Anomalous Abundance of Upper Atmosphere Sodium, 1964

Measurements of atomic sodium in the upper atmosphere by absorption spectroscopy with the Pepsios spectrometer on the Fraunhofer D(2) line during February to August 1964 at Madison. Wisconsin, have indicated abundances of about 10(10)/cm(2) for the late winter, about twice the values from a similar method in 1961-62. An abrupt decrease in abundance occurred during March in agreement with established seasonal behavior, but the abundance then increased anomalously in the summer to 8 x 10(9)/cm(2). The summertime increase may be related to observations of increased turbidity of the upper atmosphere, presumably caused by volcanic dust.