Articles | Volume 10, issue 11
Research article
15 Nov 2017
Research article |  | 15 Nov 2017

Intercomparison of Pandora stratospheric NO2 slant column product with the NDACC-certified M07 spectrometer in Lauder, New Zealand

Travis N. Knepp, Richard Querel, Paul Johnston, Larry Thomason, David Flittner, and Joseph M. Zawodny

Abstract. In September 2014, a Pandora multi-spectral photometer operated by the SAGE-III project was sent to Lauder, New Zealand, to operate side-by-side with the National Institute of Water and Atmospheric Research's (NIWA) Network for Detection of Atmospheric Composition Change (NDACC) certified zenith slant column NO2 instrument to allow intercomparison between the two instruments and for evaluation of the Pandora unit as a potential SAGE-III validation tool for stratospheric NO2. This intercomparison spanned a full year, from September 2014 to September 2015. Both datasets were produced using their respective native algorithms using a common reference spectrum (i.e., 12:00 NZDT (UTC + 13) on 26 February 2015). Throughout the entire deployment period both instruments operated in a zenith-only observation configuration. Though conversion from slant column density (SCD) to vertical-column density is routine (by application of an air mass factor), we limit the current analysis to SCD only. This omission is beneficial in that it provides an intercomparison based on similar modes of operation for the two instruments and the retrieval algorithms as opposed to introducing an air mass factor dependence in the intercomparison as well. It was observed that the current hardware configurations and retrieval algorithms are in good agreement (R > 0.95). The detailed results of this investigation are presented herein.

Short summary
The SAGE-III instrument was launched in February 2017. As with any new instrument, a significant post-launch activity is planned to validate the data products. Validation of trace gases with short photolytic lifetimes is challenging, though careful use of Pandora-type instruments may prove beneficial. A careful intercomparison of Pandora and NIWA's M07 instrument was carried out. Results show Pandora to be well correlated with M07, showing its viability as a validation tool for SAGE science.