A detailed GCM study of the factors influencing the location and strength of the storm tracks

Atmospheric general circulation model (GCM) experiments are performed to assess the importance of orography, moisture supply, land-sea contrasts, surface roughness, and sea surface temperature gradients in determining the location and strength of the storm tracks. Experiments performed to date indicate that the strong baroclinicity associated with the troughs downstream of large orographic features is important in localizing the Northern Hemisphere storm tracks. Greater latent heat release over the oceans due to the moisture supply from the wet surface is also important in strengthening the storm tracks over the oceans. Land-sea contrasts appear to affect the storm tracks by increasing baroclinicity where they produce large meridional temperature gradients and by decreasing stability downstream of continents during winter. Increased surface roughness can shorten and weaken the storm tracks over the ocean, but lack of moisture is more important than surface roughness in weakening storm tracks over land. The strong sea surface temperature gradients in the Gulf Stream and Kuroshio appear to have little effect on the storm tracks. A set of idealized GCM experiments will be performed before the conference in order to more cleanly show the relative importance of these factors in influencing the location and strength of the storm tracks.