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Polar Mesosphere Summer Echoes (PMSE) and Noctilucent Clouds  (NLC) have been routinely measured at the ALOMAR research  facility in Northern Norway (69° N, 16° E)  by lidar and radar, respectively. 2900 h of lidar  measurements by the ALOMAR Rayleigh/Mie/Raman lidar were  combined with almost 18 000 h of radar measurements by the  ALWIN VHF radar, all taken during the years 1999 to 2008, to  study simultaneous and common-volume observations of both  phenomena. PMSE and NLC are known from both theory and  observations to be positively linked. We quantify the  occurrences of PMSE and/or NLC and relations in altitude,  especially with respect to the lower layer boundaries. The  PMSE occurrence rate is with 75.3% considerably higher than  the NLC occurrence rate of 19.5%. For overlapping PMSE and  NLC observations, we confirm the coincidence of the lower  boundaries and find a standard deviation of 1.26 km, hinting  at very fast sublimation rates. However, 10.1% of all NLC  measurements occur without accompanying PMSE. Comparison of  occurrence rates with solar zenith angle reveals that NLC  without PMSE mostly occur around midnight indicating that the  ice particles were not detected by the radar due to the reduced  electron density

Coincident measurements of PMSE and NLC above ALOMAR (69° N, 16° E) by radar and lidar from 1999–2008