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J ust as climate and terrain affect the strategy of 
armies, so seasonal and geographical characteristics 
of the oceans enter into the planning of the Navy. 
Today, waves and currents and ocean temperatures 
are influencing modern naval warfare in ways that 
are different but no les. real than the limitations they 
placed on the old navies of sailing ships. 
For both submarine and anti-submarine operations 
knowledge of the weather at the surface and beneath 
the surface of the sea is of vital importance. It is 
essential for strategic planning of convoy routes, 
speeds of advance, and sailing times. It determines the 
allocation of escort craft to afford adequate pro- 
tection in each operations area. It determines whether 
it is safer to use fast unescorted ships or slower 
vessels moving in convoy. And it delineates those 
areas where air escort is needed. 
Subsurface weather information is equally important 
in the strategy of submarine operations. It outlines 
the patrol areas where enemy shipping losses are 
most likely. It determines the size of the areas allotted 
to each submarine as well as the most efficient number 
of submarines that can be used in any area of opera- 
tions. It also determines the placement of submarine 
listening posts for monitoring the movements of enemy 
task groups. 
Apart from its strategic importance, information con- 
cerning the weather beneath the surface of the sea 
is a fundamental contribution to the science of ocea- 
nography upon which the development of improved 
sonar, sofar, underwater communications, and under- 
water weapons and mines is so dependent. 
The best single index to subsurface weather conditions 
is the temperature distribution in the top layers of 
the ocean. The best instrument for measuring this 
distribution is the bathythermograph (BT)—the device 
which records how the sea temperature varies with 
depth. 
Temperature-depth measurements vary, but their 
variations are not random; they vary with area and 
with time of year. If enough BT observations are 
made, the average conditions can be determined. 
Since the strategic and research value of bathy- 
thermograph information increases as the number 
of recorded BT observations’ increases, it is essential 
that ships of the Navy continue to make observations 
and to forward the resulting information to the 
Hydrographic Office. 
