Relationship between extensive and persistent extreme cold events in China and stratospheric circulation anomalies

2016 ◽  
Vol 1 (1) ◽  
Author(s):  
Hui Yang ◽  
Xinrong Chen ◽  
Gui-Ying Yang
Keyword(s):  
Atmospheric Circulation ◽  
The Arctic ◽  
Height Anomaly ◽  
Composite Analysis ◽  
Cold Air ◽  
Atmospheric Circulations ◽  
Cold Events ◽  
Extreme Cold ◽  
Stratospheric Circulation ◽  
Circulation Anomalies

This study examines the relationship between the extensive and persistent extreme cold events (EPECEs) in China and geopotential height anomalies in the stratosphere using daily mean fields of outgoing long wave radiation (OLR) produced by the NCAR and daily atmospheric circulations produced by the NCEP/NCAR. The OLR composite analysis for the EPECE in China demonstrates that the negative OLR height anomalies (cold air) originated from Siberia influence China progressively from north to south. The largest negative OLR height anomaly (cooling event) occurs in the region to the north of the Nanling Mountains. This suggests that the OLR height anomalies can be used to represent the temporal and spatial characteristics of extreme low temperatures and cold air activities in winter in China. The composite analysis of large-scale atmospheric circulations during the EPECE reveals characteristic evolutions of stratospheric and tropospheric circulations during the extreme cold event. We demonstrate the important role of atmospheric circulation anomalies in the outbreak and dissipation of the EPECE in China. We also demonstrate that significant perturbations in the stratospheric circulation occur more than 10 days prior to the outbreak of the EPECE, with positive height anomalies in the Arctic stratosphere. These positive anomalies propagate downward from the stratosphere and affect the formation and development of the high pressure ridge in the middle troposphere over the Ural Mountains. Significant changes also occur in the atmospheric circulation in the mid-latitude stratosphere. These changes propagate downward from the stratosphere and strengthen the low pressure trough in the troposphere in the region to the east of Lake Balkhash and Lake Baikal. Therefore, the changes in the stratospheric circulation during the EPECE in China occur prior to changes in the tropospheric circulation and are very useful for predicting extreme wintertime cold temperatures in China.

scholarly journals Recent summer Arctic atmospheric circulation anomalies in a historical perspective

2015 ◽  
Vol 9 (1) ◽  
pp. 53-64 ◽  
Author(s):  
A. Belleflamme ◽  
X. Fettweis ◽  
M. Erpicum
Keyword(s):  
Atmospheric Circulation ◽  
Greenland Ice Sheet ◽  
Arctic Region ◽  
Reanalysis Data ◽  
Circulation Type ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Pressure Area ◽  
Circulation Anomalies ◽  
The Arctic Region

Abstract. A significant increase in the summertime occurrence of a high pressure area over the Beaufort Sea, the Canadian Arctic Archipelago, and Greenland has been observed since the beginning of the 2000s, and particularly between 2007 and 2012. These circulation anomalies are likely partly responsible for the enhanced Greenland ice sheet melt as well as the Arctic sea ice loss observed since 2007. Therefore, it is interesting to analyse whether similar conditions might have happened since the late 19th century over the Arctic region. We have used an atmospheric circulation type classification based on daily mean sea level pressure and 500 hPa geopotential height data from five reanalysis data sets (ERA-Interim, ERA-40, NCEP/NCAR, ERA-20C, and 20CRv2) to put the recent circulation anomalies in perspective with the atmospheric circulation variability since 1871. We found that circulation conditions similar to 2007–2012 have occurred in the past, despite a higher uncertainty of the reconstructed circulation before 1940. For example, only ERA-20C shows circulation anomalies that could explain the 1920–1930 summertime Greenland warming, in contrast to 20CRv2. While the recent anomalies exceed by a factor of 2 the interannual variability of the atmospheric circulation of the Arctic region, their origin (natural variability or global warming) remains debatable.

scholarly journals Effects of Arctic sea ice in autumn on extreme cold events over the Tibetan Plateau in the following winter: possible mechanisms

2021 ◽  
Author(s):  
Miao Bi ◽  
Qingquan Li ◽  
Song Yang ◽  
Dong Guo ◽  
Xinyong Shen ◽  
...  
Keyword(s):  
Sea Ice ◽  
Wave Train ◽  
Beaufort Sea ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
The Tibetan Plateau ◽  
The North ◽  
Arctic Sea ◽  
Cold Events ◽  
Extreme Cold

