HYDROMETEOROLOGY IN THE UNITED STATES 
field laboratories,? operated cooperatively by the 
Weather Bureau and the Corps of Engineers, in the 
mountainous regions of the western United States. 
Studies are currently under way on such features as the 
effects upon snow melt of varying degrees of forest 
cover, of elevation and character of the ground surface, 
and of meteorological factors. Study is also being made 
of the structure, density, water-storage capacity, and 
other variable characteristics of snow covers. Data 
available through the work done at these laboratories 
will undoubtedly lead to a great increase in knowledge 
of the processes involved in the melting of snow and, 
indirectly, of depths of snow critical from the stand- 
point of runoff. 
Wind Tides and Waves in Reservoirs. The hydro- 
meteorologist, because he is primarily a meteorologist, 
is called upon at times to investigate meteorological 
problems only indirectly connected with calculations of 
rates of precipitation. The height of a flood-control 
structure depends upon the maximum expected water 
level behind it; such a level will be caused primarily by 
maximum rainfall occurring with the most critical space- 
time distribution. If winds are blowing, however, the 
surface of the water cannot remain horizontal. Instead, 
a tilting of the reservoir surface results from the stress 
of the wind blowing across it. On the tilted surface, 
furthermore, waves develop which may have certain 
destructive effects. 
To computations of maximum possible precipitation, 
then, must sometimes be added estimates of maximum 
wind-duration values for critical directions. Information 
of this sort is usually obtained through a study of long 
series of synoptic weather charts and through statistical 
analyses of post-rainstorm wind records of weather 
stations. 
When the surface-wind system of a storm is known in 
considerable detail, as was the case with the Florida 
hurricane of August 1949 [81], the process of storm 
transposition can often be used. The process requires 
statistical studies of relations between winds at stations 
whose observations determine the surface-wind system, 
and winds over the project reservoir. The consistency 
in such relationships has generally been found to be 
quite significant. However, the assumption that a wind- 
storm of record could occur without structural change 
over a project reservoir limits the kinds of transpositions 
to be made. Theoretical investigations are needed to 
improve present knowledge of modifications in a wind 
system (e.g., of a hurricane) due to changes in place of 
occurrence, in direction of storm travel, and in character 
of the underlying surface. 
A “design”? windstorm derived, for instance, by the 
transposition method, must be converted into terms of 
water levels and wave heights for the project reservoir. 
The field of oceanography at present does not provide 
much information for the solution of such a problem. 
Relationships between surface winds, wind tides and 
2. The Central Sierra Snow Laboratory at Soda Springs, 
California; the Upper Columbia Snow Laboratory near Marias 
Pass, Montana; and the Willamette Snow Laboratory, Oregon. 
1045 
waves in shallow, inland reservoirs of limited extent, 
and the effects of a steadily changmg wind system, 
must be known before many important hydrologic 
design problems can be successfully attacked. 
Water Resources. Recent years have seen an increas- 
ing need for evaluation of water supply, especially in the 
western states. To appraise this all-important resource 
requires the combined efforts of the hydrometeorolo- 
gist, climatologist, and hydrologist. The problem is 
multifold, in that it embraces studies of rainfall, evapo- 
ration, transpiration, snow melt, runoff, and surface and 
underground storage. The hydrometeorologist is directly 
concerned with the association of wind, humidity, and 
other meteorological elements with factors involved in 
the water budget of an area. 
The process of evaporation exercises much control 
over the amount of water available for use. However, 
conversion of evaporation-pan measurements to actual 
ground- and reservoir-surface evaporation has not yet 
met with a satisfactory solution. Pan evaporation has 
been empirically related to such meteorological param- 
eters as wind and humidity, and there are theoretical 
equations expressing evaporation as a function of verti- 
cal gradients of wind and humidity. A great deal of 
work, theoretical and statistical, remains to be done, 
however, before statistics of meteorological factors can 
be combined to determine, with assurance, long-term 
evaporation losses. 
THE FUTURE OF HYDROMETEOROLOGY 
Systematic Organization and Use of Existing Data. 
There exists in the weather archives a wealth of in- 
formation requiring organization for hydrometeorologi- 
cal appraisal and research. Maximum recorded point- 
rainfall depths have been extracted from some of the 
records for some durations. For example, Shands and 
Ammerman [18] have tabulated maximum values for 
2)7 first-order Weather Bureau stations for a selection 
of durations from five minutes to one day. It would 
be desirable for many more durations to be considered. 
A maximum observed depth-duration curve for each 
station would be especially well received. Records of 
stations other than first-order Weather Bureau sta- 
tions, as well as those of foreign stations, should be 
similarly processed. 
Maximum observed values should not be restricted 
to those falling between fixed clock hours, days, or 
months. According to Jennings [8], the world’s record 
24-hr value was recorded at Baguio, Philippine Islands, 
on July 14-15, 1911. An accumulation of about 46 
in. was observed from noon of the 14th to noon of the 
next day. It is almost a certainty that a still greater 
depth could be selected from some other 24-hr interval 
during the storm period. Unfortunately, records needed 
for determination of such a greater depth were lost 
during World War II. 
The selection of storms hydrometeorologically ana- 
lyzed for DDA values by the Corps of Engineers and 
the Weather Bureau should be greatly augmented. 
For both theoretical and statistical research, there is 
