scholarly journals Seasonal Variations of the Synoptic-Scale Transient Eddy Activity and Polar Front Jet over East Asia

2010 ◽  
Vol 23 (12) ◽  
pp. 3222-3233 ◽  
Author(s):  
Xuejuan Ren ◽  
Xiuqun Yang ◽  
Cuijiao Chu
Keyword(s):  
East Asia ◽  
Seasonal Variations ◽  
East Asian ◽  
Polar Front ◽  
Transient Eddy ◽  
Synoptic Scale ◽  
Wind Fields ◽  
The North ◽  
Upper Level ◽  
Polar Front Jet

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.

scholarly journals Contributions of Different Combinations of the IPO and AMO to the Concurrent Variations of Summer East Asian Jets

2020 ◽  
Vol 33 (18) ◽  
pp. 7967-7982
Author(s):  
Xiucheng Xiao ◽  
Danqing Huang ◽  
Ben Yang ◽  
Jian Zhu ◽  
Peiwen Yan ◽  
...  
Keyword(s):  
East Asia ◽  
East Asian ◽  
Active Regions ◽  
Atlantic Multidecadal Oscillation ◽  
Atmospheric Model ◽  
Polar Front ◽  
Reanalysis Data ◽  
Boreal Winter ◽  
Multilinear Regression ◽  
The North

ABSTRACTHuang et al. recently reported that opposite phases of the interdecadal Pacific oscillation (IPO) and the Atlantic multidecadal oscillation (AMO) can affect the shift of the East Asian polar front jet (EAPJ) and the East Asian subtropical jet (EASJ) in the boreal winter. To give a full image of the relationship among the IPO, AMO, and concurrent variation of jets throughout the whole year, this study investigates the changes in summer jets response to the combinations of the IPO and AMO, and mostly focuses on the quantitative analysis in the role of the IPO and AMO. Both of the diagnostic analysis and atmospheric model simulations confirm that combinations of the negative phase of the IPO (“−IPO”) and the positive phase of the AMO (“+AMO”) can significantly enhance the EAPJ and reduce the EASJ in the summer, via the meridional temperature gradient and the Eady growth rate, and vice versa in the “+IPO −AMO” combination. The reanalysis data show that this relationship is particularly evident between the periods of 1999–2014 and 1979–98. Based on the simulations, the multilinear regression has indicated that −IPO plays a more important role than +AMO, particularly for the reduced EASJ. We have further revealed two pathways of the stationary Rossby wave activity anomaly, eastward from the North Atlantic to East Asia along 60°N and westward from the North Pacific to East Asia along 40°N. The two activities are associated with anomalous anticyclone along the active regions between EAPJ and EASJ, and therefore affect the jet variations.

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

2015 ◽  
Vol 28 (14) ◽  
pp. 5857-5872 ◽  
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.

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

Atmosphere ◽  
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.

scholarly journals Rapid transport of East Asian pollution to the deep tropics

2015 ◽  
Vol 15 (6) ◽  
pp. 3565-3573 ◽  
Author(s):  
M. J. Ashfold ◽  
J. A. Pyle ◽  
A. D. Robinson ◽  
E. Meneguz ◽  
M. S. M. Nadzir ◽  
...  
Keyword(s):  
East Asia ◽  
East Asian ◽  
Atmospheric Dispersion ◽  
Atmospheric Composition ◽  
Meridional Transport ◽  
Air Masses ◽  
The North ◽  
Westerly Winds ◽  
Modelling Environment ◽  
Cold Surges

Abstract. Anthropogenic emissions from East Asia have increased over recent decades. These increases have led to changes in atmospheric composition as far afield as North America under the prevailing westerly winds. Here we show that, during Northern Hemisphere (NH) winter, pollution originating in East Asia also directly affects atmospheric composition in the deep tropics. We present observations of marked intra-seasonal variability in the anthropogenic tracer perchloroethene (C2Cl4) collected at two locations in Borneo (117.84° E, 4.98° N and 118.00° E, 4.22° N) during the NH winter of 2008/2009. We use trajectories calculated with the Numerical Atmospheric-dispersion Modelling Environment to show that the observed enhancements in C2Cl4 mixing ratio are caused by rapid meridional transport, in the form of "cold surges", from the relatively polluted East Asian land mass. In these events air masses can move from ~35° N to Borneo in 4 days. We then present data from the Monitoring Atmospheric Composition and Climate reanalysis which suggest that air masses high in C2Cl4 may also contain levels of the pollutants carbon monoxide and ozone that are approximately double the typical "background" levels in Borneo. In addition to strengthening the meridional transport from the north, cold surges can enhance convection in Southeast Asia, and further trajectory calculations indicate that the polluted air masses can subsequently be lifted to the tropical upper troposphere. This suggests a potentially important connection between midlatitude pollution sources and the very low stratosphere.