AbstractExtreme cold events (ECEs) on the Tibetan Plateau (TP) exert serious impacts on agriculture and animal husbandry and are important drivers of ecological and environmental changes. We investigate the temporal and spatial characteristics of the ECEs on the TP and the possible effects of Arctic sea ice. The daily observed minimum air temperature at 73 meteorological stations on the TP during 1980–2018 and the BCC_AGCM3_MR model are used. Our results show that the main mode of winter ECEs over the TP exhibits the same spatial variation and interannual variability across the whole region and is affected by two wave trains originating from the Arctic. The southern wave train is controlled by the sea ice in the Beaufort Sea. It initiates in the Norwegian Sea, and then passes through the North Atlantic Ocean, the Arabian Sea, and the Bay of Bengal along the subtropical westerly jet stream. It enters the TP from the south and brings warm, humid air from the oceans. By contrast, the northern wave train is controlled by the sea ice in the Laptev Sea. It originates from the Barents and Kara seas, passes through Lake Baikal, and enters the TP from the north, bringing dry and cold air. A decrease in the sea ice in the Beaufort Sea causes positive potential height anomalies in the Arctic. This change enhances the pressure gradient between the Artic and the mid-latitudes, leading to westerly winds in the northern TP, which block the intrusion of cold air into the south. By contrast, a decrease in the sea ice in the Laptev Sea causes negative potential height anomalies in the Artic. This change reduces the pressure gradient between the Artic and the mid-latitudes, leading to easterly winds to the north of the TP, which favors the southward intrusion of cold polar air. A continuous decrease in the amount of sea ice in the Beaufort Sea would reduce the frequency of ECEs over the TP and further aggravate TP warming in winter.

scholarly journals Seasonal Cumulative Effect of Ural Blocking Episodes on the Frequent Cold events in China during the Early Winter of 2020/21

2022 ◽  
Author(s):  
Yao Yao ◽  
Wenqi Zhang ◽  
Dehai Luo ◽  
Linhao Zhong ◽  
Lin Pei
Keyword(s):  
Sea Ice ◽  
Cumulative Effect ◽  
Cumulative Effects ◽  
The Arctic ◽  
Early Winter ◽  
Sea Ice Extent ◽  
Cold Event ◽  
Cold Events ◽  
Extreme Cold ◽  
The Impact

AbstractStarting in mid-November, China was hit by several cold events during the early winter of 2020/21. The lowest temperature observed at Beijing station on 7 January reached −19.6°C. In this paper, we show that the outbreak of the record-breaking extreme cold event can be attributed to a huge merging Ural blocking (UB) ridge over the Eurasian region. The sea-ice cover in the Kara and East Siberia Seas (KESS) in autumn was at its lowest value since 1979, which could have served as a precursor signal. Further analysis shows that several successive UB episodes occurred from 1 September 2020 to 10 January 2021. The persistent UB that occurred in late September/early October 2020 may have made an important contribution to the October historical minimum of sea ice in the KESS region. Our results also show that, after each UB episode in winter, significant upward propagation of wave activity occurred around 60°E, which resulted in weakening the stratospheric vortex. Meanwhile, each UB episode also caused a significant reduction in sea-ice extent in KESS and a significant weakening of the westerly jet in mid-high-latitude Eurasia. Results suggest that the Arctic vortex, which is supposed to enhance seasonally, became weaker and more unstable than the climatic mean under the seasonal cumulative effects of UB episodes, KESS warming, and long-lasting negative-phase North Atlantic Oscillation (NAO-). Those seasonal cumulative effects, combined with the impact of La Niña winter, led to the frequent occurrence of extreme cold events.

scholarly journals The Predictability of Ocean Environments that Contributed to the 2020/21 Extreme Cold Events in China: 2020/21 La Niña and 2020 Arctic Sea Ice Loss

2022 ◽  
Author(s):  
Fei Zheng ◽  
Ji-Ping Liu ◽  
Xiang-Hui Fang ◽  
Mi-Rong Song ◽  
Chao-Yuan Yang ◽  
...  
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Arctic Sea Ice ◽  
La Niña ◽  
The Arctic ◽  
La Nina ◽  
Arctic Sea ◽  
Cold Events ◽  
Extreme Cold ◽  
Arctic Sea Ice Loss

