Brunt Vaisala or Buoyancy Frequency


N2 = (Rg/H(z)) · [ dT0/dz + (Rg/Cp) · (T0(z)/H(z)) ] = (Rg/H(z)) · [ dT0/dz + g/Cp ] = (Rg/H(z)) · sigma
where, T0(z) = <T(z,phi,lambda,t)>, i.e., temperature averaged over longitude lambda, latitude phi, and time t.
The static stability, sigma, is related to the buoyancy frequency as
sigma ident dT0/dz + g/Cp
The static stability is positive for stable conditions and zero or negative for unstable conditions.