Other space-based and ground-based measurements have probed some aspects of this unusual phenomenon in Earth's mesosphere (the region just above the stratosphere), but very little is known about how these clouds form over the poles, why they are being seen at lower latitudes than ever before, or why they have been growing brighter and more frequent. Some scientists have suggested that these polar mesospheric clouds may be the direct result of human-induced climate change.
Over the course of its mission, AIM has helped answer these questions by documenting for the first time the entire complex life cycle of these clouds. With this information, scientists are working to resolve many of the mysteries about how these clouds form and to better predict how they will change in the future.
Some key scientific discoveries from AIM, include:
- Noctilucent cloud numbers have steadily increased over the past decade.
- Increases in water vapor, a greenhouse gas, and decreasing upper-atmosphere temperatures — a side effect of warming near the surface — may be contributing to the increased presence of PMCs.
- Ice crystals in noctilucent clouds form on a tiny microparticles created when meteors burn up in Earth’s atmosphere.
- Heating in the mesosphere is more likely linked to circulation in the atmosphere than direct heating from the Sun.
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