AbstractSeveral consecutive extreme cold events impacted China during the first half of winter 2020/21, breaking the low-temperature records in many cities. How to make accurate climate predictions of extreme cold events is still an urgent issue. The synergistic effect of the warm Arctic and cold tropical Pacific has been demonstrated to intensify the intrusions of cold air from polar regions into middle-high latitudes, further influencing the cold conditions in China. However, climate models failed to predict these two ocean environments at expected lead times. Most seasonal climate forecasts only predicted the 2020/21 La Niña after the signal had already become apparent and significantly underestimated the observed Arctic sea ice loss in autumn 2020 with a 1–2 month advancement. In this work, the corresponding physical factors that may help improve the accuracy of seasonal climate predictions are further explored. For the 2020/21 La Niña prediction, through sensitivity experiments involving different atmospheric-oceanic initial conditions, the predominant southeasterly wind anomalies over the equatorial Pacific in spring of 2020 are diagnosed to play an irreplaceable role in triggering this cold event. A reasonable inclusion of atmospheric surface winds into the initialization will help the model predict La Niña development from the early spring of 2020. For predicting the Arctic sea ice loss in autumn 2020, an anomalously cyclonic circulation from the central Arctic Ocean predicted by the model, which swept abnormally hot air over Siberia into the Arctic Ocean, is recognized as an important contributor to successfully predicting the minimum Arctic sea ice extent.

Process understanding of a linkage between East-Asian cold-surge wiith the unprecedented Arctic warming event in early 2016

2020 ◽  
Author(s):  
Kwang-hee Han ◽  
Ho-young Ku ◽  
Baek-min Kim
Keyword(s):  
Sea Ice ◽  
Mountain Region ◽  
The Arctic ◽  
Height Anomaly ◽  
Ural Mountain ◽  
Arctic Warming ◽  
Synoptic Analysis ◽  
Eurasian Continent ◽  
Process Understanding ◽  
Cold Events

<p>At the end of December 2015, Storm Frank, a major Atlantic windstorm, intruded into the Arctic-circle along with warm air and a large amount of moisture, resulting in an unprecedented Arctic high-temperature phenomenon. In late January 2016, the Eurasian continent suffered a series of strong cold events. This study performed a synoptic analysis of a daily Northern Hemisphere SLP and 500hPa, 300hPa height anomaly using JRA-reanalysis data focusing on the process understanding of the sequential development and strengthening of Siberian high in association with the generation of the Ural blocking after the Arctic warming event. From synoptic analysis , we found that, within one month period, there exist several spells of Ural blocking occurrence instead of steady occupation of persistent high pressure over Ural Mountain region. The heat intrusion from midlatitude in association with Storm Frank caused a large wave breaking event over Atlantic sector of Arctic and initiated Ural blocking. The unprecedented warm temperature in early 10 days of January 2016 caused a large sea-ice loss and further heat injection from Barents/Kara seas helping anchoring the blocking over Ural Mountain region. In January 2016, several cold events over Eurasian continent well matched with the several spell of Ural blocking events. We suggest that daily scale interactions among warm advection, downward longwave radiation, sea-ice loss, and blocking occurrence need to be carefully considered to understand true nature of Arctic-Midlatitude linkage issue.</p>

Potential Arctic connections to eastern North American cold winters

2017 ◽  
Vol 7 (2) ◽  
pp. 232-243 ◽  
Author(s):  
James E. Overland ◽  
Muyin Wang
Keyword(s):  
Sea Ice ◽  
North American ◽  
Geopotential Height ◽  
Large Scale ◽  
Chukchi Sea ◽  
Height Anomaly ◽  
Positive Temperature ◽  
Temperature Anomalies ◽  
Cold Events ◽  
Extreme Cold

