HCl and ClO profiles inside the Antarctic vortex as observed by SMILES in November 2009: comparisons with MLS and ACE-FTS instruments

Abstract

We present vertical profiles of hydrogen chloride (HCl) and chlorine monoxide (ClO) as observed by the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the International Space Station (ISS) inside the Antarctic vortex on 19–24 November 2009. The SMILES HCl value reveals 2.8–3.1 ppbv between 450 K and 500 K levels in potential temperature (PT). The high value of HCl is highlighted since it is suggested that HCl is a main component of the total inorganic chlorine (Cly), defined as Cly ≃ HCl + ClO + chlorine nitrate (ClONO2), inside the Antarctic vortex in spring, owing to low ozone values. To confirm the quality of two SMILES level 2 (L2) data products provided by the Japan Aerospace Exploration Agency (JAXA) and Japan's National Institute of Information and Communications Technology (NICT), vis-à-vis the partitioning of Cly, comparisons are made using other satellite data from the Aura Microwave Limb Sounder (MLS) and Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). HCl values from the SMILES NICT L2 product agree to within 10% (0.3 ppbv) with the MLS HCl data between 450 and 575 K levels in PT and with the ACE-FTS HCl data between 425 and 575 K. The SMILES JAXA L2 product is 10 to 20% (0.2–0.5 ppbv) lower than that from MLS between 400 and 700 K and from ACE-FTS between 500 and 700 K. For ClO in daytime, the difference between SMILES (JAXA and NICT) and MLS is less than ±0.05 ppbv (100 %) between 500 K and 650 K with the ClO values less than 0.2 ppbv. ClONO2 values as measured by ACE-FTS also reveal 0.2 ppbv at 475–500 K level, resulting in the HCl / Cly ratios of 0.91–0.95. The HCl / Cly ratios derived from each retrieval agree to within −5 to 8 % with regard to their averages. The high HCl values and HCl / Cly ratios observed by the three instruments in the lower stratospheric Antarctic vortex are consistent with previous observations in late Austral spring.