This award will support modeling activities as part of the Deep Convective Clouds and Chemistry (DC3) field campaign. DC3 will study the impact of deep, mid-latitude continental convective clouds, including their dynamical, physical, and lightning processes, on upper tropospheric composition and chemistry. Efforts in this project will be focused on improving model representation of the production of nitrogen oxides by lightning (LNOx) and estimates of the magnitude of the production per flash and per unit flash length, as well the vertical distribution of the resulting NOx mixing ratios. Case studies will be simulated using the WRF-Chem model. DC3 observations and the model output will be analyzed to determine the magnitude of resulting ozone changes both within the storm clouds and in the downwind cloud outflow.
Prior to the DC3 mission, test cases from the DC3 regions will be simulated using the WRF model. The model output will be compared with Lightning Mapping Array data, which may suggest improvements or changes in the lightning prediction scheme. The team will then participate in the May 2011 DC3 test flights through analysis and interpretation of output from WRF-Chem forecasts run operationally for the period. This will be followed up with evaluation of the forecasts and making possible further improvements to the LNOx algorithms prior to the DC3 mission. During the May-June 2012 DC3 mission, students will be in the field interpreting the WRF-Chem forecast output for flight planning. They will examine likely areas where convection may occur, types of convection, magnitudes of predicted flash rates, amount of NOx production, altitudes of convective outflow plumes, and downstream ozone production. Following the mission, individual observed storms for case study simulations will be selected. Various lightning NOx schemes will be incorporated into WRF-Chem and evaluated using DC3 observations. The case study simulations will be designed to yield estimates of lightning NOx production per flash and per unit flash length through comparisons with the anvil observations of NOx. Model estimates of ozone changes due to convective transport and chemistry within and downwind of storms will be evaluated using field data. Relationships between vertical wind shear, flash length and lightning NOx production will be examined, as well as relationships between atmospheric aerosol content and flash rates.
This award will support the participation of two graduate students in DC3 preparation, field activities, and post-mission analysis and modeling. Improvement in the understanding of LNOx will be applied to larger-scale chemistry and climate models.
