Biogenic Emissions over Europe and VOC Oxidation

Gabriele Curci

http://pumpkin.aquila.infn.it/gabri

Gabriele Curci

1

28 May 2026

3^rd GEOS-Chem Users’ Meeting, Harvard University, April 11-13 2007

With contribution from: Paul Palmer, May Fu, Kelly Chance

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Motivation

Gabriele Curci

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28 May 2026

Biogenic emission inventories are very uncertain, e.g. even more than a factor of 5 for isoprene emissions

Effect on atmospheric chemistry is significant!

Palmer et al. developed the idea of using satellite formaldehyde (HCHO) observations to constrain North American isoprene emissions

In this work we focus on Europe

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VOC oxidation and HCHO production

Gabriele Curci

3

28 May 2026

CITY

FOREST

WIND

WIND

THIS HCHO IS WELL CORRELATED TO ITS PARENT VOC!

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GOME HCHO Seasonal Cycle in Europe

Gabriele Curci

4

28 May 2026

Formaldehyde column abundances in phase with vegetation growing season

August maximum and winter below detection limit (4x10¹⁵ molec cm^-2)

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GOME HCHO in August on a 0.5°x0.5° grid

Gabriele Curci

5

28 May 2026

GOME HCHO 1996-2000 average column

1.5

2.4

1.0

0.5

2.0

Enhanced HCHO near urban/industrial areas

Moderate HCHO columns near forested areas

Elevated HCHO offshore of the continent

[10¹⁶ molec cm^-2]

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GEOS-Chem vs GOME HCHO column

Gabriele Curci

6

28 May 2026

GOME HCHO 2°x2.5° August 1996-2000

GEOS-Chem HCHO (v736) August 2000

GEIA [Guenther 95]

MEGAN [Guenther 06]

GEOS-Chem HCHO columns with MEGAN are <50% than GEIA

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GC HCHO vs GOME:

GEIA: bias -17% and r² = 0.48

MEGAN: bias -38% and r² = 0.61

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GEOS-Chem vs EMEP ground VOC obs

Gabriele Curci

7

28 May 2026

• Routine measurement of VOCs since ’90s twice a week at EMEP background sites
• August 2000: 4 stations in Germany, 1 CZ, 1 France
• Result: there is a light advantage in using MEGAN, but data are really limited!

MEGAN better

MEGAN worse

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HCHO Production over Europe in August (1)

Gabriele Curci

8

28 May 2026

On continental scale methanol, methane and acetone provide ~60% of HCHO

Isoprene with its short lifetime (<1 h) is expected to drive HCHO variability

Monoterpene and AVOC ~10% each, but delayed HCHO production

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HCHO Production over Europe in August (2)

Gabriele Curci

9

28 May 2026

GEOS-Chem model calculations for August 2000

ISOPRENE

AVOCs

Isoprene contributes up to 40% locally to HCHO column

AVOC contribute only 5%, but reactive VOC (xylenes, ethene, …) are missing

AVOC signal in GOME HCHO was not detectable in China during summer [Fu et al., 2007]

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NOx-dependent inversion of HCHO column for Isoprene emissions

Gabriele Curci

10

28 May 2026

Yield of isoprene oxidation product non-linearly depend on ambient NO_x [e.g. Barket et al., 2004]

1. Divide domain’s grid cells in two categories according to NO₂ column content (LOW and HIGH)
2. Use GEOS-Chem to relate HCHO column to isoprene emissions for two NO_x categories

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GEOS-Chem vs GOME Isoprene emissions

Gabriele Curci

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28 May 2026

GOME Isoprene Emissions August 1996-2000

GEOS-Chem Isoprene Emissions August 2000

GEIA

MEGAN

GOME-derived isoprene emissions high in Spain, France, Italy, Eastern and South-Eastern Europe (total C in August 2.3 Tg)

GEIA (2.1 Tg): -20% and r² = 0.31

MEGAN (0.8 Tg): -67% and r² = 0.47

AVOC emissions are about 1.2 Tg

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Thanks for your attention!

Gabriele Curci

12

28 May 2026

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