Latitudinal distribution of HDO abundance above Venus' clouds by ground-based 2.3 µm spectroscopy

Abstract

The abundance of HDO above the clouds in the dayside atmosphere of Venus was measured by ground-based 2.3 μm spectroscopy over 4 days. This is the first HDO observation above the clouds in this wavelength region corresponding to a new height region. The latitudinal distributions found show no clearly defined structure. The disk-averaged mixing ratio is 0.22 ± 0.03 ppm for a representative height region of 62-67 km. This is consistent with measurements found in previous studies. Based on previous H ₂O measurements, the HDO/H ₂O ratio is found to be 140 ± 20 times larger than the telluric ratio. This lies between the ratios of 120 ± 40 and 240 ± 25, respectively, reported for the 30-40 km region by ground-based nightside spectroscopy and for the 80-100 km region by solar occultation measurement on board the Venus Express.