Preprints
https://doi.org/10.5194/acp-2022-497
https://doi.org/10.5194/acp-2022-497
 
05 Aug 2022
05 Aug 2022
Status: this preprint is currently under review for the journal ACP.

Monitoring sudden stratospheric warmings under climate change based on reanalysis data verified by radio occultation

Ying Li1, Gottfried Kirchengast2, Marc Schwaerz2, and Yunbin Yuan1 Ying Li et al.
  • 1State Key Laboratory of Geodesy and Earth’s Dynamics, Innovation Academy for Precision Measurement Science and Technology (APM), Chinese Academy of Sciences, Wuhan, 430071, China
  • 2Wegener Center for Climate and Global Change (WEGC) and Institute of Physics, University of Graz, 8010 Graz, Austria

Abstract. We develop a new approach to monitor Sudden Stratospheric Warming (SSW) events under climate change since 1980 based on reanalysis data, verified by radio occultation data. We construct gridded daily-mean temperature anomalies and employed the concept of Threshold Exceedance Areas (TEAs), the geographic areas wherein the anomalies exceed predefined thresholds (such as 30 K) to monitor the phenomena. We derived main-phase TEAs to monitor SSW warming on a daily basis and also a trailing-phase TEA to monitor potential upper stratospheric cooling in the wake of the warming phase. Based on the main-phase TEAs, three key metrics, including Main-Phase Strength (MPS), Duration (MPD) and Area (MPA), are estimated and used for the detection and classification of SSW events, enabling minor, major, and extreme event categories. An informative 42 winters’ SSW climatology 1980–2020 was developed, including the three key metrics as well as onsets date, maximum-warming-anomaly location and strength and other valuable SSW characterization information. Detection and validation against previous studies underpins that the new method is robust for SSW detection and monitoring and that it can be applied to any quality-assured reanalysis and observational data that cover the polar region and winter timeframes of interest. Within the 42 winters, 40 SSW events were detected, yielding a frequency of about 0.95/year. In the 1990s, where recent studies showed gaps, we detected several events. About 95 % of event onset dates occurred in deep winter (Dec-Jan-Feb timeframe; about 50 % in January) and three quarters have their onset location over Northern Eurasia and the adjacent polar ocean. Regarding long-term change, we also found a statistically significant increase in the duration of SSW main-phase warmings, by about 4 days from the 1980s to the 2010s, raising the average duration by 40 % from about 10 to 14 days and inducing an SSW strength increase by near 30 million km2 days (about 30 %) from about 105 to 135 million km2 days. The results can be used as a reference for further long-term studies and be a valuable basis for studying SSW impacts and links to other weather and climate phenomena, such as changes in polar vortex dynamics and in mid-latitude extreme weather.

Ying Li et al.

Status: open (until 16 Sep 2022)

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Ying Li et al.

Ying Li et al.

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Short summary
We develop a new approach to monitor Sudden Stratospheric Warming (SSW) events since 1980 and develop a 42 years’ SSW events climatology. Detection and evaluation results suggest that the new method is robust for SSW monitoring. We also found an increase in the duration of SSW main-phase warmings by about 4 days over the three decades from the 1980s to the 2010s, raising the average duration from about 10 days to 14 days and the warming strength is also found increased.
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