Vertical Distribution of Sodium in the Upper Atmosphere

The sodium twilight has been observed over the period October 1958 to December 1959 with a birefringent photometer. Abundances and vertical distributions have been found for 120 twilights. The abundance variation is similar to that found previously but is more nearly symmetrical about the solstices. A small seasonal variation in peak height is found, 3 to 5 kilometers with maximum in March. In general, changes in abundance cannot be correlated with changes in distribution; however, a few exceptions to this were found in June and July, when a large overnight increase in abundance accompanied a large decrease in the height of the whole distribution.