Simulation of carbonyl sulfide (COS) to better understand the urban biosphere signal

We suggest that COS can be used to determine which ecosystem modelbest represents the biospheresignal. Just like CO₂, COS is taken up by photosynthesis but is not given off in respiration and can thus be used as a trace gasto estimate GPP. We begin with COS surface fluxes provided by SiB and CASA, regridded to lower resolution using NDVI values, for a 9, 3, and 1 km-resolution domain over the Bay Area of San Francisco and part of the San JoaquinValley. Simulations using the atmospheric modelWRF provide the meteorological data, which along with the COS fluxes, are used to run the transport model STEM over a 20-day period in March 2015. Simulations of COS mixing ratio based on the various surface flux models are compared to observed data available from several locations (see abstract B42B-06 by Whelan, M. et al). The model that best represents COS uptake consequently also provides the most accurate simulation of CO₂ biospheresignal, and can be used to estimate fossil fuel CO₂ emissions.