Reply on RC1

Abstract

<strong class="journal-contentHeaderColor">Abstract.</strong> Absorption cross-sections (ACS) of emerging greenhouse gases (GHG) were measured to estimate the radiative efficiencies (RE) using high-resolution Fourier transform infrared spectroscopy (HR-FTIR). For quantitative spectroscopy, the Beer&ndash;Lambert parameters of absorber pressure, temperature, and optical pass length (OPL) have been accurately determined to be traceable to the primary standards. The OPL of the multipass cell (MP) mounted on the HR-FTIR spectrometer was spectroscopically calibrated. A ratio of the averaged N₂O absorptions was measured in the range of 2,217.4&ndash;2,219.0 cm^-1 with a spectral resolution of 0.026 cm^-1, yielding a ratio of OPLs between the MP and reference cell (RC). This cell-to-cell comparison (CC) method does not include the uncertainty in the referring line strength, thereby reducing the calibration uncertainty compared with a direct line-strength referring method. With the OPL-calibrated MP (3.169 &plusmn; 0.079 m), the ACSs were measured at low absorber pressures with a spectral resolution of 2 cm^-1, integrated at 10 cm^-1 intervals, and multiplied by the new narrow band model to yield the RE values. The RE values of the classic GHGs CF₄, SF₆, and NF₃ were evaluated to be 0.085 &plusmn; 0.002, 0.573 &plusmn; 0.016, and 0.195 &plusmn; 0.008 W m^-2 ppb^-1, respectively, which are consistent with previously reported values. For the emerging GHGs, the RE values were determined to be 0.201 &plusmn; 0.008 W m^-2 ppb^-1 for (CF₃)₂CFCN (heptafluoroisobutyronitrile, commercially referred to as <em>Novec-4710</em>), 0.328 &plusmn; 0.013 W m^-2 ppb^-1 for CF3OCFCF2 (perfluoro methyl vinyl ether, PMVE), and 0.544 &plusmn; 0.022 W m^-2 ppb^-1 for CF₃OCF₂CF₃ (1,1,1,2,2-pentafluoro-2-(trifluoromethoxy)ethane, PFMEE).