On the diurnal and field-scale variability of atmospheric ammonia over Dutch grasslands
Excess nitrogen deposition, particularly deposition of atmospheric ammonia (NH3), not only leads to environmental damage, but there are also serious political and societal consequences when mitigation of these harmful effects fails. We present a comprehensive approach to advance our understanding of the diurnal variability of both the NH3 concentration and surface-atmosphere exchange, combining advanced observations with turbulent resolved simulations at field-scale. The variability of atmospheric NH3 is governed by processes acting on local and non-local scales, spanning several disciplines, including meteorology, biology and chemistry. We furthermore identify a mismatch between the observed and parameterized NH3 flux at subdaily scales. To advance our understanding of this NH3 exchange, we connect NH3 flux observations to CO2 uptake and plant transpiration. In doing so, we are able to link observed NH3 emissions to stomatal exchange. We furthermore assess the impact of nearby emissions on NH3 measurements. Using a high-resolution turbulent resolved simulation framework, we find that an emission plume can affect NH3 measurements over several (1-4) kilometers distance. With our integrated approach and turbulent resolved simulation framework, we are taking research on atmospheric ammonia to a higher level of quantification and detail.