On the behaviour of the tropopause folding events over the Tibetan Plateau

Abstract. Due to its harsh natural conditions, there had not been any intensive radiosonde observations over the Tibetan Plateau (TP) until the year 2008, when a regional radiosonde observation network was implemented through a Sino–Japan joint cooperation project. This paper reports new findings on the structure of upper troposphere and lower stratosphere (UTLS) layer, and provides evidence for stratosphere and troposphere exchange (STE) over the TP. Due to sparseness of high resolution sonde data, many previous studies assumed that there was only one thermal tropopause over the TP. Actually the radiosonde temperature profiles at pre-onset time of the Asian monsoon over the TP often exhibit a multiple tropopause (MT). The MT occurs in winter time with much higher frequency than any previous estimations over the Plateau. The MT during this time period is associated with tropopause folding near the subtropical westerly jet. The MT consistently varied with the movement of the jet. The MT becomes a single tropopause with the development of the monsoon. According to their height distribution, the MT can be divided into tropical and polar characterized tropopauses. Detailed analyses of MT characteristics are reported in this paper. Although some scientists have analyzed global MT events (with data including GPS radio occultation, ERA40 data and Integrated Global Radiosonde Archive database), the frequency of their MT occurrences in winter season over the plateau is largely under-estimated. This significant difference must be caused by the coarse vertical resolution of these data. The stratospheric intruding episodes are generally associated with the presence of subtropical westerly jet stream over the Plateau. The subtropical jet causes dynamic tropopause foldings over the plateau, which have been observed by us as thermal MT events. Intrusions of high latitude stratospheric ozone rich air into the troposphere over the plateau give us a new explanation to why total column ozone in winter is higher than that in summer.

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On the behaviour of the tropopause folding events over the Tibetan Plateau

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-5113-2011 ◽

2011 ◽

Vol 11 (10) ◽

pp. 5113-5122 ◽

Cited By ~ 26

Author(s):

X. L. Chen ◽

Y. M. Ma ◽

H. Kelder ◽

Z. Su ◽

K. Yang

Keyword(s):

High Resolution ◽

Tibetan Plateau ◽

Complex Structure ◽

Winter Season ◽

Radiosonde Data ◽

The Tibetan Plateau ◽

High Resolution Data ◽

Westerly Jet ◽

Radiosonde Observation ◽

Tropopause Folding

Abstract. Due to its harsh natural conditions, there had not been any intensive radiosonde observations over the Tibetan Plateau (TP) before the year 2008, when a regional radiosonde observation network was implemented through a Sino-Japan joint cooperation project. This paper reports, on the basis of these observations, on an analysis of the structure of upper troposphere and lower stratosphere (UTLS) and provides observations of stratosphere and troposphere exchange (STE) over the TP. Due to sparseness of high resolution radiosonde data, many previous studies assumed that there was only one thermal tropopause over the TP. Actually, the radiosonde temperature profiles in winter time over the TP often exhibit a multiple tropopause (MT). The MT occurs in winter with a high frequency over the Plateau. MT events during this time are associated with tropopause folds near the subtropical westerly jet. The MT consistently varied with the movement of the jet. The MT becomes a single tropopause with the development of the monsoon. The detailed analyses of MT characteristics are reported in this paper. Earlier analyses of global MT events (with data based on GPS radio occultation, ERA-40 data and Integrated Global Radiosonde Archive database) resulted in a climatic frequency of MT occurrences in the winter season over the Plateau is not more than 40 %. Based on high resolution data of intensive radiosonde observations, our estimations of MT occurrence over the Plateau can be as high as 80 % during certain winters. This reminds us to pay more attention to the MT events above the Plateau. The influence of the coarse vertical resolution and other effects on the estimation of MT occurrence frequency are also discussed. The stratospheric intruding episodes are generally associated with the presence of subtropical jet stream over the Plateau. The complex structure of dynamic tropopause folding over the Plateau have been reflected by the thermal MT events observed by radiosondes. The intrusion of air masses from the stratosphere may contribute to a higher upper tropospheric ozone concentration in winter than in summer above the plateau.

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Role of Tibetan Plateau in Northern Drought induced by Changes in Subtropical Westerly Jet

Journal of Climate ◽

10.1175/jcli-d-20-0799.1 ◽

2021 ◽

pp. 1-40

Author(s):

Qingzhe Zhu ◽

Yuzhi Liu ◽

Tianbin Shao ◽

Run Luo ◽

Ziyuan Tan

Keyword(s):

