... C 1 and C2.(a) α 12 =0,(b) α 12 = 1, (c) α 12 =2C 1 C2C=Fig. 3 .10 . Decomposition of a knotted vortex filamentcan go through C 1 an integer number of times (Fig. 3.9c), so that Γ 1 = α 12 κ2,where ... study of Casey and Naghdi 19 91) . Then by (2 .1) , (3 .10 7), and (3 .10 9), we have∂Ω∂τ= 0 orωρ=ω0ρ0· F, (3 .13 3b)known as the Cauchy vorticity formula. Thus, the Lagrangian vorticity isstationary ... Rossby (19 36, 19 40) and Ertel (19 42), governed by (the name will be explained in Sect. 3.6 .1) DDtωρ·∇φ= 1 ρ(∇×a) ·∇φ,DφDt=0. (3 .10 6)Because (3 .10 6) is the simplest form of (3 .10 5),...