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

2018 ◽  
Vol 45 (16) ◽  
pp. 8629-8636 ◽  
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

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

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.

Inter-decadal Change of Tibetan Plateau Vortices during the past four Decades and its Possible Mechanism

2021 ◽  
Author(s):  
Zhiqiang Lin ◽  
Weidong Guo ◽  
Xiuping Yao ◽  
Jun Du ◽  
Jun Ge
Keyword(s):  
Tibetan Plateau ◽  
Wave Train ◽  
Warm Season ◽  
The Tibetan Plateau ◽  
Tropospheric Temperature ◽  
Decadal Change ◽  
Near Surface ◽  
Westerly Jet ◽  
Surrounding Areas ◽  
Tibetan Plateau Vortices

<p>The Tibetan Plateau vortices (TPVs) are mesoscale weather systems active at the near-surface of the Tibetan Plateau (TP), which are one of the major precipitation-producing systems over the TP and its surrounding areas. TPVs mainly occur in the warm season from May to September. In this paper, we investigate the inter-decadal change of TPVs in the warm seasons of 1979–2017 by analyzing five widely used reanalysis datasets. A significant change of the TPVs’ frequency appears around the mid-1990s, associated with less TPVs during 1979–1996 and more TPVs during 1997–2017. The abrupt change is caused by a transition of the Atlantic Multi-decadal Oscillation (AMO) from a cold phase to a warm phase in the mid-1990s. The shift of AMO leads to a silk-road pattern wave train and a spatially asymmetric change of tropospheric temperature. It modifies the intensity of the subtropical westerly jet and the TP heating, leading to the inter-decadal change of TPV activities.</p>

Impactful Tibetan Plateau Vortices: structure, lifecycle and environmental conditions

2020 ◽  
Author(s):  
Julia Curio ◽  
Reinhard Schiemann ◽  
Kevin Hodges ◽  
Andrew Turner ◽  
Nicholas Klingaman
Keyword(s):  
Tibetan Plateau ◽  
Atmospheric Circulation ◽  
Large Scale ◽  
Southern China ◽  
The Tibetan Plateau ◽  
Atmospheric Conditions ◽  
Local Circulation ◽  
Horizontal Structure ◽  
Westerly Jet ◽  
Tibetan Plateau Vortices

<p>The Tibetan Plateau (TP) and surrounding high mountains constitute an important forcing of the atmospheric circulation due to their height and extent, and thereby impact weather and climate in East Asia. Mesoscale Tibetan Plateau Vortices (TPVs) form over the TP and are one of the major systems generating TP precipitation. The majority of TPVs remain on the TP throughout their lifetime, while a fraction moves east off the TP. These “moving-off” TPVs can trigger extreme precipitation and severe flooding over large parts of eastern and southern China, for example in Sichuan province and the Yangtze River valley. Due to their potentially severe impacts downstream of the TP, it is first important to understand the conditions under which TPVs can move east off the TP.</p><p>In this study, we examine the vertical and horizontal structure of TPVs moving off the TP in contrast to those that do not using reanalysis in order to understand which local and/or large-scale atmospheric conditions lead TPVs to move off the TP. We use composites of atmospheric fields at different stages of the TPV lifecycle (e.g. genesis, maximum intensity, and maximum precipitation) and at different locations over and downstream of the TP, to account for the heterogeneous topography. Preliminary results suggest that the large-scale background flow, characterised by the strength and position of the subtropical westerly jet, is one of the factors determining whether a TPV moves off the TP or not.</p><p>Another important question is how and where moving-off TPVs trigger precipitation. Do TPVs transport moisture from the TP to the downstream regions? Do they move off while already precipitating? Do they trigger precipitation dynamically east of the TP? Results from a case study suggest that the TPV triggers precipitation as it moves over the edge of the TP, which then stays locked to the orography while the system is moving further east. The TPV appears to change the local atmospheric circulation in the Sichuan basin while moving off, thereby directing a flow of moist air towards the eastern slope of the TP.</p><p>Understanding how the combination of the right large-scale atmospheric conditions and a TPV-induced change in the local circulation downstream of the TP can create an impactful TPV may enable improved forecasts of TPVs and their impacts in the densely populated regions downstream of the TP.</p>

Attribution of the Tibetan Plateau to Northern Drought

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

<p>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 “world water tower” 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.</p><p>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 “engine effect” 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.</p><p> </p>

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

2010 ◽  
Vol 10 (10) ◽  
pp. 22993-23016 ◽  
Author(s):  
X. L. Chen ◽  
Y. M. Ma ◽  
H. Kelder ◽  
Z. Su ◽  
K. Yang
Keyword(s):  
Tibetan Plateau ◽  
The Tibetan Plateau ◽  
Height Distribution ◽  
Total Column Ozone ◽  
Westerly Jet ◽  
New Findings ◽  
Radiosonde Observation ◽  
Significant Difference ◽  
Tropopause Folding ◽  
Subtropical Westerly Jet

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.

