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Published June 16, 2020 | Published + Supplemental Material
Journal Article Open

Vertical Transport, Entrainment, and Scavenging Processes Affecting Trace Gases in a Modeled and Observed SEAC⁴RS Case Study

Abstract

The convectively driven transport of soluble trace gases from the lower to the upper troposphere can occur on timescales of less than an hour, and recent studies suggest that microphysical scavenging is the dominant removal process of tropospheric ozone precursors. We examine the processes responsible for vertical transport, entrainment, and scavenging of soluble ozone precursors (formaldehyde and peroxides) for midlatitude convective storms sampled on 2 September 2013 during the Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC⁴RS) study. Cloud‐resolving simulations using the Weather Research and Forecasting with Chemistry model combined with aircraft measurements were performed to understand the effect of entrainment, scavenging efficiency (SE), and ice physics processes on these trace gases. Analysis of the observations revealed that the SEs of formaldehyde (43–53%) and hydrogen peroxide (~80–90%) were consistent between SEAC⁴RS storms and the severe convection observed during the Deep Convective Clouds and Chemistry Experiment (DC3) campaign. However, methyl hydrogen peroxide SE was generally smaller in the SEAC⁴RS storms (4%–27%) compared to DC3 convection. Predicted ice retention factors exhibit different values for some species compared to DC3, and we attribute these differences to variations in net precipitation production. The analyses show that much larger production of precipitation between condensation and freezing levels for DC3 severe convection compared to smaller SEAC⁴RS storms is largely responsible for the lower amount of soluble gases transported to colder temperatures, reducing the amount of soluble gases which eventually interact with cloud ice particles.

Additional Information

© 2020 American Geophysical Union. Received 4 NOV 2019; Accepted 25 APR 2020; Accepted article online 29 APR 2020. We would like to thank NASA for supporting this research through grant NNX17AH52G. NCAR is sponsored by the National Science Foundation. C. Homeyer was funded by NSF grant AGS‐1522910. The authors thank Gabriele Pfister for providing additional WRF‐Chem information. The authors also thank Morgan Silverman and Gao Chen for providing SEAC⁴RS formaldehyde comparison. We also thank NASA for supporting the SEAC⁴RS campaign, the project leaders, and all the investigators for their data contributions. All data were obtained from the NASA Langley Research Center Atmospheric Science Data Center (https://www-air.larc.nasa.gov/cgi-bin/ArcView/seac4rs). We acknowledge use of the WRF‐Chem preprocessor tool (mozbc, fire_emiss, and bio_emiss) provided by the Atmospheric Chemistry Observations and Modeling Lab (ACOM) of NCAR and also the use of BOXMOX model provided by the University of Munich, Germany (http://boxmodeling.meteo.physik.uni-muenchen.de). Simone Tanelli's contributions were carried out at the Jet Propulsory Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004).

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Published - 2019JD031957.pdf

Supplemental Material - jgrd56231-sup-0001-sup-0001-text_si-s01.docx

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