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Development of A Bottom-up Soil NOx Inventory

This study focuses on the development of a comprehensive soil NOx inventory, considering factors such as soil temperature, soil moisture, pulsing, agriculture, and deposition. The results indicate a higher soil NOx emission estimate compared to previous models.

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Development of A Bottom-up Soil NOx Inventory

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  1. Development of A Bottom-up Soil NOx Inventory Neil E. Moore Dalhousie University R. V. Martin, A. Fiore, L. Jaeglé, S. Koumoutsaris, N. Ramankutty, M. Friedl 3rd GEOS-Chem Users’ Meeting Apr. 12, 2007

  2. Algorithm Components Soil NOx emissions within GEOS-CHEM: Soil temperature/soil moisture: Yienger and Levy (1995) Pulsing: Yienger and Levy (1995) Agriculture: Yienger and Levy (1995) Canopy recapture: Wang, Jacob, and Logan (1998) GEOS4 for the year 2000 Soil NOx total: 5.95 Tg N/yr (molec/cm2/s)

  3. Motivation Jaeglé et al. (2005) A posteriori soil NOx inventory for 2000 based on GOME Soil NOx total: 8.88 Tg N/yr GEOS-Chem soil NOx too low The first evidence of pulsing from satellite (molec/cm2/s) Jaeglé et al. (2004) Factor of 2 higher within purple box

  4. Soil Temperature/Soil Moisture The old The result Input variable: Rainfall The new (van Dijk et al. (2002)) Input variable: Soil Moisture (Δmolec/cm2/s) Δ Global Total = -0.8 Tg N/yr

  5. Pulsing The old • Triggers: • `Dry’ soil • - Sufficient Rainfall The result The new (Yan et al. (2005)) • Triggers: • - θ < 0.35 • θ increase of 0.01 • - Depends on dry period (Δmolec/cm2/s) Δ Global Total ≈ 0 Tg N/yr

  6. Fertilizer-Induced Emissions The old The new • - Dataset: 75 Tg N applied/year • - 100% of fertilizer is applied at start • Growing season is fixed (May-Aug) • Emissions are fixed (2.5% of applied fertilizer) • - Contributes 0.7 Tg N/yr to total • - Dataset: 92 Tg N applied/year (Ramankutty) • - 75% applied over first month; 25% for rest (Matson et al. (1998)) • MODIS data (Friedl) sets growing season • Fertilizers are subject to exponential loss -- exp(-t/τ). τ ranges from 1-2 months (Fenn et al. (1998)). Emissions = 2.5% of fertilizer.

  7. Fertilizer-Induced Emissions The result (τ = 1.5 months) (Δmolec/cm2/s) Δ Global Total = +0.2 Tg N/yr

  8. Deposition as a Fertilizer Source • The new: • Treat the wet and dry deposition of HNO3, NH3, NH4+, and NO32- as an additional fertilizer source. • - The fraction of these that does not runoff contributes to NOx emissions. The result (τ = 1.5 months) (Δmolec/cm2/s) Δ Global Total = +2.3 Tg N/yr

  9. Taken Together Considering all four modifications: soil temp./soil moisture, pulsing, agriculture, deposition The result (τ = 1.5 months) The final result (Δmolec/cm2/s) (molec/cm2/s) Δ Global Total = +1.9 Tg N/yr Global Total = 7.8 Tg N/yr

  10. Thank You

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