Simultaneous observation of sodium atoms, NLC and PMSE in the summer mesopause region above ALOMAR, Norway (69°N, 12°E)

Based on simultaneous observations of Na density, polar mesosphere summer echoes (PMSE) and noctilucent cloud (NLC) at ALOMAR, Norway (69°N) during the summers of 2001 and 2002, we report the strong anti-correlation of sodium atoms with NLC, suggesting that in the presence of large ice particles Na is always absent, and a weaker anti-correlation of sodium atoms with PMSE, suggesting that a population of sub-visible particles also deplete Na to a varied degree. This conclusion is in general agreement with recent reports on iron and potassium atom–ice particle anti-correlation. For this study, we use data taken with the Weber Na lidar, the ALWIN VHF radar, and the RMR lidar on 8 specific days in 2001 and 4 days in 2002 plus half-monthly average variation over the summer 2001 based on all 17 days of coincident measurements.