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

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
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.

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>

The Influence of Mechanical and Thermal Forcing by the Tibetan Plateau on Asian Climate

2007 ◽  
Vol 8 (4) ◽  
pp. 770-789 ◽  
Author(s):  
Guoxiong Wu ◽  
Yimin Liu ◽  
Qiong Zhang ◽  
Anmin Duan ◽  
Tongmei Wang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
East Asia ◽  
South China ◽  
Local Heating ◽  
Lower Troposphere ◽  
Early Spring ◽  
The Tibetan Plateau ◽  
Continental Scale ◽  
The North ◽  
Meridional Winds

Abstract This paper attempts to provide some new understanding of the mechanical as well as thermal effects of the Tibetan Plateau (TP) on the circulation and climate in Asia through diagnosis and numerical experiments. The air column over the TP descends in winter and ascends in summer and regulates the surface Asian monsoon flow. Sensible heating on the sloping lateral surfaces appears from the authors’ experiments to be the major driving source. The retarding and deflecting effects of the TP in winter generate an asymmetric dipole zonal-deviation circulation, with a large anticyclone gyre to the north and a cyclonic gyre to the south. Such a dipole deviation circulation enhances the cold outbreaks from the north over East Asia, results in a dry climate in south Asia and a moist climate over the Indochina peninsula and south China, and forms the persistent rainfall in early spring (PRES) in south China. In summer the TP heating generates a cyclonic spiral zonal-deviation circulation in the lower troposphere, which converges toward and rises over the TP. It is shown that because the TP is located east of the Eurasian continent, in summertime the meridional winds and vertical motions forced by the Eurasian continental-scale heating and the TP local heating are in phase over the eastern and central parts of the continent. The monsoon in East Asia and the dry climate in middle Asia are therefore intensified.

scholarly journals Continuous Wetting on the Tibetan Plateau during 1970–2017

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2605 ◽  
Author(s):  
Huamin Zhang ◽  
Mingjun Ding ◽  
Lanhui Li ◽  
Linshan Liu
Keyword(s):  
Tibetan Plateau ◽  
Piecewise Linear ◽  
Growing Season ◽  
Significant Trend ◽  
The Tibetan Plateau ◽  
Intensity Analysis ◽  
Standardized Precipitation Evapotranspiration Index ◽  
Piecewise Linear Regression ◽  
Increasing Trend ◽  
Surrounding Areas

Based on daily observation records at 277 meteorological stations on the Tibetan Plateau (TP) and its surrounding areas during 1970–2017, drought evolution was investigated using the Standardized Precipitation Evapotranspiration Index (SPEI). First, the spatiotemporal changes in the growing season of SPEI (SPEIgs) were re-examined using the Mann–Kendall and Sen’s slope approach—the piecewise linear regression and intensity analysis approach. Then, the persistence of the SPEIgs trend was predicted by the Hurst exponent. The results showed that the SPEIgs on the TP exhibited a significant increasing trend at the rate of 0.10 decade−1 (p < 0.05) and that there is no significant trend shift in SPEIgs (p = 0.37), indicating that the TP tended to undergo continuous wetting during 1970–2017. In contrast, the areas surrounding the TP underwent a significant trend shift from an increase to a decrease in SPEIgs around 1984 (p < 0.05), resulting in a weak decreasing trend overall. Spatially, most of the stations on the TP were characterized by an increasing trend in SPEIgs, except those on the Eastern fringe of TP. The rate of drought/wet changes was relatively fast during the 1970s and 1980s, and gradually slowed afterward on the TP. Finally, the consistent increasing trend and decreasing trend of SPEIgs on the TP and the area East of the TP were predicted to continue in the future, respectively. Our results highlight that the TP experienced a significant continuous wetting trend in the growing season during 1970–2017, and this trend is likely to continue.

Spatiotemporal patterns of snow cover retrieved from NOAA-AVHRR LTDR: a case study in the Tibetan Plateau, China

2016 ◽  
Vol 10 (5) ◽  
pp. 504-521 ◽  
Author(s):  
Siyuan Wang ◽  
Hang Yin ◽  
Qichun Yang ◽  
Hui Yin ◽  
Xiaoyue Wang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Spatiotemporal Patterns ◽  
The Tibetan Plateau ◽  
Noaa Avhrr
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