific
present the general features of the atmospheric weather information and, simultaneously, of de
circulation at the gradient level over a continent veloping the techniques necessary for handling
or hemisphere; flyabilities of air routes were the new problems. The latter was necessary
determined on the basis of general climatic sur because it soon became apparent that the older,
veys which often depicted only regional variations "classical" methods in climatology, consisting
in temperature and rainfall. In other cases, the of the simple presentation of climatic averages
problem was posed specifically enough, but ab or of the independent frequencies of occurrence
surd limitations were placed upon the meteorol of various weather elements, were hopelessly
ogist with respect to the form or manner in which inadequate for the exacting military needs. The
the solution was to be presented. development of an entirely new field, "applied
Although it was universally agreed that weather climatology" or "meteorological engineering,"
played a vital part in military operations, there was required
was an exasperating tendency for the various Each climatic investigation was, of necessity;
branches of the armed forces to take a simplified tailored to meet the specific requirements of the
view of the ease with which weather information problem of the moment. In spite of the 1,500
could be incorporated into military plans. It is or more formal climatic reports and results of
the writer's belief that the military planner was investigations published by the Weather Central
not primarily responsible for this attitude. Cli Division in Washington by the end of the war,
matologists for over half a century had devoted it was even then seldom possible to refer to the
their main efforts to producing simplified versions files and find a complete report or reports which
of the results of inherently complex weather phe would conform to the specifications of a new
nomena. It was an age of climatography, an problem. The writer sets forth this experience
age of climatic classifications based on regional as the best possible argument against assuming
variations in the mean values of one or two cli in the future that it is possible to prepare, in.
matic elements. Since the climatologist had led advance, climatic investigations according to
the way toward this simplified descriptive con some formal plan and expect them to come up to
cept, it was only natural that the layman should even a small fraction of the requirements of ap
follow. plication. It would seem just as unreasonable
But wartime requirements made it plain that to ask the professional meteorologist or climatol
climatology is not an easy subject. Its use em ogist to do this as it would be to expect members
bodies all of the complexities of meteorology and of other professions-engineers, lawyers, or doc
in addition, the added complexities of the applica- tors, for example-to serve the public through
WEATHER PROBLEMS IN STAFF PLANNING 3
the media of 'pamphlets and handbooks. This never be allowed to take the place of an intelligent
statement does not imply that it is impractical analysis carried on jointly by meteorologist and
to prepare formal climatic studies designed for a planner. General climatic studies which are
particular class of. users whose problems have issued by the climatologist with the implication
already been well-formulated. Nor does it im that they have a multitude of practical uses
ply that general or descriptive climatological merely invite independent action on the part of
papers are entirely out of order. The intended the layman. As a resu~t, the most common use
meaning is that formal climatic reports should of such reports is misuse.
TYPES OF WEATHER PROBLEMS IN STAFF PLANNING
A cursory examination of the requests for climato Of the two classes of problems, the first demanded
logical information to be used in long-range planning the closest coordination between the climatologist and
by the military indicates that, from the standpoint military planner. Sometimes climatological data nec
of the climatologist, the problems can be placed rather essary for the solution of the problem in quantitative
simply into two broad classes: (1) those in which terms were entirely lacking. To the extent that
specific information was required for the purpose of meteorological factors were involved, however, it
determining the effects of meteorological factors on was presumed that the climatologist was in the posi
an individual element of operation, and (2) those in tion to give the best estimate. In other cases, it was
which the information was for the purpose of de possible to evaluate the climatological factor com
termining the total effects of weather on the combined pletely in quantitative terms. As one might expect,
the great majority of problems fell somewhere between
elements of operations or on the actual combined
the two extremes.
operation itself. The climatological approaches to
The large number of problems that came within
problems of each class differed in major respects.
the limits of the first class were characterized by their
The first group of problems was concerned with the
great variety and also by the fact that they were
design and specifications of equipment and materiel
solved at a military level considerably below that of
with outlining the most effective or most economical
command. The problems were often minor, and
use of the individual item of equipment, or unit of
loomed large in the overall military picture only wh~n
materiel, personnel, or facility. Here the emphasis
taken collectively. Even a mere listing of the work
was placed upon the effects of individual weather
of this type accomplished by the AAF Weather Service
factors with secondary regard to geographical location.
