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.

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 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 Relationship between the thermal condition of the Tibetan Plateau and precipitation over the region from eastern Ukraine to North Caucasus during summer

2020 ◽  
Vol 142 (3-4) ◽  
pp. 1379-1395
Author(s):  
Junming Chen ◽  
Xiaoyuan Yue ◽  
Ge Liu ◽  
Sulan Nan
Keyword(s):  
Tibetan Plateau ◽  
Thermal Condition ◽  
Large Scale ◽  
Surface Air Temperature ◽  
Thermal Anomaly ◽  
Active Role ◽  
South Asian High ◽  
The Tibetan Plateau ◽  
North Caucasus ◽  
The Impact

Abstract Remarkable climate anomalies occurred in Europe in recent years, but the reasons are not entirely disclosed. This entails further exploring the physical mechanism of anomalous climate variability over Europe on the basis of previous studies. Using NCEP-NCAR reanalysis and CMAP precipitation datasets, we investigated the relationship between the thermal condition of the Tibetan Plateau (TP) and precipitation over Europe during summer and related mechanisms behind through observational analyses and simulation experiments. The results show that the summer TP surface air temperature (SAT) is significantly correlated with the simultaneous precipitation over the region from eastern Ukraine to the North Caucasus (EUNC; 43°–51° N, 34°–46° E) during the period 1979–2017. The effect of anomalous TP heating plays, to some extent, an active role in linking the summer TP SAT with EUNC precipitation. The variability of the TP SAT is a result of the anomalous TP heating, but it can reflect the variability in temperature of a thick tropospheric air column over the TP well. Corresponding to higher (lower) TP SAT, the higher (lower) temperature anomaly appears over the TP and extends westwards through the transport of anomalous temperature fluxes from the TP to the EUNC regions in the upper troposphere, resulting in the expansion (withdrawal) of the South Asian high (SAH) and associated less (more) precipitation over the EUNC region. Numerical simulations basically reproduce the above-mentioned physical process, which confirms that, through stimulating the variability of upper-tropospheric temperatures over the TP and a larger area to its west and associated upstream large-scale atmospheric circulation, the summer TP’s thermal condition can modulate and expand the impact of the SAH to the EUNC region and therefore affect the concurrent precipitation in situ. This study implies an importance of the thermal anomaly of the TP to the variability of EUNC precipitation during summer.

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.

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