Dynamic and Thermodynamic Relations of Distinctive Stratus Clouds on the Lee Side of the Tibetan Plateau in the Cold Season

2013 ◽  
Vol 26 (21) ◽  
pp. 8378-8391 ◽  
Author(s):  
Yi Zhang ◽  
Rucong Yu ◽  
Jian Li ◽  
Weihua Yuan ◽  
Minghua Zhang
Keyword(s):  
Tibetan Plateau ◽  
Large Scale ◽  
Eastern China ◽  
Cold Season ◽  
Water Vapor Transport ◽  
The Tibetan Plateau ◽  
Primary Role ◽  
Moist Air ◽  
Low Level ◽  
Stratus Clouds

Abstract Given the large discrepancies that exist in climate models for shortwave cloud forcing over eastern China (EC), the dynamic (vertical motion and horizontal circulation) and thermodynamic (stability) relations of stratus clouds and the associated cloud radiative forcing in the cold season are examined. Unlike the stratus clouds over the southeastern Pacific Ocean (as a representative of marine boundary stratus), where thermodynamic forcing plays a primary role, the stratus clouds over EC are affected by both dynamic and thermodynamic factors. The Tibetan Plateau (TP)-forced low-level large-scale lifting and high stability over EC favor the accumulation of abundant saturated moist air, which contributes to the formation of stratus clouds. The TP slows down the westerly overflow through a frictional effect, resulting in midlevel divergence, and forces the low-level surrounding flows, resulting in convergence. Both midlevel divergence and low-level convergence sustain a rising motion and vertical water vapor transport over EC. The surface cold air is advected from the Siberian high by the surrounding northerly flow, causing low-level cooling. The cooling effect is enhanced by the blocking of the YunGui Plateau. The southwesterly wind carrying warm, moist air from the east Bay of Bengal is uplifted by the HengDuan Mountains via topographical forcing; the midtropospheric westerly flow further advects the warm air downstream of the TP, moistening and warming the middle troposphere on the lee side of the TP. The low-level cooling and midlevel warming together increase the stability. The favorable dynamic and thermodynamic large-scale environment allows for the formation of stratus clouds over EC during the cold season.

Vertical Structures and Physical Properties of the Cold-Season Stratus Clouds Downstream of the Tibetan Plateau: Differences between Daytime and Nighttime

2014 ◽  
Vol 27 (18) ◽  
pp. 6857-6876 ◽  
Author(s):  
Yi Zhang ◽  
Haoming Chen ◽  
Rucong Yu
Keyword(s):  
Tibetan Plateau ◽  
Large Scale ◽  
Single Layer ◽  
Cold Season ◽  
Cloud Fraction ◽  
The Tibetan Plateau ◽  
Stratus Clouds ◽  
Microphysical Properties ◽  
Integrated Optical ◽  
Macrophysical Properties

Abstract This study compares the daytime–nighttime (DN) differences in the occurrence frequencies and macrophysical, microphysical, and radiative vertical structures of the single-layer stratus clouds downstream of the Tibetan Plateau (TP) during the boreal cold season (November–April) using four CloudSat products. The stratus cloudy profiles are selected and the midtopped stratus profiles are further classified into nimbostratus (NI) and altostratus (AS) according to the cloud-top height and column-integrated optical depth. It is found that the entire stratus and NI profiles tend to occur more frequently in the daytime, while the AS cloud occurs more frequently in the nighttime. Consistent with the DN differences in the occurrence frequencies, the AS tends to be much thicker with larger cloud fraction in the nighttime, while the NI becomes slightly thicker with larger cloud fraction in the daytime. An analysis of the ambient dynamic and thermodynamic fields associated with stratus formation suggests that it is the DN difference in the large-scale low-level lifting that leads to the corresponding differences of the occurrences and macrophysical properties. In contrast, the optical depths of the NI and AS clouds become larger and smaller from daytime to nighttime, respectively, which is attributed to the microphysical properties. The occurrence frequencies in small droplet particle sizes increase (NI) and decrease (AS) from daytime to nighttime, leading to the corresponding variations of the cloud radiative property.

