Simulations of the redistribution of formaldehyde, formic acid, and peroxides in the 10 July 1996 Stratospheric-Tropospheric Experiment: Radiation, Aerosols, and Ozone deep convection storm

By using a three-dimensional convective cloud model to simulate the 10 July 1996, Stratospheric-Tropospheric Experiment: Radiation, Aerosols, and Ozone-Deep Convection experiment storm, we investigate the fate of formaldehyde (CH₂O), formic acid (HCOOH), hydrogen peroxide (H₂O₂), and methyl hydrogen peroxide (CH₃OOH) in an isolated thunderstorm. CH₂O, H₂O₂, and CH₃OOH are important HO x radical and ozone (O₃) precursors in the upper troposphere. Thus, determining their source strength to the upper troposphere is important for estimating O₃ production. The model simulates O₃-NO x -CH₄ chemistry (no nonmethane hydrocarbon chemistry) which is affected by the cloud microphysics and production of NO x by lightning. The retention of the soluble species within ice, snow, and hail during drop freezing results in less transport of the species to the upper troposphere than when the species is degassed during drop-freezing processes. Aqueous-phase chemistry is found to be inadequate in producing sufficient quantities of HCOOH so that HCOOH could serve as a reliable indicator of cloud-processed air. The production of nitrogen oxides by lightning has little to no effect on convective outflow mixing ratios of CH₂O, H₂O₂, and CH₃OOH within 100 km of the convective cores. Thus, it is unlikely that lightning affects concentrations of HO x precursors near active convection. Scavenging of CH₂O and H₂O₂ significantly affects their concentrations in the convective outflow, although H₂O₂ mixing ratios were still similar to CH₃OOH indicating that both peroxides can contribute equally to O₃ production downwind of convection.