scholarly journals Frequency Associations between East Asian Jet Streams and the Temperature over the Barents–Kara Sea Region/Arctic Oscillation in Winter

Climate ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 107
Author(s):  
Yuefeng Li ◽  
Yuxiang Zhu ◽  
Wei Song
Keyword(s):  
East Asia ◽  
Arctic Oscillation ◽  
East Asian ◽  
Kara Sea ◽  
Wavelet Coherence ◽  
The Arctic ◽  
Jet Stream ◽  
Jet Streams ◽  
The Arctic Oscillation ◽  
Cross Wavelet

The frequency associations between jet streams over East Asia and the Arctic key temperature at 2 m (AKT2m) in the Barents–Kara Sea region (40°–75° E, 66°–82° N) and the Arctic Oscillation in winter are investigated using continuous wavelet transform, cross-wavelet transform, and wavelet coherence. The cross-wavelet transforms between the AKT2m/Arctic Oscillation and the East Asian polar front jet stream (EAPJ) suggest that the EAPJ is closely related to the AKT2m and Arctic Oscillation on an interannual (3–5-year band) timescale, but the variation in the phase angle denotes a complex frequency connection between the EAPJ and Arctic Oscillation. The squared wavelet coherence suggests that weakening of the EAPJ is associated with the rise in AKT2m during the period of abrupt climate change in East Asia. The EAPJ contains more forced components from the Arctic than the East Asian subtropical jet stream. By comparison, the relationship between AKT2m and the EAPJ is closer than that between the Arctic Oscillation and EAPJ, especially during the period of abrupt climate change in East Asia. This suggests that the EAPJ serves as a bridge for Arctic warming to affect the weather and climate over East Asia in winter. By contrast, the Arctic Oscillation does not play an important part, although it also contains information about the Arctic.

scholarly journals Relationship between the Arctic Oscillation and Cold Surges over East Asia

2011 ◽  
Vol 24 (1) ◽  
pp. 68-83 ◽  
Author(s):  
Tae-Won Park ◽  
Chang-Hoi Ho ◽  
Song Yang
Keyword(s):  
East Asia ◽  
Arctic Oscillation ◽  
Wave Train ◽  
The Arctic ◽  
Aleutian Low ◽  
Cold Surge ◽  
Dipole Structure ◽  
Cold Surges ◽  
The Arctic Oscillation ◽  
Blocking Type

Abstract The present study reveals the changes in the characteristics of cold surges over East Asia associated with the Arctic Oscillation (AO). Based on circulation features, cold surges are grouped into two general types: wave train and blocking types. The blocking type of cold surge tends to occur during negative AO periods, that is, the AO-related polarity of the blocking type. However, the wave train type is observed during both positive and negative AO periods, although the wave train features associated with negative AO are relatively weaker. The cold surges during negative AO are stronger than those during positive AO in terms of both amplitude and duration. The cold surges during positive AO in which the extent of effect is confined to inland China passes through East Asia quickly because of weaker Siberian high and Aleutian low, leading to short duration of these cold surges. In contrast, the cold surge during negative AO, characterized by a well-organized anticyclone–cyclone couplet with high pressure over continental East Asia and low pressure over Japan, brings continuous cold air into the entire East Asian region for more than one week with long-lasting cold advection. It is also found that the tracks of the cold surges during negative AO tend to occur more frequently over Korea and Japan and less frequently over China, compared with those during positive AO. The tracks are related to a west–east dipole structure of the ratio of rain conversion to snow according to AO phase, resulting in freezing precipitation or snowfall events over inland China (Korea and Japan) are likely to occur more frequently during the positive (negative) AO periods.

scholarly journals Modified Three-Dimensional Jet Indices and Their Application to East Asia

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 776 ◽  
Author(s):  
Haishan Li ◽  
Ke Fan ◽  
Zhiqing Xu ◽  
Hua Li
Keyword(s):  
East Asia ◽  
East Asian ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Jet Stream ◽  
Jet Streams ◽  
Zonal Winds ◽  
Subtropical Jet Stream ◽  
Subtropical Jet ◽  
The Relationship

A set of three-dimensional jet indices (jet speed index, jet pressure index, jet latitude index) has been proposed in previous literature to describe the variation of jet streams in both the horizontal and vertical direction. We refer to these indices at the ‘AC’ indices, after the names of the researchers involved. However, the physical meaning of the AC indices and the relationship between AC indices and climate systems are not fully understood. Further study is still needed for applying the indices in East Asia (70°–140° E). In this study, based on the understanding of the physical meaning of the AC indices, latitudinal ranges of East Asian jet streams are determined, and a set of modified AC indices is proposed. Based on the modified AC indices, the linear trends in East Asian jet streams are studied, and the relationship between East Asian jet streams and the climate is researched. The results show that the jet speed index corresponds to the meridional temperature gradient (MTG) of the middle to upper troposphere (500–200 hPa); the jet pressure index corresponds to the pressure level at which the MTG equals zero; and the jet latitude reflects the meridional MTG distribution. The latitudinal ranges of jet streams are determined based on the meridional profiles of climatological zonal-mean zonal winds. Within such a latitudinal range, the climatological zonal-mean zonal winds between 400 and 100 hPa are only westerly, and the maximum wind speed in the vertical direction at every latitude appears between 400 and 100 hPa. The jet streams can be further classified according to the features of the profiles. For East Asia (70°–140° E), jet streams can be classified into winter subtropical jet streams (15°–47.5° N), summer subtropical jet streams (27.5°–60° N), and summer polar front jet streams (60°–87.5° N). The classification of jet streams can be supported by their correspondence to the distribution of tropospheric baroclinicity. A set of modified AC indices can be acquired by using the new ranges of East Asian jet streams in the definition of the original AC indices. Descriptions of jet streams using the modified AC indices are more in accordance with the distributional features of the climatological zonal winds over East Asia, and the physical meanings of the modified AC indices are more definite than the original indices. Using the modified AC indices, we find a significant weakening trend in the strength of the summer subtropical jet stream (−0.13 m/s/10 yr) and a significant northward shift of the winter subtropical jet stream (0.22°/10 yr), and the possible reasons for these trends are studied. Finally, the relationships of East Asian jet streams in winter and summer with atmospheric circulation, temperature, and precipitation are also investigated in this study.

