scholarly journals Climatology and physical mechanisms of the tropospheric warm cores over the Tibetan Plateau and its vicinity

2021 ◽  
Author(s):  
Ke Shang ◽  
Xiaodong Liu ◽  
Buwen Dong
Keyword(s):  
Tibetan Plateau ◽  
Active Region ◽  
Large Scale ◽  
Asian Summer Monsoon ◽  
Warm Pool ◽  
Formation Mechanisms ◽  
The Tibetan Plateau ◽  
Temperature Deviation ◽  
Physical Mechanisms ◽  
Pacific Warm Pool

AbstractThe frequently observed tropospheric warm cores over the Tibetan Plateau (TP) are unique climate phenomena and are crucial to the Asian summer monsoon development. However, their climatological structure and formation mechanisms remain elusive and inconsistent among previous studies. In this work, two vertically separated warm cores, the upper-level warm cores (ULWCs) and lower-level warm cores (LLWCs), are identified based on the zonal temperature deviation. The LLWCs are basically confined below 450 hPa, and the ULWCs are mostly observed at 200–400 hPa. The active region of the LLWCs is generally within the TP domain and characterized by regional patches with high frequency occurrences. In contrast, the active region of the ULWCs is featured by a zonally elongated band along the southern TP. The physical mechanisms for the formations of these two distinct types of warm cores are revealed: the LLWCs are mainly generated and maintained by the surface diabatic heating, while the ULWCs are dominated by the large-scale circulation associated with the convection over the Indo-Pacific warm pool. During March–June, the ULWCs within the TP domain occur most frequently and the intensities attain their maxima. In March–April, the ULWCs are mainly determined by the TP adiabatic subsidence induced by the convection over the Indo-Pacific warm pool. In May–June, the warm advection induced by westerlies generates the downstream ULWCs and enhances the ULWCs formed in previous months. Hence it might be inappropriate in traditional view to attribute the tropospheric warm cores around the TP solely to the direct thermal effect of the elevated topography.

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

Atmosphere ◽  
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.

scholarly journals Large-scale atmospheric circulation control on stable water isotopes in precipitation over the northwestern and southeastern Tibetan Plateau

2016 ◽  
Author(s):  
Xiaoxin Yang ◽  
Sunil Acharya ◽  
Tandong Yao
Keyword(s):  
Tibetan Plateau ◽  
Atmospheric Circulation ◽  
Large Scale ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
The Tibetan Plateau ◽  
Stable Water Isotopes ◽  
South Asian Summer Monsoon ◽  
Westerly Jet ◽  
Large Scale Atmospheric Circulation

Abstract. The mid-latitude westerlies and South Asian Summer Monsoon (SASM) are two major atmospheric circulation systems influencing the Tibetan Plateau (TP). We report a seven-year (2007/2008–2013/2014) dataset of δ18O in precipitation (δ18Op) collected at three stations. Taxkorgan (TX) and Bulunkou (BLK) are located on the northwestern TP where westerly winds dominate while Lulang (LL) is situated on the southeastern TP where the SASM dominates. δ18O in precipitation (δ18Op) in northwestern TP varies with surface temperature (T) throughout the study period, and is depleted in 18O in precipitation during June to September when the monsoonal circulation enters the TP. Integration with model outputs suggests that large-scale atmospheric circulation plays a major role in isotopic seasonality in both regions. A teleconnection between precipitation on the northwestern TP and the El Niño-Southern Oscillation (ENSO) warm phase is suggested by changes in the relationship between δ18O and δD (e.g., reduced slope and weighted d-excess) in precipitation samples. These observations are indicative of a weakening of the mid-latitude westerly jet allowing local processes in the continental interior to become more dominant, thereby increasing the contribution of secondary evaporation from falling raindrops and kinetic fractionation. Under the conditions of a high Northern Annular Mode (NAM) the westerly jet is intensified over the southeastern TP which enhances local evaporation and continental recycling as revealed by a lower δD-δ18O slope and intercept, but higher d-excess average in contemporaneously collected precipitation samples. The significant correlation between T and δ18Op in the northwestern TP during various composite periods highlights a variation from 0.39 ‰ / ℃ (ENSO warm) to 0.77 ‰ / ℃ (high NAM), attributable to decreased (increased) water vapor availability over the northwestern TP during the ENSO warm (strong positive NAM) phase. ENSO cold and strong negative NAM phases show analogous effects on atmospheric circulation over both regions.

