An Examination of the Recent Stability of Ozonesonde Global Network Data

Abstract

The recent Assessment of Standard Operating Procedures for Ozonesondes 2.0 (WMO/ GAW Report #268) addressed questions of homogeneity and long-term stability in global electrochemical concentration cell (ECC) ozone sounding network time series. Among its recommendations was adoption of a standard for evaluating data quality in ozonesonde time series. Total column ozone (TCO) derived from the sondes compared to TCO from Aura's Ozone Monitoring Instrument (OMI) is a primary quality indicator. Comparisons of sonde ozone with Aura's Microwave Limb Sounder (MLS) are used to assess the stability of stratospheric ozone. This paper provides a comprehensive examination of global ozonesonde network data stability and accuracy since 2004 in light of the sudden post-2013 TCO "dropoff" of ∼3%-4% that was reported previously at select stations (Stauffer et al., 2020, https://doi.org/10.1029/2019GL086791). Comparisons with Aura OMI TCO averaged across the network of 60 stations are stable within about ±2% over the past 18 years. Sonde TCO has similar stability compared to three other TCO satellite instruments, and the stratospheric ozone measurements average to within ±5% of MLS from 50 to 10 hPa. Thus, sonde data are reliable for trends, but with a caveat applied for a subset of dropoff stations in the tropics and subtropics. The dropoff is associated with only one of two major ECC instrument types. A detailed examination of ECC serial numbers pinpoints the timing of the dropoff. However, we find that overall, ozonesonde data are stable and accurate compared to independent measurements over the past two decades.Plain Language Summary Ozonesondes provide accurate ozone measurements from the surface to ∼30-km altitude and are used as a reference for studies of satellite data, trends, pollution, and climate. Updated guidelines for sonde preparation and adoption of sonde total column ozone (TCO) comparisons with satellite TCO as a "data quality" reference were published in 2021 by the Assessment of Standard Operating Procedures for Ozonesondes (ASOPOS) 2.0 panel in WMO/GAW Report 268. We report the first application of the ASOPOS 2.0 protocol to TCO evaluation from the 60-station global ozonesonde network (42,042 profiles total). With Aura OMI TCO as the satellite reference (October 2004 to mid-2021), we find that TCO readings from the global ozonesonde network are remarkably stable, consistently within ±2% of the satellite. An exception occurs at only a small subset of tropical and subtropical locations that use one type of ozonesonde instrument. The latter result confirms our earlier report that a sudden TCO drop occurs at selected sites after 2013. The timing and magnitude of the dropoff are revisited. The hypothesis that ozonesonde production changes are a contributor remains, with station-specific factors possibly affecting the magnitude of the bias. Overall, global ozonesonde network data are of high quality and stability.

An ozonesonde evaluation of spaceborne observations in the Andean tropics

“…2 c,d) with respect to soundings is + 7.7 DU (3.2% difference). Offsets of like magnitudes in measurements by these sensors have been documented at other tropical stations 17 . In contrast, the difference between OMI/Aura and soundings (+ 2.7 DU or 1.2% mean difference; Fig.…”

Five years of Sentinel-5p TROPOMI operational ozone profiling and geophysical validation using ozonesonde and lidar ground-based networks

“…Launched on board of small meteorological balloons, an electrochemical ozonesonde measures the vertical distribution of atmospheric ozone partial pressure from the ground up to burst point, typically around 30 km. Measurement errors depend on the type and the preparation of the sonde instrument (Smit, 2014;Stauffer et al, 2022) as well as on how the post-processing of the acquired raw data is done. When standard operating procedures are followed, systematic differences with respect to the reference photometer at the World Calibration Centre for Ozone Sondes (WCCOS) in Jülich are negligible, with an uncertainty of up to 5 %, and except in the tropical upper troposphere, random uncertainty is less than 3-5 % below 27 km (Smit, Thompson, and the ASOPOS 2.0 Panel, 2021).…”

Reply on CC1

“…Trends of ozone in the free troposphere presented here are based on ozonesonde data from the literature. Despite the high stability of ozonesonde measurements across the global networks over several decades (Stauffer et al, 2022), the spatial sparsity of sounding stations and nonuniform sampling frequency among sites is a limitation in using these data to produce trends. These shortcomings have constrained the ability to include data from many stations in previously published analyses.…”