scholarly journals Climate modulation of the Tibetan Plateau on haze in China

2016 ◽  
Vol 16 (3) ◽  
pp. 1365-1375 ◽  
Author(s):  
X. Xu ◽  
T. Zhao ◽  
F. Liu ◽  
S. L. Gong ◽  
D. Kristovich ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Large Scale ◽  
Climate Changes ◽  
Eastern China ◽  
Atmospheric Stability ◽  
Lower Troposphere ◽  
Pollutant Emissions ◽  
The Tibetan Plateau ◽  
Thermal Forcing ◽  
Haze Pollution

Abstract. Rapid increases in pollutant emissions in conjunction with stagnant meteorological conditions result in haze pollution in China. Recent frequent haze in China has attracted worldwide attention. Here we show a relationship between the haze events and Tibetan Plateau (TP)'s environment and climate changes. Based on observational data taken over recent decades, we identify central-eastern China (CEC) as a climatological large-scale “susceptible region” of frequent haze, which is harbored by the TP with its impact on midlatitude westerly winds. The observational and modeling studies demonstrate that the interannual variations in the thermal forcing of TP are positively correlated with the incidences of wintertime haze over CEC. Further analysis indicates that the climate warming of the TP induced changes in atmospheric circulation, driving frequent haze events in CEC. The frequent haze occurrences in CEC are consistent with decreasing winter monsoon winds, intensifying downward air flows and increasing atmospheric stability in the lower troposphere over the CEC in association with upstream plateau's thermal anomalies. Therefore, variations of haze in China are related to mechanical and thermal forcing by the TP. Our results also suggest that implications of the large TP topography for environment and climate changes should be taken into account for air pollution mitigation policies in China.

Palaeomagnetic constraints on Himalayan-Tibetan tectonic evolution

1988 ◽  
Vol 326 (1589) ◽  
pp. 177-188 ◽  
Keyword(s):  
Tibetan Plateau ◽  
South China ◽  
Large Scale ◽  
Indian Subcontinent ◽  
Eastern China ◽  
Crustal Thickening ◽  
The Tibetan Plateau ◽  
South China Block ◽  
The South ◽  
Palaeomagnetic Data

Palaeomagnetic data from the Lhasa, Qiangtang and Kunlun Terranes of the Tibetan Plateau are used with data from stable Eurasia, eastern China and Indochina, to test different models of crustal thickening in the Tibetan Plateau, to attempt a Carboniferous palaeogeographic reconstruction, and to calculate the relative motion between the South China Block and the Indochina Block. The data suggest that since the onset of the India—Eurasia collision, the Lhasa Terrane has moved 2000 + 800 km north with respect to stable Eurasia. This indicates that strong internal defomation must have taken place in southern Eurasia since the collision, and thus challenges the model of large-scale underthrusting of the Indian subcontinent beneath the Tibetan Plateau as the mechanism for crustal thickening in Tibet. Palaeomagnetic results from the Kunlun Terrane show that it was at 22° south latitude during the Carboniferous. A Carboniferous reconstruction is presented in which the Kunlun and Qiangtang Terranes, several Indochina terranes, and the North and South China Blocks are grouped together. These units of continental crust all share the specific tropical and subtropical Cathaysian flora, and the group is therefore called the Cathaysian composite continent. To test the model of propagating extrusion tectonics, we have used newly available palaeomagnetic results from South China and Indochina to calculate probable displacements. This exercise suggests a rotation of about 8° of Indochina with respect to the South China Block that is smaller than the predicted rotation of 40°, A large eastward translation of the South China Block relative to the Indochina Block of about 1500 km is consistent with the palaeomagnetic data.

scholarly journals Diagnostic analysis of a regional heavy snowfall event over the Tibetan Plateau using NCEP reanalysis data and WRF

