A record of the micro‐structure of a cold front

A record is presented showing the fine structure of wind speed, azimuth and inclination, temperature and water‐vapour pressure taken over a five‐minute period within which a cold frontal passage occurred. A particular advantage of the method of recording, using rapid‐response instruments, is the graphic illustration provided of the extreme sharpness of the front. The transition zone, estimated to be 70 m in horizontal extent, passed in 8 sec, during which time the temperature fell 5°C and the water‐vapour pressure increased by 2 mb. The record, together with two others taken shortly before and after, has been analysed and the results, including the mean vertical velocities, the vertical eddy fluxes of heat, water vapour and momentum, and the K values for heat are presented. Direct evidence is submitted of the vertical eddy transfer of heat, water vapour and momentum through the transition zone.