Characteristics, trend, and precursors of extreme cold events in northwestern North America

Shi, Jian; Wu, Kaijun; Qian, Weihong; Huang, Fei; Li, Chun; Tang, Cong

doi:10.1016/j.atmosres.2020.105338

Cited by 9 publications

(4 citation statements)

References 85 publications

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“…Further to the north, positive geopotential anomalies extend along the Barents-Kara Seas (Figure 6a), indicative of a weaker polar vortex. The anomalous geopotential distribution represents the negative AO phase, which is consistent with the cold extremes in northwestern North America [30]. Opposite geopotential anomalies and AO phase occur during years of rare WELT (Figure 6b).…”

Section: Atmospheric Circulation Patterns Affecting Welt In Necsupporting

confidence: 73%

Wintertime Cold Extremes in Northeast China and Their Linkage with Sea Ice in Barents-Kara Seas

Luo

Shi

et al. 2021

Atmosphere

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The impacts of Arctic sea ice on the interannual variability of winter extreme low temperature (WELT) in Northeast China (NEC) and the associated atmospheric circulation patterns are explored in this study based on meteorological observation and the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP/NCAR) reanalysis data. Results show that WELT in NEC has prominent interannual variability. We further use ±0.8 standard deviation as the threshold to select the years of frequent and rare extreme low temperature anomalies. Using composite analysis, we find that there are significant negative geopotential height anomalies at 500 hPa over NEC and positive geopotential height anomalies along the Arctic region, which represent the intensification of the East Asian trough (EAT) and the negative Arctic Oscillation (AO) phase in the years of more frequent WELT. The opposite characteristics are detected in the years of rare WELT. Furthermore, we determine that the Barents-Kara Seas are key sea ice regions in Arctic area. In the years of frequent WELT, the decrease of autumn Barents-Kara Seas sea ice and the positive sea surface temperature anomaly can last until the following winter, which is conducive to the intensification of anticyclonic anomalies in Ural regions and the northward extension of Ural ridge (UR). The northerly flow in front of UR guides the cold air penetrating southward from polar regions. Moreover, the anomalous cyclone over East Asia deepens the EAT. The northerly wind behind EAT guides the cold air to the NEC region, causing the wintertime low temperature there. The almost opposite situation occurs in the years of rare WELT.

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Section: Atmospheric Circulation Patterns Affecting Welt In Necsupporting

confidence: 73%

Wintertime Cold Extremes in Northeast China and Their Linkage with Sea Ice in Barents-Kara Seas

Luo

Shi

et al. 2021

Atmosphere

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“…The finding that NHCPV area is inversely related to the daily AO index in all months except February comes as no surprise, as the positive AO index is linked to a poleward retreat of the polar front (Budikova, 2008). The finding of a strongly positive association between Rc and the AO in every month at the daily scale confirms that the areal retreat is tied to zonal flow in the positive phase (Thompson and Wallace, 2000) and meridional (i.e., wavy) flow in the negative phase (Shi et al 2021). The similarity of associations between the regional expression of the AO the NAOand the NHCPV, with positive (negative) NAO tied to small and more circular NHCPV, corroborates these findings.…”

Section: Teleconnection Analysismentioning

confidence: 72%

Relationship Between Atmospheric Teleconnections and the Northern Hemisphere's Circumpolar Vortex

Bushra

Rohli

2021

Earth and Space Science

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 Daily variability of the Northern Hemisphere's circumpolar vortex (NHCPV) is linked to variability in air-sea teleconnection patterns. NHCPV is more strongly correlated with the extratropical AO, NAO, and PNA teleconnections than it is correlated to the tropical ENSO phenomenon. Linkage between the NHCPV and air-sea teleconnection variability is important because the low-and high-frequency variability of the broad-scale flow influences weather systems.

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“…Differences in 500 hPa GPH (Figure 9) reveal a more detailed structure of the GPH changes, showing a negative Arctic Oscillation-like structure. Such a pattern could be a good precursor for the extremely cold events in winter in North America [32], with positive GPH anomalies in the Arctic region with two centers over Greenland and Barents Sea. The positive GPH anomaly over Greenland weakens the low-pressure system centered around Baffin Island significantly, and the high anomaly over Barents Sea extending southward enhances Ural blocking in the low-ice phase.…”

Section: Polar Vortex Response To Arctic Sea Ice Declinementioning

confidence: 94%

Cold Air Outbreaks in Winter over the Continental United States and Its Possible Linkage with Arctic Sea Ice Loss

Wang,

Yang,

Huang

2024

Atmosphere

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The mechanism for the paradox of global warming and successive cold winters in mid-latitudes remains controversial. In this study, the connection between Arctic sea ice (ASI) loss and frequent cold air outbreaks in eastern Continental United States (CONUS) is explored. Two distinct periods of high and low ASI (hereafter high- and low-ice phases) are identified for comparative study. It is demonstrated that cold air outbreaks occur more frequently during the low-ice phase compared to that during the high-ice phase. The polar vortex is weakened and shifted southward during the low-ice phase. Correspondingly, the spatial pattern of 500 hPa geopotential height (GPH), which represents the mid-tropospheric circulation, shows a clear negative Arctic Oscillation-like pattern in the low-ice phase. Specifically, positive GPH anomalies in the Arctic region with two centers, respectively located over Greenland and the Barents Sea, significantly weaken the low-pressure system centered around the Baffin Island, and enhance Ural blocking in the low-ice phase. Meanwhile, the high ridge extending from Alaska to the west coast of North America further intensifies, while the low trough over eastern CONUS deepens. As a result, the atmospheric circulation in North America becomes more conductive to frigid Arctic air outbreaks. It is concluded that the ASI loss contributes to more cold air outbreaks in winter in eastern CONUS through the polar vortex weakening with southward displacement of the polar vortex edge, which lead to the weakening of the meridional potential vorticity gradient between the Arctic and mid-latitude and thus are conducive to the strengthening and long-term maintenance of the blocking high.

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Characteristics, trend, and precursors of extreme cold events in northwestern North America

Cited by 9 publications

References 85 publications

Wintertime Cold Extremes in Northeast China and Their Linkage with Sea Ice in Barents-Kara Seas

Wintertime Cold Extremes in Northeast China and Their Linkage with Sea Ice in Barents-Kara Seas

Relationship Between Atmospheric Teleconnections and the Northern Hemisphere's Circumpolar Vortex

Cold Air Outbreaks in Winter over the Continental United States and Its Possible Linkage with Arctic Sea Ice Loss

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