Potential spicity: the winding road in search
Prof. Ruixin Huang
Woods Hole Oceanographic Institution, USA
Isopycnal analysis has been widely used in oceanography. 50 years ago, it was proposed that a thermodynamic function (spicity, 涩度) whose contours are perpendicular to those of density should be a useful thermodynamic variable. Searching for such a variable failed up till now; people gave up the hope and even said that such a function “does not exist”, and it is “devoid of physical meaning”.
We reformulated this problem in terms of a least square problem, and solved it by a two-step linearization. A nearly perfection solution is found. Density and spicity form an orthogonal coordinate system, which is a new tool in water mass analysis. First, distance between two water masses can be clearly defined in this orthogonal coordinates. Second, density-spicity curve can be used in water mass analysis. The door is now widely open and new discoveries are on the horizon.