Characteristics of the Tibetan Plateau vortices and the related large-scale circulations causing different precipitation intensity

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 &#8220;moving-off&#8221; 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.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.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.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.

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Large-scale backgrounds and crucial factors modulating the eastward moving speed of vortices moving off the Tibetan Plateau

Climate Dynamics ◽

10.1007/s00382-019-04724-1 ◽

2019 ◽

Vol 53 (3-4) ◽

pp. 1711-1722 ◽

Cited By ~ 2

Author(s):

Lun Li ◽

Renhe Zhang ◽

Min Wen

Keyword(s):

Tibetan Plateau ◽

Large Scale ◽

The Tibetan Plateau ◽

Moving Speed

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orographic Influence of the Tibetan Plateau on the Asiatic Winter Monsoon Circulation Part L Large-Scale Aspects1

Journal of the Meteorological Society of Japan Ser II ◽

10.2151/jmsj1965.59.1_40 ◽

1981 ◽

Vol 59 (1) ◽

pp. 40-65 ◽

Cited By ~ 25

Author(s):

Takio Murakami

Keyword(s):

Tibetan Plateau ◽

Large Scale ◽

Winter Monsoon ◽

Monsoon Circulation ◽

The Tibetan Plateau

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Dynamic and Thermodynamic Relations of Distinctive Stratus Clouds on the Lee Side of the Tibetan Plateau in the Cold Season

Journal of Climate ◽

10.1175/jcli-d-13-00009.1 ◽

2013 ◽

Vol 26 (21) ◽

pp. 8378-8391 ◽

Cited By ~ 19

Author(s):

Yi Zhang ◽

Rucong Yu ◽

Jian Li ◽

Weihua Yuan ◽

Minghua Zhang

Keyword(s):

Tibetan Plateau ◽

Large Scale ◽

Eastern China ◽

Cold Season ◽

Water Vapor Transport ◽

The Tibetan Plateau ◽

Primary Role ◽

Moist Air ◽

Low Level ◽

Stratus Clouds

Abstract Given the large discrepancies that exist in climate models for shortwave cloud forcing over eastern China (EC), the dynamic (vertical motion and horizontal circulation) and thermodynamic (stability) relations of stratus clouds and the associated cloud radiative forcing in the cold season are examined. Unlike the stratus clouds over the southeastern Pacific Ocean (as a representative of marine boundary stratus), where thermodynamic forcing plays a primary role, the stratus clouds over EC are affected by both dynamic and thermodynamic factors. The Tibetan Plateau (TP)-forced low-level large-scale lifting and high stability over EC favor the accumulation of abundant saturated moist air, which contributes to the formation of stratus clouds. The TP slows down the westerly overflow through a frictional effect, resulting in midlevel divergence, and forces the low-level surrounding flows, resulting in convergence. Both midlevel divergence and low-level convergence sustain a rising motion and vertical water vapor transport over EC. The surface cold air is advected from the Siberian high by the surrounding northerly flow, causing low-level cooling. The cooling effect is enhanced by the blocking of the YunGui Plateau. The southwesterly wind carrying warm, moist air from the east Bay of Bengal is uplifted by the HengDuan Mountains via topographical forcing; the midtropospheric westerly flow further advects the warm air downstream of the TP, moistening and warming the middle troposphere on the lee side of the TP. The low-level cooling and midlevel warming together increase the stability. The favorable dynamic and thermodynamic large-scale environment allows for the formation of stratus clouds over EC during the cold season.

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

Climate Dynamics ◽

10.1007/s00382-018-4420-z ◽

2018 ◽

Vol 52 (7-8) ◽

pp. 4849-4859 ◽

Cited By ~ 2

Author(s):

Lun Li ◽

Renhe Zhang ◽

Min Wen ◽

Jianping Duan

Keyword(s):

Tibetan Plateau ◽

The Tibetan Plateau ◽

Tibetan Plateau Vortices

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The Role of Shallow Convection over the Tibetan Plateau

Journal of Climate ◽

10.1175/jcli-d-16-0599.1 ◽

2017 ◽

Vol 30 (15) ◽

pp. 5791-5803 ◽

Cited By ~ 7

Author(s):

Yunying Li ◽

Minghua Zhang

Keyword(s):

Tibetan Plateau ◽

Large Scale ◽

Diabatic Heating ◽

Middle Atmosphere ◽

Atmospheric Environment ◽

Monsoon Circulation ◽

The Tibetan Plateau ◽

Shallow Convection ◽

Sensitivity Experiment ◽

Stratiform Clouds

Cumulus (Cu) from shallow convection is one of the dominant cloud types over the Tibetan Plateau (TP) in the summer according to CloudSat– CALIPSO observations. Its thermodynamic effects on the atmospheric environment and impacts on the large-scale atmospheric circulation are studied in this paper using the Community Atmospheric Model, version 5.3 (CAM5.3). It is found that the model can reasonably simulate the unique distribution of diabatic heating and Cu over the TP. Shallow convection provides the dominant diabatic heating and drying to the lower and middle atmosphere over the TP. A sensitivity experiment indicates that without Cu over the TP, large-scale condensation and stratiform clouds would increase dramatically, which induces enhanced low-level wind and moisture convergence toward the TP, resulting in significantly enhanced monsoon circulation with remote impact on the areas far beyond the TP. Cu therefore acts as a safety valve to modulate the atmospheric environment that prevents the formation of superclusters of stratiform clouds and precipitation over the TP.

