NH 3 emissions from large point sources derived from CrIS and IASI satellite observations

Abstract. Ammonia (NH 3 ) is an essential reactive nitrogen species in the biosphere and through its use in agriculture in the form of fertilizer important for sustaining human kind. The current emission levels however, are up to four times higher than in the previous century and continue to grow with uncertain consequences to human health and the environment. While NH 3 at its current levels is a hazard to the environmental and human health the atmospheric budget is still highly uncertain, which is a product of an overall lack of measurements. The capability to measure NH 3 with satellites has opened up new ways to study the atmospheric NH 3 budget. In this study we present the first estimates of NH 3 emissions, lifetimes, and plume widths from large (> ~ 5 kt/yr) agricultural and industrial point sources from CrIS satellite observations across the globe with a consistent methodology. The same methodology is also applied to the IASI (A and B) satellite observations and we show that the satellites typically provide comparable results that are within the uncertainty of the estimates. The computed NH 3 lifetime for large point sources is on average 2.35 ± 1.16 hours. For the 249 sources with emission levels detectable by the CrIS satellite, there are currently 55 locations missing (or underestimated by more than an order of magnitude) from the current HTAPv2 emission inventory, and only 72 locations with emissions within a factor 2 compared to the inventories. We find a total of 5622 kt/yr, for the sources analyzed in this study, which is equivalent to a factor ~ 2.5 between the CrIS estimated and HTAPv2 emissions. Furthermore, the study shows that it is possible to accurately detect short and long-term changes in emissions, demonstrating the possibility of using satellite observed NH 3 to constrain emission inventories.