Water Ice Onset Conditions in Polar Mesospheric Clouds
Abstract
Mesospheric clouds have been observed from the surface, in-situ, and from orbit for decades, and they are expected to show changes as global climate change alters the temperature structure, dynamics, and water vapor of the middle and upper atmosphere. Nucleation behavior can have a strong influence on particle characteristics, affecting cloud brightness and backscatter, as well as the sedimentation rate and surface area available for heterogeneous chemistry. Thus both the interpretation of PMC observations and the modeling of their implications are contingent upon understanding the nucleation process and parameters for water ice initiation under mesospheric conditions. Measurements from our laboratory have shown that water ice nucleation on a variety of dust materials at temperatures below ~ 165 K may require significant supercooling. We present here results on a variety of materials, including a low hygroscopicity mineral dust. We find that at temperatures nearing 145 K, nucleation can require relative humidity above 400%. The implications of this low-temperature nucleation behavior on cloud particle properties will be discussed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMSA21A2096J
- Keywords:
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- 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE / Aerosols and particles;
- 0320 ATMOSPHERIC COMPOSITION AND STRUCTURE / Cloud physics and chemistry