scholarly journals Numerical Study of a Southwest Vortex Rainstorm Process Influenced by the Eastward Movement of Tibetan Plateau Vortex

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Xiaoli Liu ◽  
Endian Ma ◽  
Zhibin Cao ◽  
Shuanglong Jin
Keyword(s):  
Tibetan Plateau ◽  
Sichuan Basin ◽  
Low Pressure ◽  
Ice Crystals ◽  
The Tibetan Plateau ◽  
Pressure System ◽  
Convective Clouds ◽  
Low Pressure System ◽  
Southwest Vortex ◽  
The Sichuan Basin

A number of studies revealed the possible eastward movement of the Tibetan Plateau low-pressure system in summer and indicated the enhancement effect of this process on the southwest vortex in the Sichuan Basin, which can induce strong convective precipitation and flood events in China. In this study, a numerical simulation of a southwest vortex rainstorm process was performed. The results show that the low-pressure system originated from the Tibetan Plateau affects the southwest vortex mainly at the middle level, causing the strength increase of southwest vortex (SWV), and acts as a connection between the positive vorticity centers at the upper and lower layers. For the microscopic cloud structure, the vertical updraft of the cloud cluster embedded in the SWV increases as the low-pressure system from the plateau arrives at the Sichuan Basin. Vapor and liquid cloud water at the lower level are transported upward, based on which the ice cloud at the upper level and the warm cloud at the lower level are joined to create favorable conditions for the growth of ice crystals. As the ice crystals grow up, snow and graupel particles form, which substantially elevates the precipitation. This effect leads to the rapid development of SWV rainstorm clouds and the occurrence of precipitation. In addition to the effect of the plateau vortex, the subsequent merging of the convective clouds is another important factor for heavy rainfall because it also leads to development of convective clouds, causing heavy rainfall.

scholarly journals Impacts of Convective Activity over the Tibetan Plateau on Plateau Vortex, Southwest Vortex, and Downstream Precipitation

2019 ◽  
Vol 76 (12) ◽  
pp. 3803-3830 ◽  
Author(s):  
Shen-Ming Fu ◽  
Zi Mai ◽  
Jian-Hua Sun ◽  
Wan-Li Li ◽  
Yang Ding ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Potential Vorticity ◽  
Small Proportion ◽  
Geopotential Height ◽  
Sichuan Basin ◽  
Heavy Precipitation ◽  
The Tibetan Plateau ◽  
Convective Activity ◽  
Southwest Vortex ◽  
The Sichuan Basin

Abstract In summer, convective activity over the Tibetan Plateau (TP) is vigorous, with some of it moving eastward and vacating the plateau [defined as the eastward-moving type (EMT)]. Although the EMT only accounts for a small proportion, it is closely related to heavy precipitation east of the TP. This study investigates EMT impacts based on a series of composite semi-idealized simulations and piecewise potential vorticity (PV) inversion. The main results are as follows. (i) An EMT begins to affect downstream precipitation before it vacates the TP. A weaker EMT tends to cause the main downstream rainband to reduce in intensity and move southward. (ii) The EMT contributes to the formation of an eastward-moving plateau vortex (PLV) by enhancing convergence-induced stretching. Over the TP, the PLV mainly enhances/maintains the EMT, whereas during the vacating stage, the PLV dissipates (since convergence decreases rapidly when sensible heating from the TP reduces), which substantially reduces the intensity of the EMT. (iii) After PLV dissipation, a southwest vortex (SWV) forms around the Sichuan basin mainly due to convergence-induced stretching, convection-related tilting, and background transport. Piecewise PV inversion indicates that an EMT can directly contribute to SWV formation via lowering geopotential height and enhancing cyclonic wind perturbations around the Sichuan basin (even before its vacating stage), while neither of them governs the SWV formation. Sensitivity runs show that an EMT is not necessary for SWV formation, but can modify the SWV formation time and location, as well as its displacement, which significantly affects downstream precipitation.

Influence of the synoptic systems and inversion characteristics on winter heavy air pollution in the lower atmosphere over Sichuan Basin, China

2020 ◽  
Author(s):  
Shigong Wang ◽  
Hua Fu
Keyword(s):  
Air Pollution ◽  
Sichuan Basin ◽  
Low Pressure ◽  
Urban Agglomeration ◽  
Lower Atmosphere ◽  
Horizontal Wind ◽  
Pressure System ◽  
Low Pressure System ◽  
The Sichuan Basin ◽  
Pollution Events

