Eloise A. Marais1, Alok K. Pandey2,
Martin Van Damme3, Lieven Clarisse3,
Pierre-François Coheur3, Mark W.
Shephard4, Karen E. Cady-Pereira5,
Tom Misselbrook6, Lei Zhu7, Gan
Luo8, Fangqun Yu8
1Department of Geography, University College London,
London, UK.2 School of Physics and Astronomy, University of
Leicester, Leicester, UK.3 Université libre de Bruxelles (ULB), Spectroscopy,
Quantum Chemistry and Atmospheric Remote Sensing (SQUARES), Brussels,
Belgium.4 Environment and Climate Change Canada, Toronto,
Ontario, Canada.5 Atmospheric and Environmental Research (AER),
Lexington, MA, USA.6 Department of Sustainable Agriculture Sciences,
Rothamsted Research, Okehampton, UK.7 School of Environmental Science and Engineering,
Southern University of Science and Technology, Shenzhen, China.8 Atmospheric Sciences Research Center, University at
Albany, Albany, New York, USA.
Corresponding author: Eloise A. Marais
(e.marais@ucl.ac.uk)
Key Points:
- Satellite observations of NH3 from 2 sensors (IASI,
CrIS) are used to estimate UK NH3 emissions in Mar-Sep
at fine scales (10 km, monthly)
- Satellite-derived NH3 emissions total 272 Gg from IASI
and 389 Gg from CrIS and exhibit a spring (April) and summer (July)
peak
- Bottom-up emissions used for research and policy are 27-49% less than
the satellite-derived estimates and miss the summer emissions peak
Abstract
Agricultural emissions of ammonia (NH3) impact air
quality, human health, and the vitality of aquatic and terrestrial
ecosystems. In the UK, there are few direct policies regulating
anthropogenic NH3 emissions and development of
sustainable mitigation measures necessitates reliable emissions
estimates. Here we use observations of column densities of
NH3 from two space-based sensors (IASI and CrIS) with
the GEOS-Chem model to derive top-down NH3 emissions for
the UK at fine spatial (~10 km) and time (monthly)
scales. We focus on March-September when there is adequate spectral
signal to reliably retrieve NH3. We estimate total
emissions of 272 Gg from IASI and 389 Gg from CrIS. Bottom-up emissions
are 27% less than IASI and 49% less than CrIS. There are also
differences in seasonality. Top-down and bottom-up emissions agree on a
spring April peak due to fertilizer and manure application, but there is
also a comparable summer July peak in the top-down emissions that is not
in the bottom-up emissions and appears to be associated with dairy
cattle farming. We estimate relative errors in the top-down emissions of
11-36% for IASI and 9-27% for CrIS, dominated by column density
retrieval errors. The bottom-up versus top-down emissions discrepancies
estimated in this work impact model predictions of the environmental
damage caused by NH3 emissions and warrant further
investigation.