From the ASOPOS-2020 Ozone Experts

The ASOPOS (Assessment of Standard Operating Procedures for OzoneSondes) Panel, a group of ~20 ozonesonde expert data-providers, was formed in 2004. ASOPOS, under WMO/GAW sponsorship, has issued periodic reports on ozonesonde quality assurance, including evaluations of sonde intercomparisons in the Juelich Ozonesonde Intercomparison Experiment (JOSIE) series.

Picture showing map of global ECC ozonsonde stations

The report documents include the WMO/GAW Report 201 on ozonesonde standard procedures (Smit and ASOPOS, 2014). The current ASOPOS Panel, made up of members of NDACC’s Sonde Working Group, among others, has been updating the 2014 WMO/GAW report based on lab tests by a number of ozonesonde users, including the JOSIE-SHADOZ (2017) chamber tests at the World Calibration Center for OzoneSondes in Juelich, Germany. Editors of the new ASOPOS Report, aimed for late 2020 publication, are Herman Smit (FZ-Juelich) and Anne Thompson (NASA/GSFC). The current ASOPOS group, along with four representatives from sonde manufacturers, 23 attendees in all, met 18 and 19 March 2020 in a virtual meeting hosted remotely by Bryan Johnson (with IT support from NOAA/ESRL/GMD, Boulder, CO) and Anne Thompson. Among presenters were Rene Stuebi (Meteoswiss), Bryan Johnson (NOAA), Holger Voemel (NCAR), David Tarasick (Environment & Climate Change Canada), Roeland van Malderen (RMI, Belgium). Many of the 18 March presentations centered around updates related to the recently discovered “post-2013 global total ozone dropoff” reported on at the Sept. 2019 ASOPOS meeting in Brussels. The dropoff is described in a paper in review in Geophysical Research Letters by Ryan M. Stauffer et al., and new information came from lab and field studies conducted by the various presenters. A “Total Column Ozone Dropoff Task Team” has been formed to look more deeply into causes of the problem. There is consensus that except for one station using the SPC instrument only EnSci sondes exhibit the dropoff, but the structure of the artifact ozone loss is distinct between the two regions in which the dropoff has been noted: tropical (most but not all SHADOZ sites) and Canadian stations. Thus, metadata are being analyzed for site-specific differences. Ryan Stauffer and Roeland van Malderen are the Task Team leads; four sub-teams have been organized, including one on metadata led by Debra Kollonige (NASA/GSFC). On 20 March 2020 the new ASOPOS Report author team convened and reviewed all five chapters and several Annexes. The new Report is more comprehensive than the 2014 version; it includes a chapter on ozonesonde measurement uncertainties, an overview and inventory of the current global ozonesonde network in the Introductory Chapter and a chapter on data quality indicators with more detailed metadata standards. The Editors and author team of the new Report expect to have a complete Draft version to external Peer Reviewers by July 2020.

Picture of graphs showing comparisons with Aura MLS on MLS pressure levels and total O3 comparisons with satellite overpasses

Contributed by: Anne Thompson, NDACC Co-Chair & ASOPOS 2020 Report Co-Chair