Airborne in situ vertical profiling of HDO/H<sub>2</sub><sup>16</sup>O in the subtropical troposphere during the MUSICA remote sensing validation campaign

Abstract

Abstract. Vertical profiles of water vapor (H2O) and its isotope ratio D / H expressed as δ D(H2O were measured in situ by the ISOWAT II diode-laser spectrometer during the MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water (MUSICA) airborne campaign. We present recent modifications of the instrument design. The instrument calibration on the ground as well as in flight is described. Based on the calibration measurements, the humidity-dependent uncertainty of our airborne data is determined. For the majority of the airborne data we achieved an accuracy (uncertainty of the mean) of Δ(δ D) ≈ 10‰. Vertical profiles between 150 and ~7000 m were obtained during 7 days in July and August 2013 over the subtropical North Atlantic Ocean near Tenerife. The flights were coordinated with ground-based (Network for the Detection of Atmospheric Composition Change, NDACC) and space-based (Infrared Atmospheric Sounding Interferometer, IASI) FTIR remote-sensing measurements of δ D(H2O) as a means to validate the remote sensing humidity and δ D(H2O) data products. The results of the validation are presented in detail in a separate paper (Schneider et al., 2014). The profiles were obtained with a high vertical resolution of around 3 m. By analyzing humidity and δ D(H2O) correlations we were able to identify different layers of airmasses with specific isotopic signatures. The results are discussed.

Moist processes during MJO events as diagnosed from water isotopic measurements from the IASI satellite

“…The KIT retrieval uses a broad spectral window (1190–1400 cm −1 ), a fine gridded atmospheric model, and works as a simultaneous optimal estimation of H 2 O and δ D as well as of the interfering gases (CH 4 , N 2 O, CO 2 , and HNO 3 ) and temperature [ Schneider and Hase , ]. The isotopologue products have been validated with respect to the MUSICA ground‐based FTIR remote sensing data (using spectra measured with the Network for the Detection of Atmospheric Composition Change) and to the well‐calibrated MUSICA in situ reference data (aircraft based and continuous surface based) [ Schneider et al , ; Dyroff et al , ]. The MUSICA in situ aircraft reference data (0–7 km) allow a first adequate bias correction, or calibration, of the retrieval results [ Schneider et al , ; Dyroff et al , ].…”

“…The isotopologue products have been validated with respect to the MUSICA ground‐based FTIR remote sensing data (using spectra measured with the Network for the Detection of Atmospheric Composition Change) and to the well‐calibrated MUSICA in situ reference data (aircraft based and continuous surface based) [ Schneider et al , ; Dyroff et al , ]. The MUSICA in situ aircraft reference data (0–7 km) allow a first adequate bias correction, or calibration, of the retrieval results [ Schneider et al , ; Dyroff et al , ]. The overall uncertainty for an individual observation has been estimated to about 10% and 35‰ for q and for δ D, respectively, [ Wiegele et al , ].…”

Stable isotopes in atmospheric water vapor and applications to the hydrologic cycle

“…Even FTIR (Fourier transfrom infrared) spectrometers have been deployed on high‐altitude research balloons [ Notholt et al , ] and on aircraft [ Coffey et al , ; Hanisco et al , ] for studies of water vapor in the stratosphere. Recently, Herman et al [] and Dyroff et al [] made the first lower and middle tropospheric observations at high vertical resolution and with in‐flight instrument performance analyses by measuring a calibration gas standard.…”

The SPIRIT airborne instrument: a three-channel infrared absorption spectrometer with quantum cascade lasers for in situ atmospheric trace-gas measurements

“…This technique has been implemented in aircraft [1,2], and is now more and more widespread. Most recently built airborne instruments comprise several variants, i.e., non-resonant cavities using tunable diode lasers (see, e.g., [3][4][5][6] and references therein), quantum cascade lasers (QCL; see, e.g., [7,8] and references therein), or difference frequency generation lasers [9], and resonant cavities for cavity ring-down spectroscopy (CRDS) [10][11][12], off-axis integrated cavity output spectroscopy (OA-ICOS) [13][14][15], or optical-feedback cavity enhanced absorption spectroscopy (OF-CEAS) [16]. Using lasers allows for narrow linewidths, leading to selectivity of trace gases and very low limits of detection.…”