The Synchronization between the Zonal Jet Stream and Temperature Anomalies Leads to an Extremely Freezing North America in January 2019

The atmospheric teleconnection pattern reflects large-scale variations in the atmospheric wave and jet stream, and has pronounced impacts on climate mean and extremes over various regions. This study compares those patterns that have significant circulation anomalies over the North Pacific–North American–North Atlantic sector, which directly influence surface temperature and temperature extremes over North America. We analyze the pattern associated anomalies of surface temperature and warm and cold extremes over North America, during the northern winter and summer seasons. In particular, we assess the robustness of the regional temperature and temperature extreme anomaly patterns by evaluating the field significance of these anomalies over North America, and quantify the percentages of North American temperature and temperature extreme variances explained by these patterns. The surface temperature anomalies in association with the Pacific–North American pattern (PNA), Tropical–Northern Hemisphere pattern (TNH), North Pacific pattern (NP), North Atlantic Oscillation (NAO), Arctic Oscillation (AO), Western Pacific pattern (WP), circumglobal teleconnection (CGT), and Asian–Bering–North American (ABNA) patterns are similar to those reported in previous studies based on various datasets, indicating the robustness of the results. During winter, the temperature anomaly patterns considered are field significant at the 5% level over North America, except the WP-related one. These pattern associated anomalies explained about 5–15% of the total interannual temperature variance over North America, with relatively high percentages for the ABNA and PNA patterns, and low for the WP pattern. The pattern associated warm and cold extreme anomalies resemble the corresponding surface mean temperature anomaly patterns, with differences mainly in magnitude of the anomalies. Most of the anomalous extreme patterns are field significant at the 5% level, except the WP-related patterns. These extreme anomalies explain about 5–20% of the total interannual variance over North America. During summer, the pattern-related circulation and surface temperature anomalies are weaker than those in winter. Nevertheless, all of the pattern associated temperature anomalies are of field significance at the 5% level over North America, except the PNA-related one, and explain about 5–10% of the interannual variance. In addition, the temperature extreme anomalies, in association with the circulation patterns, are comparable in summer and winter. Over North America, the NP-, WP-, ABNA-, and CGT-associated anomalies of warm extremes are field significant at the 5% level and explain about 5–15% of the interannual variance. Most of the pattern associated cold extreme anomalies are field significant at the 5% level, except the PNA and NAO related anomalies, and also explain about 5–15% of the interannual variance over North America.

Download Full-text

Distorted Pacific–North American teleconnection at the Last Glacial Maximum

Climate of the Past ◽

10.5194/cp-16-199-2020 ◽

2020 ◽

Vol 16 (1) ◽

pp. 199-209 ◽

Cited By ~ 4

Author(s):

Yongyun Hu ◽

Yan Xia ◽

Zhengyu Liu ◽

Yuchen Wang ◽

Zhengyao Lu ◽

...

Keyword(s):

North America ◽

Last Glacial Maximum ◽

North American ◽

Tropical Pacific ◽

Glacial Maximum ◽

Jet Stream ◽

Last Glacial ◽

The Last Glacial Maximum ◽

The Tropical Pacific ◽

The Last Glacial

Abstract. The Pacific–North American (PNA) teleconnection is one of the most important climate modes in the present climate condition, and it enables climate variations in the tropical Pacific to exert a significant influence on North America. Here, we show climate simulations in which the PNA teleconnection was largely distorted or broken at the Last Glacial Maximum (LGM). The distorted PNA is caused by a split in the westerly jet stream, which is ultimately forced by the large, thick Laurentide ice sheet that was present at the LGM. Changes in the jet stream greatly alter the extratropical waveguide, distorting wave propagation from the North Pacific to North America. The distorted PNA suggests that climate variability in the tropical Pacific, notably El Niño–Southern Oscillation (ENSO), would have little direct impact on North American climate at the LGM.

