The baroclinic torque, which is generated by density gradient and pressure gradient, is studied with a PIV (Particle Image Velocimetry) method. In this work, the two dimensional density gradient is formed in binary density planar boundary stratified by the gravity. The pressure gradient is introduced with penetration of a pair of two dimensional vortices into the density boundary. A series of the experiments is carried out in micro-gravity field so as to allow buoyancy-free condition. The results show that the baroclinic torque is induced on the boundary of binary density field by approaching the pair vortex to the boundary. This result indicates the possibility of numerical analysis where the baroclinic torque is introduced precisely by the discrete vortex method as one of Lagrange method at inhomogeneous density flow field.
