Optimized Umkehr profile algorithm for ozone trend analyses

Irina Petropavlovskikh (1, 2) , Koji Miyagawa (2) , Audra Mcclure-Beegle (1, 2) , Bryan Johnson (2) , Jeannette Wild (3, 4) , Susan Strahan (5, 6) , Krzysztof Wargan (6, 7) , Richard Querel (8) , Lawrence Flynn (9) , Eric Beach (10) , Gérard Ancellet (11) , Sophie Godin-Beekmann (12)

1 CIRES - Cooperative Institute for Research in Environmental Sciences
2 GML - ESRL Global Monitoring Laboratory [Boulder]
3 CISESS - Cooperative Institute for Satellite Eareth System Studies
4 CPC - NCEP Climate Prediction Center
5 USRA - Universities Space Research Association [Washington]
6 GSFC - NASA Goddard Space Flight Center
7 SSAI - Science Systems and Applications, Inc. [Lanham]
8 NIWA - National Institute of Water and Atmospheric Research [Lauder]
9 STAR - NOAA Center for Satellite Applications and Research
10 IMSG - IM Systems Group
11 TROPO - LATMOS
12 STRATO - LATMOS

The long-term record of Umkehr measurements from four NOAA Dobson spectrophotometers was reprocessed after updates to the instrument calibration procedures. In addition, a new data quality-control tool was developed for the Dobson automation software (WinDobson). This paper presents a comparison of Dobson Umkehr ozone profiles from NOAA ozone network stations (Boulder, OHP, MLO, Lauder) against several satellite records, including Aura Microwave Limb Sounder (MLS; ver. 4.2), and combined SBUV and OMPS records (NASA AGG and NOAA COH). A subset of satellite data is selected to match Dobson Umkehr observations at each station spatially (distance less than 200 km) and temporally (within 24 hours). Umkehr Averaging Kernels (AKs) are applied to vertically smooth all overpass satellite profiles prior to comparisons. The station Umkehr record consists of several instrumental records, which have different optical characterizations, and thus instrument-specific stray light contributes to the data processing errors and creates step changes in the record. This work evaluates the overall quality of Umkehr long-term measurements at NOAA ground-based stations and assesses the impact of the instrumental changes on the stability of the Umkehr ozone profile record. This paper describes a method designed to correct biases and discontinuities in the retrieved Umkehr profile that originate from the Dobson calibration process, repair, or optical realignment of the instrument. The M2GMI and GMI CTM ozone profile model output matched to station location and date of observation is used to evaluate instrumental step changes in the Umkehr record. Homogenization of the Umkehr record and discussion of the apparent stray light error in retrieved ozone profiles are the focus of this paper. Homogenization of groundbased records is of great importance for studies of long-term ozone trends and climate change.

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]

Irina Petropavlovskikh, Koji Miyagawa, Audra Mcclure-Beegle, Bryan Johnson, Jeannette Wild, et al.. Optimized Umkehr profile algorithm for ozone trend analyses. Atmospheric Measurement Techniques, 2022, 15 (6), pp.1849-1870. ⟨10.5194/amt-15-1849-2022⟩. ⟨insu-03353378v2⟩