Final published version
Licence: CC BY: Creative Commons Attribution 4.0 International License
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Article number | e2021JD035237 |
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<mark>Journal publication date</mark> | 27/09/2021 |
<mark>Journal</mark> | Journal of Geophysical Research: Atmospheres |
Issue number | 18 |
Volume | 126 |
Number of pages | 18 |
Publication Status | Published |
Early online date | 13/09/21 |
<mark>Original language</mark> | English |
Agricultural emissions of ammonia (NH 3) impact air quality, human health, and the vitality of aquatic and terrestrial ecosystems. In the UK, there are few direct policies regulating anthropogenic NH 3 emissions and development of sustainable mitigation measures necessitates reliable emissions estimates. Here, we use observations of column densities of NH 3 from two space-based sensors (IASI and CrIS) with the GEOS-Chem model to derive top-down NH 3 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 NH 3. 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 NH 3 emissions and warrant further investigation.