Some improvements of the HNO 3 spectroscopic parameters in the spectral region from 600 to 950 cm −1

Abstract

In an earlier study [Flaud JM, Brizzi G, Carlotti M, Perrin A, Ridolfi M. MIPAS database: validation of HNO 3 line parameters using MIPAS satellite measurements. Atmos Chem Phys 2006;6:1–12] the HNO 3 line parameters in the HITRAN spectroscopic database have recently been revisited in the interval corresponding to the MIPAS spectral range. For the 11.3 μm region these updates involve the line positions for the { ν 5, 2 ν 9} bands, and the intensities. However, comparisons between observed spectra recorded by MIPAS and the calculated ones in the 600–950 cm −1 region still show significant disagreements. The goal of the present paper is to solve some of these problems. Based on the analysis of N 2-broadened HNO 3 laboratory spectra recorded with a Fourier transform instrument, a new HNO 3 database was generated, including the following improvements: (i) approximate parameters for the ν 5+ ν 7− ν 7 and ν 5+ ν 6− ν 6 hot bands have been added, and (ii) the intensities for the ν 6 and ν 8 bands have been updated. (iii) The air broadening and its temperature dependence, calculated using a semi-classical approach, have been added for each HNO 3 transition. (iv) Finally, line-mixing effects have been pointed out, particularly in the ν 5+ ν 9− ν 9 Q branch, and an approach correctly modeling the resulting spectral shape is proposed.