Development and eastward movement mechanisms of the Tibetan Plateau vortices moving off the Tibetan Plateau

2018 ◽  
Vol 52 (7-8) ◽  
pp. 4849-4859 ◽  
Author(s):  
Lun Li ◽  
Renhe Zhang ◽  
Min Wen ◽  
Jianping Duan
Keyword(s):  
Tibetan Plateau ◽  
The Tibetan Plateau ◽  
Tibetan Plateau Vortices

scholarly journals Observational evidences of the influences of tropospheric subtropical and midlatitude stratospheric westerly jets on the equatorial stratospheric intraseasonal oscillations

2016 ◽  
Author(s):  
G. Karthick Kumar Reddy ◽  
T. K. Ramkumar ◽  
S. Venkatramana Reddy
Keyword(s):  
Zonal Wind ◽  
Lower Atmosphere ◽  
Theoretical Modelling ◽  
Quasi Biennial Oscillation ◽  
Medium Range Weather Forecast ◽  
Westerly Jet ◽  
Longitudinal Sector ◽  
Vertical Propagation ◽  
Biennial Oscillation ◽  
Subtropical Westerly Jet

Abstract. Using six Global Positioning System (GPS) Radio Occultation (RO) satellites (SAC-C, METOP-A and COSMIC/FORMOSAT-3, CNOFS, GRACE and TerraSAR-X) determined height profiles (1–40 km) of atmospheric temperature over the Indian tropical station of Gadanki and the European Center for Medium Range Weather Forecast (ECMWF) Interim Reanalyses (ERA-Interim) zonal wind and temperature data for four years (2009–2012), the present work reports that the tropospheric Subtropical Westerly Jet (SWJ) and the Midlatitude Stratospheric Westerly Jet (MStWJ) play important roles in controlling differently the vertical propagation of tropical Intra Seasonal Oscillations (ISO) with different period bands from the troposphere up to the stratosphere during Northern winters. In the months of December–May (Northern winter to summer, NWTS) of all these years, there is significant 10–20 day and 20–40 day oscillations in the troposphere up to the height of 13 km and above this it reappears at all heights above 21 km. The 40–80 day oscillation also shows similar characteristics except that it almost disappeared during NWTS months of the year 2010–2011 in the stratosphere. The absence of these signals in the intervening heights of ~ 17–20 km is explained on the basis that these two bands actually propagate from the tropical to subtropical region near the tropopause and then reappears in the tropical stratosphere after refracted by the subtropical westerly jet. The poleward and equatorward propagation of these bands in the troposphere and stratosphere respectively are found using the ERA-interim data. Further the two longer period bands of ISO show strong quasi-biennial oscillation in the lower atmosphere with opposite phases (when one band shows maximum the other one shows minimum in a particular year) between these two bands. It is also observed that the phase of the tropical stratospheric Quasi Biennial Oscillation (QBO) has significant control on the strength of the Mid latitude stratospheric westerly jet (MStWJ) that in turn controls the refraction of the tropical tropospheric longer (40–80 days, Longer period ISO; LISO) but not the smaller periods of ISO (SISO) back to the tropical stratosphere. In accordance with earlier theoretical modelling studies, the westerly phase of the lower stratospheric QBO occurred during NWTS months of 2010–2011 over the Indian longitudinal sector causes severe disruption of the MStWJ at 30 km height. This disruption caused the prevention of refraction back again to the tropical stratosphere of significant tropospheric LISO that arrived from the tropics through the tropopause. Further, in these four years, it is observed no direct vertical propagation of tropical tropospheric ISO to the stratosphere. The interannual variations in the tropical stratospheric LISO are related strongly to the phase of the equatorial lower stratospheric QBO in zonal wind and the strength of the MStWJ.

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