Dry Deposition of Reactive Nitrogen From Satellite Observations of Ammonia and Nitrogen Dioxide Over North America

Reactive nitrogen (N r ) is an essential nutrient to plants and a limiting element for growth in many ecosystems, but it can have harmful effects on ecosystems when in excess. Satellite‐derived surface observations are used together with a dry deposition model to estimate the dry deposition flux of the most abundant short‐lived nitrogen species, NH 3 and NO 2 , over North America during the 2013 warm season. These fluxes demonstrate that the NH 3 contribution dominates over NO 2 for most regions (comprising ~85% of their sum in Canada and ~65% in the U.S.), with some regional exceptions (e .g. Alberta and northeastern U.S.). Nationwide, ~1.35 Tg of N from these species were dry deposited in the contiguous U.S., more than double the ~0.61 Tg in Canada (excluding territories) over this period. Forest fires are shown to be the major contributor of dry deposition of N r from NH 3 in northern latitudes, leading to deposition fluxes 2–3 times greater than from expected amounts without fires.