ABSTRACT
Lunar variation in the mid-day (10–14 hrs.) critical frequencies of the F2-layer are studied for Singapore and Baguio for the periods January 1962 to December 1963 and July 1957 to July 1959 respectively. Results are presented and discussed in the light of the earlier work, with special reference to the seasonal changes in the phase of the semi-diurnal lunar component and possible reversals of phase in the range of 20–25° mag. dip.