during the war would be beyond the scope of this
This group of problems may also be regarded as
paper. But it can be said that climatological advice
falling within the "first phase" of planning for the
in some form or other was required whenever the
actual operation.
design, use, and distribution of equipment or materiel
The second group of problems concerned itself with was under consideration or the establishment of a
weather factors as they actually occur geographically military facility was being planned. The importance
and as they may be expected to affect the large-scale of the weather term, of course, varied greatly. In
combined military operation or the disposal, distribu some cases, its consideration was the determining
tion, and integrated use of facilities, equipment, factor in the plan; in other cases, analysis proved
materiel, and personnel. This is the "second phase" that it was relatively insignificant and could give way
in planning. to more important considerations.
The third phase called for the weather forecast In order to supply the weather information re
itself, the detailed discussion of which is beyond the quired in planning the large~scale combined military
scope of this paper. Nevertheless, it should be men operations included in the second class of problems,
tioned that the preparation and issuance of a short it was necessary for the AAF Weather Service not
or long-range forecast is one thing-but the planning only to develop new techniques in climatological
required for its intelligent use in operations is another. analysis, but to employ new techniques in the pre
In this sense, climatology serves to "set the stage" for the sentation of weather information as well. To the
weather forecast. extent that combined operations demanded complete
4 METEOROLOGICAL MONOGRAPHS VOL. I. No.1
coordination between land, sea, and air forces, there of climatic variables over the area to be encompassed
was the same need for coordinating the weather in by the operation; a knowledge of weather conditions
formation supplied to the various branches of the as they would occur simultaneously (or with appro
service involved in the operation. priate time lags) over the large area was required.
It was not sufficient to present information to the The large operation might have required simultaneous
military staffs as to how weather would affect each landings on three or four beachheads. In an extreme
part or phase of the operation. They required the case, the period when weather conditions would most
knowledge of how weather would affect the entire likely be favorable at all points might prove to be the
operation. For example, climatological data might period when favorable conditions at anyone of the
show that weather conditions favorable for an am single points were least likely.
phibious assault on a particular beach might be ex In each of the Allied large-scale operations-from
pected to occur on no less than 10 days during a North Africa, Sicily, Italy, Normandy to the Aleu
particular month, conditions favorable for ground tians, South and Western Pacific-a detailed analysis
operations on 10 days, and conditions favorable for of the effects of weather conditions upo'll all phases
support bombing on 10 days. Yet conditions favor of the operation was an essential part in planning for
able for a combined air-amphibious-ground assault the entire operation. Sometimes weather proved to
might never be expected during that particular month. be the factor of greatest importance in the operation;
Similarly, it was not sufficient to present informa sometimes it proved to be relatively unimportant, but
tion to the planner concerning the mean distribution experience proved that it could never be ignored.
CLIMATOLOGICAL TECHNIQUES FOR MILITARY PROBLEMS
WITH REFERENCE TO CIVILIAN APPLICATION
The examples of climatological investigations pre From the standpoint of the climatologist, it was
sented in the following pages have been selected from found that the techniques for obtaining the solutions
the many reports and manuscripts prepared by the of the practical military weather problems grouped
AAF Weather Service during the period 1941-1945. themselves, rather naturally, into four classes or
The purpose of this discussion is to describe and types:
illustrate the variety of climatological techniques em
(1) Those involving primarily theoretical tech
ployed rather than to present outstanding solutions
nIques.
of particularly difficult or important military prob
(2) Those involving purely statistical techniques.1
lems. For this reason, only those technical details
(3) Those involving the use of purely synoptic
absolutely essential for completing the illustration are
parameters.
included in either the description or figures. In
(4) Those which combined the theoretical, sta
several cases, military security prevents the inclusion
tistical, and synoptic techniques.
of all the pertinent information desired for the il
lustrations. 1 Reference to theoretical statistics is not implied here.
