Extratropical Dynamics

Understanding the location and strength of the mid-latitude storm tracks and their mutual interaction with stationary and low-frequency waves is a central problem in dynamical meteorology.  This complex of issues has risen to special importance for projecting future regional climate changes.  We are attacking these issues from a variety of perspectives:

• Understanding the structure of the mid-latitude storm tracks

• Expansion/contraction of circulation in response to global warming and the ozone hole

Observations suggest that the mid-latitude surface westerlies have moved polewards in recent decades, most clearly in the Southern Hemisphere.  Models indicate that both increasing ocean surface temperatures and the ozone hole are capable of generating shift.  The dynamical mechanisms by which both of these agents cause the circulation to expand polewards are being investigated.

• Orographic gravity wave drag

It is well-known that small scale features in the orography of the Earth’s surface, features that are sub-grid scale in global atmospheric models, can generate substantial drag on the west-to-east flow in the mid-latitude atmosphere, modifying the atmospheric circulation in important ways. We are workng to improve representation of this effect in our models. 

• Polar lows and the meteorology over the sub-polar North Atlantic