Havu, Minttu: Spatial variability of local carbon emissions and sinks in Helsinki
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This document summarizes a study estimating the spatial variability of carbon cycle components in Helsinki, Finland using the SUEWS modelling tool. The study found that CO2 emissions from human metabolism accounted for 45% of local anthropogenic emissions, while net biogenic CO2 exchange accounted for 25% of anthropogenic emissions. Spatial maps showed traffic emissions were concentrated along ring roads, building heating emissions in residential areas, and human metabolism emissions in city centers. Vegetation uptake and emissions from human metabolism were comparable to or exceeded emissions from traffic and building heating in some areas of Helsinki.
Havu, Minttu: Spatial variability of local carbon emissions and sinks in Helsinki
- 1. Spatial variability of local carbon emissions and sinks in Helsinki Minttu Havu1 , Liisa Kulmala2,3 , and Leena Järvi1,4 1Institute for Atmospheric and Earth System Research /Physics, University of Helsinki, Helsinki, Finland. 2Finnish Meteorological Institute, Helsinki, Finland. 3Institute for Atmospheric and Earth System Research /Forest, University of Helsinki, Helsinki, Finland. 4Helsinki Institute of Sustainability Science, University of Helsinki, Helsinki, Finland. 1 14/09/22 Spatial variability of local carbon emissions and sinks in Helsinki
- 2. Introduction ➢ Several cities have taken actions to strive for carbon neutrality in the coming decades ➢ Atmospheric observations can be used to monitor CO2 emissions from cities but they often do not provide information on sources ➢ Modelling tools are needed to separate the different CO2 components and assist with the monitoring of anthropogenic emissions in cities ICOS associated ecosystem station FI-Kmp in Helsinki, Finland Spatial variability of local carbon emissions and sinks in Helsinki 14/09/22 2
- 3. Aim Estimate the spatial variability of different carbon cycle components Estimate the magnitude of biogenic components and human metabolism compared to local anthropogenic emissions in the city of Helsinki, Finland Spatial variability of local carbon emissions and sinks in Helsinki 14/09/22 3 CO2 flux components in urban areas (Oke, 2018) FCO2 = Net CO2 exchange C = Combustion from traffic and building heating P = CO2 uptake by photosynthesis R = Vegetation and soil respiration Human metabolism ΔS = Storage change (not considered)
- 4. Methods – SUEWS model ➢ Used model is the Surface Urban Energy and Water balance Scheme (SUEWS, Järvi et al., 2019) ➢ Simulates surface energy and water balances and CO2 surface exchange with meteorological variables and surface information Surface types in SUEWS (Sun et al., 2018) Spatial variability of local carbon emissions and sinks in Helsinki 14/09/22 4 ➢ The model is run in Helsinki for year 2019 with hourly resolution ➢ Modelling domain is divided into 250x250 m2 grids City of Helsinki (©Kaupunkimittausosasto, 2021)
- 5. Methods – Human metabolism In SUEWS, input data needed to simulate human metabolism are ➢ population density ➢ CO2 release per person (120-280 umol CO2 s-1 cap-1 Ward et al., 2013, Moriwaki and Kanda 2004) ➢ population profile for weekdays and weekends Population densities and profiles for each 250x250 m2 grids are obtained from a 24- hour population distribution dataset based on mobile phone data for Helsinki (Bergroth et al., 2022) Bergroth et al., 2022 Spatial variability of local carbon emissions and sinks in Helsinki 14/09/22 5
- 6. The CO2 uptake by photosynthesis is modelled with canopy conductance model ➢ depends on solar radiation, air temperature, humidity and soil moisture Vegetation and soil respiration ➢ depend exponentially on air temperature In our study, both submodules used the local simulated 2 m air temperatures (Tang et al., 2021) Vegetation cover is divided into urban forests, street trees and parks depending on the dominant vegetation type in each grid Each vegetation cover having their own parametrisation Spatial variability of local carbon emissions and sinks in Helsinki 14/09/22 6 Urban forest Street trees Park areas Methods – Biogenic CO2 exchanges
