A highly variable interference has long been considered the dominant feature of water vapor for practitioners who retrieve atmospheric total column amounts and profiles from infrared solar absorption spectra. Due to the importance of water as a greenhouse gas and its possible long-term trend resulting from changes in the atmosphere and subsequent feedback effects there is renewed effort in extracting water vapor quantities from archived solar spectra, which for some sites stretch back to the 1970's.
NDACC News and Events
In the period from June–July 2009, a large scale intercomparison of UV-Visible spectrometers took place at the Cabauw meteorological observatory, a semi-rural site located in the Netherlands, 30 km South of Utrecht.
Despite its low abundance in the atmosphere, stratospheric bromine contributes up to 25% to the global ozone loss due to its high ozone depletion potential [e.g., World Meteorological Organization (WMO), 2007]. The main sources of bromine in the stratosphere are natural and anthropogenic long-lived and very short-lived brominated organic compounds [e.g., Pfeilsticker et al., 2000; Salawitch et al., 2005]. Long-term observations by in-situ ground-based networks have revealed a decline in total organic bromine from long-lived species by 3 to 5% during the 1998-2004 period [WMO, 2007].
At the 2008 NDACC Steering Committee meeting, an ad hoc working group was established to review existing and assess future Network measurement strategies and emphases in light of the broadening of Network goals over those established at its inception.
In the early days of NDACC (then NDSC), the Infrared Working Group (IRWG) targeted the retrieval of total columns of several gases considered of primary importance to the original goals of the Network. These goals focused on increasing our understanding of ozone chemistry and, in the post-Montreal Protocol period, observing the accumulation (and hopefully the eventual decline) of Cly and Fy in the stratosphere. Consequently, the initial gases targeted were ozone, nitric acid (HNO3), nitrous oxide (N2O ), chlorine nitrate (ClONO2), hydrogen chloride (HCl), and hydrogen fluoride (HF).