scholarly journals Possible mechanisms of summer cirrus clouds over the Tibetan Plateau

2020 ◽  
Vol 20 (20) ◽  
pp. 11799-11808
Author(s):  
Feng Zhang ◽  
Qiu-Run Yu ◽  
Jia-Li Mao ◽  
Chen Dan ◽  
Yanyu Wang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Large Scale ◽  
Satellite Observation ◽  
Horizontal Distribution ◽  
Cirrus Clouds ◽  
Formation Mechanisms ◽  
The Tibetan Plateau ◽  
Northern Regions ◽  
Southern Fringe ◽  
Maximum Occurrence

Abstract. The geographical distributions of summertime cirrus with different cloud top heights above the Tibetan Plateau are investigated by using the 2012–2016 Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data. The cirrus clouds with different cloud top heights exhibit an obvious difference in their horizontal distribution over the Tibetan Plateau (TP). The maximum occurrence for cirrus with a cloud top height less than 9 km starts over the western plateau and moves up to the northern regions when cirrus is between 9 and 12 km. Above 12 km, the maximum occurrence of cirrus retreats to the southern fringe of the plateau. Three kinds of formation mechanisms – large-scale orographic uplift, ice particle generation caused by temperature fluctuation, and remnants of overflow from deep-convective anvils – dominate the formation of cirrus at less than 9 km, between 9 and 12 km, and above 12 km, respectively.

Late Mesozoic−Cenozoic cooling history of the northeastern Tibetan Plateau and its foreland derived from low-temperature thermochronology

2021 ◽  
Author(s):  
Chen Wu ◽  
Andrew V. Zuza ◽  
Jie Li ◽  
Peter J. Haproff ◽  
An Yin ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Low Temperature ◽  
Large Scale ◽  
Qaidam Basin ◽  
Tectonic Deformation ◽  
Formation Mechanisms ◽  
The Tibetan Plateau ◽  
Thrust Belt ◽  
The South ◽  
Late Mesozoic

The growth history and formation mechanisms of the Cenozoic Tibetan Plateau are the subject of an intense debate with important implications for understanding the kinematics and dynamics of large-scale intracontinental deformation. Better constraints on the uplift and deformation history across the northern plateau are necessary to address how the Tibetan Plateau was constructed. To this end, we present updated field observations coupled with low-temperature thermochronology from the Qaidam basin in the south to the Qilian Shan foreland in the north. Our results show that the region experienced a late Mesozoic cooling event that is interpreted as a result of tectonic deformation prior to the India-Asia collision. Our results also reveal the onset of renewed cooling in the Eocene in the Qilian Shan region along the northern margin of the Tibetan Plateau, which we interpret to indicate the timing of initial thrusting and plateau formation along the plateau margin. The interpreted Eocene thrusting in the Qilian Shan predates Cenozoic thrust belts to the south (e.g., the Eastern Kunlun Range), which supports out-of-sequence rather than northward-migrating thrust belt development. The early Cenozoic deformation exploited the south-dipping early Paleozoic Qilian suture zone as indicated by our field mapping and the existing geophysical data. In the Miocene, strike-slip faulting was initiated along segments of the older Paleozoic suture zones in northern Tibet, which led to the development of the Kunlun and Haiyuan left-slip transpressional systems. Late Miocene deformation and uplift of the Hexi corridor and Longshou Shan directly north of the Qilian Shan thrust belt represent the most recent phase of outward plateau growth.

scholarly journals Increased Chances of Drought in Southeastern Periphery of the Tibetan Plateau Induced by Anthropogenic Warming

2017 ◽  
Vol 30 (16) ◽  
pp. 6543-6560 ◽  
Author(s):  
Shuangmei Ma ◽  
Tianjun Zhou ◽  
Oliver Angélil ◽  
Hideo Shiogama
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
Climate Models ◽  
Hadley Circulation ◽  
Warm Pool ◽  
Severe Drought ◽  
The Tibetan Plateau ◽  
Ensemble Simulations ◽  
Pacific Warm Pool ◽  
Drought Conditions

