Dynamic effects of the South Asian high on the ozone valley over the Tibetan Plateau

2012 ◽  
Vol 26 (2) ◽  
pp. 216-228 ◽  
Author(s):  
Dong Guo ◽  
Panxing Wang ◽  
Xiuji Zhou ◽  
Yu Liu ◽  
Weiliang Li
Keyword(s):  
Tibetan Plateau ◽  
South Asian ◽  
South Asian High ◽  
The Tibetan Plateau ◽  
Dynamic Effects ◽  
The South

scholarly journals Insensitivity of the Summer South Asian High Intensity to a Warming Tibetan Plateau in Modern Reanalysis Datasets

2017 ◽  
Vol 30 (8) ◽  
pp. 3009-3024 ◽  
Author(s):  
Liguang Wu ◽  
Xiaofang Feng ◽  
Mei Liang
Keyword(s):  
Tibetan Plateau ◽  
South Asian ◽  
High Intensity ◽  
Thermal Condition ◽  
Sensible Heat Flux ◽  
South Asian High ◽  
The Tibetan Plateau ◽  
The South ◽  
Condition Change ◽  
Surface Sensible Heat Flux

The South Asia high (SAH) is a prominent circulation system of the Asian summer monsoon, exerting profound influences on the weather and climate in China and surrounding regions. Its formation and maintenance is closely associated with strong summertime continental heating in the form of surface sensible heat flux and the latent heat release in connection with the Asian monsoon. In this study, the possible response of the South Asian high intensity to the thermal condition change in the Tibetan Plateau is examined with four modern reanalysis datasets, including the Modern-Era Retrospective Analysis for Research and Applications (MERRA), MERRA version 2 (MERRA-2), the European Centre for Medium-Range Weather Forecasts (ECMWF) interim reanalysis (ERA-Interim), and the Japanese 55-year Reanalysis (JRA-55). Despite the surface air warming in the four modern reanalysis datasets, reduced surface wind speed in three of the reanalysis datasets, and decreased surface sensible heat flux in the MERRA-2 dataset, there is no statistically significant trend in the SAH intensity over the period 1979–2015. One of the possible reasons is that the response of the upper-level circulation to the thermal condition change of the Tibetan Plateau occurs mainly in the 200-hPa subtropical westerly jet stream, which is located far away from the center of the South Asian high. Thus the South Asian high intensity is not particularly sensitive to the thermal condition change of the Tibetan Plateau, while the center of the South Asian high intensity over the plateau exhibits a northward trend over the period.

scholarly journals The Effect of ENSO on Tibetan Plateau Snow Depth: A Stationary Wave Teleconnection Mechanism and Implications for the South Asian Monsoons

2005 ◽  
Vol 18 (12) ◽  
pp. 2067-2079 ◽  
Author(s):  
Jeffrey Shaman ◽  
Eli Tziperman
Keyword(s):  
Tibetan Plateau ◽  
South Asian ◽  
Snow Depth ◽  
Rossby Waves ◽  
Stationary Wave ◽  
The Tibetan Plateau ◽  
The South ◽  
Central Pacific ◽  
The North ◽  
Asian Monsoons

Abstract An atmospheric stationary wave teleconnection mechanism is proposed to explain how ENSO may affect the Tibetan Plateau snow depth and thereby the south Asian monsoons. Using statistical analysis, the short available record of satellite estimates of snow depth, and ray tracing, it is shown that wintertime ENSO conditions in the central Pacific may produce stationary barotropic Rossby waves in the troposphere with a northeastward group velocity. These waves reflect off the North American jet, turning equatorward, and enter the North African–Asian jet over the eastern Atlantic Ocean. Once there, the waves move with the jet across North Africa, South Asia, the Himalayas, and China. Anomalous increases in upper-tropospheric potential vorticity and increased wintertime snowfall over the Tibetan Plateau are speculated to be associated with these Rossby waves. The increased snowfall produces a larger Tibetan Plateau snowpack, which persists through the spring and summer, and weakens the intensity of the south Asian summer monsoons.