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Spatio-Temporal Variations of Water Vapor Budget over the Tibetan Plateau in Summer and Its Relationship with the Indo-Pacific Warm Pool

Atmosphere ◽

10.3390/atmos11080828 ◽

2020 ◽

Vol 11 (8) ◽

pp. 828

Author(s):

Deli Meng ◽

Qing Dong ◽

Fanping Kong ◽

Zi Yin ◽

Yanyan Li ◽

...

Keyword(s):

Water Vapor ◽

Indian Ocean ◽

Tibetan Plateau ◽

River Basin ◽

Large Scale ◽

Warm Pool ◽

The Tibetan Plateau ◽

Southern Boundary ◽

Pacific Warm Pool ◽

Water Vapor Budget

The water vapor budget (WVB) over the Tibetan Plateau (TP) is closely related to the large-scale atmospheric moisture transportation of the surrounding mainland and oceans, especially for the Indo-Pacific warm pool (IPWP). However, the procession linkage between the WVBs over the TP and its inner basins and IPWP has not been sufficiently elucidated. In this study, the relationship between the summer WVB over the TP and the IPWP was quantitatively investigated using reanalysis datasets and satellite-observed sea surface temperature (SST). The results show that: (1) the mean total summer vapor budget (WVBt) over the TP in the period of 1979–2018 was 72.5 × 106 kg s−1. Additionally, for the 13 basins within the TP, the summer WVB has decreased from southeast to northwest; the Yarlung Zangbo River Basin had the highest WVB (33.7%), followed by the Upper Yangtze River Basin, Ganges River Basin and Qiangtang Plateau. (2) For the past several decades, the WVBt over the TP has experienced an increasing trend (3.81 × 106 kg s−1 decade−1), although the southern boundary budget (WVBs) contributed the most and is most closely related with the WVBt, while the eastern boundary budget (WVBe) experienced a decreasing trend (4.21 × 106 kg s−1 decade−1) which was almost equal to the interdecadal variations of the WVBt. (3) For the IPWP, we defined a new warm pool index of surface latent heat flux (WPI-slhf), and found that an increasing WPI-slhf would cause an anticyclone anomaly in the equatorial western Indian Ocean (near 70° E), resulting in the increased advent of water vapor to the TP. (4) On the interdecadal scale, the correlation coefficients of the variation of the summer WVBt over the TP with the WPI-slhf and Indian Ocean Dipole (IOD) signal were 0.86 and 0.85, respectively (significant at the 0.05% level). Therefore, the warming and the increasing slhf of the IPWP would significantly contribute to the increasing WVB of the TP in recent decades.

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Changes in cloud amount over the Tibetan Plateau and impacts of large-scale circulation

Atmospheric Research ◽

10.1016/j.atmosres.2020.105332 ◽

2021 ◽

Vol 249 ◽

pp. 105332

Author(s):

Qianrong Ma ◽

Qinglong You ◽

Yujun Ma ◽

Yu Cao ◽

Jie Zhang ◽

...

Keyword(s):

Tibetan Plateau ◽

Large Scale ◽

Cloud Amount ◽

The Tibetan Plateau ◽

Large Scale Circulation

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Effects of Liquid Phase Cloud Microphysical Processes in Mixed Phase Cumulus Clouds over the Tibetan Plateau

10.5194/acp-2019-1063 ◽

2019 ◽

Author(s):

Xiaoqi Xu ◽

Chunsong Lu ◽

Yangang Liu ◽

Wenhua Gao ◽

Yuan Wang ◽

...

Keyword(s):

Liquid Phase ◽

Tibetan Plateau ◽

Large Scale ◽

Precipitation Event ◽

The Tibetan Plateau ◽

Phase Precipitation ◽

Physical Reason ◽

Surface Precipitation ◽

Skill Scores ◽

Microphysical Processes

Abstract. Overprediction of precipitation over the Tibetan Plateau is often found in numerical simulations, which is thought to be related to coarse grid sizes or inaccurate large-scale forcing. In addition to confirming the important role of model grid sizes, this study shows that liquid-phase precipitation parameterization is another key culprit, and underlying physical mechanisms are revealed. A typical summer plateau precipitation event is simulated with the Weather Research and Forecasting (WRF) model by introducing different parameterizations of liquid-phase microphysical processes into the commonly used Morrison scheme, including autoconversion, accretion, and entrainment-mixing mechanisms. All simulations can reproduce the general spatial distribution and temporal variation of precipitation. The precipitation in the high-resolution domain is less overpredicted than in the low-resolution domain. The accretion process plays more important roles than other liquid-phase processes in simulating precipitation. Employing the accretion parameterization considering raindrop size makes the total surface precipitation closest to the observation which is supported by the Heidke skill scores. The physical reason is that this accretion parameterization can suppress fake accretion and liquid-phase precipitation when cloud droplets are too small to initiate precipitation.

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