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, a decision was made to remove the "Primary" and "Complementary" designations of NDACC measurement sites / stations. These original terminologies were instituted at the inception of the Network for designating a minimum of five stations with long-term measurement commitments, representing the major geographical regions of the globe (i.e., Arctic, Northern Hemisphere (NH) Midlatitudes, Tropics, Southern Hemisphere (SH) Midlatitudes, and Antarctic).
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).
Since the onset of formal operations, NDACC (formerly NDSC) has designated several specific instrument types as official measurement capabilities. These are: Dobson / Brewer Spectrometers, Fourier Transform IR Spectrometers (FTIRs), Lidars (temperature, ozone, and aerosol), Microwave Radiometers, and UV/Visible Spectrometers. Balloon Sondes (ozone and aerosol) and UV Spectroradiometers were added shortly after the Network became operational. The Network strives to maintain the operation of as many of these instrument types within the various latitude regions as possible.