"There is no doubt the middle of the Barrier is
a pretty awful locality," wrote Scott.
Simpson, in his meteorological report, has little doubt that the
temperatures met by the Polar Party were abnormal. The records "clearly
bring to light the possibility of great cold at an extremely early period
in the year within a comparatively few miles of an open sea where the
temperatures were over 40 degrees higher." "It is quite impossible to
believe that normally there is a difference of nearly 40 degrees in March
between McMurdo Sound and the South of the Barrier." The temperatures
recorded by other sledge parties in March 1912 and those recorded at Cape
Evans form additional evidence, in Simpson's opinion, that the
temperatures experienced by Scott were not such as might be expected
during normal autumn weather.
Simpson's explanation is based upon the observations made in McMurdo
Sound by sending up balloons with self-recording instruments attached.
These showed that very rapid radiation takes place from the snow surface
in winter, which cools the air in the immediate neighbourhood: a cold
layer of air is thus formed near the ground, which may be many degrees
colder than the air above it. It becomes, as it were, colder than it
ought to be. This, however, can only happen during an absence of wind:
when a wind blows the cold layer is swept away, the air is mixed and the
temperature rises.
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