Connections between the Eurasian teleconnection and concurrent variation of upper-level jets over East Asia

Abstract Seasonal variations of the synoptic-scale transient eddy activity (STEA) and the jet streams over East Asia are examined through analysis of the 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) data. Extracted from the 6-hourly upper-level wind fields, the distribution of the jet core numbers exhibits a distinct geographical border for the East Asian subtropical jet (EASJ) and the East Asian polar front jet (EAPJ) at the latitudes of the northern Tibetan Plateau (TP). In the cool seasons, two branches of the STEA and low-level baroclinicity exist over the East Asian landmass, accompanied by the two-jet state of the EASJ and EAPJ. In the warm seasons, a single jet pattern of the EASJ along the north flank of the TP is accompanied by the weakened STEA over the mid- to high latitudes of East Asia. Further analysis shows two distinct features of the seasonal variations of the STEA over East Asia, compared with that over the North Pacific. First, during the transitional period of April–June, the main STEA band over East Asia migrates northward dramatically, in conjunction with the EAPJ shifting in the same direction. Second, both the upper-level STEA and the lower-level baroclinicity poleward of the TP are prosperous in spring. The relationship between the STEA, baroclinicity, vertical wind shear, and static stability in the EAPJ region in different seasons is further investigated. It is found that in addition to the time-mean wind fields, the rapid increase in the sensible heat flux poleward side of the TP region in spring and the associated boundary layer processes are partially responsible for the spring prosperity of the local baroclinicity and the STEA.

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Seesawing of Winter Temperature Extremes between East Asia and North America

Journal of Climate ◽

10.1175/jcli-d-20-0789.1 ◽

2021 ◽

Vol 34 (11) ◽

pp. 4423-4434

Author(s):

Mi-Kyung Sung ◽

Seok-Woo Son ◽

Changhyun Yoo ◽

Jaeyoung Hwang ◽

Soon-Il An

Keyword(s):

North America ◽

East Asia ◽

North Pacific ◽

Winter Temperature ◽

Cold Weather ◽

Temperature Extremes ◽

The North ◽

Budget Analysis ◽

Upper Level ◽

The North Pacific

AbstractIn recent winters, there have been repeated observations of extreme warm and cold spells in the midlatitude countries. This has evoked questions regarding how winter temperature extremes are induced. In this study, we demonstrate that abnormally warm winter weather in East Asia can drive the onset of extremely cold weather in North America approximately one week forward. These seesawing extremes across the basin are mediated by the North Pacific Oscillation (NPO), one of the recurrent atmospheric patterns over the North Pacific. Budget analysis of the quasigeostrophic geopotential tendency equation shows that intense thermal advection over East Asia is able to trigger the growth of the NPO. Vorticity fluxes associated with the upper-level stationary trough then strengthen and maintain the NPO against thermal damping following the onset of the NPO. Differential diabatic heating accompanied by changes in circulation also positively contribute to the growth and maintenance of the NPO. These results imply that recurrent cold extremes, seemingly contrary to global warming, may be an inherent feature resulting from strengthening warm extremes.

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Classification of precursory weather patterns prior to high PM10 events over the Korean Peninsula

10.5194/egusphere-egu2020-12845 ◽

2020 ◽

Author(s):

Ho-young Ku ◽

Baek-min Kim ◽

Wonsik Choi

Keyword(s):

Surface Temperature ◽

East Asia ◽

Korean Peninsula ◽

High Concentration ◽

Pressure System ◽

Cold Surge ◽

Weather Patterns ◽

Weather Pattern ◽

Before And After ◽

Upper Level

<p>In this study, we investigated precursory regional weather patterns prior to the high PM10 events over Korean Peninsula. The criterion for high-concentration PM10 events was set at 150 ug/m3 per day, referring to the &#8220;bad&#8221; among air environmental standards. In order to examine the regional weather pattern prior to the high PM10 events, the pressure fields of upper-level and lower-level were simply synthesized expecting the existence of clear signature of stagnant weather pattern. However, the resulting patterns were statistically insignificant around East Asia. We further investigated a possibility of existence of multiple precursory patterns partly offsetting each other.&#160; Through the synoptic analysis of each case, we found that precursory weather patterns can be easily partitioned as two groups: 1) pre-existing persistent ridge and 2) Decaying east Asian cold-surge. In the case 1), persistent ridge embedded in an overall positive AO pattern sustains over East Asia both before and after the high PM10 event causing long-term accumulation of fine dusts over Korean Peninsula. In this case, warm surface temperature dominates before and after the high PM 10 event. In the case 2), upper-level trough over east Asia rapidly moves eastward along with cold-surge evolution and stagnant high pressure system sits in over Korean peninsula just after the timing of high PM event. Surface temperature suddenly changes from cold to warm dramatically.</p>

