the Expedition ARKTIS-XIX/4 of the research vessel POLARSTERN ...

1. 2 Weather situation during leg ARK XIX/4b
After leaving Spitsbergen on the evening of Sept. 21 st a gale centre with minimum
pressure below 965 hPa moved from the Norwegian Sea towards the northern part of
Norway and Bear Island. Its frontal cloud belts approached Spitsbergen in early
Sept.22 nd . In the operation area of RV POLARSTERN little west of Spitsbergen close
to 79N the northerly wind became moderate to fresh. Some snow showers and light
frost was observed. In the meantime a small low developed little northeast of
Greenland which moved southeast. It caused some hours with snowfall during the
night.
Weak anticyclonic influence followed on Sept.23 rd with good flight weather conditions
and light westerly winds in the northern part of the Fram Strait only. A trough of the
low northeast of Spitsbergen approached in the late afternoon with light snowfall and
increasing northerly wind. During the night and on Sept. 24 th northerly gale Bft 8 with
isolated storm gust and light snowfall was registered. All helicopter flights had to be
cancelled. In the meantime the gale over the northern part of the Barents Sea
developed and gained its minimum pressure around 960 hPa on Sept. 25 th .
Consequently the wind increased to Bft 9 in the northern part of the Fram Strait with
a characteristic wave height of more than 5 m. Decreasing surface pressure at the
east coast of Greenland and also decreasing intensity of the gale centre east of
Spitsbergen caused weakening pressure gradient over the Fram Strait also. In
consequence the wind decreased Bft 4 from north combined with some light snow
showers. All scientific programs could be continued. On Sept. 27 th winds turned
south with beginning of warm air advection in the upper levels of the troposphere. But
snow showers were still noticed all day long in the operation area. In the meantime
the low over the eastern part of Greenland divided into two parts: the southerly one
moved to Iceland while the other approached Spitsbergen on Sept.28 th . On board RV
POLARSTERN some hours with sleet had been observed during the night but
weather conditions became better in the morning. The northerly wind increased up to
Bft 6 and the temperature dropped more than 6 degrees within 4 hours. Further on
the anticyclonic influence increased, the weather changed to fair and the wind
became light northerly on the following day. On Sept. 30 th weak pressure gradient
caused also light and variable wind in the operation area. A small low developed near
the eastern coast of Greenland and caused heavy warm air advection in all layers of
the troposphere. So in the height of 1000 m temperature increased from –10 °C up
to 0°C within a few hours. Freezing drizzle was noticed witch stopped all flight
activities. On Oct 1 st south-easterly wind Bft 8 with heavy snowfall for some hours
near the north-western shores of Spitsbergen have be observed.
On Oct.2 nd RV POLARSTERN again approached the ice-edge near 78.8 N – 00 W.
The formation of new ice had increased heavily during the last few days. In the
beginning wind blew strong from northwest, but decreased at daytime. The air
temperature dropped below minus 10°C. This caused good flight conditions all day
long. In the evening RV POLARSTERN was southbound heading towards the new
operation area.
A gale supported by parts of the ex-hurricane “Juan” moved from Iceland to the
Norwegian Sea. It gained its minimum pressure of around 975 hPa on Oct. 3 rd . The
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