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Estimating Urban Carbon Uptake from TROPOMI SIF over the Greater Toronto Area

Many cities, including Toronto, are trying to reduce their carbon emissions; to do this, accurate quantification of both human-made and biogenic sources and sinks of CO2 are required. However, the role of urban vegetation on the carbon cycle is poorly constrained. Many studies have found that on regional scales Solar-Induced chlorophyll Fluorescence (SIF), a signal composed of photons emitted by vegetation during photosynthesis, is a valuable proxy for the amount of CO2 absorbed by vegetation, known as Gross Primary Productivity (GPP). The space-borne TROPOspheric Monitoring Instrument (TROPOMI) has the ability to measure SIF at a high temporal resolution and a moderate spatial resolution of 3.5 x 7 km at nadir with near daily coverage. However, this resolution is still too coarse to resolve details on the local scale. Using a method introduced by Turner et al. (2019) we have used overlapping TROPOMI footprints over two-week periods in conjunction with the MODerate-resolution Imaging Spectrometer's (MODIS) vegetation indices, to downscale SIF data to a resolution of 500 x 500 m over the Greater Toronto Area (GTA). This analysis has allowed us to compare the magnitude and timing of photosynthetic activity on local scales. In addition, we compare our SIF product to GPP derived from flux tower measurements located around the GTA to obtain a relationship between SIF and GPP. Results will also be compared to other satellite SIF products and GPP estimates from vegetation models. This analysis will allow us to estimate the role of vegetation in CO2 removal via photosynthesis and its seasonality in the GTA.

Event series  Brewer-Wilson Seminar Series