Kelvin–Helmholtz Waves in Precipitating Midlatitude Cyclones

Journal Article · 25 July 2018 · Journal of the Atmospheric Sciences

DOI: https://doi.org/10.1175/JAS-D-17-0365.1 · OSTI ID:1461611

Barnes, Hannah C. ^[1]; Zagrodnik, Joseph P. ^[2]; McMurdie, Lynn A. ^[2]; Rowe, Angela K. ^[2]; Houze, Robert A. ^[3]

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1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
2. Univ. of Washington, Seattle, WA (United States)
3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Univ. of Washington, Seattle, WA (United States)

This study examines Kelvin-Helmholtz (KH) waves observed by dual polarization radar in several baroclinic systems during the Olympic Mountains Experiment (OLYMPEX) field campaign along the windward side of the Olympic Mountains and in a strong stationary frontal zone in Iowa during the Iowa Flood Studies (IFloodS) field campaign. While KH waves develop regardless of the presence or absence of mountainous terrain, this study indicates that the large-scale flow can interact with the windward side of a mountain range in such a way to promote development of KH waves and to alter their physical structure (i.e., orientation and amplitude). OLYMPEX sampled numerous instances of KH waves in precipitating clouds, and this study examines their effects on microphysical processes above, near, and below the melting layer. The dual-polarization radar data indicate that KH waves above the melting layer promote aggregation. KH waves centered in the melting layer produce the most notable signatures in dual-polarization variables, with the patterns suggesting that the KH waves promote both riming and aggregation. Both above and near the melting layer ice particles show no preferred orientation likely due to tumbling in turbulent air motions. KH waves below the melting layer facilitate the generation of large drops via coalescence and/or vapor deposition, increasing mean drop size and rain rate by only slight amounts in the OLYMPEX storms.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); National Science Foundation (NSF); National Aeronautics and Space Administration (NASA)
• Grant/Contract Number: AC05-76RL01830
• OSTI ID: 1461611
• Alternate ID(s): OSTI ID: 1578032
• Report Number(s): PNNL-SA-130990
• Journal Information: Journal of the Atmospheric Sciences, Vol. 75, Issue 8; ISSN 0022-4928
• Publisher: American Meteorological SocietyCopyright Statement
• Country of Publication: United States
• Language: English