PRIMARILY THEORETICAL TECHNIQUES 5
Investigations Involving Primarily Theoretical Techniques
The rapid evolution of new methods and weapons thousands of observations covering many years of
of warfare throughout the war required of the climatol record; the charts were nicely colored; they were very
ogist a certain amount of exploration into realms readable, and otherwise quite attractive. But they
beyond the frontiers of existing observational data. had not solved the major problem concerning the
Since it was in most cases then either too late or too availability of water for life raft survivors.
early to observe, the only I;I.pproach to problems for The first climatological step in the investigation
which observational data were not available was to when undertaken by the AAF Weather Service was
use an indirect theoretical route. The rather simple to prepare seasonal charts showing the average human
example used here is not necessarily representative of water requirements for the complement of an AAF
the types of problems, but it is quite representative multiplace pneumatic life raft (five-man capacity).
of the manner of approach. These were made on the basis of the data in Table 1
The problem in this case was to determine the and the available temperature information for the
specifications for a solar-operated sea-water condenser oceans. 'N0 theoretical steps were invo lved in the
to be installed in life rafts. Several types of experi preparation of this simple series of charts.
mental stills had already been constructed in the As the second step in the investigation, it was con
laboratory and tested under known radiation condi sidered necessary to determine the fraction of the
tions off the Florida coast south of Eglin Field (ap water requirement that would be met by the use of
proximately 30° N.). It now remained to determine the one other nonexpendable source of fresh-water
whether these stills would satisfy the requirements of supply-rainfall.
field use (1). The rain-catching equipment was a 77-square-foot
Experiments had previously been conducted for the waterproof paulin, while the specific equipment issued
purpose of determining the total water intake required for water storage cons,isted of four plastic bags with
by the survivor to balance water losses at various a total capacity of five gallons, a ten-day supply at
temperatures, that is, the quantities required for bare normal temperature for five men. Because of the
maintenance. The requirements given in the follow relatively high efficiency of the rain-collecting equip
ing table were predicated upon the survivor's being ment, the limiting factors in the use of rain as a
relatively inactive, upon his taking due precautions source of drinking water proved to be storage space
to reduce water loss, and upon a low caloric intake. and the frequency and spacing of storm3 with col
The elements of time, or change of state of hydration, lectable amounts of rainfall. The total amounts of
were largely eliminated by the use of these values, rainfall were of secondary importance. Approxi
which refer to an essentially steady state. mately 0.02 inch of precipitation would supply a
one-day water requirement for the raft complement,
TABLE'l
assuming a collecting efficiency of only 50 percent.
Fresh Water Required hy Life Raft Survivors for Bare A study of available oceanic rainfall-intensity data
M~intenance at Various Temperatures indicated that the storage capacity could be com
Mean Air Temperature (0 F.) 90 80 70' 60 50 40 pletely filled by individual storms of moderate in
tensity. However, the grouping of the storms could
Water Requirements for
Bare Maintenance be such that not all of them would be useful because
(liters/day/man) ......... 2.9 1.9 1.6 1.4 1.3 1.3 of the limited storage capacity. The amount of
usable rain water varies not only with the rainfall
NOTE: Values have been determined on ,the basis of extensive
distribution, but also with the rate of consumption:
field experimentation.
To allow for loss caused by these factors, the amount
The Engineering Division, AAF Technical Service of water which would be collecte~ if the storms were
Command, who had been assigned the problem had properly distributed was reduced by a fraction
previously contacted several climatological groups and which was greatest at the lower temperatures (because
had been furnished with what the climatologist has of the lower rate of consumption) and least at the
always prepared for such occasions-a set of charts higher temperatures (because of the accelerated rate
showing the mean frequency distributions of various of consumption). Considering, then, rainfall fre
climatic elements for the world. The charts them quencies over the oceans, together with theoretical
selves were almost all that one could ask for. The information concerning the spacing and intensity
statistician would say that the means were reasonably of storms as a function of precipitation frequency and
reliable, since they were based on many hundreds' of total precipitation amounts, it was possible to compute