2021 ◽  
Author(s):  
Lian Liu ◽  
Yaoming Ma ◽  
Nan Yao ◽  
Weiqiang Ma
Keyword(s):  
Water Vapor ◽  
Tibetan Plateau ◽  
Large Scale ◽  
Stable Stratification ◽  
Reanalysis Data ◽  
The Tibetan Plateau ◽  
Diagnostic Analysis ◽  
Heavy Snowfall ◽  
Low Level ◽  
Snowfall Event

AbstractSnowstorms frequently occur in spring over the heterogeneous underlying surface of the Tibetan Plateau, causing both economic and societal damage. What the intensity of factors triggering snowstorms remains poorly understood. This study quantitatively diagnoses water vapor, the thermodynamic and dynamic conditions of a large-scale heavy snowfall event over the Tibetan Plateau using reanalysis data. Here we show, a cold vortex, the Southern Branch Trough and a meridional shear line are favorable synoptic systems. The snowfall is characterized by low-layer (− 8.3 × 10−7 g s−1 hPa−1 cm−2) and whole-layer (− 4.5 × 10−4 g s−1 cm−2) moisture convergence, low-level atmospheric convergence and high-level divergence (± 3 × 10−4 s−1), low-level positive vorticity (4.8 × 10−4 s−1) and strong vertical velocity (− 4 Pa s−1). Although the convectively-stable stratification acted to suppress snowfall, the abundant water vapor and strong orographic uplift of Himalayas and the downhill wind speed convergence overcome this to trigger the heavy snowfall event witnessed in March 2017. These diagnostic results are well consistent with those from WRF simulation. Our study acknowledges the importance of WRF in diagnostic analysis, deepens the understanding of evolution mechanisms and provides theoretical references for accurate forecasting of such events over the Tibetan Plateau. It would aid the development of effective strategies for sustainable livestock, and the mitigation and prevention of snow disasters in this region.

The Effects of Midlatitude Waves over and around the Tibetan Plateau on Submonthly Variability of the East Asian Summer Monsoon

2009 ◽  
Vol 137 (7) ◽  
pp. 2286-2304 ◽  
Author(s):  
Hatsuki Fujinami ◽  
Tetsuzo Yasunari
Keyword(s):  
Tibetan Plateau ◽  
Rossby Wave ◽  
Large Scale ◽  
Southern China ◽  
Phase Speed ◽  
The Tibetan Plateau ◽  
Low Level ◽  
Zonal Wavenumber ◽  
Upper Level ◽  
Southward Migration

Convective variability at submonthly time scales (7–25 days) over the Yangtze and Huaihe River basins (YHRBs) and associated large-scale atmospheric circulation during the mei-yu season were examined using interpolated outgoing longwave radiation (OLR) and NCEP–NCAR reanalysis data for 12 yr having active submonthly convective fluctuation over the YHRBs within the period 1979–2004. Correlations between convection anomalies over the YHRBs and upper-level streamfunction anomalies at every grid point show two contrasting patterns. One pattern exhibits high correlations along the northern to eastern peripheries of the Tibetan Plateau (defined as the NET pattern), whereas the other has high correlations across the Tibetan Plateau (defined as the AT pattern). Composite analysis of the NET pattern shows slow southward migration of convection anomalies from the northeastern periphery of the Tibetan Plateau to southern China, in relation to southward migration of the mei-yu front caused by simultaneous amplification of upper- and low-level waves north of the YHRBs. In the AT pattern, convection anomalies migrate eastward from the western Tibetan Plateau to the YHRBs. A low-level vortex is created at the lee of the plateau by eastward-moving upper-level wave packets and associated convection from the plateau. Rossby wave trains along the Asian jet characterize the upper-level circulation anomalies in the two patterns. The basic state of the Asian jet during the mei-yu season differs between the two patterns, especially around the Tibetan Plateau. The Asian jet has a northward arclike structure in NET years, while a zonal jet dominates in AT years. These differences could alter the Rossby wave train propagation route. Furthermore, the larger zonal wavenumber of AT waves (∼7–8) than of NET waves (∼6) means faster zonal phase speed relative to the ground in the AT pattern than in the NET pattern. These differences likely explain the meridional amplification of waves north of the YHRBs in the NET pattern and the eastward wave movement across the plateau in the AT pattern.

