New Insight Into the Microphysics of Mixed-phase Orographic Clouds Gained by StormVEx

Hallar, G., University of Utah

Cloud Processes

Aerosol Processes

Lowenthal D, A Hallar, R David, I McCubbin, R Borys, and G Mace. 2019. "Mixed-phase orographic cloud microphysics during StormVEx and IFRACS." Atmospheric Chemistry and Physics, 19(8), 10.5194/acp-19-5387-2019.


Recent picture of Storm Peak Laboratory probe stand with FSSP-100, Cloud Imaging Probe (CIP), Precipitation Imaging Probe (PIP), and sonic anemometer on top.



Recent picture of Storm Peak Laboratory probe stand with FSSP-100, Cloud Imaging Probe (CIP), Precipitation Imaging Probe (PIP), and sonic anemometer on top.

Science

Wintertime mixed-phase orographic cloud measurements were conducted at the Storm Peak Laboratory (SPL) during the Storm Peak Lab Cloud Property Validation Experiment (StormVEx) in 2011. The data include an unprecedented duration of simultaneous measurements of supercooled liquid cloud droplet and ice particle size distributions.  A relationship between large cloud droplet concentration (25–35 µm) and small ice particles (75–200 µm) under cold (<−8 C) but not warm (>−8 C) conditions was observed.

Impact

A relationship between large cloud droplets and small ice crystals suggests that droplet freezing (contact or immersion) was involved in ice production at Storm Peak Laboratory. This relationship was only evident at temperatures below −8◦C.  The lack of a relationship at warm temperatures would appear to preclude secondary ice formation by the Hallett–Mossop process. 

Summary

These results highlight the value of long-term cloud measurements at mountain sites for studies pertaining to statistical relationships among microphysical properties and temporal variation of clouds, the relationship between the ice and liquid phases, and ice production mechanisms.