20 Jul 2023
 | 20 Jul 2023
Status: this preprint is open for discussion.

Observational relationships between ammonia, carbon dioxide and water vapor under a wide range of meteorological and turbulent conditions: RITA-2021 campaign

Ruben Bastiaan Schulte, Jordi Vilà-Guerau de Arellano, Shelley van der Graaf, Susanna Rutledge-Jonker, Jun Zhang, and Margreet Catharijne van Zanten

Abstract. We present a comprehensive observational approach, aiming to establish relations between the surface-atmosphere exchange of ammonia (NH3) and the CO2 uptake and transpiration by vegetation. In doing so, we study relationships useful for the the improvement and development of NH3 flux representations and their dependences. The NH3 concentration and flux are measured using a novel open-path miniDOAS measurement setup, taken during the five week RITA-2021 campaign (25 August until 12 October 2021) at the Ruisdael Observatory at Cabauw, the Netherlands. After filtering for unobstructed flow, sufficient turbulent mixing and CO2 uptake, we find the diurnal variability of the NH3 flux to be characterized by daytime emissions (0.05 μg m-2 s-1 on average) and deposition at sunrise and sunset (-0.05 μg m-2 s-1 on average). We first compare the NH3 flux to the observed gross primary production (GPP), representing CO2 uptake, and latent heat flux (LvE), representing to evapotranspiration. Next we study the observations following the main drivers of the dynamic vegetation response, which are photosynthetically active radiation (PAR), temperature (T) and the water vapor pressure deficit (VPD). Our findings show indication of the dominance of stomatal emission of NH3, with high correlation between the observed emissions and both net LvE (0.70) and PAR (0.72), as well as close similarities in the diurnal variability of the NH3 flux and GPP. However, the efforts to establish relationships are hampered due to the amount of diversity of NH3 sources of the active agricultural region and low data availability after filtering. Our findings show the need to collocate meteorological, carbon and nitrogen studies to advance on our understanding of NH3 deposition and its representation.

Ruben Bastiaan Schulte et al.

Status: open (until 06 Oct 2023)

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Ruben Bastiaan Schulte et al.

Ruben Bastiaan Schulte et al.


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Short summary
We analysed measurements, aiming to find relations between the surface atmosphere exchange of NH3 and the CO2 uptake and transpiration by vegetation. We found high correlation between the daytime NH3 emissions and latent heat flux and the photosynthetically active radiation. There exist very few simultaneous measurements of NH3, CO2 fluxes and meteorological variables at subdiurnal timescales. This study paves the way for finding more robust relations between NH3 exchange flux and CO2 uptake.