Convective transport and scavenging of peroxides by thunderstorms observed over the central U.S. during DC3

Abstract

One 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.

The influence of deep convection on HCHO and H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; in the upper troposphere over Europe

“…Our results partly contradict the analysis of DC3 measurements Bela et al, 2016;Barth et al, 2016) that yielded much higher scavenging efficiencies. If we assume an average scavenging efficiency of 50 % for HCHO, as reported by Fried et al (2016), the measured HCHO mixing ratio of 1.45 ppbv in the outflow corresponds to a minimum inflow mixing ratio of 3 ppbv, neglecting entrainment and photochemical processing in the outflow area.…”

“…Unfortunately, differences in the storm dynamics and microphysics between DC3 and HOOVER cannot be investigated since these details are not available for HOOVER. Differences to DC3 might be due to degassing from evaporating hydrometeors since the HOOVER measurements were performed in cloud-free air at considerable distance from the convective core, while the DC3 observations were made in the anvil Bela et al, 2016;Barth et al, 2016).…”

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

“…In the case of the IF, the time ranges are resolved to the nearest second, and these ranges are consistent with those listed in Barth et al . []. In the case of the OF, the time ranges are given on the 1 min merge sampling periods since the subsequent analysis employ the 1 min resolved wind vectors superimposed on the radar images.…”

“…As a result, our OF time ranges encompass the ranges listed by Barth et al . [] but are slightly larger. Also, as will be discussed, individual 1 min sampling periods within the tabulated ranges may not be included because they include stratospheric influence periods and/or periods with no outflow from the storm core under study.…”

“…We note that this extrapolation yields mixing ratios at the storm core tops, whereas those tabulated by Barth et al . [] and Bela et al . [] employ average OF values, which produce midanvil OFs that are slightly lower than the extrapolated values here.…”