The southeastern periphery of the Tibetan Plateau (SEPTP) was hit by an extraordinarily severe drought in the autumn of 2009. Overall, the SEPTP has been gripped by a sustained drought for six consecutive years. To better understand the physical causes of these types of severe and frequent droughts and thus to improve their prediction and enhance the ability to adapt, many research efforts have been devoted to the disastrous droughts in the SEPTP. Nonetheless, whether the likelihood and strength of the severe droughts in the SEPTP, such as that in the autumn of 2009, have been affected by anthropogenic climate change remains unknown. This study first identifies the atmospheric circulation regime responsible for the SEPTP droughts and then explores how human-induced climate change has affected the severe droughts in the SEPTP. It is found that the drought conditions in the SEPTP have been driven by the Indian–Pacific warm pool (IPWP) sea surface temperature (SST) through strengthening of the local Hadley circulation and anomalously cyclonic motion over the South China Sea. Ensemble simulations of climate models demonstrate a robust increase in the dry and warm meteorological conditions seen during the 2009 SEPTP autumn drought due to anthropogenic global warming. Given that warming is expected to continue into the future, these results suggest that it is likely that drought conditions will become more common in the SEPTP.

scholarly journals Analysis of cirrus cloud over the Tibetan Plateau from CALIPSO data: an altitude perspective

2020 ◽  
Author(s):  
Feng Zhang ◽  
Qiu-Run Yu ◽  
Yanyu Wang ◽  
Qianshan He ◽  
Tiantao Cheng ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Gravity Wave ◽  
Large Scale ◽  
Satellite Observation ◽  
Formation Mechanisms ◽  
Cirrus Cloud ◽  
The Tibetan Plateau ◽  
Northern Regions ◽  
Southern Fringe ◽  
Maximum Occurrence

Abstract. Using the 5-year summer Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data, the geographical distributions of cirrus over the Tibetan Plateau have been studied according to the cloud top height. The cirrus number at the corresponding heights exhibit striking differences over the plateau. The maximum occurrence for cirrus top below 9 km starts over the western plateau and moves up to the northern regions when cirrus is between 9–12 km. Above 12 km, the maximum occurrence of cirrus retreats to the southern fringe of the plateau. These characteristics are linked to three kinds of formation mechanisms: large-scale orographic uplift, ice particles generation caused by gravity wave and remnants of overflow from deep convective anvils, respectively.

Persistent Weakening Trend in the Spring Sensible Heat Source over the Tibetan Plateau and Its Impact on the Asian Summer Monsoon

2011 ◽  
Vol 24 (21) ◽  
pp. 5671-5682 ◽  
Author(s):  
Anmin Duan ◽  
Fei Li ◽  
Meirong Wang ◽  
Guoxiong Wu
Keyword(s):  
Tibetan Plateau ◽  
Summer Monsoon ◽  
Large Scale ◽  
Asian Summer Monsoon ◽  
East Asian ◽  
The Tibetan Plateau ◽  
South Asian Summer Monsoon ◽  
Spatial Nonuniformity ◽  
Asian Summer ◽  
The Tropics

Abstract Using a dataset extended by the addition of data for 2004–08, this study reexamined the trend in the sensible heating (SH) flux at 73 meteorological stations over the Tibetan Plateau (TP) during 1980–2008 and investigated its impact on monsoon precipitation in the surrounding region. In contrast to ongoing climate warming, a weakening trend in SH is persistent over most of the plateau, despite a sharp increase in the ground–air temperature difference in 2004–08. The weakening trend in SH over the TP is primarily a response to the spatial nonuniformity of large-scale warming over the East Asian continent, which is characterized by much greater warming amplitude at mid- and high latitudes than over the tropics and subtropics. Furthermore, the suppressed air pump effect, which is driven by SH over the TP and acts as a strong forcing source, gives rise to reduced precipitation along the southern and eastern slopes of the plateau, and increased rainfall over northeastern India and the Bay of Bengal. No significantly stable correlation exists between the SH source over the TP and the overall trend or interdecadal variability in the East Asian or South Asian summer monsoon.

scholarly journals The Variability of Summer Atmospheric Water Cycle over the Tibetan Plateau and Its Response to the Indo-Pacific Warm Pool

2021 ◽  
Vol 13 (22) ◽  
pp. 4676
Author(s):  
Deli Meng ◽  
Wanjiao Song ◽  
Qing Dong ◽  
Zi Yin ◽  
Wenbo Zhao
Keyword(s):  
Water Vapor ◽  
Tibetan Plateau ◽  
Water Cycle ◽  
Warm Pool ◽  
Vapor Transport ◽  
Water Vapor Transport ◽  
The Tibetan Plateau ◽  
Atmospheric Water ◽  
Maritime Continent ◽  
Pacific Warm Pool

