International Polar Year 2007–2008 - WMO

impact of the targeted observations was assessed
by Irvine et al., (2009), who found that the impact of
the sondes was mixed. Only two out of the five cases
showed clear forecast improvement; the maximum
forecast improvement seen over the verifying region
was the reduction of approximately 5% of the forecast
error 24 hours into the forecast. In one of these cases,
the improvement propagates into the verification
region with a developing polar low. The impact of
targeted sonde observations on the 1-3 day forecasts
for northern Europe was evaluated using the U.K. Met
Office four-dimensional variational data assimilation
scheme and a 24 km grid length limited-area version
of the Unified Model (MetUM). Targeted sonde data
was assimilated operationally into the MetUM.
A study that focused particularly on local
communities (objective “iv” above) was Storm Studies
of the Artic (STAR, Hanesiak et al., 2010). It was not
an international IPY project, but cooperated closely
with projects participating in the IPY-THORPEX
cluster. It included enhanced observations in the
eastern Canadian Arctic and studied gap flow, airsea
interactions, orographic precipitation and
interaction of cyclones with topography etc. With
14 research flights from Baffin Island, surface- and
satellite-based instruments, STAR aimed to improve
understanding and prediction of severe Arctic storms
and their hazards. One of the more important tasks
included developing a conceptual model of storms
and associated phenomena in the region. Another
important task was to evaluate operational and model
forecasts of events to examine where improvements
need to be made and under what circumstances.
The Norwegian IPY-THORPEX project (Kristjansson
et al., submitted) sought to improve weather forecasts
of phenomena typical for the high latitudes through a
combined modelling and observational effort (mainly
objectives i, ii and iii). The crux of the observational
effort was a 3-week international field campaign out
of Northern Norway in early 2008, combining airborne
and surface-based observations. The main platform of
the field campaign was the DLR (German Aerospace
Center) Falcon research aircraft, equipped with LIDAR
systems for profiling of aerosols, humidity and wind,
in addition to in situ measurements and dropsondes.
A total of 11 missions were flown, providing unique
observations of polar lows, an Arctic front and
orographic low-level jets near Spitsbergen, the coast
of Northern Norway and the east coast of Greenland.
Two major polar low developments over the
Norwegian Sea were captured during the campaign.
One of them (3-4 March 2008) was reasonably well
predicted by operational models, while in the other
case (16-17 March 2008) the operational models had
Fig. 2.1-8. Example
of an easterly tip jet
showing QuikSCATderived
10-m winds
for the morning of 21
February 2007 (the
satellite passes are
from 0718 and 0900
UTC). The colours
show wind speed (m
s–1). The vectors are
shown every third
pixel (i.e. every 0.75°)
(Renfrew et al., 2008).
s C I e n C e P r o g r a m 147