Using Satellite and Lagrangian Modeling to Estimate Urban CO2 Emissions in Hongkong

Using Satellite and Lagrangian Modeling to Estimate Urban CO2 Emissions in HongkongYue Zhou and Hui SuUrban areas are responsible for emitting more than 70% of global fossil fuel carbon dioxide (CO2) emissions. Hongkong is one of the most world’s populated cities and accurate inversion of CO2 emissions using satellite form this region remains high uncertainty. However, urban CO₂ emissions are mainly derived from satellite using simple statistical methods, and there is less research to link between upwind emission sources and downwind CO₂ enhancements using models.To better understand of urban emission estimation from space, we use X-Stochastic Time-Inverted Lagrangian Transport model (“X-STILT”) (Wu et al., 2018) to simulate XCO2 enhancements in the summer of 2024 based on the Open-source Data Inventory for Anthropogenic CO2 (ODIAC) emission inventory for Hongkong. Independent satellite observations from NASA’s Orbiting Carbon Observatory‐3 (OCO‐3) satellite can provide wide area column average dry air mole fraction of carbon dioxide (XCO2) of entire urban areas. Furthermore, we perform a CarbonTracker-Lagrange inverse model to compare XCO2 simulations with observations. We found X-STILT model is able to reproduce most XCO2 enhancement observations. This study provides valuable insights into both urban emissions quantifying and mitigation decision making.References: Wu et al.,: A Lagrangian approach towards extracting signals of urban CO2  emissions from satellite observations of atmospheric column CO2  (XCO2): X-Stochastic Time-Inverted Lagrangian
 Transport model  (“X-STILT v1”)