Gravity waves traveling upwards from the lower atmosphere caused
this unusual banded structure in airglow above China in late
November.
These ripples are high in the upper
atmosphere. They’re thought to be caused by gravity waves. Photo
copyright 2016 Xiao Shuai. Photo processing by Jeff Dai. Used
with permission.
Jeff Dai, who has contributed
many
beautiful photos to EarthSky, wrote in late November:
A ‘mesospheric bore’ was captured from Mount Balang, Sichuan,
China on November 24. The photographer reported seeing it with
the unaided eye. The direction of these photos were toward the
south, and the foreground mountain was illuminated by the rising
moon.
Location: 30°53’54’’N and 102°54’03E.
Date and time: November 24, 2-4 a.m. (GMT +8)
Atmospheric scientist Yue Jia at Hampton
University, University of Maryland College Park and NASA Goddard
Space Flight Center explained:
This propagating sudden brightening or darkening of the
nightglow followed by a train of waves is called ‘the
mesospheric bore.’ It’s a type of
undular bore [a wave disturbance in Earth’s atmosphere].
This phenomenon occurs at ~90 km [55 miles] high … Scientists
speculate that this phenomenon is caused by
atmospheric gravity waves trapped inside a
temperature inversion layer.
He also sent a link to
the classic scientific paper on the mesospheric bore phenomenon.
Need more on mesospheric bores?
Atmospheric Optics has some good info, as always.
A different perspective on the November 24, 2016 mesospheric
bore over China. Photo copyright 2016 Xiao Shuai. Photo
processing by Jeff Dai. Used with permission.
Jeff Dai asked that we add this
description of gravity waves, which is from
a 2015 research study on the subject:
Gravity waves (disturbances to the density structure of the
atmosphere whose restoring forces are gravity and buoyancy)
comprise the principal form of energy exchange between the lower
and upper atmosphere. Wave breaking drives the mean upper
atmospheric circulation, determining boundary conditions to
stratospheric pro- cesses, which in turn influence tropospheric
weather and climate patterns on various spatial and temporal
scales.
The Day/Night Band (DNB) on the NOAA/NASA Suomi National
Polar-orbiting Partnership environmental satellite also recorded
the event on 18:45 UTC, or 02:45 local time in Sichuan, China.
The preliminary analysis is that the bore was propagating
southwards, perpendicular to the axis of the frontal feature.
Read more about this image.
Bottom line: A ‘mesospheric bore’ was
captured from Mount Balang, Sichuan, China on November 24, 2016.
http://earthsky.org/todays-image/mesospheric-bore-china-nov-24-2016