The ALOMAR Rayleigh/Mie/Raman lidar: status after 30 years of operation

Abstract. The ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research) Rayleigh/Mie/Raman (RMR) lidar is an active remote sensing instrument for investigation of the Arctic middle atmosphere on a routine basis during day and night. It was installed on the island of Andøya in northern Norway (69° N, 16° E) in summer 1994. During the past 30 years of operation, more than 20 200 h of atmospheric data have been measured, approximately 60 % thereof during sunlit conditions. At present, the RMR lidar is the only system measuring aerosols, temperature, and horizontal winds simultaneously and during daytime in the middle atmosphere. We report on the current status of the lidar, including major upgrades made during recent years. This involves a new generation of power lasers and new systems for synchronization, data acquisition, and spectral monitoring of each single laser pulse. Lidar measurements benefit significantly from a control system for augmented operation with automated rule-based decisions, which allows complete remote operation of the lidar. This was necessary in particular during the COVID-19 pandemic, as it was impossible to access the lidar from outside Norway for almost 1.5 years. We show examples that illustrate the performance of the RMR lidar in investigating aerosol layers, temperature, and horizontal winds, partly with a time resolution below 1 s.