A secondary circulation is a circulation induced in a rotating system. For example, the primary circulation of Earth's atmosphere is zonal

Zonal

Zonal can refer to:* Zonal and meridional, directions on a globe* Zonal and poloidal, directions in a toroidal magnetically confined plasma* Zonal polynomial, a symmetric multivariate polynomial...

. If however a parcel of air, that moves in a purely zonal direction, is accelerated or decelerated zonally, the Coriolis force will add a meridional component to its velocity. This meridional circulation is then the secondary circulation.

See also

• Hough function
  Hough function
  In applied mathematics, the Hough functions are the eigenfunctions of Laplace's tidal equations which govern fluid motion on a rotating sphere. As such, they are relevant in geophysics and meteorology where they form part of the solutions for atmospheric and ocean waves.Each Hough mode is a...
  
  
• Primitive equations
  Primitive equations
  The primitive equations are a set of nonlinear differential equations that are used to approximate global atmospheric flow and are used in most atmospheric models...
  
  
• Secondary flow
  Secondary flow
  In fluid dynamics, a secondary flow is a relatively minor flow superimposed on the primary flow, where the primary flow usually matches very closely the flow pattern predicted using simple analytical techniques and assuming the fluid is inviscid...