Line parameters of H2O around 0.8 μm studied by tuneable diode laser spectroscopy

The absorption spectrum of H2O has been extensively studied over the past decades in the near-infrared and visible regions, but there remain significant discrepancies in the 10,000-12,500 cm−1 range even for the most intense lines. We have studied 24 lines of H2O using an external-cavity diode laser emitting in the 810-830 nm range, in order to measure absolute line intensities as well as air- and self-broadening coefficients. Comparisons were made with values obtained from the HITRAN database and also with other parameters from recent experiments or predicted calculations. It is suggested that neglecting the effects of H2O collisional narrowing in radiative transfer calculations of the Earth's atmosphere may have a small but significant impact on the radiative budget of the Earth.