Evaluation of interactive and prescribed agricultural ammonia emissions for simulating atmospheric composition in CAM-chem

Abstract

Abstract. Ammonia (NH3) plays a central role in the chemistry of inorganic secondary aerosols in the atmosphere. The largest emission sector for NH3 is agriculture, where NH3 is volatilized from livestock wastes and fertilized soils. Although the NH3 volatilization from soils is driven by the soil temperature and moisture, many atmospheric chemistry models prescribe the emission using yearly emission inventories and climatological seasonal variations. Here we evaluate an alternative approach where the NH3 emissions from agriculture are simulated interactively using the process model FANv2 (Flow of Agricultural Nitrogen, version 2) coupled to the Community Atmospheric Model with Chemistry (CAM-chem). We run a set of 6-year global simulations using the NH3 emission from FANv2 and three global emission inventories (EDGAR, CEDS and HTAP) and evaluate the model performance using a global set of multi-component (atmospheric NH3 and NH4+, and NH4+ wet deposition) in situ observations. Over East Asia, Europe and North America, the simulations with different emissions perform similarly when compared with the observed geographical patterns. The seasonal distributions of NH3 emissions differ between the inventories, and the comparison to observations suggests that both FANv2 and the inventories would benefit from more realistic timing of fertilizer applications. The largest differences between the simulations occur over data-scarce regions. In Africa, the emissions simulated by FANv2 are 200 %–300 % higher than in the inventories, and the available in situ observations from western and central Africa, as well as NH3 retrievals from the Infrared Atmospheric Sounding Interferometer (IASI) instrument, are consistent with the higher NH3 emissions as simulated by FANv2. Overall, in simulating ammonia and ammonium concentrations over regions with detailed regional emission inventories, the inventories based on these details (HTAP, CEDS) capture the atmospheric concentrations and their seasonal variability the best. However these inventories cannot capture the impact of meteorological variability on the emissions, nor can these inventories couple the emissions to the biogeochemical cycles and their changes with climate drivers. Finally, we show with sensitivity experiments that the simulated time-averaged nitrate concentration in air is sensitive to the temporal resolution of the NH3 emissions. Over the CASTNET monitoring network covering the US, resolving the NH3 emissions hourly instead monthly reduced the positive model bias from approximately 80 % to 60 % of the observed yearly mean nitrate concentration. This suggests that some of the commonly reported overestimation of aerosol nitrate over the US may be related to unresolved temporal variability in the NH3 emissions.

County-level ammonia emissions monitored worldwide

“…It is possible that there are emissions from smaller scale fires, which sometimes can be missed in the Fire Radiative Power (FRP) products from instruments such as VIIRS and MODIS 35 and consequently might increase the uncertainty of our emission estimate in this location. However, another potential explanation is that the local agricultural emissions are underestimated in the current inventories 36,37 . The emission patterns, and especially the higher emissions found for Nigeria, match closely to distribution of livestock animals 33,38 .…”

One-Third of Global Population at Cancer Risk due to Elevated Volatile Organic Compounds Levels

“…Further details on CAM6-Chem model configuration and evaluation have been described explicitly on our previous study 5 and elsewhere. 44,[47][48][49] Health Risk Assessment…”

Development of a CFD model to simulate the dispersion of atmospheric NH3 in a semi-open barn

“…NH 3 emissions into the atmosphere affect human health, the climate, and ecosystems, due to the formation of secondary aerosols. Despite many studies on the subject, there is inadequate knowledge of agricultural sources (Liu et al, 2022;Luo, 2022;Viatte et al, 2022;Vira et al, 2022;Wang et al, 2022). The increase in global demand for food has caused an increase in the concentration of NH 3 produced by dairy farms.…”

“…On the other hand, alkaline environments reduce aerosol uptake and NH 3 removal, making dry depositions the dominant removal pathways. The patterns in the concentration of atmospheric NH 3 are affected depending on environmental factors (Vira et al, 2022).…”

“…According to Vira et al (2022) and Wang et al (2022), livestock waste and fertilized soils are the highest sources of NH 3 emissions. Temperature and moisture drive NH 3 emissions.…”