Vertical column abundance of atmospheric OH at solar maximum from Fritz Peak, Colorado

Abstract

New measurements of the vertical column abundance of atmospheric hydroxyl have been taken at Fritz Peak Observatory, Colorado, through the period of maximum solar activity of Solar Cycle 21. The OH abundance increase of about 12%/year observed since 1976 ended with the peak solar activity in 1980. The overhead‐sun column abundance increased from 5.4 × 10¹³/cm² in 1977 to 9.5 × 10¹³/cm² in 1980. The 1981 observations show a subsequent average decrease of about 3%. The seasonal average abundances for the entire 1976–1981 period show a good linear correlation with the corresponding sunspot number averages. A high‐sun enhancement of about 2 × 10¹³/cm² occurred during the 1979–1980 period; the resulting steep sec χ‐distribution has persisted into 1981.