Far-field temperature and geopotential height fields associated with eastern North American early winter (DEC-JAN) extreme cold events are documented since 1950. Based on 19 cases of monthly extreme cold events, two large-scale patterns emerge. First, a strong Alaskan Ridge (AR) can develop with higher 700 hPa geopotential heights and positive temperature anomalies from Alaska south along the coastal northeastern Pacific Ocean, and low eastern North American geopotential height anomalies, the well-known North American ridge/trough pattern. A second subset of cases is a Greenland-Baffin Blocking (GBB) pattern that have positive temperature anomalies centered west of Greenland with a cut off tropospheric polar vortex feature over eastern North America; cold temperature anomalies extend from southeastern United States northwestward into central Canada. Both of these historical large-scale patterns associated with eastern North American cold events (AR and GBB) have the potential for future reinforcement by sea ice loss and associated warm Arctic regional temperature anomalies. An example of a GBB case is 15-22 December 2010 and an extreme AR case is in early 4-14 December 2016. In both cases lack of sea ice and warm temperature anomalies were colocated with local maximums in the geopotential height anomaly fields. Future regional delay of fall freeze up in the Chukchi Sea and Baffin Bay regions could reinforce these geopotential height patterns once they occur, but is not likely to initiate AR and GBB type events.

scholarly journals Recent summer Arctic atmospheric circulation anomalies in a historical perspective

2014 ◽  
Vol 8 (5) ◽  
pp. 4823-4847 ◽  
Author(s):  
A. Belleflamme ◽  
X. Fettweis ◽  
M. Erpicum
Keyword(s):  
Sea Ice ◽  
Atmospheric Circulation ◽  
Greenland Ice Sheet ◽  
Arctic Region ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Arctic Sea ◽  
Circulation Anomalies ◽  
Arctic Sea Ice Loss ◽  
The Arctic Region

Abstract. A significant increase in the summertime occurrence of a high pressure area over the Beaufort Sea and Greenland has been observed from the beginning of the 2000's, and particularly between 2007 and 2012. These circulation anomalies are likely partly responsible for the enhanced Greenland ice sheet melt as well as the Arctic sea ice loss observed since 2007. Therefore, it is interesting to analyse whether similar conditions might have happened since the late 19th century over the Arctic region. We have used an atmospheric circulation type classification based on daily mean sea level pressure and 500 hPa geopotential height data from four reanalysis datasets (ERA-Interim, ERA-40, NCEP/NCAR, and 20CRv2) to put the recent circulation anomalies in perspective with the atmospheric circulation variability since 1871. We found that circulation conditions similar to 2007–2012 have occurred in the past, despite a higher uncertainty of the reconstructed circulation before 1940. But the recent anomalies largely exceed the interannual variability of the atmospheric circulation of the Arctic region. These circulation anomalies are linked with the North Atlantic Oscillation suggesting that they are not limited to the Arctic. Finally, they favour summertime Arctic sea ice loss.

A Comparison of South American and African Preferential Pathways for Extreme Cold Events

2013 ◽  
Vol 141 (6) ◽  
pp. 2066-2086 ◽  
Author(s):  
Nicholas D. Metz ◽  
Heather M. Archambault ◽  
Alan F. Srock ◽  
Thomas J. Galarneau ◽  
Lance F. Bosart
Keyword(s):  
Primary Objective ◽  
South American ◽  
Cold Air ◽  
Weather Forecasts ◽  
The Andes ◽  
Cold Events ◽  
Extreme Cold ◽  
African Highlands ◽  
Preferential Pathways ◽  
Lapse Rates

Abstract In the Southern Hemisphere, a relatively well-known preferential pathway along which cold air surges equatorward is situated to the east of the Andes Mountains. In this study, a second preferred pathway is identified to the east of the African Highlands, with additional minor pathways identified east of the Brazilian Highlands and Madagascar. The primary objective of this study is to compare climatological and synoptic characteristics of extreme cold events (ECEs) along the Andes and African Highlands pathways. ECEs are defined as the top 1% coldest 925-hPa temperatures within the Andes and the African Highlands pathways using the 1977–2001 subset of the 2.5° × 2.5° 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40). ECEs within the Andes and African Highlands pathways are associated with dynamically forced anticyclogenesis and have low-level characteristics that vary substantially. Along the Andes pathway, ECEs feature 925-hPa temperatures as much as 17°C below normal, with 925-hPa southerly winds ranging from 0 to 10 m s−1 and 925–700-hPa lapse rates as low as −3°C km−1. In contrast, ECEs along the African Highlands pathway feature 925-hPa temperatures up to 10°C below normal, with 925-hPa southerly winds ranging from 5 to 15 m s−1, and 925–700-hPa lapse rates generally between 2° and 5°C km−1. Composite analyses reveal that despite stronger southerly winds, ECEs along the African Highlands pathway are typically not as cold or stable as those along the Andes pathway because cold air from Antarctica must traverse a longer distance over water to reach Africa.

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