scholarly journals The Deep Atmospheric Boundary Layer and Its Significance to the Stratosphere and Troposphere Exchange over the Tibetan Plateau

PLoS ONE ◽  
2013 ◽  
Vol 8 (2) ◽  
pp. e56909 ◽  
Author(s):  
Xuelong Chen ◽  
Juan A. Añel ◽  
Zhongbo Su ◽  
Laura de la Torre ◽  
Hennie Kelder ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Tibetan Plateau ◽  
Atmospheric Boundary Layer ◽  
The Tibetan Plateau

scholarly journals The Daytime Evolution of the Atmospheric Boundary Layer and Convection over the Tibetan Plateau: Observations and Simulations

2004 ◽  
Vol 82 (6) ◽  
pp. 1777-1792 ◽  
Author(s):  
Kun YANG ◽  
Toshio KOIKE ◽  
Hideyuki FUJII ◽  
Toru TAMURA ◽  
Xiangde XU ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Tibetan Plateau ◽  
Atmospheric Boundary Layer ◽  
The Tibetan Plateau

scholarly journals Characteristics of the summer atmospheric boundary layer height over the Tibetan Plateau and influential factors

2020 ◽  
Author(s):  
Junhui Che ◽  
Ping Zhao
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Tibetan Plateau ◽  
Solar Radiation ◽  
Atmospheric Boundary Layer ◽  
Sensible Heat Flux ◽  
Influential Factors ◽  
The Tibetan Plateau ◽  
Height Distribution ◽  
Sensible Heat

Abstract. Based on intensive sounding, surface sensible heat flux, solar radiation, and soil moisture observational datasets from the Third Tibetan Plateau Atmospheric Scientific Experiment and the routine meteorological operational sounding and total cloudiness datasets in the Tibetan Plateau (TP) for the period 2013–2015, we investigate the features of summer atmospheric boundary layer (ABL) over the TP and its major influential factors. It is found that the convective boundary layer (CBL) and the neutral boundary layer (NBL) show remarkable diurnal variations over the TP, while the stable boundary layer (SBL) diurnal variation is weak. In the early morning, the ABL height distribution is narrow, with a small west-east difference. The SBL accounts for 85 % of the TP ABL. At noon, there is a wide distribution in the ABL height up to 4000 m. The CBL accounts for 77 % of the TP ABL, with more than 50 % of the CBL height above 1900 m. The ABL height exhibits a large west-east difference, with a mean height above 2000 m in the western TP and around 1500 m in the eastern TP. In the late afternoon, the CBL and SBL dominate the western and eastern TP, respectively, resulting in a larger west-east difference of 1054.2 m between the western and eastern TP. The high ABL height in a cold environment over the western TP (relative to the plain areas) is similar to that in some extreme hot and arid areas such as Dunhuang and Taklimakan Deserts. For the western (eastern) TP, there is low (high) total cloud coverage, with large (small) solar radiation at the surface and dry (wet) soil. These features result in high (low) sensible heat flux and thus promotes (inhibits) the local ABL development.

scholarly journals Characteristics of the summer atmospheric boundary layer height over the Tibetan Plateau and influential factors

2021 ◽  
Vol 21 (7) ◽  
pp. 5253-5268
Author(s):  
Junhui Che ◽  
Ping Zhao
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Tibetan Plateau ◽  
Solar Radiation ◽  
Atmospheric Boundary Layer ◽  
Diurnal Variation ◽  
Sensible Heat Flux ◽  
Influential Factors ◽  
The Tibetan Plateau ◽  
Sensible Heat

