Abstract
Abstract. The Compact Rayleigh Autonomous Lidar (CORAL) is the first fully autonomous middle atmosphere lidar system to provide density and temperature profiles from 15 to approximately 90 km altitude. From October 2019 to October 2020, CORAL acquired temperature profiles on 243 out of the 365 nights (66 %) above Río Grande, southern Argentina, a cadence which is 3–8 times larger as compared to conventional human-operated lidars. The result is an unprecedented data set with measurements on 2 out of 3 nights on average and high temporal (20 min) and vertical (900 m) resolution. The first studies using CORAL data have shown, for example, the evolution of a strong atmospheric gravity wave event and its impact on the stratospheric circulation. We describe the instrument and its novel software which enables automatic and unattended observations over periods of more than a year. A frequency-doubled diode-pumped pulsed Nd:YAG laser is used as the light source, and backscattered photons are detected using three elastic channels (532 nm wavelength) and one Raman channel (608 nm wavelength). Automatic tracking of the laser beam is realized by the implementation of the conical scan (conscan) method. The CORAL software detects blue sky conditions and makes the decision to start the instrument based on local meteorological measurements, detection of stars in all-sky images, and analysis of European Center for Medium-range Weather Forecasts Integrated Forecasting System data. After the instrument is up and running, the strength of the lidar return signal is used as additional information to assess sky conditions. Safety features in the software allow for the operation of the lidar even in marginal weather, which is a prerequisite to achieving the very high observation cadence.
Highlights
For several decades, light detection and ranging (LiDAR; spelled lidar) has been used to profile the atmosphere and retrieve information on aerosols, trace gases, and atmospheric density, temperature, and wind
In contrast to their tropospheric counterparts, the mesospheric lidars were rather complex experiments requiring a great deal of labor to set up and operate, with some systems filling entire buildings
These lidars were run only during campaigns, or, e.g., in the case of stations belonging to the Network for the Detection of Atmospheric Composition Change, operation was limited to certain days per week when the weather forecast looked favorable and trained operators were available
Summary
Light detection and ranging (LiDAR; spelled lidar) has been used to profile the atmosphere and retrieve information on aerosols, trace gases, and atmospheric density, temperature, and wind (see, e.g., Fujii, 2005). Soon thereafter more powerful lasers and sensitive detectors led to detection of stratospheric aerosols by lidar (e.g., Collis, 1965; Schuster, 1970) It took until the early 1980s before the lidar technology was developed far enough to enable measurements of atmospheric density and temperature in the mesosphere (Hauchecorne and Chanin, 1980). In contrast to their tropospheric counterparts, the mesospheric lidars were rather complex experiments requiring a great deal of labor to set up and operate, with some systems filling entire buildings (von Zahn et al, 2000). Gravity wave climatologies which do not require a dense sampling were published by, e.g., Wilson et al (1991), Sivakumar et al (2006), Rauthe et al (2008), Li et al (2010), Mzé et al (2014), and Kaifler et al (2015b)
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