Evaluation of the homogenization adjustments applied to european temperature records in the global historical climatology network dataset

0555991 - ÚVGZ 2023 RIV CH eng J - Journal Article
O'Neill, P. - Connolly, R. - Connolly, M. - Soon, W. - Chimani, B. - Crok, M. - de Vos, R. - Harde, H. - Kajaba, P. - Nojarov, P. - Przybylak, R. - Rasol, D. - Skrynyk, O. - Skrynyk, O. - Štěpánek, Petr - Wypych, A. - Zahradníček, Pavel
Evaluation of the homogenization adjustments applied to european temperature records in the global historical climatology network dataset.
Atmosphere. Roč. 13, č. 2 (2022), č. článku 285. E-ISSN 2073-4433
R&D Projects: GA MŠMT(CZ) EF16_019/0000797
Institutional support: RVO:86652079
Keywords : air-temperature * time-series * meteorological observations * data set * period * bias * discontinuities * urbanization * variability * circulation * temperature homogenization * non-climatic biases * station metadata * climate change * European temperature changes
OECD category: Climatic research
Impact factor: 2.9, year: 2022
Method of publishing: Open access
https://www.mdpi.com/2073-4433/13/2/285

The widely used Global Historical Climatology Network (GHCN) monthly temperature dataset is available in two formats-non-homogenized and homogenized. Since 2011, this homogenized dataset has been updated almost daily by applying the ,,Pairwise Homogenization Algorithm,, (PHA) to the non-homogenized datasets. Previous studies found that the PHA can perform well at correcting synthetic time series when certain artificial biases are introduced. However, its performance with real world data has been less well studied. Therefore, the homogenized GHCN datasets (Version 3 and 4) were downloaded almost daily over a 10-year period (2011-2021) yielding 3689 different updates to the datasets. The different breakpoints identified were analyzed for a set of stations from 24 European countries for which station history metadata were available. A remarkable inconsistency in the identified breakpoints (and hence adjustments applied) was revealed. Of the adjustments applied for GHCN Version 4, 64% (61% for Version 3) were identified on less than 25% of runs, while only 16% of the adjustments (21% for Version 3) were identified consistently for more than 75% of the runs. The consistency of PHA adjustments improved when the breakpoints corresponded to documented station history metadata events. However, only 19% of the breakpoints (18% for Version 3) were associated with a documented event within 1 year, and 67% (69% for Version 3) were not associated with any documented event. Therefore, while the PHA remains a useful tool in the community's homogenization toolbox, many of the PHA adjustments applied to the homogenized GHCN dataset may have been spurious. Using station metadata to assess the reliability of PHA adjustments might potentially help to identify some of these spurious adjustments.
Permanent Link: http://hdl.handle.net/11104/0330427