- 7. Methods – Anthropogenic emissions Traffic emissions ➢ mean daily traffic rate ➢ Unit emission factor for traffic Mean traffic rates for each grid obtained from city of Helsinki database Spatial variability of local carbon emissions and sinks in Helsinki 14/09/22 7 CO2 emissions from building heating ➢ population density ➢ heating degree days and temperature-related coefficients ➢ fraction of local heating that causes CO2 emissions (e.g. wood burning) ➢ emission factor for fuels used in building energy use In this study, we consider only local emissions, not single-point sources such as power plants and industrial activities In Helsinki, most buildings use district heating, only 38 % of the detached houses use firewood for heating Daily traffic rates in Helsinki (©City of Helsinki)
- 8. CO 2 flux (umol m -2 s -1 ) SUEWS has been shown to perform well in Helsinki Evaluated against ➢ Eddy covariance measurements (Järvi et al., 2019) ➢ Tree level measurements (Havu et al., 2022) Time (h) Summer 2012 Kumpula Summer 2012 Torni Spatial variability of local carbon emissions and sinks in Helsinki 14/09/22 8
- 9. Results – Spatial variability of net CO2 exchange Cumulative annual sums for different components for the whole city of Helsinki in 2019 Total 91.3 kt C year-1 Local % Net % Photosynthesis -193.1 -30.1 -25 -5 Respiration 163.0 Metabolism 54.3 45 9 Traffic 67.0 55 11 Buildings 0.1 0* 80 Spatial variability of local carbon emissions and sinks in Helsinki 14/09/22 9 *0.08% Emissions from power plants in Helsinki 470 kt C ekv.
- 10. Spatial variability of local carbon emissions and sinks in Helsinki 14/09/22 10 Traffic Human metabolism Building heating Net biogenic CO2 CO2 exchange of different components ➢ Traffic emissions concentrated on the ring road ➢ Building heating emissions concentrated in residential areas ➢ Emissions from human metabolism concentrated in the city centrum ➢ Net biogenic exchange strongest in urban forests
- 11. Results – Spatial variability How the CO2 emissions from human metabolism and vegetation compare to the emissions from traffic and building heating Spatial variability of local carbon emissions and sinks in Helsinki 14/09/22 11 CO2 emissions/sinks from vegetation compared to anthropogenic emissions CO2 emissions from human metabolism compared to anthropogenic emissions
- 12. Results – Spatial variability Spatial variability of local carbon emissions and sinks in Helsinki 14/09/22 11 CO2 emissions/sinks from vegetation compared to anthropogenic emissions CO2 emissions from human metabolism compared to anthropogenic emissions How the CO2 emissions from human metabolism and vegetation compare to the emissions from traffic and building heating
- 13. Conclusions ➢ The spatial variability of different carbon cycle components were estimated with SUEWS in the city of Helsinki ➢ The CO2 emissions from human metabolism were 45 % of the local anthropogenic emissions ➢ The net biogenic CO2 exchange was 25 % compared to the local anthropogenic emissions Spatial variability of local carbon emissions and sinks in Helsinki 14/09/22 12
- 14. Thank you! 13 14/09/22 Spatial variability of local carbon emissions and sinks in Helsinki Bergroth, Claudia, et al. "A 24-hour population distribution dataset based on mobile phone data from Helsinki Metropolitan Area, Finland." Scientific data 9.1 (2022): 1-19. Havu, Minttu, et al. "Carbon sequestration potential of street tree plantings in Helsinki." Biogeosciences 19.8 (2022): 2121-2143. Järvi, Leena, et al. "Spatial modeling of local-scale biogenic and anthropogenic carbon dioxide emissions in Helsinki." Journal of Geophysical Research: Atmospheres 124.15 (2019): 8363-8384. Moriwaki, R., and M. Kanda. "Seasonal and diurnal fluxes of radiation, heat, water vapor, and carbon dioxide over a suburban area." Journal of Applied Meteorology 43.11 (2004): 1700-1710. Tang, Yihao, et al. "Urban meteorological forcing data for building energy simulations." Building and Environment 204 (2021): 108088. Ward, H. C., Jonathan G. Evans, and Christine Susan B. Grimmond. "Multi-season eddy covariance observations of energy, water and carbon fluxes over a suburban area in Swindon, UK." Atmospheric Chemistry and Physics 13.9 (2013): 4645-4666. Contact: minttu.havu@helsinki.fi