The characteristics of extreme cold events and cold air outbreaks in the eastern United States

2018 ◽  
Vol 38 ◽  
pp. e807-e820 ◽  
Author(s):  
Erik T. Smith ◽  
Scott C. Sheridan
Keyword(s):  
United States ◽  
Eastern United States ◽  
Cold Air ◽  
Cold Events ◽  
Extreme Cold ◽  
Cold Air Outbreaks

A Climatological Analysis of the Linkages between Tropopause Polar Vortices, Cold Pools, and Cold Air Outbreaks over the Central and Eastern United States

2021 ◽  
Vol 149 (1) ◽  
pp. 189-206
Author(s):  
Kevin A. Biernat ◽  
Lance F. Bosart ◽  
Daniel Keyser
Keyword(s):  
United States ◽  
The United States ◽  
Eastern United States ◽  
Cold Air ◽  
Cold Pools ◽  
Middle Latitudes ◽  
Coherent Vortices ◽  
Northern Regions ◽  
Northern United States ◽  
Cold Air Outbreaks

AbstractCoherent vortices in the vicinity of the tropopause, referred to as tropopause polar vortices (TPVs), may be associated with tropospheric-deep cold pools. TPVs and associated cold pools transported from high latitudes to middle latitudes may play important roles in the development of cold air outbreaks (CAOs). The purpose of this study is to examine climatological linkages between TPVs, cold pools, and CAOs occurring in the central and eastern United States. To conduct this study, 1979–2015 climatologies of TPVs and cold pools are constructed using the ERA-Interim dataset and an objective tracking algorithm, and are compared to a 1979–2015 climatology of CAOs occurring in six NCEI-defined climate regions over the central and eastern United States. The climatologies of TPVs and cold pools indicate that central and eastern North America is a preferred corridor for their equatorward transport, and that the occurrence frequency of TPVs and cold pools is higher over northern regions of the United States compared to southern regions of the United States. Correspondingly, there is a higher percentage of CAOs linked to cold pools associated with TPVs over northern regions of the United States (32.1%–35.7%) compared to southern regions of the United States (4.4%–12.5%). TPVs and cold pools contributing to CAOs form most frequently over northern Canada and the Canadian Archipelago, and generally move southeastward toward southern Canada and the northern United States. TPVs and cold pools contributing to CAOs tend to be statistically significantly colder and longer lived when compared to all TPVs and cold pools transported to middle latitudes.

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.

The behavior of extreme cold air outbreaks under greenhouse warming

2006 ◽  
Vol 26 (9) ◽  
pp. 1133-1147 ◽  
Author(s):  
S. Vavrus ◽  
J. E. Walsh ◽  
W. L. Chapman ◽  
D. Portis
Keyword(s):  
Greenhouse Warming ◽  
Cold Air ◽  
Extreme Cold ◽  
Cold Air Outbreaks

MJO Modulation on 2009/10 Winter Snowstorms in the United States*

2012 ◽  
Vol 25 (3) ◽  
pp. 978-991 ◽  
Author(s):  
Ja-Yeon Moon ◽  
Bin Wang ◽  
Kyung-Ja Ha
Keyword(s):  
United States ◽  
High Latitude ◽  
Intraseasonal Variability ◽  
The United States ◽  
Teleconnection Pattern ◽  
Eastern United States ◽  
Moist Air ◽  
Central Pacific ◽  
Cold Air ◽  
Atmospheric Teleconnection

Abstract During the winter of 2009/10, a number of record-breaking snowfall events registered in the eastern United States are shown to have been modulated by the pulsation of tropical MJO through an atmospheric teleconnection pattern. The intraseasonal variability over the eastern subtropical Pacific near Mexico (the equatorial central Pacific) had reached the maximum (second largest) strength since 1979/80. From late December to mid-February, the convection over these two regions experienced a remarkable wet–dry–wet cycle; correspondingly, the daily snowfall over the eastern United States also exhibited a wet–dry–wet cycle. As the MJO convection reached the central Pacific, a teleconnection pattern extended to North America, resulting in a westward-tilted deep anomalous trough anchored over the eastern United States, producing a low-level pressure dipole anomaly with an anticyclone (cyclone) centered at the U.S. West (East) Coast. The convection over the Indian Ocean varied in phase with the central Pacific convection, reinforcing the extratropical atmospheric teleconnection pattern. As a result, the enhanced high-latitude cold air penetrated southward, affecting the central and eastern United States. Meanwhile, warmer moist air was transported from the tropical central Pacific by the existing El Niño through Mexico to the southern United States along with the upper-level subtropical westerly jet, which extended from the subtropical Pacific to the Atlantic Ocean. As such, the eastern United States was located in a convergence zone between the enhanced cold air from the high latitude and the warm, moist air supplied from the subtropics, resulting in favorable conditions for extremely heavy snowfall.

scholarly journals Synoptic Analysis of Cold Air Outbreaks over the California Central Valley

2017 ◽  
Vol 30 (23) ◽  
pp. 9417-9433 ◽  
Author(s):  
Richard Grotjahn ◽  
Rui Zhang
Keyword(s):  
North American ◽  
West Coast ◽  
Large Scale ◽  
Central Valley ◽  
Gulf Of Alaska ◽  
Surface Flow ◽  
Cold Air ◽  
Extreme Cold ◽  
Continental Interior ◽  
Cold Air Outbreaks

How does extreme cold air reach the California Central Valley (CCV) and most of the U.S. west coast? This question is answered using composite patterns for the 10 coldest cold air outbreaks (CAOs) to reach the CCV during 1979–2013. While unusually cold air over California occurs in all events by design, how it arrives there is complicated and varies. The only other feature present in all events for several days prior to CAO onset is unusually strong surface high pressure in and south of the Gulf of Alaska. This high has low-level cold air on its west side and a deep layer of cold air moving southward on its east side. Cold air aloft flows parallel to the North American west coast and sinks as it approaches the CCV. Farther west, warm advection builds a ridge aloft. The large-scale meteorological pattern (LSMP) is equivalent barotropic. The LSMP’s ridge over Alaska, trough near California, and ridge over the southeastern United States appear in all cases by onset and resemble the Pacific–North American teleconnection pattern. Cross sections show cold air flowing from the continental interior consistent with a strong pressure gradient created by extreme cold in the continental interior. Where and when the interior cold and surface flow occurs varies between events. A geopotential height trough associated with that cold air aloft passes over the CCV before onset fostering sinking behind that is reinforced by the cold air advection below. Although sinking, as a locally defined anomaly, the cold intensifies as it migrates from the polar region to the climatologically warmer CCV.

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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