Download Full-text

On the Role of the Eastern Pacific Teleconnection in ENSO Impacts on Wintertime Weather over East Asia and North America

Journal of Climate ◽

10.1175/jcli-d-17-0789.1 ◽

2019 ◽

Vol 32 (4) ◽

pp. 1217-1234 ◽

Cited By ~ 2

Author(s):

Ying Dai ◽

Benkui Tan

Keyword(s):

North America ◽

Surface Temperature ◽

East Asia ◽

El Niño ◽

El Nino ◽

Eastern Pacific ◽

Frequency Of Occurrence ◽

Temperature Anomalies ◽

La Nina ◽

Weather Events

Previous studies have mainly focused on the influence of El Niño–Southern Oscillation (ENSO) on seasonal-mean conditions over East Asia and North America. This study, instead, proposes an ENSO pathway that influences the weather events over East Asia and North America, in which the eastern Pacific teleconnection pattern (EP) plays an important role. On the one hand, the EP pattern can induce significant surface temperature anomalies over East Asia during its development and mature stages, with the positive (negative) EPs causing colder (warmer) than normal weather events. Besides, the frequency of occurrence of EPs is significantly modulated by ENSO, with 50% of the positive EPs occurring in La Niña winters, and 47% of the negative EPs occurring in El Niño winters. As a result, in El Niño winters, more negative and fewer positive EPs tend to occur, and thus more warm and fewer cold weather events are expected in East Asia. For La Niña winters, the reverse is true. On the other hand, for the EP pattern without its canonical convection pattern (referred to as the nonconvective EP), extremely cold anomalies over the northern United States and western Canada are induced in its negative phase. Moreover, when there are positive sea surface temperature anomalies in the central equatorial Pacific, the frequency of occurrence of negative nonconvective EPs is 2.0 times greater than the climatological value, and thus an enhanced likelihood of extremely cold spells over North America may be expected.

Download Full-text

Effects of western Pacific intraseasonal convection on surface air temperature anomalies over North America

International Journal of Climatology ◽

10.1002/joc.6373 ◽

2019 ◽

Vol 40 (6) ◽

pp. 2913-2923 ◽

Cited By ~ 2

Author(s):

Ying Yang ◽

Zhiwei Zhu ◽

Tim Li ◽

Mengying Yao

Keyword(s):

North America ◽

Air Temperature ◽

Surface Air Temperature ◽

Western Pacific ◽

Temperature Anomalies ◽

Air Temperature Anomalies

Download Full-text

Radiative and Dynamical Forcing of the Surface and Atmospheric Temperature Anomalies Associated with the Northern Annular Mode

Journal of Climate ◽

10.1175/jcli-d-12-00431.1 ◽

2013 ◽

Vol 26 (14) ◽

pp. 5124-5138 ◽

Cited By ~ 16

Author(s):

Yi Deng ◽

Tae-Won Park ◽

Ming Cai

Keyword(s):

Water Vapor ◽

North America ◽

Surface Temperature ◽

Surface Albedo ◽

Temperature Response ◽

Atmospheric Temperature ◽

Atmospheric Dynamics ◽

Surface Dynamics ◽

Northern Annular Mode ◽

Temperature Anomalies

Abstract On the basis of the total energy balance within an atmosphere–surface column, an attribution analysis is conducted for the Northern Hemisphere (NH) atmospheric and surface temperature response to the northern annular mode (NAM) in boreal winter. The local temperature anomaly in the European Centre for Medium-Range Weather Forecasts (ECMWF) Interim Re-Analysis (ERA-Interim) is decomposed into partial temperature anomalies because of changes in atmospheric dynamics, water vapor, clouds, ozone, surface albedo, and surface dynamics with the coupled atmosphere–surface climate feedback–response analysis method (CFRAM). Large-scale ascent/descent as part of the NAM-related mean meridional circulation anomaly adiabatically drives the main portion of the observed zonally averaged atmospheric temperature response, particularly the tropospheric cooling/warming over northern extratropics. Contributions from diabatic processes are generally small but could be locally important, especially at lower latitudes where radiatively active substances such as clouds and water vapor are more abundant. For example, in the tropical upper troposphere and stratosphere, both cloud and ozone forcings are critical in leading to the observed NAM-related temperature anomalies. Radiative forcing due to changes in water vapor acts as the main driver of the surface warming of southern North America during a positive phase of NAM, with atmospheric dynamics providing additional warming. In the negative phase of NAM, surface albedo change drives the surface cooling of southern North America, with atmospheric dynamics providing additional cooling. Over the subpolar North Atlantic and northern Eurasia, atmospheric dynamical processes again become the largest contributor to the NAM-related surface temperature anomalies, although changes in water vapor and clouds also contribute positively to the observed surface temperature anomalies while change in surface dynamics contributes negatively to the observed temperature anomalies.

