SCIENCE
OBJECTIVES
The AIM goal can be characterized by six specific scientific
questions. The first five of these deal with mechanisms for PMC formation,
i.e., when and where they occur and how they respond to changes in their
thermal, chemical and dynamical environments. The AIM mission will answer
these five questions directly. The sixth question links PMCs to the larger
question of mesospheric climate change. The models we will develop and
validate to answer the first five questions will be used to address this
last question.
The six objectives are:
1. PMC Microphysics: What is the global morphology of PMC
particle size, occurrence frequency and dependence upon H2O and temperature?
2. Gravity Wave Effects: Do gravity waves (GWs) enhance
PMC formation by perturbing the required temperature for condensation
and nucleation?
3. Temperature Variability: How does dynamical variability
control the length of the cold summer mesopause season, its latitudinal
extent and possible interhemispheric asymmetry?
4. Hydrogen Chemistry: What are the relative roles of gas
phase chemistry, surface chemistry, condensation/sublimation and dynamics
in determining the variability of water vapor in the polar mesosphere?
5. PMC Nucleation Environment: Is PMC formation controlled
solely by changes in the frost point or do extraterrestrial forcings such
as cosmic dust influx or ionization sources play a role?
6. Long-Term Mesospheric Change: What is needed to establish
a physical basis for the study of mesospheric climate change
and its relationship to global change?
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