08 Nov 2023
 | 08 Nov 2023
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Revising VOC emissions speciation improves global simulations of ethane and propane

Matthew James Rowlinson, Lucy Carpenter, Katie Read, Shalini Punjabi, Adedayo Adedeji, Luke Fakes, Ally Lewis, Ben Richmond, Neil Passant, Tim Murrells, Barron Henderson, Kelvin Bates, Deltev Helmig, and Mat Evans

Abstract. Non-Methane Volatile Organic Compounds (NMVOCs) generate ozone (O3) when they are oxidized in the presence of oxides of nitrogen, modulate the oxidative capacity of the atmosphere and can lead to the formation of aerosol. Here, we assess the capability of a chemical transport model (GEOS-Chem) to simulate NMVOC concentrations by comparing ethane, propane and higher alkane observations in remote regions from the NOAA Flask Network and the World Meteorological Organization’s Global Atmosphere Watch (GAW) network. Using the Community Emissions Data System (CEDS) inventory we find a significant underestimate in the simulated concentration of both ethane (35 %) and propane (64 %), consistent with previous studies. We run a new simulation where the total mass of anthropogenic NMVOC emitted in a grid box is the same as that used in CEDS, but with the NMVOC speciation derived from regional inventories. For US emissions we use the National Emissions Inventory (NEI), for Europe we use the UK National Atmospheric Emissions Inventory (NAEI), and for China, the Multi-resolution Emission Inventory for China (MEIC). These changes lead to a large increase in the modelled concentrations of ethane, improving the mean model bias from -35 % to -3.8 %. Simulated propane also improves (from -64 % to -48.0 % mean model bias), but there remains a substantial model underestimate. There were relatively minor changes to other NMVOCs. The low bias in simulated global ethane concentration is essentially removed, resolving one long-term issue in global simulations. Propane concentrations are improved but remain significantly underestimated, suggesting the potential for a missing global propane source. The change in the NMVOC emission speciation results in only minor changes in tropospheric O3 and OH concentrations.

Matthew James Rowlinson et al.

Status: open (until 24 Dec 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Matthew James Rowlinson et al.

Matthew James Rowlinson et al.


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Short summary
Ethane and propane are volatile organic compounds emitted during human activities which contribute to the formation of ozone, a greenhouse gas, and affect the chemistry of the lower atmosphere. Atmospheric models tend to do a poor job at reproducing the abundance of these compounds in the atmosphere. By using regional estimates of their emission, rather than globally consistent estimates, we can significantly improve the simulation of ethane in the model and make some improvement for propane.