Noctilucent Clouds On Edge Of Forever

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‘LASP’ Abbreviation What Is Below

In Boulder, Colorado, there exists Laboratory for Atmospheric and Space Physics (LASP), which has pioneered the CIPS/AIM satellites for cloud formation.

AIM is the first satellite mission dedicated to the study of Noctilucent or “night-shining” clouds (NLCs). It has provided the first global-scale view of the clouds over the entire 2007 northern hemisphere season, and is almost complete with the southern. Very little is known about the basic physics of these clouds.

The Weirdness Of ‘NLCs’

Noctilucent clouds in the upper atmosphere have been rarely seen. NASA sent up satellites to investigate the typically ‘invisible’. That mission, called Aeronomy of Ice in the Mesosphere (AIM), is designed to study the highest clouds in the atmosphere. Only astronauts were available after a launch to see such sites. Now, Watchers on earth have seen them too, glowing after sunset in the night sky. Astronaut Don Petit (NASA TV) estimated the height of those NLCs at 80-100km … “literally on the fringes of space.”

The AIM satellite has three instruments providing information on all NLCs. Cloud Imaging and Particle Size (CIPS) Instrument Overview, CDE (Cosmic Dust Experiment), and SOFIE (Solar Occultation For Ice Experiment). CDE collects dust measuring cosmic dust input, which is a key factor in NLC formation. SOFIE measures temperature, water vapor, ozone, nitric oxide and methane.

Noctilucent clouds over Finland
Noctilucent clouds over Finland. The orange hues near the horizon are ordinary sunset colors, notes Gary Thomas. NLCs, on the other hand, are usually luminous bluewhite or sometimes just pale white, he says.

The amazing similarity between NLC structure observed by CIPS and what’s seen in tropospheric clouds, suggests the mesosphere may share some of the same processes responsible for earth’s weather near the surface.

What Does A ‘Nadir’ Do?

The CIPS measures the panoramic image of UV radiation, scattered by clouds and atmosphere. It determines cloud presence in the polar atmosphere, viewing in the nadir direction. “Nadir” is a direction directly below the zenith, which is directly overhead. The nadir is the local vertical direction pointing to the force of gravity at that location. It can also be the lowest point by a celestial body during its orbit around an object. The astrometric horizon is perpendicular to the line connecting the zenith and the nadir (diagram below).

CIPS data includes measurements of cloud parameters (albedo, particle radius, ice water content) during each satellite orbit. The near-polar orbit causes the observation paths to overlap at latitudes higher than 70o, so the entire polar cap is mapped with 15-orbits/day. CIPS images are acquired simultaneously by each camera every 43 seconds. Many locations are viewed at 7 different scattering angles, providing a direct measurement of the cloud scattering phase function (Cloud Albedo vs Scattering Angle).

As previously suspected, the population of very small ice particles is believed to be responsible for strong radar echoes from the summertime mesosphere. These cloud structures, resolved for the first time by the CIPS imager, exhibit complex features present in normal tropospheric clouds. Through 9/12, there was mesospheric cloud tracking for an additional 7 more seasons. CIPS will provide data addressing major questions.

AIM has now provided detailed pictures of NLCs never collected before. These colorful clouds appear every day, are widespread, and highly variable on hourly to daily time scales. We know brightness varies over horizontal scales of a few kilometers, and over small regions the clouds are 10x brighter than previously measured.

From AIM, movies of daily cloud albedo for NLC seasons are continuing to be obtained. They have increased in brightness during AIM duration, seen more often, and occur at lower latitudes. Strange, but before the launch of AIM (4/2/07), there was no AIM satellite taking pictures, which were almost nonexistent.

Left Blames ‘AGW’ on ‘NLC’ Unknowns

These clouds at the edge of space [http://aim.hamptonu.edu/] were earlier called Polar Mesospheric Clouds (PMCs), and glow. They have increased in brightness over time, are being seen more often, and supposedly occur at lower latitudes.

They are located near the polar mesopause in both hemispheres (50m above surface). Composed of ice crystals (MAVEN To The Rescue of NASA

Amazing how NASA is so knowledgeable about NLCs, but are so behind the ‘8-ball’ with AGW.

Satellite MAVEN (Mars Atmosphere and Volatile EvolutioN) is scheduled for near future exploration of Mars. LASP is leading the MAVEN mission to study the ionosphere, and past climate. It will be launched on 11/18/13, and will arrive on 9/22/14.