GFDL - Geophysical Fluid Dynamics Laboratory

Sensitivity of the NOy budget over the United States to anthropogenic and lightning NOx in summer

October 1st, 2010

The study by Fang et al. [2010] examines the implications of new estimates of the anthropogenic and lightning nitrogen oxide (NOx) sources for the budget of oxidized nitrogen (NOy) over the United States in summer using a 3-D global chemical transport model (MOZART-4). NOy export and burden response less than linearly to either NOx emission changes due to the NOy partitioning change and the corresponding lifetime change. Lightning NOxcontributes 24%−43% of the free tropospheric (FT) NOy export from the U.S. to the North Atlantic and 28%−34% to the NOy wet deposition over the United States. Increasing lightning NOx decreases the fractional contribution of PAN to total NOy export and decreases the FT ozone (O3) production efficiency. Therefore, a model with biased low lightning NOx would lead to biased high downwind O3 responses due to anthropogenic NOx emission regulations. Better constraints on the lightning NOx source are required to more confidently assess the impacts of anthropogenic emission regulations on air quality over downwind regions.

Relative contribution of the major NOy components to the total NOy flux through the east wall (67.5°W, from 24°N–48°N) of the United States in the NOx04LowLght (green), the NOx04HighLght (blue), and the NOx99HighLght (red) simulations.
Relative contribution of the major NOy components to the total NOy flux through the east wall (67.5°W, from 24°N–48°N) of the United States in the NOx04LowLght (green), the NOx04HighLght (blue), and the NOx99HighLght (red) simulations.

Reference:

Fang, Y, Arlene M Fiore, Larry Horowitz, Hiram Levy II, Y Hu, and A G. Russell, 2010, Sensitivity of the NOy budget over the United States to anthropogenic and lightning NOx in summer. Journal of Geophysical Research, 115, D18312, doi:10.1029/2010JD014079.