Electrochemical concentration cell ozonesonde measurements are an important source of highly resolved vertical profiles of ozone (O3) with long‐term data records for deriving O3 trends, model development, satellite validation, and air quality studies. Ozonesonde stations employ a range of operational and data processing procedures, metadata reporting, and instrument changes that have resulted in inhomogeneities within individual station data records. A major milestone is the first reprocessing of seven Southern Hemisphere ADditional OZonesondes (SHADOZ) station ozonesonde records to account for errors and biases in operating/processing procedures. Ascension Island, Hanoi, Irene, Kuala Lumpur, La Réunion, Natal, and Watukosek station records all show an overall increase in O3 after reprocessing. Watukosek shows the largest increase of 9.0 ± 2.1 Dobson Units (DU) in total column O3; Irene and Hanoi show a 5.5 ± 2.5 DU increase, while remaining sites show statistically insignificant enhancements. Negligible to modest O3 enhancements are observed after reprocessing in the troposphere (up to 8%) and stratosphere (up to 6%), except at La Réunion for which the application of background currents reduces tropospheric O3 (−2.1 ± 1.3 DU). Inhomogeneities due to ozonesonde/solution‐type changes at Ascension, Natal, and La Réunion are resolved with the application of transfer functions. Comparisons with EP‐TOMS, Aura's Ozone Monitoring Instrument and Microwave Limb Sounder (MLS) satellite O3 overpasses show an overall improvement in agreement after reprocessing. Most reprocessed data sets show a significant reduction in biases with MLS at the ozone maximum region (50–10 hPa). Changes in radiosonde/ozonesonde system and nonstandard solution types can account for remaining discrepancies observed at several sites when compared to satellites.

Abstract. NOAA's program of long-term monitoring of the vertical distribution of ozone with electrochemical concentration cell (ECC) ozonesondes has undergone a number of changes over the 50-year record. In order to produce a homogenous data set, these changes must be documented and, where necessary, appropriate corrections applied. This is the first comprehensive and consistent reprocessing of NOAA's ozonesonde data records that corrects for these changes using the rawest form of the data (cell current and pump temperature) in native resolution as well as a point-by-point uncertainty calculation that is unique to each sounding. The reprocessing is carried out uniformly at all eight ozonesonde sites in NOAA's network with differences in sensing solution and ozonesonde types accounted for in the same way at all sites. The corrections used to homogenize the NOAA ozonesonde data records greatly improve the ozonesonde measurements with an average one sigma uncertainty of ±4-6 % in the stratosphere and ±5-20 % in the troposphere. A comparison of the integrated column ozone from the ozonesonde profile with co-located Dobson spectrophotometers total column ozone measurements shows agreement within ±5 % for > 70 % of the profiles. Very good agreement is also found in the stratosphere between ozonesonde profiles and profiles retrieved from the Solar Backscatter Ultraviolet (SBUV) instruments.