In a stationary rotating system, such a quantity is constructed, that is related to the absolute vorticity component in the direction of ∇θ×u. Here, θ is the potential temperature, and u is the wind velocity. In a nondissipative and adiabatic case, this quantity is materially conserved along the streamline. By the conservation property, if the pressure increases (decreases) along the streamline, then the circulation on the {∇θ, u} plane decreases (increases) there. This quantity is the derivative of the Bernoulli function B in the direction of ∇θ. In a dissipative case, wherein the Bernoulli function is decreased along the streamline, the gradient of the Bernoulli function is generated. As a result, this quantity is increased or decreased by the dissipation, just in the same way as the potential vorticity generation due to dissipation.