A Post‐2013 Dropoff in Total Ozone at a Third of Global Ozonesonde Stations: Electrochemical Concentration Cell Instrument Artifacts?

Abstract

An international effort to improve ozonesonde data quality and to reevaluate historical records has made significant improvements in the accuracy of global network data. However, between 2014 and 2016, ozonesonde total column ozone (TCO; O3) at 14 of 37 regularly reporting stations exhibited a sudden dropoff relative to satellite measurements. The ozonesonde TCO drop is 3–7% compared to satellite and ground‐based TCO, and 5–10% or more compared to satellite stratospheric O3 profiles, compromising the use of recent data for trends, although they remain reliable for other uses. Hardware changes in the ozonesonde instrument are likely a major factor in the O3 dropoff, but no single property of the ozonesonde explains the findings. The bias remains in recent data. Research to understand the dropoff is in progress; this letter is intended as a caution to users of the data. Our findings underscore the importance of regular ozonesonde data evaluation.

COVID‐19 Crisis Reduces Free Tropospheric Ozone Across the Northern Hemisphere

“…The CAMS analyses (Figure 3d) show that 2020 meteorological conditions and springtime Arctic stratospheric ozone depletion resulted in ozone reductions of 5%-10% above 9 km, consistent with the observations. Time series of the tropospheric anomaly (averaged from April to August, and from 1 to 8 km altitude) are shown in 10.1029/2020GL091987 5 of 11 Stauffer et al, 2020). The drop-off is much smaller (<<1%) in the troposphere, and should be negligible here.…”

“… c Stations affected by a drop‐off in ECC sonde sensitivity >3% in the stratosphere, after 2015 (see Stauffer et al., 2020). The drop‐off is much smaller (<<1%) in the troposphere, and should be negligible here.…”

A new method to correct the electrochemical concentration cell (ECC) ozonesonde time response and its implications for “background current” and pump efficiency

“…It provides observations of high fidelity and high vertical resolution, which among others are considered a reference for satellite-based remote-sensing observations. Its operation has been described in detail elsewhere (e.g., Komhyr, 1969;Komhyr and Harris, 1971;Smit and ASOPOS panel (2014); Sterling et al, 2018;Tarasick et al, 2020).…”

“…where P O 3 is in millipascals; I O 3 in microamperes is the cell current attributed to the reaction of ozone with iodide; c = 4.309 × 10 −4 is the ratio of the ideal gas constant and Faraday constant divided by the yield ratio of two electrons per ozone molecule; T in kelvin is the air temperature entering the cell, approximated by the temperature of the pump; t 100 in seconds is the flow rate time to pump 100 mL; and γ is a pressure-dependent pump flow correction factor. Other efficiency corrections may be included in γ (e.g., Sterling et al, 2018;Tarasick et al, 2020) but are omitted here for simplicity. Throughout the ECC ozonesonde community, these instruments are operated using predominantly three chemical solution recipes; these differ mostly in the relative concentration of the potassium iodide and the concentration of the buffer (see Johnson et al, 2002).…”

“…This recipe is referred to as the 0.5 % KI, halfbuffer solution. Sterling et al (2018) introduced a third solution, in which only the strength of the buffer was reduced by a factor of 10 while maintaining the original concentration of potassium iodide. This solution will be referred to as 1 % KI, 1/10th buffer solution and has been used across the NOAA ozonesonde network as well as in Costa Rica.…”