Measurement and modelling of the dynamics of NH 3 surface–atmosphere exchange over the Amazonian rainforest

Biogeosciences

article

Ramsay, Robbie¹  Di Marco, Chiara F.¹  Heal, Mathew R.²  Sörgel, Matthias³  Artaxo, Paulo⁵  Andreae, Meinrat O.³  Nemitz, Eiko¹ 

[1] UK Centre for Ecology and Hydrology (UKCEH);School of Chemistry, University of Edinburgh;Biogeochemistry Department, Max Planck Institute for Chemistry;now at: Atmospheric Chemistry Department, Max Planck Institute for Chemistry;Instituto de Física, Universidade de São Paulo;Scripps Institution of Oceanography, University of California San Diego

DOI  :  10.5194/bg-18-2809-2021

学科分类：大气科学

来源: Copernicus Publications

【 摘 要 】

Local and regional modelling of NH 3 surface exchange is required to quantify nitrogen deposition to, and emissions from, the biosphere. However, measurements and model parameterisations for many remote ecosystems – such as tropical rainforest – remain sparse. Using 1 month of hourly measurements of NH 3 fluxes and meteorological parameters over a remote Amazon rainforest site (Amazon Tall Tower Observatory, ATTO), six model parameterisations based on a bidirectional, single-layer canopy compensation point resistance model were developed to simulate observations of NH 3 surface exchange. Canopy resistance was linked to either relative humidity at the canopy level (RH z 0 ′ ), vapour pressure deficit, or a parameter value based on leaf wetness measurements. The ratio of apoplastic NH 4 + to H + concentration, Γ s , during this campaign was inferred to be 38.5  ±  15.8. The parameterisation that reproduced the observed net exchange of NH 3 most accurately was the model that used a cuticular resistance ( R w ) parameterisation based on leaf wetness measurements and a value of Γ s =50 (Pearson correlation r =0.71 ). Conversely, the model that performed the worst at replicating measured NH 3 fluxes used an R w value modelled using RH z 0 ′ and the inferred value of Γ s =38.5 ( r =0.45 ). The results indicate that a single-layer canopy compensation point model is appropriate for simulating NH 3 fluxes from tropical rainforest during the Amazonian dry season and confirmed that a direct measurement of (a non-binary) leaf wetness parameter improves the ability to estimate R w . Current inferential methods for determining Γ s were noted as having difficulties in the humid conditions present at a rainforest site.

【 授权许可】

CC BY