A post-2013 dropoff in total ozone at a third of global ozonesonde stations: Electrochemical concentration cell instrument artifacts?

However, between 2014 and 2016, ozonesonde total column ozone (TCO; O-3) 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 O(3)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 O(3)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.