Beacon Transcript – The noctilucent clouds which appear every year over the South Pole seem to be puzzling scientists as the night-glow effect went for an early start this year.
Noctilucent or the night-glowing clouds are an event which unfolds every year over the South Pole. As they usually start manifesting in late November or early December, this year saw their beginning in mid-November.
As the clouds usually appeared in the same period, NASA used them so as to analyze the surrounding mesosphere.
Lina Tran, a NASA scientist, went to explain the phenomenon and the agency’s practices in a blog post.
The mesosphere is the atmospheric layer situated directly over the stratosphere and which separates our planet’s atmosphere from the outer space.
As the mesosphere encircles our planet some 50 miles above its surface, its blue night-clouds are in a category of their own.
The noctilucent clouds are, as such, set apart from other clouds by their higher altitudes as most such formation types occur at much lower altitudes.
As Tran went to explain, the noctilucent clouds offer clues as to the connection between the mesosphere and other weather, climate, and atmosphere features.
The night-glow clouds are considered to be summer phenomena as they appear above the Arctic in July and August. Their Antarctic appearance is usually noted in November and December.
This is also the most humid period of the mesosphere, as water vapors waft from lower altitudes.
It is also the layer’s coldest period as it registers temperatures as low as – 210 Fahrenheit degrees. This extreme temperature is determined by the air flow patterns of the respective seasons.
Noctilucent clouds are famous for their vivid color as they appear bright blue when seen from outer space. From the Earth’s surface, they look like shining and wispy formations.
Besides being uncommonly cold, Gary Thomas, a noctilucent clouds experts, also pointed out that they are incredibly dry.
Whilst most clouds are composed of water or ice droplets gathered around common dust particles, noctilucent clouds are based on a different dust.
Their night glow and luminescence are determined by their meteor dust composition as they gather the fine debris left by the disintegrating astral bodies.
According to the aforementioned Lina Tran, this is also the reason behind their vibrant blue color they produce when reflecting sunlight.
Back in 2007, NASA sent the AIM or Aeronomy of Ice in the Mesosphere spacecraft so as to better study the natural phenomenon.
As it they have now been studying the noctilucent clouds for almost a decade, scientists have also noticed their increasingly earlier appearance.
This year’s date, November 17, marks the earliest yet appearance of such clouds, as the scientists are still uncertain and remain puzzled as to what caused this changes.
Besides appearing earlier, the clouds were also noted to have spread. Their first registered appearances occurred in the late 19th century in the polar regions.
However, in more recent years, the night-glowing clouds could be observed from as near the Equatorial line as the United States-based Utah and Colorado.
Global warming and greenhouse gasses are amongst the most possible causes of the noctilucent clouds’ increasingly earlier appearance.
The global warming phenomenon was also, at a time, considered amongst the determining factors of the clouds’ appearance before the actual cause was discovered.
Image Source: Wikimedia