APPLIED CLIMATOLOGY 
ard climatological texts [19]. The procedure is reason- 
ably straightforward for stations in proximity. But 
how does the reliability decrease with distance? Further, 
how reliable are the techniques of constant differences 
Taste II. Approximate NUMBER OF YEARS NEEDED TO 
OBTAIN A STABLE FREQUENCY DISTRIBUTION 
Moun- 
Islands aire 
Climatic element Shore | Plains 
Extratropical regions 
Temperature................... 10 15 15 25 
SIViniG hie sace eee od ee Doo eee 3 6 5 10 
@loudinessa ce es. t ee eee 4 4 8 12 
Wiglailiig7 eos Suse ieee a see eee 5 5 5 8 
Precipitation amounts.......... 25 30 40 50 
Tropical regions 
Temperature. .................. 5 8 10 15 
JE IOUTIUC TIN ae oy boro Orc eae il 2 3 6 
@loudinessi-mn ies cin shims. 2 3 4 6 
Waistlilitveriets ms. ce + accise nil 3 3 4 6 
Precipitation amounts.......... 30 40 40 50 
or constant ratios if the two stations have completely 
different topography or exposure? Finally, suppose the 
short-record station has temperature and precipitation 
records but the practical problem requires knowledge 
of humidity, and such observations are available from 
the long-record station. How far can comparative tech- 
niques be applied? In the past, investigators have usually 
relied on the synoptic technique but have bypassed 
statistical procedures. This leaves open a fruitful field 
for future research. 
A strikingly parallel question arises when there are no 
records of any kind available for the point at which in- 
formation is desired. Major undertakings warrant the 
establishment of a temporary climatic station. The 
data thus collected can serve for comparison. How long 
should such an auxiliary record be maintained? In case 
ot microclimatic investigations a few clear nights may 
suffice in order to establish, for example, the spots in 
an orchard which are most likely to be affected by 
frost. But the problem has never been studied on a 
broad scale. 
Closely related is the general climatic question of the 
density of station networks. Should the weather services 
maintain for climatological purposes only a few climatic 
bench marks and shift other stations at frequent in- 
tervals in order to get a quicker coverage of a large 
territory? And what is the optimal distance for records 
of the different elements? [15, 74]. 
There is a need for the development of better sta- 
tistical techniques specifically adapted to climatological 
problems. The classical methods developed for genetics 
or quality control may cover some problems, but satis- 
factory as they may be for the original purpose for 
which they were designed, they are not necessarily 
universally useful. For one thing, the basic assumption 
of independence of observations underlying most of them 
is almost never fulfilled for meteorological events. Inter- 
dependence in time and space, such as persistence, is 
979 
almost always present in our data. Some work along 
this line has been done, especially as applied to singu- 
larities [6, 7, 12]. Many statistical tests are valid only 
for the so-called normal frequency distributions. Quite 
a few climatic values are not normally distributed and 
even mathematical transformations cannot always pro- 
duce statistical normality. More adequate techniques 
are gradually being developed. Attention has been given 
to theories of extreme values [39] and to the multimodal 
distributions often found in climatological work [21]. 
There is a great need for the formulation of new criteria 
of the significance applicable to climatic data. A great 
deal of the modern statistical theory of time series has 
not yet found entrance into climatological work [65]. 
Classes of Problems in Applied Climatology 
There are four major categories of problems in applied 
climatology. The major objectives of these are in the 
fields of (1) designs and specifications, (2) location and 
operation of a facility or equipment, (8) planning of an 
operation, and (4) relations between climatic and bio- 
logical processes. 
In the first class of problems we are usually con- 
fronted with a question about most frequent or extreme 
conditions. Sometimes the whole frequency spectrum 
is involved. Almost always long series of observations 
are required. In practice, wherever a good series of 
data is available, this group comprises the simplest type 
of problem. Even so, the climatic factor is usually very 
important because it often determines a major capital 
investment and the end product has to endure for a 
considerable length of time. 
The second class of problems, dealing with location 
and operation of a facility or equipment, requires gen- 
erally a greater degree of sophistication in the climato- 
logical analysis. The practical question is usually the 
choice of optimal conditions among several possibilities. 
The climatic factors are normally only one group out of 
many others which have equal or greater importance. 
The analysis will therefore have to illuminate the 
various advantages and disadvantages which arise from 
the climatic environment. Frequency distributions, ex- 
tremes, interrelations of various climatic factors, and 
their relative importance must be presented to the 
chent. 
At the present time perhaps the greatest demand 
upon the climatologist is for an interpretation of cli- 
matic factors that enter into the third class of prob- 
lems, the planning of an operation. This demand grew 
out of wartime experiences when weather conditions 
affected every military operation. In the absence of 
reliable long-range forecasts the chances had to be 
assessed on the basis of climatic risks. The peacetime 
applications are as numerous as the military ones. The 
basic climatic problems of strategic bombing, for ex- 
ample, are not much different from those of long- 
distance commercial airline operations; the climatic 
conditions affecting the logistics for maintaiming an 
army in the field are essentially the same as the in- 
dustrial distribution problems of peacetime; the 
weather influences on soil trafficability for military 