The Tibetan Plateau (TP), atmosphere, and Indo-Pacific warm pool (IPWP) together constitute a regional land–atmosphere–ocean water vapor transport system. This study uses remote sensing data, reanalysis data, and observational data to explore the spatiotemporal variations of the summer atmospheric water cycle over the TP and its possible response to the air-sea interaction in the IPWP during the period 1958–2019. The results reveal that the atmospheric water cycle process over the TP presented an interannual and interdecadal strengthening trend. The climatic precipitation recycle ratio (PRR) over the TP was 18%, and the stronger the evapotranspiration, the higher the PRR. On the interdecadal scale, the change in evapotranspiration has a significant negative correlation with the Pacific Decadal Oscillation (PDO) index. The variability of the water vapor transport (WVT) over the TP was controlled by the dynamic and thermal conditions inside the plateau and the external air-sea interaction processes of the IPWP. When the summer monsoon over the TP was strong, there was an anomalous cyclonic WVT, which increased the water vapor budget (WVB) over the TP. The central and eastern tropical Pacific, the maritime continent and the western Indian Ocean together constituted the triple Sea Surface Temperature (SST) anomaly, which enhanced the convective activity over the IPWP and induced a significant easterly wind anomaly in the middle and lower troposphere, and then generated pronounced easterly WVT anomalies from the tropical Pacific to the maritime continent and the Bay of Bengal. Affected by the air-sea changes in the IPWP, the combined effects of the upstream strengthening and the downstream weakening in the water vapor transport process, directly and indirectly, increased the water vapor transport and budget of TP.

scholarly journals Upstream Subtropical Signals Preceding the Asian Summer Monsoon Circulation

2004 ◽  
Vol 17 (21) ◽  
pp. 4213-4229 ◽  
Author(s):  
Song Yang ◽  
K-M. Lau ◽  
S-H. Yoo ◽  
J. L. Kinter ◽  
K. Miyakoda ◽  
...  
Keyword(s):  
Middle East ◽  
Tibetan Plateau ◽  
Summer Monsoon ◽  
Large Scale ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
Jet Stream ◽  
The Tibetan Plateau ◽  
Physical Processes ◽  
Asian Summer

Abstract In this study, the authors address several issues with respect to the antecedent signals of the large-scale Asian summer monsoon that were earlier identified by Webster and Yang. In particular, they revisit the changes in the subtropical upper-tropospheric westerlies preceding the monsoon, depict the detailed structure of the monsoon's antecedent signals, and investigate the physical processes from the signals to the monsoon. They also explore the teleconnection of these signals to various large-scale climate phenomena and emphasize the importance of the upstream location of the signals relative to the Tibetan Plateau and the monsoon. Before a strong (weak) Asian summer monsoon, the 200-mb westerlies over subtropical Asia are weak (strong) during the previous winter and spring. A significant feature of these signals is represented by the variability of the Middle East jet stream whose changes are linked to the Arctic Oscillation, North Atlantic Oscillation, El Niño–Southern Oscillation, and other climate phenomena. When this jet stream intensifies and shifts southeastward, cold air intrudes frequently from eastern Europe into the Middle East and southwestern Asia. As a result, in subtropical Asia, snow and precipitation increase, the ground wetness increases, and surface temperature decreases. A strengthening Middle East jet stream is also accompanied by increases in both stationary wave activity flux and higher-frequency eddy activities. The Tibetan Plateau acts to block these westerly activities propagating eastward and increase the persistence of the low-temperature anomalies, which in turn prolongs the atmospheric signals from winter to spring. A strong link is found between the persistent low-temperature anomalies and the decrease in geopotential height over southern Asia, including the Tibetan Plateau, in spring. The latter indicates a late establishment of the South Asian high, and implies a delay in the atmospheric transition from winter to summer conditions and in the development of the summer monsoon. The preceding scenario for a strong Middle East jet stream and a weaker Asian monsoon can be applied accordingly for the discussion of the physical processes from a weak jet stream to a strong monsoon. The current results of the relationship between the extratropical process and Asian monsoon resemble several features of the tropical–extratropical interaction mechanism for the tropospheric biennial oscillation (TBO). While the role of tropical heating is emphasized in the TBO mechanism, compared to the variability of the sea surface temperature related to El Niño–Southern Oscillation, the extratropical process examined in this study is more strongly linked to the Asian summer monsoon.

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