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Clouds and Precipitation Observation and Research


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 Jeff French

 

Proposed Projects

 

Improving Cloud Characterization from Instrumented Aircraft (NSF)

PI Jeff French (no collaborators)

Much of what we know about detailed cloud properties such as cloud hydrometeor size, shape, phase, and concentration, are derived from in situ measurements made on board instrumented aircraft. However, there remain significant gaps in our ability to measure such properties from aircraft, many of which are tied to inherent limitations of and/or uncertainties associated with the instruments that are used to make cloud hydrometeor measurements. Of particular challenge are measurements associated with the microphysical properties of ice in clouds. The long-term goal of this researchis to improve our ability to identify and characterize ice and liquid phase hydrometeors from aircraft thereby increasing the value of in situ airborne cloud data sets. To that end, we will develop a new laboratory device with the capability to produce both liquid and ice hydrometeors of repeatable size. The particles can then, with very precise placement, be passed through sample volumes of cloud particle instruments in a controlled environment. This capability will allow us for the first time to accurately reconstruct how these instruments respond to small ice hydrometeors. This research program will address long-standing uncertainties and will provide data to quantify how the current generation of airborne cloud probes respond to small ice.

 


Current Projects

 

SNOWIE: Seeded and Natural Orographic Wintertime clouds: the Idaho Experiment (NSF) 

PI Jeff French w/ co-PIs Bart Geerts (Univ. Wyoming), Bob Rauber (Univ. Illinois), Katja Friedrich (Univ. Colorado), Roy Rasmussen & Sarah Tessendorf (NCAR)

SNOWIE is a comprehensive observational and modeling research program to address longstanding uncertainties regarding the effectiveness of orographic winter precipitation enhancement through cloud seeding. The overarching goal is to understand the natural dynamical and microphysical processes by which precipitation forms and evolves within orographic winter storms and to determine the physical processes by which cloud seeding with silver iodide (AgI), either from ground generators or aircraft, impacts the amount and spatial distribution of snow falling across a river basin. A field campaign will be conducted in the Payette Mountains of Idaho in coordination with Idaho Power Company (IPC) who maintains an operational seeding program in the region. The core scientific objectives are to: (1) Evaluate the role of mesoscale and microscale dynamics and of the underlying terrain in the formation, growth, and fallout of natural ice crystals in winter storms through observations; (2) Investigate how the natural snow growth process is altered as a result of airborne AgI seeding through both observations and model simulations, and (3) Evaluate the effects of ground seeding on snowfall amount and distribution.

students: Adam Majewski (MS/PhD, expected spring 2018/2021), Melinda Hatt (MS, expected spring 2019)

 

University of Wyoming King Air (UWKA) as a National Facility (NSF)

PI Al Rodi w/ co-PI Jeff French (Univ. Wyoming)

The Department of Atmospheric Science operates a specially instrumented Beechcraft King Air model 200T (UWKA) for Atmospheric Research. In addition to serving the needs of the faculty within the department, the UWKA is available to support investigators across the nation through a cooperative agreement between the University and the National Science Foundation. As part of this agreement and to ensure the UWKA remains a cutting edge research tool to investigate atmospheric phenomena, considerable effort is placed on instrument/measurement development and evaluation. Dr. French focuses his research on developing tools and techniques to improve in-situ measurements from the UWKA. Specifically, he has developed a cloud physics laboratory quantifying errors and uncertainties associated with cloud droplet measurements. He also is leading an effort to improve processing of data collected from aircraft-based cloud imaging probes and bulk water-mass probes. This work is critical to many aspects of the other projects Dr. French is a part of as well as the broader user community of the UWKA.

students: Spencer Faber (MS, summer 2017), Darcy Jacobson (MS, fall 2017)

 


Past Projects

 

Convective Precipitation Experiment: Microphysics and Entrainment Dependencies COPE-MED (NSF)

PI Sonia Lasher-Trapp (Univ. Illinois) w/ co-PIs Dave Leon and Jeff French (Univ. Wyoming)

The COnvective Precipitation Experiment (COPE) was a large, UK-led campaign that took place in the summer of 2013 over the southwestern peninsula of the UK. While COPE was designed to study the entire evolution of convective precipitation, the US contingent (COPE-MED) investigates the interplay between microphysical processes that compete for condensate with an aim to better understand under what conditions certain processes dominate. In particular, COPE-MED aims to gain knowledge regarding the importance of 'warm rain' (collision-coalescence) for the overall production of precipitation in UK convective clouds -- either through the direct production or indirectly, possibly by augmenting the production of secondary ice. The Univ. of Wyoming King Air participated in the 2 month-long field campaign and measurments from in situ cloud microphysics instruments on the aircraft along with those from the Wyoming Cloud Radar and a ground-based x-band radar operated by our UK colleagues, provides the basis for our continuing analysis of the COPE data set.

students and postDocs:  Jason Sulskis (MS, spring 2016), Dave Plummer (PostDoc, 2014-2016), Bobby Jackson (PostDoc, 2015-2016)

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