Stratospheric HF column abundances above Kitt Peak (31.9°N latitude): trends from 1977 to 2001 and correlations with stratospheric HCl columns

• Published in: Journal of quantitative spectroscopy & radiative transfer Vol. 74; no. 2; pp. 205 - 216
• Main Authors: Rinsland, C.P., Zander, R., Mahieu, E., Chiou, L.S., Goldman, A., Jones, N.B.
• Format: Journal Article Web Resource
• Language: English
• Published: Elsevier Ltd 15-07-2002; Pergamon-Elsevier Science Ltd
• Subjects: Atmospheric chemistry; Hydrogen fluoride; Infrared spectroscopy; Physical, chemical, mathematical & earth Sciences; Physics; Physique; Physique, chimie, mathématiques & sciences de la terre; Remote sensing; Stratosphere; USA, Arizona; Stratosphere; Infrared spectroscopy; Hydrogen fluoride; Atmospheric chemistry; Remote sensing
• ISSN: 0022-4073; 1879-1352
• DOI: 10.1016/S0022-4073(01)00233-3

Time series of stratospheric hydrogen fluoride (HF) column abundances have been derived from infrared solar absorption spectra recorded for 195 days between May 1977 and June 2001 at a spectral resolution of typically
0.01
cm
−1
. The measurements were made at the US National Solar Observatory facility on Kitt Peak, Arizona, USA (31.9°N, 111.6°W,
2.09
km
altitude) and have been analyzed with the SFIT2 algorithm, which is based on a semi-empirical application of the optimal estimation method. The measurements show a continuous buildup of the stratospheric HF column over the 24-yr period superimposed on short-term variations and a seasonal cycle with spring maxima and autumn minima. The measured stratospheric HF columns increased by a factor of 4.7, from
2.03×10
14
molecule
cm
−2
in May 1977 to
9.49×10
14
molecule
cm
−2
in June 2001. A best fit with a model that assumes an exponential increase in the stratospheric HF column with time superimposed on a sinusoidal seasonal cycle yields an average rate of stratospheric HF column increase of
(4.30±0.15%
yr
−1)
, 1 sigma. The rate of increase is nearly a factor of two less than that derived previously from 1977 to 1990 Kitt Peak total columns, which indicates a significant slowdown in the increase rate during the 1990s, consistent with the trends from recent near-global lower mesospheric satellite remote and surface in situ measurements. Day-to-day stratospheric HF columns are highly correlated with the same day stratospheric HCl columns as a result of common transport of lower and higher latitude air to above the station. Extrapolation of the linear relation between the two sets of stratospheric columns indicates a background HCl column of
1×10
15
molecule
cm
−2
for zero HF, consistent with a previous estimate from 1977 to 1990 HF and HCl Kitt Peak total column measurements and a 1973 HCl measurement above the station.