Development of A Bottom-up Soil NOx Inventory

Neil E. Moore

Dalhousie University

3^rd GEOS-Chem Users’ Meeting

Apr. 12, 2007

R. V. Martin, A. Fiore, L. Jaeglé, S. Koumoutsaris, N. Ramankutty, M. Friedl

Algorithm Components

Soil NO_x 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 NO_x total:

5.95 Tg N/yr

(molec/cm²/s)

Motivation

A posteriori soil NO_x inventory for 2000 based on GOME

Soil NO_x total:

8.88 Tg N/yr

GEOS-Chem soil NO_x too low

Jaeglé et al. (2005)

Jaeglé et al. (2004)

The first evidence of pulsing from satellite

Factor of 2 higher within purple box

(molec/cm²/s)

Soil Temperature/Soil Moisture

(Δ molec/cm²/s)

The old

The new (van Dijk et al. (2002))

The result

Input variable:

Rainfall

Input variable:

Soil Moisture

Δ Global Total = -0.8 Tg N/yr

Pulsing

The old

The new (Yan et al. (2005))

Triggers:

• `Dry’ soil

- Sufficient Rainfall

Triggers:

- θ < 0.35

• θ increase of 0.01

- Depends on dry period

Δ Global Total ≈ 0 Tg N/yr

The result

(Δ molec/cm²/s)

Fertilizer-Induced Emissions

The old

- 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

The new

- 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.

Fertilizer-Induced Emissions

Δ Global Total = +0.2 Tg N/yr

The result (τ = 1.5 months)

(Δ molec/cm²/s)

Deposition as a Fertilizer Source

The new:

• Treat the wet and dry deposition of HNO₃, NH₃, NH₄⁺, and NO₃^2- as an additional fertilizer source.

- The fraction of these that does not runoff contributes to NO_x emissions.

The result (τ = 1.5 months)

Δ Global Total = +2.3 Tg N/yr

(Δ molec/cm²/s)

Taken Together

Considering all four modifications:

soil temp./soil moisture, pulsing, agriculture, deposition

The result (τ = 1.5 months)

The final result

Δ Global Total = +1.9 Tg N/yr

Global Total = 7.8 Tg N/yr

(molec/cm²/s)

(Δ molec/cm²/s)

Thank You