Reconciling Remote and In-Situ Measurements of CH4 Dispersion in a Convective Boundary Layer with Multi-Model CFD Simulations

In an effort to establish the validity and accuracy of airborne, image based, CH4 remote sensing instruments. We employed Los Alamos National Laboratory's high-resolution large eddy simulation model HiGrad to simulate the atmospheric boundary layer (ABL), and controlled CH4 releases measured during a field campaign in July of 2013. A statistically similar ABL to that observed during the field campaign was produced by downscaling NCEP's North American Model analysis fields assimilated through the Weather Research and Forecasting (WRF) numerical weather prediction model. These relatively coarse scale, observationally seeded simulations were then incorporated as initial and boundary conditions to drive high-resolution simulations with HiGrad. The resulting HiGrad simulations were compared against in-situ tower-based measurements from the field campaign, in order to establish a ground-truth validation of the multi-model simulation approach for both meteorology and CH4 dispersion. Subsequently, the high-resolution simulations were used to provide a statistically similar baseline of vertical column integrated CH4 concentration in the ABL, against which the new remote-sensing instrument observations could be compared. This multi-model approach to realizing a modeled ABL representative of that observed during the field campaign shows promise for future combined modeling and observation efforts aimed at specific real world case studies of ABL processes.