Measurement and Modeling of the Vertical Nitrous Oxide (N2O) Gradient and Flux in Dryland Agricultural Fields.

N₂O is a potent greenhouse gas and its fluxes from agricultural fields are often an order of magnitude or lower than CO₂ fluxes. The logistics of measuring atmospheric N₂O fluxes make it a difficult measurement to attempt (e.g. power hungry and large instruments and high detection limits). Measuring N₂O fluxes via micrometeorological techniques is relatively new and needed to reach continuous field-scale measurements compared to point measurements from soil chamber arrays. However, this method relies on the ability to accurately measure small N₂O gradients. This work combines data from static soil chambers with a tower mounted N₂O gradient system and turbulence data on two eddy covariance towers from April 2015 through May 2015.

The goal of the work is to combine the EC tower measurements with the WindTrax model to better understand the gradient and fluxes of N₂O from a dryland agricultural field and how best to apply the flux gradient method. WindTrax is a backward Lagrangian stochastic (bLs) model that is seeded with known measurements to calculate back-trajectories to determine the source region and flux values of a particular trace gas. WindTrax will be seeded with measured values to determine if the model can replicate the N₂O gradient and fluxes under different conditions and what combination of measurements produces the most accurate results. Without improvements in micrometeorological measurements of N₂O, achieving field-scale flux values will require a combination of model and measurement approaches