Increased persistence of large-scale circulation regimes over Asia in the era of amplified Arctic warming, past and future

Abstract

Extreme weather events in Asia have been occurring with increasing frequency as the globe warms in response to rising concentrations of greenhouse gases. Many of these events arise from weather regimes that persist over a region for days or even weeks, resulting in disruptive heatwaves, droughts, flooding, snowfalls, and cold spells. We investigate changes in the persistence of large-scale weather systems through a pattern-recognition approach based on daily 500 hPa geopotential height anomalies over the Asian continent. By tracking consecutive days that the atmosphere resides in a particular pattern, we identify long-duration events (LDEs), defined as lasting longer than three days, and measure their frequency of occurrence over time in each pattern. We find that regimes featuring positive height anomalies in high latitudes are occurring more often as the Arctic warms faster than mid-latitudes, both in the recent past and in model projections for the twenty-first century assuming unabated greenhouse gas emissions. The increased dominance of these patterns corresponds to a higher likelihood of LDEs, suggesting that persistent weather conditions will occur more frequently. By mapping observed temperature and precipitation extremes onto each atmospheric regime, we gain insight into the types of disruptive weather events that will become more prevalent as particular patterns become more common.

Measuring “Weather Whiplash” Events in North America: A New Large‐Scale Regime Approach

“…(While the f ‐test detected significant (>90%) trends in nodes #2 and #6, the number of LDEs is too small to be consequential). These findings are consistent with our earlier work on weather‐regime persistence (Francis et al., 2018, 2020; Vihma et al., 2019). Specifically, Francis et al.…”

“…(While the f-test detected significant (>90%) trends in nodes #2 and #6, the number of LDEs is too small to be consequential). These findings are consistent with our earlier work on weather-regime persistence (Francis et al, 2018(Francis et al, , 2020Vihma et al, 2019). Specifically, Francis et al (2018) found an increased occurrence of LDEs, particularly in patterns featuring positive height anomalies in high latitudes of the North American domain, the same as that used in the present study.…”

“…Results using different thresholds (3-7 days), both in previous studies and this one, did not change our conclusions. For further detail and justification, see Francis et al (2018Francis et al ( , 2020 and Vihma et al (2019). (Kalnay et al, 1996).…”

“…Our analysis produces a total of 948 (annual), 239 (winter), and 228 (summer) WWEs over the 72-year record, which translates to an annual-or seasonal-mean frequency of 13.2, 3.3, and 3.2, respectively. These events are relatively rare because LDEs themselves occur infrequently (Figure S6 in Supporting Information S1, and also see Francis et al, 2018Francis et al, , 2020.…”

Risk of short‐term biodiversity loss under more persistent precipitation regimes

“…Global climate change is causing more persistent weather in the midlatitudes (Coumou et al, 2018; Francis et al, 2020; Pfleiderer et al, 2019). Amplified arctic warming reduces the temperature difference with the equator, resulting in more sluggish circulation patterns and a “wavier” jet stream (Coumou et al, 2018; Mann et al, 2017).…”