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SUMMARY:Polar lows: recent research on the dynamics of intense high-latitu
 de cyclones - Prof. Thomas Spengler\, University of Bergen
DTSTART:20151029T110000Z
DTEND:20151029T120000Z
UID:TALK62066@talks.cam.ac.uk
CONTACT:Dr. Pranab Deb
DESCRIPTION:Polar lows are severe\, maritime mesoscale cyclones\, developi
 ng over the ice-free ocean at high-latitudes. Despite recent improvements 
 in numerical weather prediction\, polar lows still represent a major chall
 enge for forecasting in polar areas. Hence\, understanding the underlying 
 dynamical pathway and identifying favourable atmospheric conditions are es
 sential to make improvements in our forecasting skills.\nWe discuss the sy
 noptic conditions in which polar lows form\, where we utilise a dynamical 
 feature of the sub-synoptic environment associated with the genesis of pol
 ar lows to distinguish between different dynamical pathways of polar low d
 evelopment and determine the characteristics of those environment. Based o
 n the angle between the thermal wind and the mean wind\, two subsets of po
 lar lows are identified: forward-shear polar lows\, where the thermal and 
 mean wind are in the same direction\, and reverse shear polar lows\, for w
 hich the thermal and mean wind are in opposing directions. Both environmen
 ts are equally likely associated with polar low development. However\, the
  environments exhibit distinctly different synoptic and sub-synoptic confi
 gurations. \nFurthermore\, we present idealised simulations to examine the
  influence of moisture\, baroclinicity\, and static stability on developme
 nt utilising an idealised baroclinic channel model. The experiments show t
 hat disturbances are able to amplify in the absence of an upper-level pert
 urbation\, surface fluxes\, friction\, or radiation. Separation between de
 veloping and non-developing disturbances is feasible by considering the ba
 roclinic and diabatic contributions to eddy available potential energy. De
 veloping disturbances show a clear diabatic dominance during the early sta
 ge of development. A comparison with the conceptual framework of the Diaba
 tic Rossby Vortex (DRV) growth mechanism provides insight into the dynamic
 al pathway potentially underlying the enhanced amplification. We also iden
 tified threshold values for moisture content and baroclinicity.\n
LOCATION:British Antarctic Survey\, Room 330B
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