Variability and trends in stratospheric NO2 in Antarctic summer, and implications for stratospheric NOy P. A. Cook and H. K. Roscoe British Antarctic Survey, Madingley Rd, Cambridge CB3 0ET, UK
Abstract. NO2 measurements during 1990–2007, obtained from a zenith-sky
spectrometer in the Antarctic, are analysed to determine the long-term
changes in NO2. An atmospheric photochemical box model and a radiative
transfer model are used to improve the accuracy of determination of the
vertical columns from the slant column measurements, and to deduce the
amount of NOy from NO2. We find that the NO2 and NOy columns in
midsummer have large inter-annual variability superimposed on a broad
maximum in 2000, with little or no overall trend over the full time period.
These changes are robust to a variety of alternative settings when
determining vertical columns from slant columns or determining NOy from
NO2. They may signify similar changes in speed of the Brewer-Dobson
circulation but with opposite sign, i.e. a broad minimum around 2000.
Multiple regressions show significant correlation with solar and
quasi-biennial-oscillation indices, and weak correlation with El Nino, but
no significant overall trend, corresponding to an increase in Brewer-Dobson
circulation of 1.4±3.5%/decade. There remains an unexplained cycle
of amplitude and period at least 15% and 17 years, with minimum speed in
Citation: Cook, P. A. and Roscoe, H. K.: Variability and trends in stratospheric NO2 in Antarctic summer, and implications for stratospheric NOy, Atmos. Chem. Phys., 9, 3601-3612, doi:10.5194/acp-9-3601-2009, 2009.