Abstract
Abstract. We present a re-analysis of upper stratospheric ClO measurements from the ground-based millimeter-wave instrument from January 1992 to February 2012. These measurements are made as part of the Network for the Detection of Atmospheric Composition Change (NDACC) from Mauna Kea, Hawaii, (19.8° N, 204.5° E). Here, we use daytime and nighttime measurements together to form a day–night spectrum, from which the difference in the day and night profiles is retrieved. These results are then compared to the day–night difference profiles from the Upper Atmosphere Research Satellite (UARS) and Aura Microwave Limb Sounder (MLS) instruments. We also compare them to our previous analyses of the same data, in which we retrieved the daytime ClO profile. The major focus will be on comparing the year-to-year and long-term changes in ClO derived by the two analysis methods, and comparing these results to the long-term changes reported by others. We conclude that the re-analyzed data set has less short-term variability and exhibits a more constant long-term trend that is more consistent with other observations. Data from 1995 to 2012 indicate a linear decline of mid-stratospheric ClO of 0.64 ± 0.15% yr−1 (2σ).
Highlights
Introduction from ScottBase) were processed after interpolation of the nighttime spectra over a narrow region around the ClO fre-Chlorine monoxide (ClO) in the stratosphere is the product of catalytic destruction of ozone by chlorine released from anthropogenic compounds, especially CFCs
This was subtracted from the full daytime spectrum, to Sproodluidce Eanaersttihmate of the ClO
(Solomon et al, 2006) is shown separately; the Microwave Limb Sounder (MLS)–Mauna Kea ClO profiles (MKO) In Figure 7, we show time series of the ClO peak mixing difference is everywhere less than the MKO accuracy
Summary
In June 2009, the millimeter-wavelength receiver failed. It was repaired and rebuilt at the University of Massachusetts, and returned to service in December 2009. In each is shown the daytime and nighttime average, and the nighttime spectrum after interpolation over the 50 MHz wide region around the ClO line frequency (which we call “interpolated night” for brevity). This “interpolated night” spectrum provides a good estimate of all spectral components besides those contributed by the ClO emission.
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