The Recent Increase in the Occurrence of a Boreal Summer Teleconnection and Its Relationship with Temperature Extremes

Abstract

This study has investigated the relationship between temperature extremes and a subseasonal hemispheric teleconnection pattern over the Northern Hemisphere during boreal summer. By applying self-organizing map (SOM) analysis to 200-hPa geopotential fields from the European Centre for Medium-Range Weather Forecasts interim reanalysis (ERA-Interim) for the period 1979–2012, a teleconnection pattern is identified that increased dramatically in its occurrence after the late 1990s. This pattern is characterized by a zonal wavenumber-5 pattern with anomalous high pressure cores over eastern Europe, northeastern Asia, the eastern North Pacific, the eastern United States, and Greenland. These high pressure centers coincide with regions of increasingly frequent temperature extremes in recent decades. To investigate the temporal evolution of the identified SOM pattern, time-lagged composites were performed relative to the days in which the 200-hPa geopotential field most closely resembled the SOM pattern. From day −10 to day 0, a wave train propagated from the central tropical Pacific to the Canadian Arctic Archipelago and Greenland. This poleward wave propagation was followed by the establishment of quasi-stationary high pressure centers over Greenland, Europe, and Asia. This study suggests that more frequent occurrence of the hemispheric teleconnection is linked to more severe and longer extreme weather events over the Northern Hemisphere since the late 1990s.

Consecutive extreme flooding and heat wave in Japan: Are they becoming a norm?

“…While traveling synoptic waves are known to intensify Baiu rainfall (Sampe and Xie, ), the aforementioned wave‐7 structure is stationary (Figure S1b) and not transient. The polarity and position of this stationary wave train coincide with the observation that the persistence of circumglobal teleconnection with wave numbers 5–7 has increased (Wang et al, ; Lee et al, ; Coumou et al, ). By July 10, 2018, the short‐wave train had dissipated and, as a result, did not contribute to the heat wave (Figure S1b).…”

Anthropogenically-driven increases in the risks of summertime compound hot extremes

“…6, see synoptic-scale analysis in refs. 30,31 ). So, regions observing stronger increases in anticyclonic conditions generally see larger increases in frequency of compound hot extremes (compare Supplementary Fig.…”

Diagnosing Physical Mechanisms Leading to Pure Heat Waves Versus Pure Tropical Nights Over the Korean Peninsula

“…They suggested that the influence of El Nino-Southern Oscillation on Korean HW has begun to weaken in recent years, whereas that of the Arctic Oscillation has strengthened. Previous studies also have revealed that HW events are closely associated with planetary waves (Lee et al, 2017;Mann et al, 2017;Teng et al, 2013 identified, such as anthropogenic factors (Fischer & Knutti, 2015), soil moisture, and land-atmosphere interactions (Fischer, Seneviratne, Vidale, et al, 2007;Lorenz et al, 2010). In contrast, TN events are closely associated with humidity.…”