P-VECTOR METHOD FOR DETERMINING ABSOLUTE VELOCITY FROM HYDROGRAPHIC DATA

Several major techniques (Stommel-Schott method, Wunsch method, and Be rnoulli method) that have been developed to quantitatively estimate th e geostrophic velocity at the reference level, have the same order of dynamical sophistication (geostrophy, hydrostatic, and density conserv ation.) From a technical point of view, the Stommel-Schott method is a n overdetermined system (the number of equations is much larger than t he number of variables), however, the Wunsch method is an underdetermi ned system (the number of equations is much smaller than the number of variables). Based on the same dynamical and thermodynamical framework , a simple, well-posed system (P-vector method) is proposed in this st udy. Consistent with geostrophy, the system is assumed non-dissipative . The conservation of mass and potential vorticity leads to the condit ion that the velocity vector is perpendicular to both density (p) and potential vorticity (q=f partial derivative p/partial derivative z) gr adients, and that the velocity can be represented as V(x, y, z) = r(x, y, z)P (x, y, z), where P = (del p X del q)/\del p x del q\. The unit vector, P, is computed from the density field, and the parameter r(x, y, z) is determined by the thermal-wind relation. Furthermore, an err or reduction scheme is also proposed in this study.