Download Full-text

Reduction in Northern Midlatitude 2-m Temperature Variability due to Arctic Sea Ice Loss

Journal of Climate ◽

10.1175/jcli-d-18-0692.1 ◽

2019 ◽

Vol 32 (16) ◽

pp. 5021-5035 ◽

Cited By ~ 3

Author(s):

Thomas W. Collow ◽

Wanqiu Wang ◽

Arun Kumar

Keyword(s):

North America ◽

Sea Ice ◽

Carbon Dioxide Concentration ◽

Arctic Sea Ice ◽

Temperature Variability ◽

Northern Eurasia ◽

Seasonal Temperature ◽

Temperature Anomalies ◽

Arctic Sea ◽

Arctic Sea Ice Loss

Abstract In this study, we investigate links between Arctic sea ice loss and the variability of 2-m temperatures over a 6-month period (November–April) over two domains centered over northern Eurasia and northern North America. Based on data from the Climate Forecast System Reanalysis (CFSR), there has been an increase (a decrease) in recent seasonal temperature variability over Eurasia (North America), which can be attributed to cooling (warming) during the winter months. Decreases in the intraseasonal variability of temperature anomalies, however, are noted in both regions for the November–April period. This study investigates the role of different forcings on the changes seen in the reanalysis product using Atmospheric Model Intercomparison Project simulations forced with repeating sea surface temperature, sea ice, and carbon dioxide concentration relative to climatologies from two different base periods, 1981–90 and 2005–14. The seasonal temperature and intraseasonal anomaly variabilities are examined, and we find that only the simulations with reduction in sea ice (2005–14 base-period sea ice concentration) produce significant decreases in intraseasonal temperature anomaly variability over these regions, agreeing with the CFSR analysis. Runs that reduce sea ice also result in a significant decrease in the frequency and magnitude of extreme warm and cold temperature anomalies. It is proposed that the weakened latitudinal temperature gradient, resulting from decreased sea ice, leads to reduced meridional temperature advection variability, which in turn contributes to the reduction in the variability of temperature anomalies.

Download Full-text

Unraveling the Teleconnection Mechanisms that Induce Wintertime Temperature Anomalies over the Northern Hemisphere Continents in Response to the MJO

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-16-0036.1 ◽

2016 ◽

Vol 73 (9) ◽

pp. 3557-3571 ◽

Cited By ~ 43

Author(s):

Kyong-Hwan Seo ◽

Hyun-Ju Lee ◽

Dargan M. W. Frierson

Keyword(s):

North America ◽

Eastern Europe ◽

Northern Hemisphere ◽

Air Temperature ◽

Surface Air Temperature ◽

Arctic Sea Ice ◽

The Arctic ◽

Temperature Variations ◽

Temperature Anomalies ◽

Air Temperature Variations

Abstract Significant extratropical surface air temperature variations arise as a result of teleconnections induced by the Madden–Julian oscillation (MJO). The authors elucidate the detailed physical processes responsible for the development of temperature anomalies over Northern Hemisphere continents in response to MJO-induced heating using an intraseasonal perturbation thermodynamic equation and a wave activity tracing technique. A quantitative assessment demonstrates that surface air temperature variations are due to dynamical processes associated with a meridionally propagating Rossby wave train. Over East Asia, a local Hadley circulation causes adiabatic subsidence following MJO phase 3 to be a main driver for the warming. Meanwhile, for North America and eastern Europe, horizontal temperature advection by northerlies or southerlies is the key process for warming or cooling. A ray-tracing analysis illustrates that Rossby waves with zonal wavenumbers 2 and 3 influence the surface warming over North America and a faster wavenumber 4 affects surface temperature over eastern Europe. Although recent studies demonstrate the impacts of the Arctic Oscillation, Arctic sea ice melting, and Eurasian snow cover variations on extremely cold wintertime episodes over the NH extratropics, the weather and climate there are still considerably modulated through teleconnections induced by the tropical heat forcing. In addition, the authors show that the MJO is a real source of predictability for strong warm/cold events over these continents, suggesting a higher possibility of making a skillful forecast of temperature extremes with over 1 month of lead time.

