The synoptic meaning of helicity

Summary Helicity, a scalar quantity resulting from the inner product of velocity and vorticity, has until now mostly been used in the field of mesoscale meteorology and boundary layer meteorology. Goals of this paper are the derivation of the flux form of the helicity equation in general form without neglection of friction and Coriolis force and the examination of helicity patterns of larger scales. The general helicity equation is approximated for the synoptic and frontal scale by use of the scale analysis. High helicity values are bounded to fronts, such that helicity determines their positions. Finally the helicity patterns at different heights and helicity sources and sinks are discussed for a case study of a cyclogenesis over the Atlantic.With 6 Figures