Nitrosat’s objectives are to provide measurements of the two main reactive nitrogen species in the troposphere, NO2 and NH3, with the sensitivity and spatial resolution required to address a series of pressing science issues in relation to the cycle of reactive nitrogen species and to quantify their impacts on the atmosphere, health and ecosystems.
1.
Quantify the emissions of NH3 and NO2 on the landscape scales, to expose individual sources and characterize the temporal patterns of their emissions.
Nitrosat will provide a complete and comprehensive mapping of NH3 and NO2 atmospheric abundances at sub-km scale, which will yield a unique view of the main individual anthropogenic emitters and of the area sources of reactive nitrogen around the globe. With a revisit time of better than once a month and a duration of several years, Nitrosat will allow monitoring the temporal variability and changes in these emissions, in relation to meteorology, environmental policies and transformational adaptation in economy and agriculture.
2.
Quantify the relative contribution of agriculture, in its diversity of sectors and practices, to the total emissions of reactive nitrogen.
With its unmatched spatial resolution Nitrosat will yield top-down constraint on emissions of reactive nitrogen from farming practices and other important sectors, including industries, road traffic and biomass burning. It will allow disentangling in particular the contribution of agriculture to the total emissions, which is essential to address a grand challenge of the 21st century, of producing more food within environmental limits.
3.
Quantify the contribution of reactive nitrogen to air pollution and its impact on human health.
Nitrosat will assess sources and pollution dispersion at landscape scales (urban, suburban and rural). Further, Nitrosat will largely improve exposure assessments, which are pivotal in air pollution studies and still a serious limitation in many current air quality models. In addition, it will uniquely contribute, in combination with these models, to evaluate the effectiveness of local or regional air quality control strategies (the main focus being O3, aerosol, and their precursors) on NOx or on NH3, individually or together. The assimilation of Nitrosat measurements will foster the development of high spatially resolved air quality and exposure models.
4.
Constrain the atmospheric dispersion and surface deposition of reactive nitrogen and its impacts on ecosystems and climate; and contribute to monitoring policy progress to reduce nitrogen deposition in Natura 2000 areas in Europe.
Nitrosat will provide distributions of NH3 and NO2 on the scales that are needed to constrain the critical processes driving nitrogen dispersion and chemistry and subsequent deposition fluxes over terrestrial systems, coastal areas and oceans, including biodiversity hotspots.
5.
Reduce uncertainties in the contribution of reactive nitrogen to climate forcing, atmospheric chemistry and interactions between biogeochemical cycles.
Nitrosat will help, with the expected improved estimates of N deposition, to narrow uncertainties with regard to one of the key climate questions, which is how and how much the nitrogen and carbon cycles are interacting. Improved N deposition fluxes will provide additional constraints on N2O emissions and associated impact on radiative forcing. Nitrosat will provide through the local-to-global measurements of NH3 and NO2 and high-level modelling activities, insight onto several atmospheric (O3, aerosol information), oceanic (nutrients) and terrestrial (land cover, biomass) essential climate variables (ECVs).
To achieve these objectives, Nitrosat will be mapping near-surface atmospheric NH3 and NO2 at 500 m footprint, which is the required spatial scale to differentiate, identify and quantify the main point and area sources in a single satellite overpass.
Source regions will be probed from once a week to once a month to reveal the seasonal patterns.
Nitrosat 