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Effects of Scavenging, Entrainment, and Aqueous Chemistry on Peroxides and Formaldehyde in Deep Convective Outflow Over the Central and Southeast United States
Author(s) -
Bela Megan M.,
Barth Mary C.,
Toon Owen Brian,
Fried Alan,
Ziegler Conrad,
Cummings Kristin A.,
Li Yunyao,
Pickering Kenneth E.,
Homeyer Cameron R.,
Morrison Hugh,
Yang Qing,
Mecikalski Retha M.,
Carey Larry,
Biggerstaff Michael I.,
Betten Daniel P.,
Alford A. Addison
Publication year - 2018
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1029/2018jd028271
Subject(s) - scavenging , outflow , chemistry , entrainment (biomusicology) , storm , convective storm detection , troposphere , aqueous solution , atmospheric sciences , formaldehyde , convection , meteorology , organic chemistry , geology , physics , antioxidant , acoustics , rhythm
Deep convective transport of gaseous precursors to ozone (O 3 ) and aerosols to the upper troposphere is affected by liquid phase and mixed‐phase scavenging, entrainment of free tropospheric air and aqueous chemistry. The contributions of these processes are examined using aircraft measurements obtained in storm inflow and outflow during the 2012 Deep Convective Clouds and Chemistry (DC3) experiment combined with high‐resolution (d x ≤3 km) WRF‐Chem simulations of a severe storm, an air mass storm, and a mesoscale convective system (MCS). The simulation results for the MCS suggest that formaldehyde (CH 2 O) is not retained in ice when cloud water freezes, in agreement with previous studies of the severe storm. By analyzing WRF‐Chem trajectories, the effects of scavenging, entrainment, and aqueous chemistry on outflow mixing ratios of CH 2 O, methyl hydroperoxide (CH 3 OOH), and hydrogen peroxide (H 2 O 2 ) are quantified. Liquid phase microphysical scavenging was the dominant process reducing CH 2 O and H 2 O 2 outflow mixing ratios in all three storms. Aqueous chemistry did not significantly affect outflow mixing ratios of all three species. In the severe storm and MCS, the higher than expected reductions in CH 3 OOH mixing ratios in the storm cores were primarily due to entrainment of low‐background CH 3 OOH. In the air mass storm, lower CH 3 OOH and H 2 O 2 scavenging efficiencies (SEs) than in the MCS were partly due to entrainment of higher background CH 3 OOH and H 2 O 2 . Overestimated rain and hail production in WRF‐Chem reduces the confidence in ice retention fraction values determined for the peroxides and CH 2 O.