The southern season for noctilucent clouds (NLCs) has come to an end.
And something unexpected is perplexing scientists!
NASA’s AIM spacecraft observed the last wisps of electric-blue over Antarctica on Feb. 20, 2015. The end of the season was no surprise: The polar clouds always subside in late summer.
Looking back over the entire season, however, reveals something unexpected. In an 8-year plot of Antarctic noctilucent cloud frequencies, the 2014-2015 season is clearly different from the rest:
These curves show the abundance (“frequency”) of the clouds vs. time for 120 days around every southern summer solstice for the past 8 years.
As shown by the red curve, this past season was not like the others. The clouds were much more variable, and there was an enormous decrease in cloud frequency 15 to 25 days after the summer solstice. That’s actually when the clouds are usually most abundant.
What does this mean?
It is unknown but scientists are analysing the data.
[quote_box_center]Previous research shows that NLCs are a sensitive indicator of long-range teleconnections in Earth’s atmosphere, which link weather and climate across hemispheres. The strange behavior of noctilucent clouds in 2014-2015 could be a sign of previously unknown linkages. Preliminary indications are that it is indeed due to inter-hemispheric teleconnections.[/quote_box_center]
Now attention turns to the northern hemisphere, where the season for noctilucent clouds typically begins in May. Will the northern season ahead be as strangely variable as the southern season?
