On the use of satellite observations to fill gaps in the Halley station total ozone record

Lily N Zhang,Natalya A Kramarova,Susan Solomon,Mark Weber,John P Burrows,Jonathan D Shanklin,David P Haffner,Pieternel F Levelt,Steve Colwell,Kane A Stone,Joshua D Eveson

doi:10.5194/acp-21-9829-2021

Abstract

Abstract. Measurements by the Dobson ozone spectrophotometer at the British Antarctic Survey's (BAS) Halley research station form a record of Antarctic total column ozone that dates back to 1956. Due to its location, length, and completeness, the record has been, and continues to be, uniquely important for studies of long-term changes in Antarctic ozone. However, a crack in the ice shelf on which it resides forced the station to abruptly close in February of 2017, leading to a gap of two ozone hole seasons in its historic record. We develop and test a method for filling in the record of Halley total ozone by combining and adjusting overpass data from a range of different satellite instruments. Comparisons to the Dobson suggest that our method reproduces monthly ground-based total ozone values with an average difference of 1.1 ± 6.2 DU for the satellites used to fill in the 2017–2018 gap. We show that our approach more closely reproduces the Dobson measurements than simply using the raw satellite average or data from a single satellite instrument. The method also provides a check on the consistency of the provisional data from the automated Dobson used at Halley after 2018 with earlier manual Dobson data and suggests that there were likely inconsistencies between the two. The filled Halley dataset provides further support that the Antarctic ozone hole is healing, not only during September but also in January.

Highlights

Using the Halley Dobson record, Farman et al (1985) were the first to identify the austral springtime Antarctic ozone hole, a discovery that would change the fundamental scientific understanding of atmospheric ozone chemistry and contribute to environmental policy at the international level via the Montreal Protocol (Birmpili, 2018)
Initial comparisons revealed that the use of the Serdyuchenko ozone absorption cross sections (Serdyuchenko et al, 2014) in the current GOME-2 data analysis method resulted in a 2 %–3 % positive bias in total ozone when compared to the Bass and Paur cross sections (Paur and Bass, 1985) employed at Halley
We developed a method to fill in missing data in the historic Halley record of total ozone (Farman et al, 1985; Jones and Shanklin, 1995) using satellite overpass data, with a particular focus on the period of 2017–2018 when the Halley station was abruptly closed for safety reasons associated with a crack in the ice shelf

Summary

Introduction

Using the Halley Dobson record, Farman et al (1985) were the first to identify the austral springtime Antarctic ozone hole, a discovery that would change the fundamental scientific understanding of atmospheric ozone chemistry and contribute to environmental policy at the international level via the Montreal Protocol (Birmpili, 2018). The length of the Halley Dobson record as well as the Halley station’s particular location relative to the polar vortex and solar terminator have made it historically important and uniquely valuable to modern studies of Antarctic total ozone. No ozone data were taken during the austral springs of 2017 or 2018, breaking the continuity of this unique record of the springtime ozone hole.

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