Preprints
https://doi.org/10.5194/egusphere-2024-2318
https://doi.org/10.5194/egusphere-2024-2318
01 Aug 2024
 | 01 Aug 2024

Lidar measurements of noctilucent clouds at Rio Grande, Tierra del Fuego, Argentina

Natalie Kaifler, Bernd Kaifler, Markus Rapp, Guiping Liu, Diego Janches, Gerd Baumgarten, and Jose-Luis Hormaechea

Abstract. Noctilucent clouds (NLC) are sensitive tracers of upper mesospheric temperature, water vapor and dynamics and thus open windows to study our atmosphere from very large to very small scales, including topics of climate, circulation, waves and turbulence. At northern hemisphere mid-latitudes, the occurrence of NLC seems to increase with time. NLC are weaker in the southern hemisphere, but no vertical soundings at southern hemisphere mid-latitudes had been available until now. We determine the properties of NLC above a southern-hemisphere mid-latitude site at 53.8° S in southern Argentina. The Compact Rayleigh Autonomous Lidar provides high-resolution vertical lidar soundings since 2017. Noctilucent clouds are detected every summer, with the earliest (latest) detection on 29 November (29 January), in total 19 events of 33.8 h length, at an average height of 83.3 km, with a maximum brightness of 24 × 10-10/m/sr, an occurrence rate of 6 % and a maximum in the morning hours (5–7 UT, i.e. 2–4 LT). The latter coincides with a positive amplitude of the semi-diurnal tide of the meridional wind as measured by the Southern Argentina Agile Meteor Radar. The ambient temperature above the site is on average too high to support local ice formation. We find no correlation with the solar flux; indeed, the latest season of 2023/2024 shows the most NLC detections. This leaves transport from more southerly, colder regions and potentially increasing upper mesospheric water vapor levels as a result of increasing space traffic as possible explanations for the occurrence and unexpectedly large brightness of NLC above Rio Grande.

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Natalie Kaifler, Bernd Kaifler, Markus Rapp, Guiping Liu, Diego Janches, Gerd Baumgarten, and Jose-Luis Hormaechea

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2318', Anonymous Referee #1, 27 Aug 2024
  • RC2: 'Comment on egusphere-2024-2318', Anonymous Referee #2, 19 Sep 2024

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2318', Anonymous Referee #1, 27 Aug 2024
  • RC2: 'Comment on egusphere-2024-2318', Anonymous Referee #2, 19 Sep 2024
Natalie Kaifler, Bernd Kaifler, Markus Rapp, Guiping Liu, Diego Janches, Gerd Baumgarten, and Jose-Luis Hormaechea

Data sets

Lidar profiles Natalie Kaifler https://halo-db.pa.op.dlr.de/mission/111

Natalie Kaifler, Bernd Kaifler, Markus Rapp, Guiping Liu, Diego Janches, Gerd Baumgarten, and Jose-Luis Hormaechea

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Noctilucent clouds form in the extremely cold temperatures in the high-latitude summer mesosphere (altitudes of 75-85km). Their formation requires the right combination of water vapour concentrations and temperatures. It has been speculated for example, that increasing frequency of occurrence of such clouds might result from increases in methane concentrations, with the methane being converted into water vapour in the upper stratosphere and mesosphere. This paper reports observations of noctilucent clouds, made using an automated lidar system in southern Argentina, at unexpectedly low latitudes compared to previous Southern Hemisphere observations. Possible explanations, including systematic moistening of the mesosphere by space traffic, are discussed.
Short summary
Noctilucent clouds (NLC) are silvery clouds that can be viewed during twilight and indicate atmospheric conditions like temperature and water vapor in the upper mesosphere. High-resolution measurements from a remote-sensing laser instrument provide NLC height, brightness and occurrence rate since 2017. Most observations occur in the morning hours, likely caused by strong tidal winds, and NLC ice particles are thus transported from elsewhere to the observing location in the southern hemisphere.