scholarly journals Movement, drivers and bimodality of the South Asian High

2016 ◽  
Vol 16 (22) ◽  
pp. 14755-14774 ◽  
Author(s):  
Matthias Nützel ◽  
Martin Dameris ◽  
Hella Garny
Keyword(s):  
South Asian ◽  
Wave Radiation ◽  
South Asian High ◽  
The Tibetan Plateau ◽  
The South ◽  
Model Studies ◽  
Monsoon System ◽  
Eastern Border ◽  
Environmental Prediction ◽  
The Tropics

Abstract. The South Asian High (SAH) is an important component of the summer monsoon system in Asia. In this study we investigate the location and drivers of the SAH at 100 hPa during the boreal summers of 1979 to 2014 on interannual, seasonal and synoptic timescales using seven reanalyses and observational data. Our comparison of the different reanalyses focuses especially on the bimodality of the SAH, i.e. the two preferred modes of the SAH centre location: the Iranian Plateau to the west and the Tibetan Plateau to the east. We find that only the National Centers for Environmental Prediction–National Center of Atmospheric Research (NCEP–NCAR) reanalysis shows a clear bimodal structure of the SAH centre distribution with respect to daily and pentad (5 day) mean data. Furthermore, the distribution of the SAH centre location is highly variable from year to year. As in simple model studies, which connect the SAH to heating in the tropics, we find that the mean seasonal cycle of the SAH and its centre are dominated by the expansion of convection in the South Asian region (70–130° E  ×  15–30° N) on the south-eastern border of the SAH. A composite analysis of precipitation and outgoing long-wave radiation data with respect to the location of the SAH centre reveals that a more westward (eastward) location of the SAH is related to stronger (weaker) convection and rainfall over India and weaker (stronger) precipitation over the western Pacific.

scholarly journals Association between regional monsoon onset in South Asia and Tibetan Plateau thermal forcing

2021 ◽  
Author(s):  
Die Hu ◽  
Anmin Duan ◽  
Ping Zhang
Keyword(s):  
Tibetan Plateau ◽  
South Asian ◽  
Summer Monsoon ◽  
General Circulation ◽  
Diabatic Heating ◽  
Monsoon Onset ◽  
South Asian High ◽  
The Tibetan Plateau ◽  
South Asian Summer Monsoon ◽  
Thermal Forcing

Abstract By using multiple data sources and two sensitivity experiments using the atmospheric general circulation model of CAM4.0, we investigated the effect of thermal forcing over the Tibetan Plateau (TP) on the onset of the South Asian summer monsoon, including over the Arabian Sea (AS) and India. Results indicate that the seesaw pattern of diabatic heating over the TP, with a southeastern–northwestern inverse distribution in May, shows a robust relationship with the date of monsoon onset over the AS and India, which is independent of the influences from ocean signals. A positive diabatic heating seesaw pattern can enhance the ascending (descending) motion over the southeastern (northwestern) TP, corresponding to above (below) normal in- situ precipitation. Temperature budget diagnosis reveals that the adiabatic heating by the anomalous vertical motion and relevant horizontal advection of temperature convergence in the mid-upper troposphere are contributors to the warming over the TP. Consequently, the transition of the meridional temperature gradient over South Asian regions occurs earlier. Furthermore, the diabatic heating over the TP induces an enhanced and westward-extended South Asian high (SAH), which together with the easterly along the southern flank of the SAH superimpose on the low-level westerly flow over the AS and India, resulting in intensive upper-level divergence-pumping and upward motion. This anomalous circulation configuration in lower and upper levels further facilitates an earlier onset of summer monsoon in these two regions. These findings are corroborated in the sensitivity runs based on CAM4.0.

scholarly journals Reexamining the barrier effect of Tibetan Plateau on the South Asian summer monsoon

2013 ◽  
Vol 9 (4) ◽  
pp. 5019-5036
Author(s):  
G.-S. Chen ◽  
Z. Liu ◽  
J. E. Kutzbach
Keyword(s):  
Tibetan Plateau ◽  
South Asian ◽  
Summer Monsoon ◽  
Asian Monsoon ◽  
Asian Summer Monsoon ◽  
Monsoon Circulation ◽  
The Tibetan Plateau ◽  
South Asian Summer Monsoon ◽  
The South ◽  
Monsoon System