A Multiscale Analysis of the Extreme Weather Events over Western Russia and Northern Pakistan during July 2010

2012 ◽  
Vol 140 (5) ◽  
pp. 1639-1664 ◽  
Author(s):  
Thomas J. Galarneau ◽  
Thomas M. Hamill ◽  
Randall M. Dole ◽  
Judith Perlwitz
Keyword(s):  
Tibetan Plateau ◽  
Heat Wave ◽  
Multiscale Analysis ◽  
Large Scale ◽  
The Tibetan Plateau ◽  
Northern Pakistan ◽  
Key Factors ◽  
Energy Dispersion ◽  
Low Level ◽  
Low Level Jet

Abstract This manuscript presents a detailed multiscale analysis—using observations, model analyses, and ensemble forecasts—of the extreme heat wave over Russia and historic floods over Pakistan during late July 2010, with an emphasis on the floods over northern Pakistan. The results show that recirculation of air and dynamically driven subsidence occurring with the intensification of the blocking anticyclone in late July 2010 were key factors for producing the exceptionally warm temperatures over western Russia. Downstream energy dispersion from the blocking region led to trough deepening northwest of Pakistan and ridge building over the Tibetan Plateau, thereby providing the linkage between the Russian heat wave and Pakistan flood events on the large scale, in agreement with previous studies. The extratropical downstream energy dispersion and enhanced convective outflow on the large scale associated with the active phase of the Madden–Julian oscillation facilitated the formation of an intense upper-level jet northwest of Pakistan. During this same period an intense southeasterly, low-level, barrier jet–like feature formed over northern Pakistan in conjunction with a westward-moving monsoon depression. This low-level jet and deep easterly flow on the equatorward flank of an anomalous anticyclone over the Tibetan Plateau further enhanced the transport of deep tropical moisture into Pakistan and produced a sustained upslope flow and an extended period of active convection, thereby providing an important contribution leading to the exceptional rainfall amounts. The deep easterly flow and intense low-level jet were features that were absent during previous convective episodes over northern Pakistan in 2010, and hence, were likely key factors in the increased severity of the late July event.

scholarly journals Observations of water vapor mixing ratio profile and flux in the Tibetan Plateau based on the lidar technique

2016 ◽  
Vol 9 (3) ◽  
pp. 1399-1413 ◽  
Author(s):  
Songhua Wu ◽  
Guangyao Dai ◽  
Xiaoquan Song ◽  
Bingyi Liu ◽  
Liping Liu
Keyword(s):  
Boundary Layer ◽  
Water Vapor ◽  
Tibetan Plateau ◽  
Large Scale ◽  
Lower Troposphere ◽  
Water Vapor Transport ◽  
The Tibetan Plateau ◽  
Mixing Ratio ◽  
Wind Lidar ◽  
Water Vapor Mixing Ratio

Abstract. As a part of the third Tibetan Plateau Experiment of Atmospheric Sciences (TIPEX III) in China, a Raman water vapor, cloud and aerosol lidar and a coherent wind lidar were operated in Naqu (31.48° N, 92.06° E) with a mean elevation of more than 4500 m a.m.s.l. in summer of 2014. During the field campaign, the water vapor mixing ratio profiles were obtained and validated by radiosonde observations. The mean water vapor mixing ratio in Naqu in July and August was about 9.4 g kg−1 and the values vary from 6.0 to 11.7 g kg−1 near the ground according to the lidar measurements, from which a diurnal variation of water vapor mixing ratio in the planetary boundary layer was also illustrated in this high-elevation area. Furthermore, using concurrent measurements of vertical wind speed profiles from the coherent wind lidar, we calculated the vertical flux of water vapor that indicates the water vapor transport through updraft and downdraft. The fluxes were for a case at night with large-scale non-turbulent upward transport of moisture. It is the first application, to our knowledge, to operate continuously atmospheric observations by utilizing multi-disciplinary lidars at the altitude higher than 4000 m, which is significant for research on the hydrologic cycle in the atmospheric boundary layer and lower troposphere in the Tibetan Plateau.

