Mesospheric Temperature During the Extreme Midlatitude Noctilucent Cloud Event on 18/19 July 2016

Abstract

A rare noctilucent cloud (NLC) event was observed at 48.8∘ N, 13.7∘ E above GERman Experimental Seismic System station in southern Germany on 18/19 July 2016 using the Compact Rayleigh Autonomous Lidar. Strong southward winds due to a quasi 2‐day planetary wave allowed for the influx of mesospheric polar air to midlatitudes on this day. The NLC observed by lidar was preceded by strong NLC displays in Cloud Imaging and Particle Size (CIPS) Experiment satellite images above the North Sea and by strong mesospheric summer radar echoes 800 km north of the lidar site and was also observed visually in central Europe. The NLC occurred at low altitude and was bright and thin with strong oscillations in altitude and brightness. Darkness allowed for high‐resolution temperature measurements at NLC altitudes. The ice particles were embedded in the upper part of a cold region with temperatures below 150 K. Significantly higher temperatures were found directly above the cloud with large vertical temperature gradients of 25 K/km at the top boundary. Spectral analysis reveals that NLC particles existed within cold phases of gravity waves within a region of high static stability. In order to study the evolution of NLC brightness in this environment, we drive the microphysical model Community Aerosol and Radiation Model for Atmospheres with lidar temperature soundings. We find that NLC particles can survive and grow in the conditions defining this midlatitude event. We conclude that the ice particles did not nucleate at the site of observation but were meridionally transported and vertically confined to a thin layer due to a large vertical temperature gradient, wind reversal, and low levels of mesospheric turbulence.

Lidar observations of large-amplitude mountain waves in the stratosphere above Tierra del Fuego, Argentina

“…It is the first of a new class of high-power, autonomously operating lidars allowing for high vertical and high temporal resolution measurements of atmospheric density during night-time. Data from CORAL and its twin TELMA obtained during several multi-month campaigns in both hemispheres have been used for studies of gravity waves and other phenomena of the mesosphere like tides and noctilucent clouds [39][40][41][42][43] www.nature.com/scientificreports/ ics within the ARISE (Atmospheric Dynamics Research InfraStructure in Europe) project 44 . CORAL operates autonomously during clear sky conditions in darkness.…”

“…It is the first of a new class of high-power, autonomously operating lidars allowing for high vertical and high temporal resolution measurements of atmospheric density during night-time. Data from CORAL and its twin TELMA obtained during several multi-month campaigns in both hemispheres have been used for studies of gravity waves and other phenomena of the mesosphere like tides and noctilucent clouds 39 – 43 . The Rayleigh lidar emits 12 W power at 532 nm wavelength and receives backscattered photons with a 63 cm diameter telescope using three height-cascaded elastic detector channels and one Raman channel.…”

A Compact Rayleigh Autonomous Lidar (CORAL) for the middle atmosphere

“…Since these are relatively rare events, collecting as much observations as possible greatly improves the chances for finding cases where the downward propagating waves are not masked by interference with strong upward propagating waves. During a previous campaign in the Bavarian Forrest, Germany CORAL also was able to capture a rare mid-latitude Noctilucent Cloud event (Kaifler et al, 2018).…”

Retrieval of intrinsic mesospheric gravity wave parameters using lidar and airglow temperature and meteor radar wind data

“…CORAL is a Rayleigh backscatter lidar for the middle atmosphere. It incorporates a 12 W laser operated at 532 nm wavelength as transmitter, a 63 cm diameter receiving telescope and two height-cascaded receiving channels equipped with Avalanche Photo Diodes run in photon-counting mode (Kaifler et al, 2017(Kaifler et al, , 2018. CORAL was designed with the capability for remote control and automatic operation in order to maximize operation hours.…”

“…Due to limitations in power and/or efficiency of Rayleigh lidars, often a gap remains in the upper mesosphere between the top altitude of Rayleigh lidar temperature profiles and coincident sodium lidar measurements. Recent developments in Rayleigh lidar technology allow for high-resolution temperature and GW measurements at altitudes above ∼85 km within the OH layer (Kaifler et al, 2017(Kaifler et al, , 2018. Also, modern OH imaging instruments utilize different OH emission lines to perform spectroscopy in order to derive the spatial temperature field, thus facilitating a synergy of OH layer imaging and vertical lidar soundings that has not been possible before.…”