Geoscience Reference
In-Depth Information
Some early studies of Arctic fronts include those of Reed (
1960
) using Northern
Hemisphere weather maps; R. Bryson (
1966
) using streamlines and air mass anal-
ysis for North America; and R. Barry (
1967
), who as a young and enthusiastic
researcher examined the preferred location of Arctic fronts over North America for
January, April, July, and October using the Canadian frontal analyses. In a study for
Eurasia, S. Krebs and Barry (
1970
) took a somewhat different approach of plotting
the northernmost frontal boundaries depicted on Northern Hemisphere daily syn-
optic weather maps for July 1952-1956 to determine the median location, as well
as the quartiles and outer deciles of the latitudinal distribution of fronts in relation
to the forest (the tundra ecotone). They also analyzed the latitudinal gradient of
1,000-500 hPa thickness.
In the Canadian three-front model, Arctic fronts were objectively differentiated
from polar fronts. But what if one instead plotted on a map the location of all fronts
over some time period? Would one find geographically-preferred regions of high-
latitude frontal activity separate from the major locus of polar fronts? That this is
indeed the case finds its origins in the remarkable study of Dzerdzeevskii (
1945
)
and a subsequent paper by R. Reed and B. Kunkel (
1960
). The latter study was
based on fronts plotted on summer (June-August) sea level pressure analyses for the
1952-1956 period. It revealed a belt of high frontal frequencies extending along the
northern shores of Siberia and Alaska and southeastward across Canada. Reed and
Kunkel argued that low frontal frequencies over Kamchatka and the high frequen-
cies off Japan “make it abundantly clear that the polar front remains separate from,
and well to the south of, the Arctic frontal zone” (p. 496). Their analysis of winter
frontal frequencies failed to show a separate high-latitude feature. Consequently,
the Arctic frontal zone as a geographical feature was considered to exist in summer
only, in agreement with Dzerdzeevskii (
1945
). We will return to the problem of the
Arctic frontal zone later.
Investigation of stratospheric dynamics only became possible around 1960 when
a sufficient number of sounding balloon ascents began to reach the 25 hPa level
(~25 km) and higher on a routine basis. The first detailed characterizations of the
circulation in the Arctic stratosphere were prepared by the Arctic Meteorology
Research Group at McGill University (Hare,
1960a
,
1960b
,
1961
) and the Institute
of Meteorology at the Free University of Berlin under R. Scherhag (
1960
). R.
Murgatroyd (
1969
) presents an early overview of stratospheric structure and dynam-
ics based on balloon and rocket data. Efforts were intensified through the Climatic
Impacts Assessment Program in the United States in the 1970s, owing to the need
to assess the effects of supersonic aircraft on the stratosphere (Reiter,
1975
). From
the late 1970s onward, the availability of data from satellite sounders has greatly
augmented our knowledge of the structure and composition of the stratosphere and
the problem of stratospheric ozone depletion. In the past decade, it has become
increasingly recognized that the circulations of the stratosphere and troposphere are
intimately connected, and that these connections may be an important component
of Arctic climate variability.
