Monday, June 12, 2006

Hurrah for us - we're now screwing up the mesosphere!

We are pumping matter into the mesosphere. We have now succeded in producing so much pollution in the troposphere that, not only is percolating in large quantity up into the stratosphere, it is now climbing up into the mesosphere!

According to NASA, there are

Astronauts onboard the International Space Station have been observing electric blue "noctilucent" clouds from Earth-orbit.

On June 10th, another wave of electric-blue noctilucent clouds spread across northern Europe.
"This is my first sighting of these beautiful clouds," says
Alan C. Tough of Elgin, Moray, Scotland. "Well worth the wait!"

Noctilucent clouds (NLCs) are a mystery. They float through the outer reaches of Earth's atmosphere at the very edge of space. Some scientists think the clouds are seeded by space dust and fed by rocket exhaust. Others suspect they're a sign of global warming. Later this year, NASA plans to launch a satellite named AIM to investigate. Want to see them yourself? Look west after sunset for sinuous, blue-glowing ripples in the sky.
The North East Noctilucent Cloud Observers Group gives this explanation of the phenomenon:

Noctilucent Clouds or NLC are visible during the summer months of each hemisphere, mid-May to mid-August in the Northern Hemisphere and mid-November to mid-February in the Southern Hemisphere but only from a specific latitudinal zone. This zone is 50-65° North or South, with 57° being the best latitude to observe NLC from. June and July and December and January are the best months to observe NLC for each respective hemisphere. These zones are a compromise. South of 50° and the sky is too dark, due to the sun being more than 12° below the horizon (astronomical twilight) and north of 65° and the sky is too light as the sun is less than 6° below the horizon (civil twilight). NLC are so optically thin that they scatter less than 1 part in 1000 of light incident upon them. Hence the sky is too bright to observe them during civil twilight. At the end of civil twilight the clouds become visible as sky brightness has decreased by a factor of several hundred. In the specific latitudinal zone the sun stays between 6-12° below the horizon most of the night (nautical twilight). Consequently the sky is dark enough to observe NLC. The low angle of the sun below the horizon also allow the high altitudes at which the NLC reside to be in direct sunlight. Therefore NLC are visible due to reflected sunlight and do not generate any light of their own.
Pekka Parviainen has taken photographs of NLCs for decades.

Here is one of them:

NASA will soon investigate these clouds with the AIM Mission.

Aeronomy of Ice in the Mesosphere

The AIM satellite mission will explore Polar Mesospheric Clouds (PMCs), also called noctilucent clouds, to find out why they form and why they are changing. Results from this mission will provide the basis for study of long-term variability in the mesospheric climate.


The overall goal of the Aeronomy of Ice in the Mesosphere (AIM) experiment is to resolve why Polar Mesospheric Clouds (PMCs) form and why they vary. By measuring PMCs and the thermal, chemical and dynamical environment in which they form, we will quantify the connection between these clouds and the meteorology of the polar mesosphere. In the end, this will provide the basis for study of longterm variability in the mesospheric climate and its relationship to global change.

The results of AIM will be a rigorous validation of predictive models that can reliably use past PMC changes and present trends as indicators of global change. This goal will be achieved by measuring PMC abundances, spatial distribution, particle size distributions, gravity wave activity, cosmic dust influx to the atmosphere and precise, vertical profile measurements of temperature, H2O, OH, CH4, O3, CO2, NO, and aerosols. These data can be obtained only by a complement of instruments on an orbiting spacecraft because of the need for global coverage and because extinction and foreground emissions compromise optical sensing from the ground.

NASA Facts: AIM Fact

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