The common occurrence of highly supercooled drizzle and rain near the coastal regions of the western United States
Sullivan, Ryan C.
MetadataShow full item record
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.
The article of record as published may be found at http://dx.doi.org/10.1002/jgrd.50529.
RightsThis publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
Showing items related by title, author, creator and subject.
Smith, Neil Tyler (Monterey, California. Naval Postgraduate School, 2000-09);Cloud researchers have documented a variety of processes at work in the formation and dissipation of clouds in the marine boundary layer (MBL). Cloud rifts occasionally mark a distinct exception to the continuity and broad ...
Aerosol and Cloud Microphysical Characteristics of Rifts and Gradients in Maritime Stratocumulus Clouds, 2006 Sharon, Tarah M.; Albrecht, Bruce A.; Jonsson, Haflidi H.; Minnis, Patrick; Khaiyer, Mandana M.; van Reken, Timothy M.; Seinfeld, John; Flagan, Rick (2006-03);A cloud rift is characterized as a large-scale, persistent area of broken, low-reflectivity stratocumulus clouds usually surrounded by a solid deck of stratocumulus. A rift observed off the coast of California was investigated ...
Aircraft Measurements of Total Mercury and Monomethyl Mercury in Summertime Marine Stratus Cloudwater from Coastal California, USA Weiss-Penzias, Peter; Sorooshian, Armin; Coale, Kenneth; Heim, Wesley; Crosbie, Ewan; Dadashazar, Hossein; MacDonald, Alexander B.; Wang, Zhen; Jonsson, Haflidi (ACS, 2018);Water samples from marine stratus clouds were collected during 16 aircraft flights above the Pacific Ocean near the Central California coast during the summer of 2016. These samples were analyzed for total mercury (THg), ...