CO2-Broadening of Water-Vapor Lines

Investigation of water vapor on Mars with PFS/SW of Mars Express

“…Although it is an important spectroscopic parameter there is little experimental information or even agreement on its exact value in the considered wavenumber range. To be able to quantify the retrieval error, the results of this work, using line parameters calculated according to Gamache et al (1995), were compared with results that were produced with a constant line broadening parameter of 1.3 (e.g., used by Fedorova et al, 2006). In this case the retrieved H 2 O abundances differ by about 10-15%.…”

“…Because the spectral line database is created for the terrestrial atmosphere, the correction for CO 2 -dominated air is done with a line broadening parameter. For this work the line widths were corrected according to the values calculated by Gamache et al (1995). However, one has to keep in mind that the broadening factors are different from line to line and can vary between 0.9 and 1.9 which leads to a large uncertainty in the retrieval.…”

Mars’ water vapor mapping by the SPICAM IR spectrometer: Five martian years of observations

“…It is traditionally used for many applications in the Earth's atmosphere. And third, to account for the CO 2 broadening of water vapor lines in the Mars atmosphere, we adopt the broadening scale factor of 1.7, following Gamache et al (1995) and recent work by Brown et al (2007); i.e., we multiplied the air-broadened half-widths from the HITRAN 2004 database by 1.7. In the previous study a broadening factor of 1.3 was adopted.…”

Constraints on water vapor vertical distribution at the Phoenix landing site during summer from MGS TES day and night observations

“…The parameter arises due to the spectral parameters (line width, strength, broadening) in the GEISA and HITRAN (Husson et al, 1992;Rothman et al, 2003) databases being given for terrestrial air (nitrogen/oxygen mixture). Different authors used different approaches to estimate pressure broadening coefficient in their retrievals and came up with different values: Smith (2002) Gamache et al (1995), which resulted in an averaged value of 1.7 and column abundances that were 15% lower than the TES abundances; Fedorova et al (2009) used the value of 1.7, but for water lines in the spectral range 1-1.7 lm. We adopt the value of 1.5 used by Smith (2002), as it is supported by the recent analysis of the CO 2 broadening of the water vapor rotational lines (Brown et al, 2007).…”