Abstract
AbstractOne of the objectives of the Deep Convective Clouds and Chemistry (DC3) field experiment was to determine the scavenging of soluble trace gases by thunderstorms. We present an analysis of scavenging of hydrogen peroxide (H2O2) and methyl hydrogen peroxide (CH3OOH) from six DC3 cases that occurred in Oklahoma and northeast Colorado. Estimates of H2O2 scavenging efficiencies are comparable to previous studies ranging from 79 to 97% with relative uncertainties of 5–25%. CH3OOH scavenging efficiencies ranged from 12 to 84% with relative uncertainties of 18–558%. The wide range of CH3OOH scavenging efficiencies is surprising, as previous studies suggested that CH3OOH scavenging efficiencies would be <10%. Cloud chemistry model simulations of one DC3 storm produced CH3OOH scavenging efficiencies of 26–61% depending on the ice retention factor of CH3OOH during cloud drop freezing, suggesting ice physics impacts CH3OOH scavenging. The highest CH3OOH scavenging efficiencies occurred in two severe thunderstorms, but there is no obvious correlation between the CH3OOH scavenging efficiency and the storm thermodynamic environment. We found a moderate correlation between the estimated entrainment rates and CH3OOH scavenging efficiencies. Changes in gas‐phase chemistry due to lightning production of nitric oxide and aqueous‐phase chemistry have little effect on CH3OOH scavenging efficiencies. To determine why CH3OOH can be substantially removed from storms, future studies should examine effects of entrainment rate, retention of CH3OOH in frozen cloud particles during drop freezing, and lightning‐NOx production.
Highlights
To understand the radiative impact of ozone in the upper troposphere (UT), ozone chemical sources in the UT must be quantified
We present an analysis of scavenging of hydrogen peroxide (H2O2) and methyl hydrogen peroxide (CH3OOH) from six DC3 cases that occurred in Oklahoma and northeast Colorado
A comparison of the outflow peroxide mixing ratios to the background UT shows that the outflow H2O2 is always less than the background UT, on average, while the outflow CH3OOH is always greater than the background UT, on average
Summary
To understand the radiative impact of ozone in the upper troposphere (UT), ozone chemical sources in the UT must be quantified. Many key HOx precursors, including formaldehyde (CH2O), hydrogen peroxide (H2O2), and methyl hydrogen peroxide (CH3OOH), are soluble and can be partially removed from the atmosphere via dissolution into cloud drops that grow into rain, snow, graupel, and hail precipitating to the ground. Quantifying the fraction of HOx precursors that are scavenged (or transported to the UT) improves the estimation of O3 production in convective outflow regions. A. Fried et al (Convective transport of formaldehyde to the upper troposphere and lower stratosphere and associated scavenging in thunderstorms over the central United States during the 2012 DC3 study, submitted to Journal of Geophysical Research, 2016) perform a similar analysis for CH2O, while Bela et al [2016] evaluate the convective transport of nitric acid, H2O2, CH2O, sulfur dioxide, and CH3OOH in a three-dimensional cloud chemistry model with observations and calculate the fraction of these species removed for four DC3 thunderstorm cases. Gas-phase chemistry alone does not deplete either H2O2 or CH3OOH appreciably during transit from cloud base to cloud top
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
