ODM2 Units Type Controlled Vocabulary ODM2 Working Group A vocabulary for describing the type of the Unit or the more general quantity that the Unit represents. Potential vorticity Potential vorticity (PV) is a quantity which is proportional to the dot product of vorticity and stratification that, following a parcel of air or water, can only be changed by diabatic or frictional processes. It is a useful concept for understanding the generation of vorticity in cyclogenesis (the birth and development of a cyclone), especially along the polar front, and in analyzing flow in the ocean. [Wikipedia: https://en.wikipedia.org/wiki/Potential_vorticity] Fluid Mechanics UDUnits http://dbpedia.org/page/Potential_vorticity