Dynamical processes related to cyclone development near Greenland

A cyclone that caused heavy snowfall and winds exceeding 30 m/s over E-Greenland and N-Iceland on 20-21 September 2003 is investigated. Numerical simulations are conducted to assess the role of Greenland's orography for the development, as well as to evaluate the significance of other factors such as latent heating, SST and SST gradients. The simulations reveal that the cyclone evolution is strongly affected by the orography of Greenland. When orography is removed, a deep, well organized baroclinic low develops rapidly and moves eastward at 75°N. Conversely, in the control run the evolution of the primary baroclinic low is greatly suppressed by the orographic retardation of the warm air ahead of and the cold air behind the low. At the same time, a secondary low off Greenland's east coast at 68°N intensifies due to a coupling between an approaching upper level PV-anomaly and a lower level PV-anomaly generated from lee effects. This secondary low then moves eastward and causes extreme weather conditions, as observed. Further sensitivity experiments show that latent heating contributes to deepen the low, while SST gradients and SST in general contribute relatively little.