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Temperature Variation over East Asia during the Lifecycle of Weak Stratospheric Polar Vortex

Journal of Climate ◽

10.1175/jcli-d-14-00790.1 ◽

2015 ◽

Vol 28 (14) ◽

pp. 5857-5872 ◽

Cited By ~ 15

Author(s):

Sung-Ho Woo ◽

Baek-Min Kim ◽

Jong-Seong Kug

Keyword(s):

East Asia ◽

Temperature Variation ◽

Large Scale ◽

East Asian ◽

Polar Vortex ◽

Tropospheric Temperature ◽

Stratospheric Polar Vortex ◽

The North ◽

Stratospheric Circulation ◽

Upper Level

Abstract The authors investigate the circulation change during the life cycle of a weak stratospheric polar vortex (WSV) event and its impact on temperature variation over East Asia. The lower-tropospheric temperature over East Asia strongly fluctuates despite the slow decay of stratospheric circulation and the continuously negative Arctic Oscillation (AO) pattern during the WSV event. The temperature fluctuation is critically influenced by the variation of the East Asian upper-level coastal trough (EAT), which may be coupled to the stratospheric circulation during the WSV events. The EAT is deepened anomalously during the Peak phase (from lag −5 to lag 5 day) of the WSV, and East Asian temperature is lowest during this phase. During the next period (Decay-1 phase: from lag 6 to lag 16 day), in spite of the slowly decaying WSV condition, the cold temperature anomaly over East Asia is suddenly weakened; this change is caused by a westward-propagating signal of an anticyclonic anomaly from the North Pacific to East Asia. After about two weeks (Decay-2 phase: from lag 17 to lag 27 day), the cold conditions over East Asia are restrengthened by an intensification of EAT, which is related to the eastward propagation of a large-scale wave packet originating from a negative North Atlantic Oscillation (NAO)-type structure in the Decay-1 phase and its delayed influence on the East Asia region.

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A Case Study of the Cutoff Process and Latent Heating Effect in an Upper-Level Cold-Core Low during the Mei-Yu Season in East Asia

Monthly Weather Review ◽

10.1175/mwr-d-11-00306.1 ◽

2012 ◽

Vol 140 (6) ◽

pp. 1725-1747 ◽

Cited By ~ 2

Author(s):

Mark Yin-Mao Wang ◽

George Tai-Jen Chen ◽

Chung-Chieh Wang ◽

Ying-Hwa Kuo

Keyword(s):

East Asia ◽

Sensitivity Test ◽

Latent Heating ◽

Model Sensitivity ◽

Westerly Flow ◽

Cutoff Low ◽

Upper Level ◽

Background Shear ◽

Jet Streak ◽

Cold Core

Abstract Using observational data and model sensitivity test, the present study diagnosed the evolution of an upper-level trough over 2–7 May 1998 during the mei-yu season in East Asia, with a focus on the role of latent heating downstream from the trough on the cutoff process and the formation of the cold-core low (CCL). Compared with conceptual models based on dry dynamics, the formation process of this cutoff low (COL) was inconsistent with the model of migratory jet streak–trough interaction, but the evolution of the upper-level trough (including its narrowing and rotation of axis) and the scale of the resultant COL generally agreed with the theory of interaction between trough and mean westerly flow with anticyclonic background shear. East/southeast of the trough, active and persistent convection appeared and induced 1) divergent ageostrophic flow near the tropopause, 2) an increase in mid- to upper-level thickness due to effective heating, and 3) amplification of an upper-level ridge downstream. Through a model sensitivity test, the diabatic heating is suggested to play a key role in the formation of the current CCL as the trough moved and extended southeastward to approach the amplifying ridge. Because of the east/southeast ageostrophic flow, the trough encountered a critical layer and became distorted, and its southern segment eventually detached to form a COL. When latent heating is turned off, the model produced a trough evolution anticipated by the dry theory but without cutoff. Such a role played by the moist process downstream of the trough during cutoff in the mei-yu season has not been previously noted in the literature.

