Bruno Carli

Optimized forward model and retrieval scheme for MIPAS near-real-time data processing.

An optimized code to perform the near-real-time retrieval of profiles of pressure, temperature, and volume mixing ratio (VMR) of five key species (O(3), H(2)O, HNO(3), CH(4), and N(2)O) from infrared limb spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) experiment on board the European Space Agency (ESA) Environmental Satellite ENVISAT-1 was developed as part of a ESA-supported study. The implementation uses the global fit approach on selected narrow spectral intervals (microwindows) to retrieve each profile in sequence. The trade-off between run time and accuracy of the retrieval was optimized from both the physical and the mathematical points of view, with optimizations in the program structure, in the radiative transfer model, and in the computation of the retrieval Jacobian. The attained performances of the retrieval code are noise error on temperature <2 K at all the altitudes covered by the typical MIPAS scan (8-53 km with 3-km resolution), noise error on tangent pressure <3%, and noise error on VMR of the target species <5% at most of the altitudes covered by the standard MIPAS scan, with a total run time of less than 1 min on a modern workstation.

Submillimeter high-resolution FT spectrometer for atmospheric studies

The rationale, design, and performance of a high-resolution Fourier transform spectrometer are discussed. The instrument was employed in the measurement of stratospheric emissionin the 7–90-cm−1 spectral interval with a 0.0033-cm−1 resolution (unapodized) from a balloon-borne platform at ~40-km altitude.

New assignments in the submillimeter emission spectrum of the stratosphere

New line assignments in the spectrum of the stratospheric submillimeter emission, measured with unapodized resolution of 0.0033 cm−1, have been made. Positive evidence for the presence of symmetric and asymmetric ozone isotopes, water vapour excited to the (010) level, and HCN is given.

The far infrared spectrum of 14N16O2

High resolution Fourier transform spectra in the 8–200 cm-1 spectral region have been used to analyse the pure rotation spectrum of nitrogen dioxide. In this way, the spin rotation levels of the (000) state were accurately measured for Ka up to 14 and N up to 54. Using a hamiltonian which takes the spin-rotation and the hyperfine operators explicitly into account, it has been possible to derive a complete set of molecular parameters (rotational, spin-rotation and hyperfine constants) for the (000) state of 14N16O2 from these experimental data and from the available microwave measurements. Numerous perturbations due to the hyperfine Fermi contact operator were analysed as well as a local resonance [42 0 42, J = 41·5] ↔ [41 2 40, J = 41·5] due to the electron spin-rotation interaction. Finally, a synthetic spectrum of the (000) ← (000) band of 14N16O2 including all hyperfine transitions has been computed, covering the 0–235 cm-1 spectral region.

Detection of atomic oxygen and further line assignments in the far-infrared stratospheric spectrum

The analysis of the high resolution far infrared emission spectrum of the stratosphere has made possible the identification of two features due to atomic oxygen. Several other new features have been assigned on the basis of updated line compilations. The possible detection of HBr, HO2 and H2O2 in the far infrared is discussed.

Fourier spectroscopy of the stratospheric emission

Emission spectra of the stratosphere have been recorded from balloon altitude with an unapodized resolution of 0.0033 cm−1 in the submillimeter (SM) spectral range. Preliminary results on constituent identification are presented in this paper.

SAFIRE-A: Spectroscopy of the Atmosphere Using Far-Infrared Emission/Airborne

A new instrument named SAFIRE-A (Spectroscopy of the Atmosphere using Far-Infrared Emission/Airborne), which can operate on high-altitude platforms, has been developed for the study of the atmospheric composition through limb-scanning emission measurements. The instrument is a polarizing Fourier transform spectrometer that operates in the far infrared with a resolution of 0.004 cm(−1). SAFIRE-A uses efficient photon noise limited detectors and a novel optical configuration, which provide a cold pupil and field stop as well as cold narrow bandpass filters to enhance its sensitivity. The instrument was successfully operated on an M-55 stratospheric research aircraft in the polar regions during the winter 1996–97 Airborne Polar Experiment. The instrument design, aircraft integration, and performances attained in the field campaign are described and discussed. The atmospheric emission spectrum is measured with an rms noise accuracy of 0.5 K (measured in brightness temperature) in each spectral element near 20 cm(−1) with a 30-s measurement time.

The Fourier spectrum of CH3OH: The region between 8 and 40 cm−1

Abstract The experimental Fourier spectrum of CH 3 OH has been investigated between 8 and 40 cm −1 . Good agreement was found between the experimental measurements and the results of the computational routines available up to now when low J values ( J ≲ 10) are involved. At higher J , the line assignments are possible by means of Taylor expansions of the energy levels. A catalog of almost 1500 lines, two-thirds of which have been assigned, is presented.

The submillimeter-wave spectrum and spectroscopic constants of SO2 in the ground state

Abstract The submillimeter-wave spectrum of SO 2 has been recorded with 0.004 cm −1 resolution in the region 8–90 cm −1 . About 2000 lines were observed, 1500 of which have been assigned to the ground state rotational transitions of 32 SO 2 . Molecular constants up to the 10th order have been derived, combining our data with the available microwave data in the literature. SO 2 rotational spectrum line positions up to 90 cm −1 can be reproduced from these constants, within the experimental accuracy (2 × 10 −4 cm −1 ).

Analysis of far-infrared emission Fourier transform spectra

An analysis method that uses the nonlinear least-squares fit technique has been developed for emission spectra obtained with a Fourier transform spectrometer. This method is used for the analysis of submillimeter-region atmospheric emission spectra obtained with a balloon-borne FT spectrometer that was carried out as a correlative measurement for the LIMS satellite experiment. The emitting gas concentrations, the instrument line shape, and the instrument response functions have been simultaneously retrieved. The retrieved mixing ratios of H2O and O3 in the stratosphere from four spectral intervals have standard deviations of ~10%, and the average values agree to within 10% of corresponding results from the LIMS satellite experiment which used a broadband emission radiometer in the IR region.