Abstract. The important roles of the Tibetan Plateau (TP) atmospheric boundary layer (ABL) in climate, weather, and air quality have long been recognized, but little is known about the TP ABL climatological features and their west–east discrepancies due to the scarce data in the western TP. Based on observational datasets of intensive sounding, surface sensible heat flux, solar radiation, and soil moisture from the Third Tibetan Plateau Atmospheric Scientific Experiment (TIPEX-III) and the routine meteorological-operational-sounding and ground-based cloud cover datasets in the Tibetan Plateau for the period 2013–2015, we investigate the west–east differences in summer ABL features over the TP and the associated influential factors for the first time. It is found that the heights of both the convective boundary layer (CBL) and the neutral boundary layer (NBL) exhibit a diurnal variation and a west–east difference in the TP, while these features are not remarkable for the stable boundary layer (SBL). Moreover, the ABL shows significant discrepancies in the amplitude of the diurnal variation and the persistent time of the development between the eastern and western TP. In the early morning (08:00 BJT, Beijing time), the ABL height distribution is narrow, with a mean height below 450 m a.g.l. (above ground level) and a small west–east difference. The SBL observed at this moment accounts for 85 % of the total TP ABL. There is a wide distribution in the ABL height up to 4000 m a.g.l. and a large west–east difference for the total ABL height at noon (14:00 BJT), with a mean height above 2000 m a.g.l. in the western TP and around 1500 m a.g.l. in the eastern TP. The CBL accounts for 77 % of the total TP ABL at this moment, with more than 50 % of the CBL above 1900 m a.g.l. In the late afternoon (20:00 BJT), the CBL and SBL dominate the western and eastern TP, respectively, which results in a larger west–east difference of 1054.2 m between the western and eastern TP. The high ABL height in a cold environment over the western TP (relative to the plain areas) is similar to that in some extreme hot and arid areas such as Dunhuang and Taklimakan deserts. In general, for the western (eastern) TP, there is low (high) total cloud coverage, with large (small) solar radiation at the surface and dry (wet) soil. These features lead to high (low) sensible heat flux and thus promote (inhibit) the local ABL development. This study provides new insights for west–east structures of the summer ABL height, occurrence frequency, and diurnal amplitude over the TP region and the associated reasons.

scholarly journals Sub-seasonal Variability in the Boundary Layer Sources for Transport into the Tropopause Layer in the Asian Monsoon Region

2017 ◽  
Author(s):  
Bin Chen ◽  
Bärbel Vogel ◽  
Xiangde Xu ◽  
Shuai Yang
Keyword(s):  
Boundary Layer ◽  
Tibetan Plateau ◽  
Mass Transport ◽  
Seasonal Variability ◽  
The Tibetan Plateau ◽  
Southern Slope ◽  
Seasonal Behavior ◽  
Air Mass ◽  
Source Regions ◽  
Wide Range

Abstract. The Asian summer monsoon (ASM) is associated with an upper-level anticyclone and acts as a well-recognized conduit for troposphere-to-stratosphere transport. The Lagrangian dispersion and transport model FLEXPART forced by ERA-Interim data from 2001–2013 was used to perform climatological modeling of the summer season (May–July). This study examines the properties of the air mass transport from the atmospheric boundary layer (BL) to the tropopause layer (TL), with particular focus on the sub-seasonal variability in the tracer-independent BL sources and the potential controlling mechanisms. The results show that, climatologically, the three most impactful BL source regions are northern India, the Tibetan Plateau, and the southern slope of the Himalayas. These regions are consistent with the locations of sources identified in previous studies. However, upon closer inspection, the different source regions to the BL-to-TL air mass transport are not constant in location or shape and are strongly affected by sub-seasonal variability. The contributions from the Tibetan Plateau are most significant in early May but decrease slightly in mid-May to mid-June. In contrast, the contributions from India and the southern slope of the Himalayas increase dramatically, with peak values occurring in mid-July. Empirical Orthogonal Function (EOF) analysis provides further evidence that the BL sources in the ASM region vary across a wide range of spatiotemporal scales. The sub-seasonal behavior of these BL sources is closely related to the strength of persistent deep convection activity over the northern Bay of Bengal and its neighboring areas.

scholarly journals Land-surface processes and summer-cloud-precipitation characteristics in the Tibetan Plateau and their effects on downstream weather: a review and perspective

2020 ◽  
Vol 7 (3) ◽  
pp. 500-515 ◽  
Author(s):  
Yunfei Fu ◽  
Yaoming Ma ◽  
Lei Zhong ◽  
Yuanjian Yang ◽  
Xueliang Guo ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Tibetan Plateau ◽  
Land Surface ◽  
Sensible Heat Flux ◽  
Vertical Direction ◽  
Heat Fluxes ◽  
Surface Processes ◽  
Convective Precipitation ◽  
The Tibetan Plateau ◽  
Land Surface Processes

