First reprocessing of Southern Hemisphere ADditional OZonesondes (SHADOZ) profile records (1998–2015): 1. Methodology and evaluation
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Witte, Jacquelyn C., Anne M. Thompson, Herman G. J. Smit, Masatomo Fujiwara, Françoise Posny, Gert J. R. Coetzee, Edward T. Northam, et al. “First Reprocessing of Southern Hemisphere ADditional OZonesondes (SHADOZ) Profile Records (1998–2015): 1. Methodology and Evaluation.” Journal of Geophysical Research: Atmospheres 122, no. 12 (2017): 6611–36. https://doi.org/10.1002/2016JD026403.
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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Abstract
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.