Water Vapor ◽

Tibetan Plateau ◽

North China ◽

Lower Troposphere ◽

Vapor Transport ◽

Water Vapor Transport ◽

The Tibetan Plateau ◽

Westerly Jet ◽

The Impact ◽

Subtropical Westerly Jet

AbstractThe Tibetan Plateau (TP), the “Water Tower of Asia”, plays an important role in the water cycle. However, few studies have linked the TP’s water vapor supply with the climate over North China. In this study, we found that changes in the subtropical westerly jet (SWJ) dynamically induce drought in North China, and the TP plays an important role in this relationship. During July-August for the period of 1981-2019, the SWJ center between 75°E and 105°E obviously shifted northward at a rate of 0.04° per year. Correspondingly, the zonal winds in the southern subtropics were incredibly weakened, causing the outflow of water vapor from the TP to decrease dramatically. Combined with numerical simulations, we discovered that a reduction in water vapor transport from the TP can obviously decrease the precipitation over North China. Sensitivity experiments demonstrated that if the water vapor outflow from the eastern border of the TP decreases by 52.74%, the precipitation in North China will decrease by 12.69% due to a decrease in the local cloud fraction caused by a diminished water vapor content in the atmosphere. Therefore, although less water vapor transport occurs in the upper troposphere than in the lower troposphere, the impact of transport from the TP in the former on the downstream precipitation cannot be ignored.

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Attribution of the Tibetan Plateau to Northern Drought

10.5194/egusphere-egu2020-6239 ◽

2020 ◽

Author(s):

Jianping Huang ◽

Yuzhi Liu ◽

Yaohui Li ◽

Qingzhe Zhu ◽

Shanshan Wang

Keyword(s):

Water Vapor ◽

Tibetan Plateau ◽

Hadley Circulation ◽

Dynamic Mechanism ◽

The Tibetan Plateau ◽

Large Engine ◽

Westerly Jet ◽

Key Driver ◽

Upper Level ◽

Subtropical Westerly Jet

The Tibetan Plateau (TP), which is located in Asia and has an average elevation of over 4000 m, acts as a raised source of heat and an isolated region of humidity in the atmosphere. The TP serves as a &#8220;world water tower&#8221; because it stores large amounts of water as glaciers, lakes, and rivers. Furthermore, previous studies have found that the easterly outflow of water vapor and clouds away from the TP contributes significantly to precipitation over downstream regions. However, the dynamic mechanism behind these observations is still unclear. It is known that the key driver in the transportation of air and water resources from the TP is the wind field. Under global warming, the pole ward expansion of the Hadley circulation and the thermal effect of the terrain over the TP forces the mid-latitude subtropical westerly jet(SWJ) to shift. However, the true effects of the SWJ are unclear.Here, we propose a dynamic mechanism of the northern drought attributable to the TP in summer. The TP, similar to a very large engine, drives the nearby movement of water vapor, clouds, and aerosols. This &#8220;engine effect&#8221; controls precipitation near the TP and can trigger flooding or droughts in downstream regions. The northern drought is driven by the collocation of the subtropical westerly jet (SWJ) position and the TP engine effect. The meridional shift in the SWJ is the determining factor of the northern drought in summer. When the SWJ shifts northward, the upper-level westerly wind is weakened; thus, the water vapor, clouds or dusty clouds over the TP are transported to north less often, reducing precipitation and causing more frequent droughts. In contrast, when the SWJ shifts southward, the northern area of China experiences increased precipitation in summer.&#160;

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Subtropical Westerly Jet Influence on Occurrence of Western Disturbances and Tibetan Plateau Vortices

Geophysical Research Letters ◽

10.1029/2018gl077734 ◽

2018 ◽

Vol 45 (16) ◽

pp. 8629-8636 ◽

Cited By ~ 10

Author(s):

K. M. R. Hunt ◽

J. Curio ◽

A. G. Turner ◽

R. Schiemann

Keyword(s):

Tibetan Plateau ◽

Western Disturbances ◽

Westerly Jet ◽

Tibetan Plateau Vortices ◽

Subtropical Westerly Jet

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Seasonal Features and a Case Study of Tropopause Folds over the Tibetan Plateau

Advances in Meteorology ◽

10.1155/2019/4375123 ◽

2019 ◽

Vol 2019 ◽

pp. 1-12 ◽

Cited By ~ 3

Author(s):

Jiali Luo ◽

Wenjun Liang ◽

Pingping Xu ◽

Haiyang Xue ◽

Min Zhang ◽

...

Keyword(s):

