Effects of Scavenging, Entrainment, and Aqueous Chemistry on Peroxides and Formaldehyde in Deep Convective Outflow Over the Central and Southeast United States

Megan M Bela; Mary C Barth; Owen Brian Toon; Alan Fried; Conrad Ziegler; Kristin A Cummings; Yunyao Li; Kenneth E Pickering; Cameron R Homeyer; Hugh Morrison; Qing Yang; Retha M Mecikalski; Larry Carey; Michael I Biggerstaff; Daniel P Betten; A Addison Alford

doi:10.1029/2018jd028271

Effects of Scavenging, Entrainment, and Aqueous Chemistry on Peroxides and Formaldehyde in Deep Convective Outflow Over the Central and Southeast United States

J Geophys Res Atmos. 2018 Jul 27;123(14):7594-7614. doi: 10.1029/2018jd028271. Epub 2018 Jun 9.

Authors

Megan M Bela^{1

2

3

4}, Mary C Barth⁵, Owen Brian Toon^{1

2}, Alan Fried⁶, Conrad Ziegler⁷, Kristin A Cummings^{8

9}, Yunyao Li⁸, Kenneth E Pickering^{8

10}, Cameron R Homeyer¹¹, Hugh Morrison⁵, Qing Yang¹², Retha M Mecikalski¹³, Larry Carey¹³, Michael I Biggerstaff¹¹, Daniel P Betten¹¹, A Addison Alford¹¹

Affiliations

¹ Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, Boulder, CO, USA.
² Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA.
³ Cooperative Institute for Research in the Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA.
⁴ Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA.
⁵ National Center for Atmospheric Research, Boulder, CO, USA.
⁶ Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO, USA.
⁷ National Severe Storms Laboratory, National Oceanic and Atmospheric Administration, Norman, OK, USA.
⁸ Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD, USA.
⁹ Kennedy Space Center, National Aeronautics and Space Administration, Merritt Island, FL, USA.
¹⁰ Goddard Space Flight Center, National Aeronautics and Space Administration, Greenbelt, MD, USA.
¹¹ School of Meteorology, University of Oklahoma, Norman, OK, USA.
¹² Pacific Northwest National Laboratory, Richland,WA, USA.
¹³ Department of Atmospheric Science, University of Alabama, Huntsville, AL, USA.

Abstract

Deep convective transport of gaseous precursors to ozone (O₃) 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 (dx ≤ 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 (CH₂O) 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 CH₂O, methyl hydroperoxide (CH₃OOH), and hydrogen peroxide (H₂O₂) are quantified. Liquid phase microphysical scavenging was the dominant process reducing CH₂O and H₂O₂ 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 CH₃OOH mixing ratios in the storm cores were primarily due to entrainment of low-background CH₃OOH. In the air mass storm, lower CH₃OOH and H₂O₂ scavenging efficiencies (SEs) than in the MCS were partly due to entrainment of higher background CH₃OOH and H₂O₂. Overestimated rain and hail production in WRF-Chem reduces the confidence in ice retention fraction values determined for the peroxides and CH₂O.

Grants and funding

SCMD-EarthScienceSystem/Science Earth Science System NASA/United States