Formaldehyde Photochemistry in the Upper Troposphere in and Near Convective Storms During the DC3 Study

The 2012 Deep Convective Clouds and Chemistry (DC3) campaign in the summer of 2012 provided an opportunity to study the impacts of deep convection on various reactive and soluble precursors of ozone and HOx radicals in the upper troposphere and lower stratosphere over North America. Formaldehyde (CH2O) is one such gas. Formaldehyde measurements on the NASA DC-8 aircraft by difference frequency generation infrared absorption spectroscopy (DFGAS) and laser-induced fluorescence along with DFGAS measurements on the NSF/NCAR GV aircraft were acquired in the inflow and outflow of numerous storms over the course of this study. An overview of these measurements with past measurements over the continental U.S. will be given for both context and to illustrate the magnitude of CH2O perturbations caused by deep continental convection. A number of case studies were identified for comparison of these measurements with the NASA Langley Lagrangian photochemical box model and the WRF-Chem model. The former is constrained by time varying observations of CH2O precursors in both the boundary layer and upper troposphere to determine the magnitude of CH2O produced by gas-phase photochemistry in both the storm core and the outflow at various times for different storm types. These determinations will be used as a constraint on CH2O scavenging efficiency results obtained by a 3-component mixture method and as a means to assess the magnitude of potential CH2O production mechanisms from other sources such as heterogeneous production when smoke plumes intercept clouds.