Tibetan Plateau ◽

High Frequency ◽

Reanalysis Data ◽

The Tibetan Plateau ◽

Transport Pathway ◽

Westerly Jet ◽

Meridional Winds ◽

Surrounding Areas ◽

High Potential Vorticity

Tropopause fold is the primary mechanism for stratosphere-troposphere exchange (STE) at the midlatitudes. Investigation of the features of tropopause folds over the Tibetan Plateau (TP) is important since the TP is a hotspot in global STE. In this study, we investigated seasonal features of the tropopause fold events over the TP using the 40-year ERA-Interim reanalysis data. The development of a tropopause folding case is specifically examined. The results show that shallow tropopause folds occur mostly in spring, while medium and deep folds occur mostly in winter. The multiyear mean monthly frequency of shallow tropopause folds over the TP reaches its maximum value of about 7% in May and then decreases gradually to its minimum value of 1% in August and increases again since September. Deep folds rarely occur in summer and autumn. Both the seasonal cycle and seasonal distribution of total tropopause folds over the TP are dominated by shallow folds. The relative high-frequency areas of medium and deep folds are located over the southern edge of the TP. The westerly jet movement controls the displacement of the high-frequency folding region over the TP. The region of high-frequency tropopause folds is located in the southern portion of the plateau in spring and moves northward in summer. The jet migrates back to the south in autumn and is located along about 30°N in winter, and the region where folds occur most frequently also shifts southward correspondingly. A medium fold event that occurred on 29 December 2018 is used to demonstrate the evolution of a tropopause fold case over the TP in winter; that is, the folding structure moves from west to east, the tropopause pressure is greater than 320 hPa over the folding region, while it is about 200 hPa in the surrounding areas, and the stratospheric air with high potential vorticity (PV) is transported from the high latitudes to the plateau by meridional winds. A trajectory model result verifies the transport pathway of the air parcels during the intrusion event.

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Dominant Modes of Tropospheric Ozone Variation over East Asia from GOME Observations

Advances in Meteorology ◽

10.1155/2015/879578 ◽

2015 ◽

Vol 2015 ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

Yi Liu ◽

Yuli Zhang ◽

Yong Wang ◽

Chuanxi Liu ◽

Zhaonan Cai ◽

...

Keyword(s):

East Asia ◽

Tropospheric Ozone ◽

Asian Summer Monsoon ◽

Principal Component ◽

Total Variance ◽

Ozone Production ◽

The Tibetan Plateau ◽

Westerly Jet ◽

Sign Distribution ◽

Subtropical Westerly Jet

The variation in tropospheric ozone over East Asia was analyzed using tropospheric column ozone data measured by the Global Ozone Monitoring Experiment (GOME) satellite. An empirical orthogonal function (EOF) analysis was carried out to derive the dominant modes of the variation in the tropospheric ozone volume-mixing ratio (TOVMR). The EOF1 mode, which explained 61.5% of the total variance, showed a same-sign distribution over all of East Asia, with a belt of enhanced ozone concentrations around 40°N. The principal component of EOF1 (PC1) suggested that photochemical ozone production together with Brewer-Dobson circulation and subtropical westerly jet plays important roles in modulating the seasonal variation of the TOVMR; ozone-rich air produced by photochemical processes was transported from the stratosphere to the troposphere by BD circulation and this ozone-rich air was then blocked by the subtropical westerly jet and accumulated north of the jet. The EOF2 mode explained 29.2% of the total variance with an opposite-sign pattern on the north and south side of 35°N. When anticyclonic circulation transported ozone-poor air from the upwelling area over the Bay of Bengal towards the Tibetan Plateau during the onset of the Asian summer monsoon, tropospheric ozone in this region decreased dramatically.

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Late Miocene–Quaternary rapid stepwise uplift of the NE Tibetan Plateau and its effects on climatic and environmental changes

Quaternary Research ◽

10.1016/j.yqres.2014.01.002 ◽

2014 ◽

Vol 81 (3) ◽

pp. 400-423 ◽

Cited By ~ 154

Author(s):

Jijun Li ◽

Xiaomin Fang ◽

Chunhui Song ◽

Baotian Pan ◽

Yuzhen Ma ◽

...

Keyword(s):

Tibetan Plateau ◽

Environmental Changes ◽

Yellow River ◽

Source Area ◽

Yellow River Basin ◽

Tectonic Geomorphology ◽

The Tibetan Plateau ◽

Asian Winter Monsoon ◽

New Findings ◽

Ne Tibetan Plateau

AbstractThe way in which the NE Tibetan Plateau uplifted and its impact on climatic change are crucial to understanding the evolution of the Tibetan Plateau and the development of the present geomorphology and climate of Central and East Asia. This paper is not a comprehensive review of current thinking but instead synthesises our past decades of work together with a number of new findings. The dating of Late Cenozoic basin sediments and the tectonic geomorphology of the NE Tibetan Plateau demonstrates that the rapid persistent rise of this plateau began ~8 ± 1 Ma followed by stepwise accelerated rise at ~3.6 Ma, 2.6 Ma, 1.8–1.7 Ma, 1.2–0.6 Ma and 0.15 Ma. The Yellow River basin developed at ~1.7 Ma and evolved to its present pattern through stepwise backward-expansion toward its source area in response to the stepwise uplift of the plateau. High-resolution multi-climatic proxy records from the basins and terrace sediments indicate a persistent stepwise accelerated enhancement of the East Asian winter monsoon and drying of the Asian interior coupled with the episodic tectonic uplift since ~8 Ma and later also with the global cooling since ~3.2 Ma, suggesting a major role for tectonic forcing of the cooling.

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