Jacobian
From Glossary of Meteorology
Jacobian
The determinant formed by the n2 partial derivatives of n functions of n variables, when the derivatives of each function occupy one row of the determinant.
For the case of two functions f(x, y) and g(x, y), the Jacobian J(f, g) is sometimes also written The geostrophic advection of any scalar ψ may be written where g is the acceleration of gravity, f the Coriolis parameter, and z the isobaric contour height.