Remote sampling of a CO_2 point source in an urban setting

摘要

High frequency CO_2 and wind speed measurements were used to examine the urban baseline eddy covariance CO_2 flux and analyse the CO_2 rich plume from a local power station. A reliable relationship between high frequency CO_2 maxima and the rate of CO_2 emission at the power station was established. This relationship was shown to be highly dependant on wind speed. The ensemble mean plume was found to be Gaussian in horizontal profile with a width dependant on wind speed. The relationship between peak CO_2 mixing ratio and averaging time was shown to be a simple power law with a time exponent of approximately 0.5. The large, short pulses in CO_2 mixing ratio in the power plant plume were found to have an approximately Lorentzian shape. These pulses generated negative vertical eddy flux measurements so data from the plume sector were necessarily excluded from the flux baseline results. The plume-excluded flux had a similar magnitude and variability to those reported in other urban CO_2 flux studies despite this site not being ideal due to the proximity of roughness elements to the measurement point.