<p>The Sichuan Basin is located in the eastern part of the Tibetan Plateau, and there is a rapidly developing urban agglomeration over there. Therefore, heavy air pollution events have frequently occurred over many cities in recent decades. In this study, We explored the effects of weather systems on winter heavy air pollution from more than 10 cases of heavy air pollution events occurred during 2006-2018. Most of them were affected by a dry low-pressure system at 700 hPa, at the same time , they were also influenced by the inversion with several layers in the lower atmosphere. It is interesting that the synergistic effects of synoptic patterns and inversions caused by topography on heavy air pollution events. When the urban agglomeration was in front of the low-pressure system and the weather conditions were controlled by a warm southerly air flow, a strong temperature inversion appeared above the atmospheric boundary layer acting as a lid. The local secondary circulation was forced by both of them and was confined within the atmospheric boundary layer. At that time, the horizontal wind speed in the lower atmosphere was low.  As a result, vertical mixing and horizontal dispersion in the atmosphere were poor, a heavy air pollution event was gradually caused. After the low-pressure system had passed over the urban agglomeration, the weather conditions over there were controlled by a dry and cold air flow from the northwest at 700 hPa, foregoing strong inversion layer gradually dissipated, the secondary circulation enhanced and uplifted, and the horizontal wind speed in the lower atmosphere also increased, resulting in a sharp decrease in the concentration of air pollutants. In sum, the strong inversion layers above the lower atmosphere were induced by the low-pressure systems at 700 hPa, both happened a synergistic effect and played a key role in the formation of heavy air pollution during the winter months in this urban agglomeration of The Sichuan Basin. Finally, it was presented that a new conceptual model is about meteorological causes of winter heavy air pollution  in the Sichuan Basin.</p>

scholarly journals The Warming Tibetan Plateau improves winter air quality in the Sichuan Basin, China

2020 ◽  
Author(s):  
Shuyu Zhao ◽  
Tian Feng ◽  
Xuexi Tie ◽  
Zebin Wang
Keyword(s):  
Climate Change ◽  
Air Pollution ◽  
Air Quality ◽  
Tibetan Plateau ◽  
Sichuan Basin ◽  
The Tibetan Plateau ◽  
Aerosol Formation ◽  
Warming Rate ◽  
The Sichuan Basin ◽  
The Impact

Abstract. Impacts of global climate change on the occurrence and development of air pollution have attracted more attentions. This study investigates impacts of the warming Tibetan Plateau on air quality in the Sichuan Basin. Meteorological observations and ERA-interim reanalysis data reveal that the Tibetan Plateau has been rapidly warming during the last 40 years (1979–2017), particularly in winter when the warming rate is approximately twice as much as the annual warming rate. Since 2013, the winter temperature over the plateau has even risen by 2 °C. Here, we use the WRF-CHEM model to assess the impact of the 2 °C warming on air quality in the Sichuan Basin. The model results show that the 2 °C warming causes an increase in the Planetary Boundary Layer (PBL) height and a decrease in the relative humidity (RH) in the basin. The elevated PBL height strengthens vertical diffusion of PM2.5, while the decreased RH significantly reduces secondary aerosol formation. Overall, PM2.5 concentration is reduced by 17.5 % (~ 25.1 μg m−3), of which the reduction in primary and secondary aerosols is 5.4 μg m−3 and 19.7 μg m−3, respectively. These results reveal that the recent warming plateau has improved air quality in the basin, to some certain extent, mitigating the air pollution therein. Nevertheless, climate system is particularly complicated, and more studies are needed to demonstrate the impact of climate change on air quality in the downstream regions as the plateau is likely to continue warming.

scholarly journals Monsoon Low Pressure System–Like Variability in an Idealized Moist Model

2020 ◽  
Vol 33 (6) ◽  
pp. 2051-2074 ◽  
Author(s):  
Spencer K. Clark ◽  
Yi Ming ◽  
Ángel F. Adames
Keyword(s):  
Potential Vorticity ◽  
General Circulation ◽  
Circulation Model ◽  
Low Pressure ◽  
The Tibetan Plateau ◽  
Pressure System ◽  
Asian Monsoon Region ◽  
Advection Term ◽  
Prior Literature ◽  
Low Pressure System

AbstractIn this paper, it is shown that westward-propagating monsoon low pressure system–like disturbances in the South Asian monsoon region can be simulated in an idealized moist general circulation model through the addition of a simplified parameterization of land. Land is parameterized as having one-tenth the heat capacity of the surrounding slab ocean, with evaporation limited by a bucket hydrology model. In this model, the prominent topography of the Tibetan Plateau does not appear to be necessary for these storm systems to form or propagate; therefore, focus is placed on the simulation with land but no topography. The properties of the simulated storms are elucidated using regression analysis and compared to results from composites of storms from comprehensive GCMs in prior literature and reanalysis. The storms share a similar vertical profile in anomalous Ertel potential vorticity to those in reanalysis. Propagation, however, does not seem to be strongly dictated by beta drift. Rather, it seems to be more closely consistent with linear moisture vortex instability theory, with the exception of the importance of the vertical advection term in the Ertel potential vorticity budget toward the growth and maintenance of disturbances. The results presented here suggest that a simplified GCM configuration might be able to be used to gain a clearer understanding of the sensitivity of monsoon low pressure systems to changes in the mean state climate.

scholarly journals Block rotation: Tectonic response of the Sichuan basin to the southeastward growth of the Tibetan Plateau along the Xianshuihe‐Xiaojiang fault

Tectonics ◽  
2014 ◽  
Vol 33 (5) ◽  
pp. 686-718 ◽  
Author(s):  
Erchie Wang ◽  
Kai Meng ◽  
Zhe Su ◽  
Qingren Meng ◽  
Jean J. Chu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Sichuan Basin ◽  
The Tibetan Plateau ◽  
Block Rotation ◽  
The Sichuan Basin ◽  
Xiaojiang Fault
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