Observations of fogs at Misawa Fishing Port in the Aomori district wer
e made with a tethered balloon system and a doppler sodar system from
15 June to 11 July in 1993. Minute analyses were made of time changes
of fags for a long period from the evening on 7 July to the next noon
and for a short period from 6 to 13JST on July. The results show that
the atmosphere at the cloud top becomes stable from the view point of
CTEI (cloud-top entrainment instability) about 2 hours before the intr
usion of the fog and becomes neutral (or unstable) just before fog dis
sipation.