Abstract
A three-dimensional analysis of a cold front with squall lines was made, using 6-hourly aerological data around Japan on 12th and 13th Dec.,1957. A squall front was analysed in front of the cold front, where the direct circulation was prominent. A strong southerly low-level jet was observed ahead of the cold front. Estimation of the order of magnitude of each term on the equation of motion was made, which showed strengthening or weakening of southerly jet υ was mainly due to the horizontal advection. As to the change of u-momentum, the ageostrophic wind component was large and comparable with the horizontal advection term.
The actual wind followed the geostrophic one with a lag time of several hours, which caused large ageostrophic wind components.
The pattern of the observed rain fall amount coincided with the expected one computed by the total amount of liberated heat by condensation.