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Evaluations of Upper-Level Turbulence Diagnostics Performance Using the Graphical Turbulence Guidance (GTG) System and Pilot Reports (PIREPs) over East Asia

Journal of Applied Meteorology and Climatology ◽

10.1175/jamc-d-10-05017.1 ◽

2011 ◽

Vol 50 (9) ◽

pp. 1936-1951 ◽

Cited By ~ 28

Author(s):

Jung-Hoon Kim ◽

Hye-Yeong Chun ◽

Robert D. Sharman ◽

Teddie L. Keller

Keyword(s):

East Asia ◽

Lead Time ◽

Large Scale ◽

Weather Prediction ◽

Analysis Data ◽

Atmospheric Conditions ◽

Jet Streams ◽

Forecast Lead Time ◽

Upper Level ◽

Nwp Model

AbstractThe forecast skill of upper-level turbulence diagnostics is evaluated using available turbulence observations [viz., pilot reports (PIREPs)] over East Asia. The six years (2003–08) of PIREPs used in this study include null, light, and moderate-or-greater intensity categories. The turbulence diagnostics used are a subset of indices in the Graphical Turbulence Guidance (GTG) system. To investigate the optimal performance of the component GTG diagnostics and GTG combinations over East Asia, various statistical evaluations and sensitivity tests are performed. To examine the dependency of the GTG system on the operational numerical weather prediction (NWP) model, the GTG system is applied to both the Regional Data Assimilation and Prediction System (RDAPS) analysis data and Global Forecasting System (GFS) analysis and forecast data with 30-km and 0.3125° (T382) horizontal grid spacings. The dependency of the temporal variation in the PIREP and GFS data and the forecast lead time of the GFS-based GTG combination are also investigated. It is found that the forecasting performance of the GTG system varies with year and season according to the annual and seasonal variations in the large-scale atmospheric conditions over the East Asia region. The wintertime GTG skill is the highest, because most GTG component diagnostics are related to jet streams and upper-level fronts. The GTG skill improves as the number of PIREP samples and the vertical resolution of the underlying NWP analysis data increase, and the GTG performance decreases as the forecast lead time increases from 0 to 12 h.

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Analysis of the Interactions between the 200 hPa Jet and Air Pollutants in the Near-Surface Layer over East Asia in Summer

Atmosphere ◽

10.3390/atmos12070886 ◽

2021 ◽

Vol 12 (7) ◽

pp. 886

Author(s):

Wen Wei ◽

Bingliang Zhuang ◽

Huijuan Lin ◽

Yu Shu ◽

Tijian Wang ◽

...

Keyword(s):

Surface Layer ◽

East Asia ◽

Air Pollutants ◽

North China Plain ◽

East Asian ◽

Near Surface ◽

The North ◽

The North China Plain ◽

Upper Level ◽

Upper Level Jet

The rapid economic development in East Asia has led to serious air pollution problems in the near-surface layer. Studies have shown that there is an interaction between air pollution and the East Asian upper-level jet, which is an important weather system controlling the climate in East Asia. Therefore, it is of great significance to study the relationship between the surface layer air pollutants and the upper-level jet stream in East Asia. Based on the daily wind and vertical velocity data provided by the National Centers for Environmental Prediction/National Center for Atmospheric Research as well as the surface pollutant and meteorological variable data provided by the Science Data Bank, we use statistical analysis methods to study the relationship between the East Asian upper-level jet and the high-concentration area of near-surface air pollutants in summer. Meanwhile, the mechanisms of the interaction are preliminarily discussed. The results show that the North China Plain and the Tarim Basin are the high-value areas of the particulate matter (PM) in summer during 2013–2018, and the ozone (O3) concentration in the near-surface atmospheric layer in the North China Plain is also high. The average concentrations of the PM2.5, PM10 and O3 in the North China Plain are 45.09, 70.28 and 131.27 μg·m−3, respectively, and the days with the concentration exceeding the standard reach 401, 461 and 488, respectively. During this period, there is an increasing trend in the O3 concentration and a decreasing trend in the PM concentration. The average ratio of the PM2.5 to PM10 is approximately 0.65 with a decreasing trend. The air pollutant concentration in this region has a significant relationship with the location of the East Asian upper-level jet. The low wind speed at the surface level under the control of the upper-level jet is the main reason for the high pollutant concentration besides the pollutant emission. They relate to each other through the surface humidity and the meridional and zonal wind. Meanwhile, the concentrations of the PM2.5 and PM10 are high in the near-surface layer in the Tarim Basin, and the average concentrations are 45.19 and 49.08 μg·m−3, respectively. The days with the concentration exceeding the standard are 265 and 193, respectively. The interannual variation in the PM concentration shows an increasing trend first and then a decreasing trend. The average ratio of PM2.5 to PM10 in this region reaches approximately 0.9. The ratio reaches the highest in 2013 and 2014 and then decreases to and maintains at approximately 0.85. The concentration of air pollutants in the basin has a significant relationship with the intensity of the upper-level jet in East Asia. The weakening of the upper-level jet will lead to a decrease in the surface humidity in the northern part of the basin, an increase in the surface temperature in the western part of the basin and a decrease in the surface zonal wind in the eastern part of the basin, which will result in a higher PM concentration.

