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An Updated Examination of the Post-2013 Ozonesonde Total Column Ozone “Dropoff”

R.M. Stauffer1, A.M. Thompson1, D.E. Kollonige1,2, D. Tarasick3, H. Vömel4, G.A. Morris5, R.V. Malderen6, B.J. Johnson7, P. Cullis8,7, R. Stübi9 and H.G.J. Smit10

1NASA Goddard Space Flight Center (GSFC), Atmospheric Chemistry and Dynamics Laboratory, Greenbelt, MD 20771; 301-614-5552, E-mail: ryan.m.stauffer@nasa.gov
2Science Systems and Applications, Inc. (SSAI), Lanham, MD 20706
3Air Quality Research Division, Environment and Climate Change Canada (ECCC), Downsview, Ontario, Canada
4National Center for Atmospheric Research (NCAR), Boulder, CO 80307
5St. Edward's University, Austin, TX 78704
6Royal Meteorological Institute of Belgium, Brussels, Belgium
7NOAA Global Monitoring Laboratory (GML), Boulder, CO 80305
8Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, CO 80309
9Federal Office of Meteorology and Climatology, MeteoSwiss
10Institute of Chemistry and Dynamics of the Geosphere: Troposphere, Research Centre Juelich, Germany

Last year we presented the discovery of a sudden decline in ozonesonde total column ozone (TCO) and stratospheric ozone, the ≥3% TCO “dropoff” after 2013, for roughly a third of global stations (Stauffer et al., 2020; GRL). Our analyses have been updated to include more ozonesonde stations and another year or two of comparisons with independent satellite and ground-based data sets. We currently estimate that the TCO dropoff affects fewer than 25% of global ozonesonde stations, is limited to one electrochemical concentration cell (ECC) ozonesonde type, and is evident only at Southern Hemisphere ADditional OZonesondes (SHADOZ) and Canadian stations. Less than half of stations launching the affected ECC ozonesonde type display the dropoff, and sonde data from the remaining >75% of global stations remain stable, accurate and suitable for stratospheric trends analysis. The latest investigations of ozonesonde laboratory tests and examination of metadata for affected station records strongly suggest a site-specific component yet to be identified. The dropoff has remained steady or is improving at all stations where it occurs (i.e., the problem is not getting worse). This presentation provides the latest information on the TCO dropoff and the recent efforts by the Assessment of Standard Operating Procedures for OzoneSondes v2 Panel (ASOPOS 2.0) Dropoff Task Team to solve the problem.

Figure 1

Figure 1. A composite of ozonesonde and satellite (OMI and OMPS) TCO comparisons partitioned by En-Sci ECC ozonesonde serial number for dropoff-affected (top, red) and unaffected (bottom, blue) stations. Affected stations display a 3-6% TCO dropoff generally beginning with #25000 serial numbers, but unaffected stations, launching ozonesondes with similar serial numbers, display no such behavior. This indicates the strong likelihood of a site-specific component to the TCO dropoff.