Abstract Correct understanding of the land-surface processes and cloud-precipitation processes in the Tibetan Plateau (TP) is an important prerequisite for the study and forecast of the downstream activities of weather systems and one of the key points for understanding the global atmospheric movement. In order to show the achievements that have been made, this paper reviews the progress on the observations for the atmospheric boundary layer, land-surface heat fluxes, cloud-precipitation distributions and vertical structures by using ground- and space-based multiplatform, multisensor instruments and the effect of the cloud system in the TP on the downstream weather. The results show that the form drag related to the topography, land–atmosphere momentum and scalar fluxes is an important part of the parameterization process. The sensible heat flux decreased especially in the central and northern TP caused by the decrease in wind speeds and the differences in the ground-air temperatures. Observations show that the cloud and precipitation over the TP have a strong diurnal variation. Studies also show the compressed-air column in the troposphere by the higher-altitude terrain of the TP makes particles inside clouds vary at a shorter distance in the vertical direction than those in the non-plateau area so that precipitation intensity over the TP is usually small with short duration, and the vertical structure of the convective precipitation over the TP is obviously different from that in other regions. In addition, the influence of the TP on severe weather downstream is preliminarily understood from the mechanism. It is necessary to use model simulations and observation techniques to reveal the difference between cloud precipitation in the TP and non-plateau areas in order to understand the cloud microphysical parameters over the TP and the processes of the land boundary layer affecting cloud, precipitation and weather in the downstream regions.

scholarly journals A numerical process study on the rapid transport of stratospheric air down to the surface over western North America and the Tibetan Plateau

2019 ◽  
Vol 19 (9) ◽  
pp. 6535-6549 ◽  
Author(s):  
Bojan Škerlak ◽  
Stephan Pfahl ◽  
Michael Sprenger ◽  
Heini Wernli
Keyword(s):  
Boundary Layer ◽  
Tibetan Plateau ◽  
Surface Ozone ◽  
Vertical Transport ◽  
The Tibetan Plateau ◽  
Near Surface ◽  
Air Mass ◽  
Ozone Concentrations ◽  
Rapid Transport ◽  
Upper Level

Abstract. Upper-level fronts are often associated with the rapid transport of stratospheric air along tilted isentropes to the middle or lower troposphere, where this air leads to significantly enhanced ozone concentrations. These plumes of originally stratospheric air can only occasionally be observed at the surface because (i) stable boundary layers prevent an efficient vertical transport down to the surface, and (ii) even if boundary layer turbulence were strong enough to enable this transport, the originally stratospheric air mass can be diluted by mixing, such that only a weak stratospheric signal can be recorded at the surface. Most documented examples of stratospheric air reaching the surface occurred in mountainous regions. This study investigates two such events, using a passive stratospheric air mass tracer in a mesoscale model to explore the processes that enable the transport down to the surface. The events occurred in early May 2006 in the Rocky Mountains and in mid-June 2006 on the Tibetan Plateau. In both cases, a tropopause fold associated with an upper-level front enabled stratospheric air to enter the troposphere. In our model simulation of the North American case, the strong frontal zone reaches down to 700 hPa and leads to a fairly direct vertical transport of the stratospheric tracer along the tilted isentropes to the surface. In the Tibetan Plateau case, however, no near-surface front exists and a reservoir of high stratospheric tracer concentrations initially forms at 300–400 hPa, without further isentropic descent. However, entrainment at the top of the very deep boundary layer (reaching to 300 hPa over the Tibetan Plateau) and turbulence within the boundary layer allows for downward transport of stratospheric air to the surface. Despite the strongly differing dynamical processes, stratospheric tracer concentrations at the surface reach peak values of 10 %–20 % of the imposed stratospheric value in both cases, corroborating the potential of deep stratosphere-to-troposphere transport events to significantly influence surface ozone concentrations in these regions.

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