Download Full-text

Occurrence and mechanisms of extreme winter air temperatures in the Arctic and surrounding continents

10.5194/egusphere-egu2020-19188 ◽

2020 ◽

Author(s):

Timo Vihma ◽

Petteri Uotila ◽

Tuomas Naakka ◽

Tiina Nygård

Keyword(s):

High Pressure ◽

North America ◽

Sea Ice ◽

Central Europe ◽

Northern China ◽

The Arctic ◽

Extreme Weather Events ◽

Jet Stream ◽

Cold Air ◽

Weather Events

The recent rapid warming of the Arctic atmosphere and ocean and related sea ice decline have been associated with increasing occurrence of extreme weather events in the Arctic. Applying ERA-Interim reanalysis, we identify 100 days with largest positive and negative anomalies (compared to local climatology) in 2-m air temperature (T2m) in the Northern Hemisphere in winter during 2005-2019, and address various physical mechanisms contributing to these events. The mechanisms responsible for warm extremes in the Arctic are often associated with a meandering Polar front jet stream, favouring cases of large transports of heat and moisture from mid-latitudes to the Arctic. In addition, subsidence heating often contributes to warm extremes in the Arctic, allowing them to occur also under high-pressure conditions. The coldest T2m anomalies north of 30oN mostly occur in regions that are also climatologically cold, i.e., cannot be strongly affected by cold-air advection. This suggests a dominating role local surface energy budget and boundary-layer processes.Extreme weather events often interact with anomalies in sea ice concentration. Cases of strong winds transporting warm, moist air masses to the Arctic provide both dynamic and thermodynamic forcing for large sea ice anomalies, and during winter the openings in sea ice field contribute to air temperature extremes via large heat fluxes from the ocean to atmosphere.Coldest winter extremes in mid-latitudes are typically associated with meandering jet stream and high-pressure blockings, but show differences between Central Europe, North America and northern China. In Central Europe the coldest events are typically associated with cold-air advection from the East or Northeast, whereas during the coldest events in North American East Coast the cold air is transported from the North. In northern China, the coldest events often occur under high-pressure conditions with weak winds. Accordingly, the role of cold-air advection is much smaller than in the case of the coldest events in North America.

Download Full-text

A Robust Intensification of Wintertime Jet Stream Extremes in Future Climates

10.5194/egusphere-egu21-14521 ◽

2021 ◽

Author(s):

Ben Harvey

Keyword(s):

North America ◽

North Atlantic ◽

Western Europe ◽

Subsequent Development ◽

Jet Stream ◽

Wind Speeds ◽

The North ◽

Sequence Of Events ◽

The North Atlantic ◽

Jet Streak

The east coast of North America experienced a record-breaking jet stream event on 20 Feb 2019, with peak wind speeds exceeding 110 m/s observed by weather balloons over Nova Scotia. At the time this was the strongest wind speed ever recorded over North America. The extreme `jet streak' propagated out over the North Atlantic where it played a key role in the subsequent development of a large and rapidly deepening cyclone on 22 Feb 2019. The cyclone had little societal impact because it did not make landfall. It did however act to amplify a large scale Rossby wave, producing a strong poleward advection of warm air towards western Europe, and leading to record-breaking February warmth in several European countries on 27 Feb 2019. The whole sequence of events took just over a week to complete.This case provides an illustration of how climate extremes (here the record warmth in western Europe) are often the result of complex and chaotic nonlinear interactions of the atmosphere on weather timescales. The particular sequence of events is not uncommon, but both the strength of the initial jet streak over North America and the resulting temperatures in Europe were. Given the observed trend in surface temperatures, it seems likely that the temperatures were at least partly enhanced in a passive way by the warming climate. A more difficult question to answer is whether climate change is also impacting the frequency or amplitude of the preceding sequence of weather events. As a first step to answering this question, this study asks the question: do we expect extreme jet streak events to intensify in future?Based on an analysis of CMIP simulations over the North Atlantic, we find a robust intensification of wintertime jet extremes in future climates, with the strongest instantaneous wind speeds increasing in every model. This contrasts with the strength of the time mean jet streams, which do not exhibit a robust change across the ensemble. Possible reasons for the differing behaviour of the mean winds and the extreme winds are discussed and a hypothesis is suggested to explain the robust increase in the latter.

Download Full-text