scholarly journals Climate modulation of the Tibetan Plateau on haze in China

2015 ◽  
Vol 15 (20) ◽  
pp. 28915-28937 ◽  
Author(s):  
X. Xu ◽  
T. Zhao ◽  
F. Liu ◽  
S. L. Gong ◽  
D. Kristovich ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Large Scale ◽  
Climate Changes ◽  
Eastern China ◽  
Atmospheric Stability ◽  
Lower Troposphere ◽  
Pollutant Emissions ◽  
The Tibetan Plateau ◽  
Thermal Forcing ◽  
Haze Pollution

Abstract. Rapid increases in pollutant emissions in conjunction with stagnant meteorological conditions result in haze pollution in China. Recent frequent haze in China has attracted worldwide attention. Here we show a relationship between the haze events and Tibetan Plateau (TP)'s environment and climate changes. Based on observational data taken over recent decades, we identify central-eastern China (CEC) as a climatological large-scale "susceptible region" of frequent haze, which is harbored by the TP with its impact on mid-latitude westerly winds. The observational and modeling studies demonstrate that the interannual variations in the thermal forcing of TP are positively correlated with the incidences of wintertime haze over CEC. Further analysis indicates that the TP-climate warming induced changes in atmospheric circulation driving frequent haze events in CEC. The frequent haze occurrences in CEC are consistent with decreasing winter monsoon winds, intensifying downward air flows and increasing atmospheric stability in the lower troposphere over the CEC in association with upstream plateau's thermal anomalies. Therefore, variations of haze in China are related to mechanical and thermal forcing by the TP. Our results also suggest that implications of the large TP-topography for environment and climate changes should be taken into account for air pollution mitigation policies in China.

scholarly journals No Significant Shift of Warming Trend over the Last Two Decades on the Mid-South of Tibetan Plateau

Atmosphere ◽  
2019 ◽  
Vol 10 (7) ◽  
pp. 416 ◽  
Author(s):  
Li ◽  
Zhang ◽  
Qi ◽  
Wang ◽  
Liu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Piecewise Linear ◽  
Warming Trend ◽  
Cold Season ◽  
Maximum Temperature ◽  
Temperature Phase ◽  
Significant Shift ◽  
The Tibetan Plateau ◽  
Primary Role ◽  
Warming Hiatus

Climate warming on the Tibetan Plateau has been regarded as an important driving force of regional environmental change. Although several studies have analyzed the shift of warming trends on this plateau within the context of a recent global warming “hiatus” since 1998, their disparate findings have hindered a comprehensive and regional understanding. Based on the daily mean temperature (Tmean), maximum temperature (Tmax), and minimum temperature (Tmin) collected from meteorological stations on the period of 1961–2017, we re-examined the timing and magnitude of temperature phase change using piecewise linear regression on the mid-south of Tibetan Plateau. The results show that among the trends in regional annual Tmean, Tmax and Tmin, the statistically significant change-point was observed only in annual Tmax (p < 0.01). The warming trend of annual Tmax has accelerated significantly since 1992 and has exceeded that of annual Tmin after 2000, causing a remarkable reversal from decline to increase in diurnal temperature range (DTR) (p < 0.01). Spatially, the occurrence time of change-points in Tmean, Tmax, and Tmin varied among stations, but most of them occurred before the mid-1990s. Besides, the trend shifts in Tmax/DTR during the cold season played a primary role in the significant trend shifts in annual Tmax/DTR. This study underscores that there is no significant shift of warming trends over the last two decades on the mid-south of Tibetan Plateau.

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