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The Linkage between Upper-Level Jet Streams over East Asia and East Asian Winter Monsoon Variability

Journal of Climate ◽

10.1175/jcli-d-15-0160.1 ◽

2015 ◽

Vol 28 (22) ◽

pp. 9013-9028 ◽

Cited By ~ 25

Author(s):

Xiao Luo ◽

Yaocun Zhang

Keyword(s):

East Asia ◽

Barents Sea ◽

East Asian Winter Monsoon ◽

East Asian ◽

Winter Monsoon ◽

The Arctic ◽

The Tibetan Plateau ◽

East Asian Trough ◽

Asian Winter Monsoon ◽

Upper Level

Abstract This study investigates the linkage between East Asian winter monsoon (EAWM) variability and upper-level jets, with particular focus on the East Asian polar front jet (PJ) and its concurrent variation with the subtropical jet located to the south of the Tibetan Plateau (TSJ). The winter upper-level zonal wind variations over the Asian landmass (70°–120°E) are dominated by two principal modes (i.e., meridional displacement of the PJ and out-of-phase variation in the intensity of the TSJ and PJ) and they are closely linked to the EAWM northern mode and southern mode, respectively. Southward shifting of the PJ concurs with northwestward displacement of the Siberian high (SH), an enhanced northern East Asian trough, leading to cold winter in northern East Asia. Meanwhile the simultaneous TSJ intensification and PJ weakening is linked to an amplified SH, a southward shift of the Aleutian low (AL), a strengthened southern East Asian trough, and a wavelike anomaly pattern extending from western Barents Sea downstream to East Asia at the 500-hPa level. Equatorward shift of the PJ is associated with La Niña conditions in the tropics and sea ice anomalies over the Arctic. An intensified TSJ and weakened PJ are preceded by autumn warming over the central and eastern Pacific Ocean and are linked to circulation anomalies induced by the extensions of stationary Rossby waves, as well as synoptic-scale transient eddy activity anomalies. Therefore, a combination of external forcing and internal atmospheric dynamics plays a role in driving the variations of two leading EOFs, and there is potential for seasonal forecasting of both modes.

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Enriched East Asian oxygen isotope of precipitation indicates reduced summer seasonality in regional climate and westerlies

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1922602117 ◽

2020 ◽

Vol 117 (26) ◽

pp. 14745-14750 ◽

Cited By ~ 5

Author(s):

John C. H. Chiang ◽

Michael J. Herman ◽

Kei Yoshimura ◽

Inez Y. Fung

Keyword(s):

East Asia ◽

Oxygen Isotope ◽

Large Scale ◽

Interannual Variation ◽

Regional Climate ◽

East Asian ◽

Precipitation Amount ◽

The Tibetan Plateau ◽

Proximate Cause ◽

Upper Level

Speleothem oxygen isotope records over East Asia reveal apparently large and rapid paleoclimate changes over the last several hundred thousand years. However, what the isotopic variation actually represent in terms of the regional climate and circulation is debated. We present an answer that emerges from an analysis of the interannual variation in amount-weighted annual δ18O of precipitation over East Asia as simulated by an isotope-enabled model constrained by large-scale atmospheric reanalysis fields.18O-enriched years have reduced summer seasonality both in terms of precipitation isotopes and in the large-scale circulation. Changes occur between June and October, where the δ18O of precipitation (δ18Op) transitions from the isotopically heavier winter to the lighter summer regime. For18O-enriched years, this transition is less pronounced. Variations in precipitation amount alone are insufficient to explain the amount-weighted annual δ18Opbetween18O-enriched and18O-depleted years. Reduced summer seasonality is also expressed in the low-level monsoonal southerlies and upper-level westerlies; for the latter, the northward migration across the Tibetan Plateau in the summer is less pronounced. Our result thus implicates the westerlies across the plateau as the proximate cause of East Asian paleomonsoon changes, manifested as a modulation of its summer peak.

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