Observation and simulation of atmospheric carbon dioxide in Vancouver

• Main Author: Reid, Kenneth Howard
• Language: English
• Published: 2009
• Subjects: Air > Pollution > British Columbia > Vancouver; Air quality > British Columbia > Vancouver; Carbon dioxide
• Online Access: http://hdl.handle.net/2429/3923

Climate change expected from increasing atmospheric CO₂ concentrations has been studied widely (IPCC, 1990). Further, it is recognized that cities are a major source of anthropogenic CO₂. However, few studies of CO₂ concentrations in, or near, cities have been conducted. A LI-COR infrared gas analyzer was operated at the Sunset Tower in a suburban region of Vancouver during different time periods in 1993 and 1994. Sampling revealed important information on seasonal and diurnal variations. The observed summertime concentrations show a clear diurnal signal around the expected upwind background concentration, and are described by a late afternoon minimum, and overnight maximum. The afternoon CO₂ minimum is attributed to the strength of biospheric photosynthesis and strong mixing of local anthropogenic sources within a large mixed layer. Poor nighttime mixing, lower mixed depths, and biospheric respiration account for the observed nighttime maximum, often more than 80 ppmv greater than the background concentration. A simple numerical multiple-box transport model was developed to simulate the observed diurnal pattern of CO₂ concentration at the suburban site. CO₂ emissions inventories for important mobile sources, stationary sources, and biospheric sources and sinks are calculated as input to the model for upwind fetch areas. Other CO₂ inputs include advection, entrainment from above the mixed layer and determination of the mixed layer depth. Results of both observations and modelling show large diurnal variation in CO₂ concentrations, and the importance of boundary layer structure (as defined by the mixed layer) on concentrations at a specific location. In terms of CO₂, the role of the city is placed in it global context.