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The concentration of CO2 in the atmosphere is strongly influenced by vegetation photosynthesis, respiration, and soil activity. To accurately estimate urban anthropogenic CO2 emissions, it is essential to understand the carbon flux of vegetation in the city. Compared with rural areas, vegetation inside the cities is distributed more inhomogeneously and sometimes shows different behaviours. Therefore, we have tested and updated different versions of VPRM to achieve accurate high-resolution biogenic CO2 fluxes for urban areas. In the framework of the ICOS Cities project, we have tested multiple VPRM models with 10-meter spatial and hourly temporal resolution for the cities of Munich and Zurich. This involved deriving vegetation indices from Sentinel-2 satellite products, generating a detailed vegetation land cover dataset by merging multiple land cover and geospatial datasets, and using temperature and shortwave radiation fields from the Weather Research and Forecasting model (WRF). Additionally, we recalibrated the VPRM parameters using observations from flux towers across Europe. We tested three existing versions of VPRM, namely the standard VPRM (Mahadevan et al., 2008), UrbanVPRM (Hardiman et al., 2017), and a modified VPRM (Gourdji et al., 2022). While the standard VPRM was developed for non-urban vegetation, the UrbanVPRM and the modified VPRM were specifically designed to better represent vegetation and soil respiration. We thus expect them to be more capable of describing biogenic fluxes in cities. The results of all models are cross compared in the urban areas and evaluated using various observational data. This includes CO2 flux measurements from eddy covariance towers, sap flux density of selected trees and soil and grass respiration inside cities, among other metrics. Our research findings will contribute to precise estimation of high-resolution biogenic CO2 fluxes, specifically in the urban areas. Reference Mahadevan, Pathmathevan, et al. A satellitebased biosphere parameterization for net ecosystem CO2 exchange: Vegetation Photosynthesis and Respiration Model (VPRM). Global Biogeochemical Cycles 22.2 (2008). Hardiman, Brady S., et al. "Accounting for urban biogenic fluxes in regional carbon budgets." Science of the Total Environment 592 (2017): 366-372. Gourdji, Sharon M., et al. "A modified Vegetation Photosynthesis and Respiration Model (VPRM) for the eastern USA and Canada, evaluated with comparison to atmospheric observations and other biospheric models." Journal of Geophysical Research: Biogeosciences 127.1 (2022): e2021JG006290.
Li et al. (Fri,) studied this question.