Abstract. The Tibetan Plateau has been conventionally treated as an elevated heat source driving the Asian monsoon system, especially for the South Asian monsoon. Numerous model simulations with general circulation models (GCMs) support this hypothesis with the finding that the Asian monsoon system is weak or absent with all elevated topographies removed. A recent model simulation shows that the South Asian summer monsoon circulation is little affected with only the Himalayas (no Tibetan Plateau) kept as a barrier, leading to a hypothesis of the barrier "blocking" mechanism of the Tibetan Plateau. In this paper, a new series of experiments are designed to reexamine this barrier effect. We find that with the barrier, the large-scale summer monsoon circulation over South Asia is simulated in general agreement with the full Tibetan Plateau, which is consistent with the previous finding. However there remains significant differences in both wind field and precipitation field elsewhere, suggesting a role of the full Tibetan Plateau as well. Moreover, the proposed barrier "blocking" mechanism is not found in our experiments. The energy of the low-level air and the convection is lower/weaker over the Indian subcontinent in the full Tibetan Plateau experiment than that in the no-Tibetan Plateau experiment or the barrier only experiment, which is opposite to the barrier "blocking" hypothesis. Instead, there is a similar candle-like latent heating in the middle troposphere along the south edge of the Tibetan Plateau in both the full Tibetan Plateau and the barrier experiments, whereas this "candle heating" disappears in the no-Tibetan Plateau experiment. We propose that this candle heating is the key to understand the mechanisms of the Tibetan Plateau on the South Asian monsoon. Future studies are needed to check the source of the "candle heating" and its effect on the Asian monsoon.

scholarly journals Quantifying snow-darkening and atmospheric radiative effects of black carbon and dust on the South-Asian Monsoon and hydrological cycle: Experiments using variable resolution CESM

2019 ◽  
Author(s):  
Stefan Rahimi ◽  
Xiaohong Liu ◽  
Chenglai Wu ◽  
William K. Lau ◽  
Hunter Brown ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Black Carbon ◽  
South Asian ◽  
Asian Monsoon ◽  
Hydrological Cycle ◽  
South Asian Monsoon ◽  
The Tibetan Plateau ◽  
The South ◽  
Variable Resolution ◽  
Absorbing Aerosols

Abstract. Black carbon (BC) and dust impart significant effects on the south-Asian monsoon (SAM), which is responsible for ~80 % of the region’s annual precipitation. This study implements a variable-resolution (VR) version of Community Earth System Model (CESM) to quantify the impacts of absorbing BC and dust on the SAM. This study focuses on the snow darkening effect (SDE), as well as how these aerosols interact with incoming and outgoing radiation to facilitate an atmospheric response (i.e., aerosol radiation interactions (ARI)). By running sensitivity experiments, the individual effects of SDE and ARI are quantified, and a theoretical framework is applied to assess these aerosols’ impacts on the SAM. It is found that ARI of absorbing aerosols warm the atmospheric column in a belt coincident with the May-June averaged location of the subtropical jet, bringing forth anomalous upper-tropospheric (lower-tropospheric) anticyclogenesis (cyclogenesis) and divergence (convergence). This anomalous arrangement in the mass fields brings forth enhanced rising vertical motion across south Asia and a stronger westerly low-level jet, the latter of which furnishes the Indian subcontinent with enhanced Arabian Gulf moisture. This leads to precipitation increases of +2 mm d−1 or more across much of northern India from May through August, with larger anomalies in the western Indian mountains and southern TP mountain ranges due to orographic and anabatic enhancement. Across the Tibetan Plateau foothills, SDE by BC aerosol drives large precipitation anomalies of >6 mm d−1, comparable to ARI of absorbing aerosols from April through August. Runoff changes accompany precipitation and Tibetan Plateau snow changes, which have consequences for south-Asian water resources.

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