Public interest for noctilucent clouds rose sharply in 2019 after record-setting outbreak across the northern hemisphere. The 2020 season is expected to start mid- to late-May or early June, but at the moment, it doesn't seem like 2020 will be a repeat of 2019.
In an attempt to provide NLC season forecast for this year, Lynn Harvey of the University of Colorado's Laboratory for Atmospheric and Space Physics has taken a look at moisture and temperature data -- key ingredients of NLCs -- collected by NASA's Microwave Limb Sounder (MLS).
MLS experiments measure naturally-occurring microwave thermal emission from the limb (edge) of Earth's atmosphere to remotely sense vertical profiles of atmospheric gases, temperature, pressure, and cloud ice. The overall objective of these experiments is to provide information that will help improve our understanding of Earth's atmosphere and global change.
In terms of summer mesopause temperature and water vapor, the year looks average, as seen in the following plots:
Image credit: Lynn Harvey/LASP, SpaceWeather.com
"So far, 2020 is shaping up to be fairly average," Harvey told Dr. Tony Phillips of SpaceWeather.com. "Based on the MLS data, I would guess that the first NLCs will be spotted in two weeks or so," she says.
Supercharged by extra moisture in the mesosphere, the 2019 northern hemisphere noctilucent cloud season started at the end of May and then increased significantly over the next two weeks, with NLCs seen as low as San Francisco Bay Area, California for the first time ever and throughout most of Europe since then.
Some observers even noticed rare red NLCs on June 21. "It happened around midnight," said Marek Nikodem of Szubin, Poland. "The top of the clouds developed a reddish-purple canopy." It didn't last long, but he was able to photograph the amber crown before it faded away."
Un plan plus large des spectaculaires noctiluque du 21.06.2019. Cela permet de voir l'ampleur, bien qu'il manque la partie au dessus de La Défense ( visible sur mon compte Flickr loicmi )#NLCfrance #NLCS @meteofrance #nlc_france @severeweatherEU #meteoparis pic.twitter.com/Mk92leKikT— Loic M (@Loic_M) June 22, 2019
#timelapse of the epic #noctilucent cloud display on Monday night my favourite #cloud since I was a kid and only the second time I've seen them! 80 km high @CloudAppSoc @ICASLeeds @AtmosScience @bbcweather @NatGeoPhotos @weatherchannel @JimCantore @severeweatherEU pic.twitter.com/b6JeySw3WK— Ben Pickering (@wx_radar) June 21, 2019
We had a little #NLCnow in #Havnsø #Denmark. A beautyful quite night :-) @NLCalerts @ADphotography24 @dartanner @mikesaltsman194 @treetanner @AngelBrise67 @AngryTheInch @chunder10 @TamithaSkov @DRVejret @GoVisitDenmark @tv2vejrcenter pic.twitter.com/zBqcaKZmwJ— Lone Athanasakis (@Lathanafoto) June 23, 2019
The first known observation of NLCs dates back to 1885, two years after the 1883 eruption of Krakatoa.
At first, they were only seen at higher latitudes, but have recently started appearing ever lower in latitudes.
Featured image credit: NightLightFilms, Adrien Mauduit