scholarly journals Genetic studies of human diversity in East Asia

2007 ◽  
Vol 362 (1482) ◽  
pp. 987-996 ◽  
Author(s):  
Feng Zhang ◽  
Bing Su ◽  
Ya-ping Zhang ◽  
Li Jin
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
East Asia ◽  
Pacific Islands ◽  
East Asian ◽  
Human Populations ◽  
Genetic Studies ◽  
The North ◽  
Asian Populations ◽  
Genetic Diversity And Structure

East Asia is one of the most important regions for studying evolution and genetic diversity of human populations. Recognizing the relevance of characterizing the genetic diversity and structure of East Asian populations for understanding their genetic history and designing and interpreting genetic studies of human diseases, in recent years researchers in China have made substantial efforts to collect samples and generate data especially for markers on Y chromosomes and mtDNA. The hallmark of these efforts is the discovery and confirmation of consistent distinction between northern and southern East Asian populations at genetic markers across the genome. With the confirmation of an African origin for East Asian populations and the observation of a dominating impact of the gene flow entering East Asia from the south in early human settlement, interpretation of the north–south division in this context poses the challenge to the field. Other areas of interest that have been studied include the gene flow between East Asia and its neighbouring regions (i.e. Central Asia, the Sub-continent, America and the Pacific Islands), the origin of Sino-Tibetan populations and expansion of the Chinese.

scholarly journals Impact of Stratospheric Sudden Warming on East Asian Winter Monsoons

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Quanliang Chen ◽  
Luyang Xu ◽  
Hongke Cai
Keyword(s):  
East Asia ◽  
North Pacific ◽  
East Asian ◽  
Planetary Waves ◽  
The Arctic ◽  
Reanalysis Dataset ◽  
Stratospheric Sudden Warming ◽  
The North ◽  
Tropospheric Circulation ◽  
The North Pacific

Fifty-two Stratospheric sudden warming (SSW) events that occurred from 1957 to 2002 were analyzed based on the 40-year European Centre for Medium-Range Weather Forecasts Reanalysis dataset. Those that could descent to the troposphere were composited to investigate their impacts on the East Asian winter monsoon (EAWM). It reveals that when the SSW occurs, the Arctic Oscillation (AO) and the North Pacific Oscillation (NPO) are both in the negative phase and that the tropospheric circulation is quite wave-like. The Siberian high and the Aleutian low are both strengthened, leading to an increased gradient between the Asian continent and the North Pacific. Hence, a strong EAWM is observed with widespread cooling over inland and coastal East Asia. After the peak of the SSW, in contrast, the tropospheric circulation is quite zonally symmetric with negative phases of AO and NPO. The mid-tropospheric East Asian trough deepens and shifts eastward. This configuration facilitates warming over the East Asian inland and cooling over the coastal East Asia centered over Japan. The activities of planetary waves during the lifecycle of the SSW were analyzed. The anomalous propagation and the attendant altered amplitude of the planetary waves can well explain the observed circulation and the EAWM.

scholarly journals Seesawing of Winter Temperature Extremes between East Asia and North America

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.

Summer Upper-Level Vortex over the North Pacific

2001 ◽  
Vol 82 (9) ◽  
pp. 1991-2006 ◽  
Author(s):  
Tsing-Chang Chen ◽  
Ming-Cheng Yen ◽  
Gin-Rong Liu ◽  
Shu-Yu Wang
Keyword(s):  
North Pacific ◽  
East Asian ◽  
Lower Troposphere ◽  
Reanalysis Data ◽  
Secondary Circulation ◽  
Speed Increase ◽  
The North ◽  
Vortex Size ◽  
Upper Level ◽  
The North Pacific

The midocean trough in the North Pacific may form a favorable environment for the genesis of some synoptic disturbances. In contrast, the North Pacific anticyclone may hinder the downward penetration of these disturbances into the lower troposphere and prevent the moisture supply to these disturbances from the lower troposphere. Because no thick clouds, rainfall, and destructive surface winds are associated with these disturbances to attract attention, they have not been analyzed or documented. Actually, the upper-level wind speed within these disturbances is sometimes as strong as tropical cyclones and has the possibility of causing air traffic hazards in the western subtropic Pacific. With infrared images of the Japanese Geostationary Meteorological Satellite and the NCEP–NCAR reanalysis data, 25 North Pacific disturbances were identified over six summers (1993–98). Two aspects of these disturbances were explored: spatial structure and basic dynamics. For their structure, the disturbances possess a well-organized vortex in the middle to upper troposphere with a descending dry/cold core encircled by the moist ascending air around the vortex periphery; the secondary circulation of the vortex is opposite to other types of synoptic disturbances. Since vorticity reaches maximum values along the midocean trough line, barotrophic instability is suggested as a likely genesis mechanism of the vortex. After the vortex is formed, the horizontal advection of total vorticity results in its westward propagation, while the secondary circulation hinders this movement. Along its westward moving course, close to East Asia, there is a reduction in vortex size and a tangential speed increase inversely proportional to the vortex size. Diminishing its horizontal convergence/descending motion by the upper-tropospheric East Asian high and the lower-tropospheric monsoon low, the vortex eventually dissipates along the East Asian coast.

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