APPENDIX A: METEOROLOGICAL ANALYSES
OF THE PEGASUS RUNWAY SITE
AUSTIN HOGAN
creases slightly as wind speed increases in the
INTRODUCTION
easterly sectors, but temperatures less than 30C
Glacial ablation areas are attractive as sites for
were recorded concurrent with all wind speeds
Antarctic airstrips (Mellor and Swithinbank 1990).
less than 11 m/s. A seeming anomaly of the Ross
These areas are characterized by net loss, rather
Ice Shelf is that relatively warm air arrives on
than accumulation of snow in the recent climatic
strong winds from the polar direction. Storm
winds with air warmer than 20C and speeds of
era, and usually they display relatively even ice
surfaces with good load bearing capability. Of-
11 to 21 m/s are relatively common in the south-
ten, strong winds are responsible for keeping these
east and south sectors in September.
areas snow free. The same winds characteristic of
October, and sometimes early November,
many ablation areas may possibly be sufficiently
present weather that frustrates air operations at
frequent to make use of such an airstrip challeng-
McMurdo. At the Pegasus site, winds are some-
ing or dangerous. However, the strong winds may
what stronger than at Williams Field, and sub-
zero (F) air accompanies fair weather winds until
diminish in the brief Antarctic summer, allowing
an airstrip to operate during its most needed time.
early November. Surface air then warms as fair
This Appendix discusses for the Pegasus site,
weather winds weaken, but strong storm winds
available recorded meteorological data, analysis
from the south to southeast persist, sometimes
of the fragmentary data from recent and historic
through the first week in December.
visits to the area, and an analytical approach for
The summer at Pegasus is characterized by
lower wind speeds, air temperature near 0C, and
establishing some characteristics of the spring and
summer in this region.
an absence of winds from the warm stormy south
sector. Summer coincides with the high sun, be-
ginning by 8 December, and ending shortly after
14 January. The most frequent winds are from
METEOROLOGICAL OBSERVATIONS
north to east directions, apparently influenced by
AT THE PEGASUS SITE
downslope winds from Ross Island. There is a
Concurrent with site evaluation and initial engi-
diurnal variation in wind direction on nearly one-
neering work to evaluate the Pegasus site for
half of the summer days, when westerly surface
wheeled runway potential, two AWS were posi-
winds accompany the sun's passage over the
tioned near what would be the runway ends. They
Royal Society Range. The last half of summer has
are designated "Pegasus North" and "Pegasus
even lower wind speeds, and a more noticeable
South." Data gathered by the AWS were aimed at
diurnal variation than the first half.
providing insight to the local meteorology. The
Frequent aircraft operations from the Pegasus
AWS data are quite fragmented during the late
runway should consider the following general
winter (AugustSeptember) surrounding the
meteorological trends.
WINFLY (winter fly-in) opening of the new Antarc-
Sustained strong winds occur throughout win-
tic summer season. The data become more frequent
ter and spring from the south-southeast. These
during the spring (15 October30 November), and
winds are considerably warmer than would be
are quite complete during the peak of the Antarc-
expected from examining climatic records from
tic summer (8 December14 January). The AWS
McMurdo or Scott Base, and may produce un-
designated "Pegasus North" provides the more
usual drift patterns due to their warmth. Opera-
complete data set and is used almost exclusively
tional information may be obtained by monitoring
in the following analysis.
the air temperature at AWS situated south of
Periods of calm or winds from the generally
Pegasus on the Ross Ice Shelf. Since warming
benign westerly sectors are rare during August
accompanies acceleration of the surface wind, the
and September. The most frequent winds are from
initial warming occurs on the southerly extremes
the northeast and east, and about one-third of the
of the shelf, and the wind speed increases as the
time they exceed 5 m/s. The air temperature in-
warm air proceeds north.
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