PDF, 5.8 MB - Arctic Climate System Study

Recent Advances in our
Understanding of Polar Lows
John Turner
British Antarctic Survey
Cambridge, UK

Outline
• The polar low spectrum
• Occurrence
• Modelling studies
• The possible climatological importance
of polar lows
• Future research needs

The Nature of Polar Lows
• Occur poleward of the Polar Front
• Mesoscale

Reverse Shear Polar Lows

The Boundary Layer Front
Type of Polar Low

A Cold Core Vortex Polar Low
Over the Labrador Sea

Woetman Nielsen’s Case ‘P’ 13-16 October 1993
Image taken at 13:49 GMT 14 October
1993
Norway

A 48 h forecast of
MSLP and 10 m wind
vectors using the
Danish HIRLAM
model.
Data time 00 14 Oct 93
Verifying 00 16 Oct 93

Surface analysis at 00
GMT 16 October 1993

Possible Climatological Importance
• Individual polar lows can have fluxes of heat
of up to 1,000 Wm**2
• The loss of heat from the ocean could
trigger downward convection in the ocean
• But the frequent occurrence of polar lows
would be needed in an area for this to be
of climatological importance
• Modelling studies are needed to assess
their importance

Future Research Needs
• Little published on systems over the Chuckchi and
Kara Seas
• Climatological occurrence still poorly understood.
Could be addressed by studies with high
resolution analyses or satellite imagery
• Still debate over how convection acts to intensify
the lows – CISK, WISHE
• Greatest insight into polar lows can be obtained
from high resolution model runs, which can also
contribute to forecasting of the lows