Quantification of Global Ammonia Sources constrained by a Bayesian Inversion Technique (COMBAT)

Nitrogen is a basic component of life and it is present both in proteins and DNA. Its basic chemical form in nature is the non-reactive gaseous N₂.

However, in the 20th Century humans converted N₂ into more reactive forms. Today, NH₃ (ammonia) sustains life and almost 40% of the global population owes its life to NH₃ through the use of fertilisers’ in food production. Though, implications of ammonia for population and environment have received a lot of attention in the last decades.

On one hand, its presence in the atmosphere in low concentrations is beneficial as it makes the rain less acidic by neutralising sulphuric acid aerosols. On the other hand, increased emissions of NH3 result in reactions with sulphuric and nitric acids contributing 30%-50% to the total PM_2.5 and PM₁₀ mass.

Enhanced production of ammonium aerosols can cause premature mortality as they penetrate human respiratory system and deposit in the lungs. Furthermore, ammonium aerosols affect the Earth’s radiative balance, both directly by scattering incoming radiation and indirectly as cloud condensation nuclei causing a positive climate feedback (warming).

Despite its importance, NH3 is one of the most poorly quantified gases with a limited number of continuous ammonia measurements in Europe, America or Asia.

However, the lack of observations is covered by satellites and nowadays satellite algorithms are advanced enough to provide daily global concentrations of atmospheric NH₃.

We use the existing knowledge of Lagrangian dispersion modelling and Bayesian inversion in NILU accompanied by continuous and satellite measurements to quantify regional (Europe) and global emissions of NH₃.

The optimised fluxes of NH₃ are studied and the impact to the environment and the population is examined. The methodology is designed to maximize the utility of empirical data for the least understood aspects and use models for source identification, which cannot be inferred from measurements alone.

The main points of COMBAT’s developments and progress:

(Publications – see below.)

– The coupling of FLEXPART model with the Kinetic PreProcessor (KPP) to account for chemistry has resulted in a Conference publication (16th IGAC Scientific Confeence). A publication will be lead by the University of Bremen.

– The methodology to calculate NH3 emissions from satellite measurements was adapted to the needs of LSCE and this has resulted in a Conference publication (16th IGAC Scientific Confeence). A publication on this will be lead by the LSCE .

– Satellite measurements of NH3 from CrIS product are being processed to the inverse modelling framework. This will result in a publication focusing in Europe using the new reanalysis product from ECMWF (ERA5).