the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 Apr 2025
A Framework for Gridded Estimates of Ammonia Emissions from Agriculture in South Asia
Abstract. Emissions of ammonia (NH3) from agricultural activities are a major threat to ecosystems and human health. Its quantification via emissions inventories is vital to the understanding of mitigation strategies and policy formation. South Asia, specifically the South Asian Association for Regional Cooperation (SAARC), is a global hotspot of NH3 emissions from agriculture but also an area of great uncertainty due to a lack of data that are representative of local practices. This study presents a framework into which indigenous data can be ingested to adjust such estimates, to provide spatially distributed (0.1° × 0.1°) emissions in five agricultural sectors for improved input data for atmospheric chemistry transport models, by moving away from Tier 1 methods for emission inventories. Results incorporate data such as lower emission factors of NH3 following the application of Urea (13 % of total nitrogen lost as NH3-N) to provide a total estimated emission of NH3 in the SAARC of ~6 Tg, with high values (> 5 g NH3 m-2 a-1) in the Indian states Haryana, Punjab and Uttar Pradesh in the Indo-Gangetic Plain (IGP).
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RC1: 'Comment on essd-2025-75', Anonymous Referee #1, 13 Aug 2025
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This manuscript presents a comprehensive and regionally tailored framework for estimating agricultural ammonia (NH₃) emissions in South Asia, an area critical for understanding reactive nitrogen pollution, yet underrepresented in high-resolution emission inventories. The proposed framework uses a hybrid Tier 1/2 methodology, incorporating national and subnational data (e.g., fertilizer use, livestock systems, crop distribution) at a high spatial resolution of 0.1° x 0.1°. The dataset offers significant value due to its spatial granularity, region-specific emission factors (particularly for urea), and transparent methodology. This makes it a promising tool for atmospheric modeling, policy planning, and future updates. However, several issues need to be addressed to ensure that the dataset meets the standards of accessibility, reproducibility, and robustness required by ESSD.
Key Concerns:
- Data Accessibility: The gridded dataset lacks direct accessibility due to the absence of a persistent identifier (e.g., DOI) or a direct link to a stable, publicly accessible data repository.
- Emission Factor (EF) Consistency: The manuscript applies a uniform emission factor for urea without considering pH variability, which could affect the accuracy of NH₃ emissions estimates.
- Uncertainty Analysis: The manuscript does not provide a quantitative uncertainty analysis for the final gridded product, including error propagation and uncertainty ranges, which is critical for evaluating the reliability of the estimates.
- Reproducibility of Input Data: The manuscript relies on "personal communication" for certain input data, raising concerns regarding the reproducibility and transparency of the study.
Given the manuscript's valuable methodological contribution and the importance of the estimates, major revisions are required to align with ESSD's standards for data accessibility, reproducibility, and rigorous uncertainty quantification.
List of Major Revisions Required:
- Data Accessibility: The manuscript should provide a persistent identifier (e.g., DOI) or a direct link to a publicly accessible and stable data repository for the 0.1° x 0.1° gridded dataset.
- Uncertainty Analysis: A quantitative uncertainty analysis is needed for the final gridded estimates, including error propagation and uncertainty ranges.
- Reproducibility of Input Data: Any data cited as "personal communication" must either be made available as supplementary material or detailed justifications should be provided, including a discussion of the implications for reproducibility.
- Urea EF Consistency: The uniform application of the urea emission factor without accounting for pH variability should be clarified and justified, or the potential impacts on accuracy should be discussed.
Specific Comments:
- Table 1 Correction: The "Maldives 1.2" formatting error in Table 1 should be corrected.
- Abbreviations List: It is suggested to include a list of abbreviations to improve readability.
- Metadata Enhancement: The dataset in EIDC should be accompanied by a README file, including:
- Explanation of the file structure
- Units of measurement
- Reference to this manuscript
Citation: https://doi.org/10.5194/essd-2025-75-RC1
Data sets
Gridded emissions of ammonia (NH3) from agricultural sources in South Asia at 0.1 degrees resolution, 2015 S. J. Tomlinson et al. https://doi.org/10.5285/e0114a4f-32c2-41d9-9c2a-c46f365d4c30
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