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The amplitude, the temperature dependence and the physical origin of the water vapor absorption continuum are a long standing issue in molecular spectroscopy with direct impact in atmospheric and planetary sciences. In the recent years, we have determined the self-continuum absorption of water vapor at different spectral points of the atmospheric windows at 4.0, 2.1, 1.6 and 1.25 μm, by highly sensitive cavity enhanced laser techniques. These accurate experimental constraints have been used to adjust the last version (V3.2) of the semi-empirical MT_CKD model (Mlawer–Tobin_Clough–Kneizys–Davies) widely incorporated in atmospheric radiative transfer codes. In the present work, the self-continuum cross-sections, CS, are newly determined at 3.3 μm (3007 cm−1) and 2.0 μm (5000 cm−1) by optical-feedback-cavity enhanced absorption spectroscopy (OFCEAS) and cavity ring-down spectroscopy (CRDS), respectively. These new data allow completing the spectral coverage of the 4.0 and 2.1 μm windows, respectively, and testing the recently released V3.2 version of the MT_CKD3 continuum. By complementing high temperature literature data to the present data, the temperature dependence of the self continuum is presented. 1 Institute of Engineering Univ. Grenoble Alpes

Measurements of the mole fraction of the CO2 and its isotopes were performed in Paris during the MEGAPOLI winter campaign (January–February 2010). Radiocarbon (14CO2) measurements were used to identify the relative contributions of 77% CO2 from fossil fuel consumption (CO2ff from liquid and gas combustion) and 23% from biospheric CO2 (CO2 from the use of biofuels and from human and plant respiration: CO2bio). These percentages correspond to average mole fractions of 26.4 ppm and 8.2 ppm for CO2ff and CO2bio, respectively. The 13CO2 analysis indicated that gas and liquid fuel contributed 70% and 30%, respectively, of the CO2 emission from fossil fuel use. Continuous measurements of CO and NOx and the ratios CO/CO2ff and NOx/CO2ff derived from radiocarbon measurements during four days make it possible to estimate the fossil fuel CO2 contribution over the entire campaign. The ratios CO/CO2ff and NOx/CO2ff are functions of air mass origin and exhibited daily ranges of 7.9 to 14.5 ppb ppm−1 and 1.1 to 4.3 ppb ppm−1, respectively. These ratios are consistent with different emission inventories given the uncertainties of the different approaches. By using both tracers to derive the fossil fuel CO2, we observed similar diurnal cycles with two maxima during rush hour traffic.

Measurements of the mole fraction of the CO2 and its isotopes were performed in Paris during the MEGAPOLI winter campaign (January–February 2010). Radiocarbon (14CO2) measurements were used to identify the relative contributions of 77% CO2 from fossil fuel consumption (CO2ff from liquid and gas combustion) and 23% from biospheric CO2 (CO2 from the use of biofuels and from human and plant respiration: CO2bio). These percentages correspond to average mole fractions of 26.4 ppm and 8.2 ppm for CO2ff and CO2bio, respectively. The 13CO2 analysis indicated that gas and liquid fuel contributed 70% and 30%, respectively, of the CO2 emission from fossil fuel use. Continuous measurements of CO and NOx and the ratios CO/CO2ff and NOx/CO2ff derived from radiocarbon measurements during four days make it possible to estimate the fossil fuel CO2 contribution over the entire campaign. The ratios CO/CO2ff and NOx/CO2ff are functions of air mass origin and exhibited daily ranges of 7.9 to 14.5 ppb ppm−1 and 1.1 to 4.3 ppb ppm−1, respectively. These ratios are sufficiently consistent with different emission inventories given the uncertainties of the different approaches.