edu.ucar.opensky::articles:13140 UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact 2025-12-26T03:40:05.082490 ISO 19115-2 Geographic Information - Metadata - Part 2: Extensions for Imagery and Gridded Data ISO 19115-2:2009(E) https://n2t.org/ark:/85065/d7xk8ggg The common occurrence of highly supercooled drizzle and rain near the coastal regions of the western United States 2013-09-16T00:00:00Z publication https://n2t.org/ark:/85065/d7xk8ggg https://doi.org/10.1002/jgrd.50529 Rosenfeld, D. author Chemke, R. author DeMott, P. author Sullivan, R. author Rasmussen, Roy M. author McDonough, Francis author Comstock, J. author Schmid, B. author Tomlinson, J. author Jonsson, H. author Suski, K. author Cazorla, A. author Prather, K. author UCAR/NCAR - Library publisher Highly supercooled rain and drizzle from cloud tops at -12 to -21°C down to the 0° isotherm was documented by aircraft observations in clouds over a wide range of meteorological situations under relatively pristine marine aerosol conditions. The Gulfstream-1 aircraft during the CalWater campaign in February and early March 2011 measured clouds over the coastal waters of northern California, orographically triggered convective clouds over the foothills of the Sierra Nevada, and orographic layer clouds over Yosemite National Park. Supercooled drizzle in layer clouds near Juneau, Alaska, was measured by the Wyoming King Air as part of a FAA project to study aircraft icing in this region. Low concentrations of cloud condensation nuclei (CCN) were commonly observed in all of these clouds, allowing for the formation of clouds with small concentrations of mostly large drops that coalesced into supercooled drizzle and raindrops. Another common observation was the absence of ice nuclei (IN) and/or ice crystals in measurable concentrations, associated with persistent supercooled drizzle and rain. Average ice crystal concentrations were 0.007 l⁻¹ at the top of convective clouds at −12°C and 0.03 l⁻¹ in the case of layer clouds at −21°C. In combination, these two conditions of low concentrations of CCN and very few IN provide ideal conditions for the formation of highly supercooled drizzle and rain. These results help explain the anomalously high incidences of aircraft icing at cold temperatures in U.S. west coast clouds and highlight the need to include aerosol effects when simulating aircraft icing with cloud models. UCAR/NCAR - Library OpenSky Support PO Box 3000 Boulder CO 80307-3000 opensky@ucar.edu http://opensky.ucar.edu/ homepage pointOfContact PDF Text theme Resource Type 2016-01-01T00:00:00Z publication Copyright 2013 American Geophysical Union. None eng geoscientificInformation