The importance of non-quasigeostrophic forcing during the development of a blocking anticyclone

Non-quasigeostrophic (NQG) processes present prior to and during the development of a blocking anticyclone over the southern tip of Greenland on 21 January 1979 are diagnosed by comparing energy quantities and height tendencies determined from quasigeostrophic (QG) estimates with the same quantities obtained from more general formulations. Energetics results indicate that NQG processes strengthened the intensity of the block and a precursor explosive cyclone. The height tendency fields show that the QG calculations, which generally yielded height changes that were larger than the more general height tendency model, produced smaller height changes associated with the northward amplification of the ridge from which the block ultimately formed. Further, these smaller values were primarily due to the QG vorticity advection. This suggests that NQG vorticity advection, which usually acted to moderate the wave developments, enhanced the block development. -from Authors