• Some properties that contrast with frontal cyclones:
  1. do not form along a front: but instead form well back in the cold air sector behind a cold front.
  2. smaller in size: typically 500 km instead of 2-4000 km
  3. shallower, detectable mainly in lower troposphere, say below 400 mb elevation.

• Common properties of their environs:
  1. conditionally stable lapse rate (a moist layer with a psuedo-adiabatic lapse rate -- add a little heat or force the airmass to rise and convection can be vigorous)
  2. cold air advecting over a warm (typically ocean) surface (creates the unstable lapse rate in lower troposphere)
  3. strong low level "baroclinicity" (horizontal temperature gradient) may form near a "boundary" (such as a coastline, or the edge between open sea and sea ice.)

• Spotting polar lows:
  • in satellite pictures: a distinct comma-shaped cloud behind a larger low pressure system cloud mass. e.g. fig 10.14.
  • look for trough in sea level pressure, or 850, or 700 mb heights.

• Examples:
  • in Carlson: figs 10.14, 10.15
  • in room 124 HH computers: look in the "PolarLow" sub-directory under "atm111" on the shared "e drive" of computer ATM50. The polar low directory has a variety of charts & imagery for a polar low off our coast in November 1997.
  • in Bader et al 1995 book Images in Weather Forecasting, a Practical Guide for Interpreting Satellite and Radar Imagery: see section 5.6 starting on p. 331. Most of these are at very high latitude however.

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