Abstract
A family of remarkable mesoscale disturbances was observed on the western side of the cold vortex of smaller scale which had passed the central Japan on January 16, 1965. The cold air is bounded by a steep inversion layer and the mesoscale undulation is superposed on its western slope. By the special aerological observation network whose covering area is about one fifth of the routine network, a characteristic wind field is revealed. It is convergence and cyclonic vorticity in the lower part and divergence and anticyclonic vorticity in the upper part of the cold air and it implies a mesoscale convective system. Correspondingly lower level depression and upper level high are found in the pressure field.
A series of disturbances of a 2-3 hour period which moved eastward with a velocity of 85 km/hr and was closely related to the precipitation was revealed in the surface pressure field. Detailed quantitative analyses were made on the pressure and wind anomaly field. The analyses were obtained by applying the 2.5hr running mean in order to pick up the disturbances mentioned above. The scale of disturbance was found to be of the order of 250×108m2. The convergence area followed the pressure depression with positive vorticity area to the south and negative vorticity field to the north. Thus the principal balance of the vorticity equation was established between the vorticity change and the twisting term. While the balance of the divergence equation was approximately obtained between the divergence change and the pressure field as was suggested in our previous paper. However a discrepancy was observed mainly in the convergent area. This fact is well explained by introducing the effect of cumulus convection activity in that area.