Interdecadal change between the Arctic Oscillation and East Asian climate during 1900-2015 winters

2017 ◽  
Vol 37 (14) ◽  
pp. 4791-4802 ◽  
Author(s):  
Yang Liu ◽  
Shengping He ◽  
Fei Li ◽  
Huijun Wang ◽  
Yali Zhu
Keyword(s):  
Arctic Oscillation ◽  
East Asian ◽  
The Arctic ◽  
Interdecadal Change ◽  
East Asian Climate ◽  
The Arctic Oscillation

scholarly journals Combined Effects of the MJO and the Arctic Oscillation on the Intraseasonal Eastern China Winter Temperature Variations

2019 ◽  
Vol 32 (8) ◽  
pp. 2295-2311 ◽  
Author(s):  
Lei Song ◽  
Renguang Wu
Keyword(s):  
East Asia ◽  
High Latitude ◽  
Western Europe ◽  
Arctic Oscillation ◽  
Wave Train ◽  
Eastern China ◽  
The Arctic ◽  
Wave Source ◽  
Temperature Anomalies ◽  
The Arctic Oscillation

AbstractThe present study reveals that the Madden–Julian oscillation (MJO)-related temperature anomalies over East Asia have notable differences among positive, neutral, and negative Arctic Oscillation (AO) phases. In MJO phases 2–3, cold anomalies over eastern China occur mainly during positive AO. In MJO phase 7, warm anomalies over eastern China are observed mostly during neutral AO, and in MJO phase 8 warm anomalies appear in positive and neutral AO. Regional mean temperature anomalies over northeastern East Asia tend to be negative during negative AO but positive during positive AO in six of eight MJO phases. In MJO phases 2–3, the AO-related mid- to high-latitude wave train over Eurasia and the MJO convection-triggered poleward wave train work together in contributing to negative height anomalies over eastern China and leading to cold anomalies there. The mid- to high-latitude wave train is stronger when the AO is negative than positive, which is associated with stronger zonal winds. In MJO phases 7–8, the positive AO-related mid- to high-latitude wave train over Eurasia and the MJO-induced poleward wave train cooperate in inducing positive height anomalies and leading to warm anomalies over eastern China. The mid- to high-latitude wave train is the main contributor to negative height anomalies over eastern China when the AO is negative during MJO phases 7–8. Meanwhile, the intensity of the South Asian wave source associated with the MJO convection is subjected to the modulation of southeastward dispersion of wave energy from western Europe during negative AO.

scholarly journals Multidecadal Changes in the Influence of the Arctic Oscillation on the East Asian Surface Air Temperature in Boreal Winter

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 757 ◽  
Author(s):  
Hainan Gong ◽  
Lin Wang ◽  
Wen Chen
Keyword(s):  
East Asia ◽  
Air Temperature ◽  
North Pacific ◽  
Arctic Oscillation ◽  
Regional Climate ◽  
East Asian ◽  
Surface Air Temperature ◽  
The Arctic ◽  
Boreal Winter ◽  
The Impact

The time-varying influences of the wintertime Arctic Oscillation (AO) on the concurrent East Asian surface air temperature (EAT) are investigated based on JRA-55 reanalysis data. Results reveal that there are multidecadal variations in the influences of wintertime AO on the EAT during 1958–2018. Before the mid-1980s, the impact of winter AO on the simultaneous EAT is weak and confined northward of 40° N over East Asia. After the mid-1980s, by contrast, the winter AO’s influence is stronger and can extend southward of 25° N over East Asia. The multidecadal variations of the winter AO–EAT relationship are mainly modulated by the magnitudes of the North Pacific center of the winter AO. During the periods with strong North Pacific center of the winter AO, in association with the positive phase of the winter AO, the low-level southeasterly anomalies on the west side of the anticyclone over North Pacific bring warm air from the ocean to East Asia and lead to a significant winter AO–EAT relationship. In contrast, the southerly anomalies are weak and even reversed to northerly over the coast of East Asia during the periods with weak North Pacific center of winter AO, which confines the influence of winter AO on northern East Asia and lead to an insignificant winter AO–EAT relationship. Our finding provides new insight into the understanding of the decadal changes of AO’s impacts on the regional climate.

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