Summary of the Chemistry Transport in Deep Convection Cloud Modeling Workshop Intercomparison

The cloud chemistry case of the 6th International Cloud Modeling Workshop investigated transport of ozone (O₃), carbon monoxide (CO), and NOx in deep convection as simulated by several cloud-scale chemistry models. The purpose of the intercomparison was to assess the capability of each model to transport chemical species from the boundary layer to the upper troposphere including the entrainment of free tropospheric air. Parameterizations of lightning-produced NOx and transport of the soluble species nitric acid, hydrogen peroxide, and formaldehyde were also compared. The results from several models can now be used to document the variability among reputable cloud chemistry convective models for a given storm. Six models simulated the 10 July 1996 STERAO storm, which was observed in northeastern Colorado. Observations of CO, O₃, and NOx in the anvil were compared to modeled mixing ratios of these species. Generally, the model results were in good agreement with each other and with the observations for CO and O₃. Models that included the production of NOx by lightning were able to produce NOx mixing ratios of similar magnitude as observed values. Analysis of the anvil winds and species concentrations give an estimate of the mass flux of species to the upper troposphere. The fluxes from preliminary model results replicate analyzed fluxes from the observations to about ±30% for air and ±25% for CO. As part of documenting the variability among cloud-scale chemistry models, we will further archive characteristics of the model results. These characteristics include cloud area, cloud top, mass fluxes into the storm, into the UT, and onto the ground, and scavenging fraction of soluble species.