blog & news

Longterm urban eddy covariance observations of methane and other trace gases reveal characteristic anthropogenic emission hotspots

Extended Poster EGU25-5202

Synopsis: Long-term urban eddy covariance observations of methane, CO₂ and other trace gases allow to constrain important emission sources. We find that most methane is released activity driven towards the top of the urban inertial sublayer (and not necessarily only at ground level) via post-meter emissions from gas furnace operations. Unburned methane then escapes through chimneys into the urban atmosphere.

„Methane emissions in urban areas“ weiterlesen

Mapping CH4 in urban areas is still challenging because emissions are often diffuse. A new study https://doi.org/10.1016/j.atmosenv.2024.120743 finds evidence of urban superemitters that can substantially incrase emissions.

„Mapping urban methane (CH4) emissions“ weiterlesen

A recent paper by Pfannerstil highlights the potential of airborne eddy flux measurements (Temperature-dependent emissions dominate aerosol and ozone formation in Los Angeles | Science). They show that up to 60% of the VOC reactivity is associated with biogenic emissions. Despite the great strides that have been made in reducing urban pollution in major North America and European cities, there is much that remains unclear about the causes of such pollution. Mapping urban haze | Science

 

We are proud to be part of the new FWF funded project on the future of mountain forests under a drier climate. 

The Future of Mountain Forests – Universität Innsbruck (uibk.ac.at)

Mountain regions are especially affected by climatic changes and mountain forests are expected to be exposed to increasing drought stress. This project aims at analysing if and how drier conditions influence carbon and water balances from tree to forest level, change plant stress responses and interactions with microbial communities, and affect ecosystem services. 

The overarching research objective of the Biosphere-Atmosphere Interactions group is to quantify the two-way interactions and feedbacks between Alpine ecosystems and the atmosphere. The emission of reactive biogenic trace gases by terrestrial ecosystems as precursors of air pollutants and secondary organic aerosols and the associated warming (e.g. because of positive feedbacks of tropospheric ozone on net primary productivity) and cooling (due to aerosol-radiation and aerosol-cloud interactions) is amongst the most poorly constrained feedbacks in the climate system. Within this activity we will develop a framework to investigate  positive and negative feedbacks on tropospheric chemistry from major Alpine ecosystems affected by ongoing climate change.

 

The fraction of ozone near the surface in urban areas tends to be overestimated in atmospheric models. New observations at the IAO reveal a possible explanation, which is presented in the following paper https://www.science.org/doi/10.1126/sciadv.add2365

Short summary: Long-term eddy covariance measurements of O₃, NO and NO₂, combined with models and remote sensing observations over an urban area,  allowed disentangling important physical and chemical processes. When generalized our findings suggest that the depositional ozone flux near the surface in urban environments is negligible compared to the flux caused by chemical conversion of ozone. This leads to an underestimation of the Leighton ratio, and is a key process for modulating urban NO₂ mixing ratios. 

Entering our 6th year of #urban #CO2 flux observations.

We will start posting flux data on http://www.europe-fluxdata.eu/

So far we have collected 5 years of CO2 (H2O), heat, momentum and NOx fluxes, 3+ years of O3 fluxes, 2+ years of CH4 fluxes and 6+ years of intermittent VOC fluxes.

some recent papers:

https://www.sciencedirect.com/science/article/pii/S0048969722017557
https://acp.copernicus.org/articles/22/6559/2022/
https://acp.copernicus.org/articles/22/5603/2022/
https://acp.copernicus.org/articles/21/3091/2021/
https://journals.ametsoc.org/view/journals/bams/101/6/BAMS-D-19-0270.A.xml
https://www.nature.com/articles/s41598-017-02699-9?sf98484848=1
https://www.pnas.org/doi/abs/10.1073/pnas.1714715115

@tomkarl@atmoschem.org

The paper by Nicolini et al., shows the variability and reduction potential of CO2 emissions across Europe.
Data show first measured evidence of a consistent reduction of CO2 emissions, proportional to the stringency of restrictions.

Publication

Analysis of air quaility data in Vienna (Brancher et al., 2021)  shows a reduction of NO2 by 20% during the hard Lockdown in 2020, but no significant changes in Ox.

„Air pollution in Vienna during 2020 lockdown“ weiterlesen

Methane (CH₄)  is an important greenhouse gas in the atmosphere. The methane emission budget has a sizeable anthropogenic contribution, which makes methane the most important non-CO₂ greenhouse gas released from anthropogenic activities. Methane emissions play a key role in hydroxyl consumption, thus contributing to complex interactions central to atmospheric chemistry and climate. Reduction of CH₄ emissions can provide quick and cost effective cuts in global warming, but requires a sound understanding of the different anthropogenic sources. Although the total global CH₄ budget is relatively well understood, the contributions of individual sources to CH₄ emissions are poorly constrained. Anthropogenic methane emissions in Austria are largely based on Tier 1 bottom-up scaling and urban emission sources are subject to significant  uncertainty.  In collaboration with the JRC Ispra, we propose a holistic top-down approach to constrain methane emissions on the local to urban scale based on eddy flux observations of methane along with a suite of additional chemical markers.

IAO Flux Tower in Innsbruck

During the lockdown we find larger emission reductions for classic air pollutants (NOx, NMVOC) than for CO2 – are traffic NOx emissions still underestimated? More: 

https://acp.copernicus.org/articles/21/3091/2021/