Near-infrared open-path measurement of CO sub(2) concentration in the urban atmosphere

Average concentration of carbon dioxide (CO sub(2)) has been measured over a path length of 5.1 km in the lower troposphere by the method of differential optical absorption spectroscopy (DOAS) using a near-infrared light source based on amplified spontaneous emission. The analysis of CO sub(2) absorption intensity around 1575 nm observed during 10 days over the Chiba city area has revealed that the CO2 CO2 concentration varied in the range of around 360-450 ppmv, with presumable influence of air mass advection from nearby industrial facilities. In addition, a good correlation has been found in relative humidity values between the DOAS and meteorological station data. As a whole, the present result indicates the usefulness of such a DOAS approach for measuring the concentration of CO sub(2) averaged over an optical path of a few kilometers in the lower troposphere. (C) 2015 Optical Society of America