The impact of convective overshooting on the thermal structure over the Tibetan Plateau in summer based on TRMM, COSMIC, radiosonde and reanalysis data

AbstractIn this paper, we examine convective overshooting and its effects on the thermal structure of the troposphere and lower stratosphere in the Tibetan Plateau in summer by matching the Tropical Rainfall Measuring Mission (TRMM) with Integrated Global Radiosonde Archive (IGRA), Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC), European Centre for Medium-Range Weather Forecasts 5th Reanalysis (ERA-5), the Japanese Meteorological Association 55-year reanalysis (JRA-55) and the National Aeronautics and Space Administration Modern-Era Retrospective analysis for Research and Applications, Versions2 (MERRA-2). It was found that convective overshooting mainly occurs in the central and eastern part of the Tibetan Plateau, and its frequency varies from 0.01 × 10−4 to 0.91 × 10−4. The convective overshooting warms the low middle tropopause and cools the tropopause nearby significantly, which can also makes air get wetter. The tropopause of the convective overshooting is substantially lower than the mean tropopause. Statistical results calculated from the five datasets are generally consistent; however, each dataset has its own strengths and weaknesses. The high spatiotemporal resolution temperature profiles from ERA-5 along with the high vertical resolution temperature profiles from COSMIC can be combined to accurately study convective overshooting in the Tibetan Plateau.

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Bayesian Assimilation of Multiscale Precipitation Data and Sparse Ground Gauge Observations in Mountainous Areas

Journal of Hydrometeorology ◽

10.1175/jhm-d-18-0218.1 ◽

2019 ◽

Vol 20 (8) ◽

pp. 1473-1494 ◽

Cited By ~ 2

Author(s):

Yuhan Wang ◽

Jinsong Chen ◽

Dawen Yang

Keyword(s):

Tibetan Plateau ◽

Large Scale ◽

Daily Precipitation ◽

Tropical Rainfall Measuring Mission ◽

Reanalysis Data ◽

Satellite Observations ◽

The Tibetan Plateau ◽

Precipitation Data ◽

Mountainous Areas ◽

Terrain Effects

Abstract Estimating the spatial distribution of precipitation is important for understanding ecohydrological processes at catchment scales. However, this estimation is difficult in mountainous areas because ground-based observation stations are often sparsely located and do not represent the spatial variability of precipitation. In this study, we develop a Bayesian assimilation method based on data collected on the Tibetan Plateau from 1980 to 2014 to estimate monthly and daily precipitation. To accomplish this, point-scale ground meteorological observations are combined with large-scale precipitation data such as satellite observations or reanalysis data. First, we remove the terrain effects from ground observations by fitting the precipitation data as functions of elevation, and then we spatially interpolate the residuals to 5-km-resolution grids to obtain monthly and daily precipitation. Additionally, we use Tropical Rainfall Measuring Mission (TRMM) satellite observations and ERA-Interim reanalysis data. Cross-validation methods are used to evaluate our method; the results show that our method not only captures the change in precipitation with terrain but also significantly reduces the associated uncertainty. The improvements are more evident in the main river source areas on the edge of the Tibetan Plateau, where elevation changes dramatically, and in high-altitude areas, where the ground gauges are sparse compared with those in low-altitude areas. Our assimilation method is applicable to other regions and is particularly useful for mountainous watersheds where ground meteorological stations are sparse and precipitation is considerably influenced by terrain.

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Spatio-Temporal Variation Characteristics of Snow Depth and Snow Cover Days over the Tibetan Plateau

Water ◽

10.3390/w13030307 ◽

2021 ◽

Vol 13 (3) ◽

pp. 307

Author(s):

Chi Zhang ◽

Naixia Mou ◽

Jiqiang Niu ◽

Lingxian Zhang ◽

Feng Liu

Keyword(s):

Tibetan Plateau ◽

Snow Cover ◽

Snow Depth ◽

Feedback Effect ◽

Effect Of Temperature ◽

The Tibetan Plateau ◽

Reanalysis Dataset ◽

Spatio Temporal ◽

The Impact ◽

Main Factor

Changes in snow cover over the Tibetan Plateau (TP) have a significant impact on agriculture, hydrology, and ecological environment of surrounding areas. This study investigates the spatio-temporal pattern of snow depth (SD) and snow cover days (SCD), as well as the impact of temperature and precipitation on snow cover over TP from 1979 to 2018 by using the ERA5 reanalysis dataset, and uses the Mann–Kendall test for significance. The results indicate that (1) the average annual SD and SCD in the southern and western edge areas of TP are relatively high, reaching 10 cm and 120 d or more, respectively. (2) In the past 40 years, SD (s = 0.04 cm decade−1, p = 0.81) and SCD (s = −2.3 d decade−1, p = 0.10) over TP did not change significantly. (3) The positive feedback effect of precipitation is the main factor affecting SD, while the negative feedback effect of temperature is the main factor affecting SCD. This study improves the understanding of snow cover change and is conducive to the further study of climate change on TP.

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The impact of atmospheric stability and wind shear on vertical cloud overlap over the Tibetan Plateau

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-7329-2018 ◽

2018 ◽

Vol 18 (10) ◽

pp. 7329-7343 ◽

Cited By ~ 8

Author(s):

Jiming Li ◽

Qiaoyi Lv ◽

Bida Jian ◽

Min Zhang ◽

Chuanfeng Zhao ◽

...

Keyword(s):

Tibetan Plateau ◽

Wind Shear ◽

Cloud Cover ◽

Atmospheric Stability ◽

Length Scale ◽

The Tibetan Plateau ◽

Total Cloud Cover ◽

Atmospheric Models ◽

The Impact ◽

Overlap Parameter

Abstract. Studies have shown that changes in cloud cover are responsible for the rapid climate warming over the Tibetan Plateau (TP) in the past 3 decades. To simulate the total cloud cover, atmospheric models have to reasonably represent the characteristics of vertical overlap between cloud layers. Until now, however, this subject has received little attention due to the limited availability of observations, especially over the TP. Based on the above information, the main aim of this study is to examine the properties of cloud overlaps over the TP region and to build an empirical relationship between cloud overlap properties and large-scale atmospheric dynamics using 4 years (2007–2010) of data from the CloudSat cloud product and collocated ERA-Interim reanalysis data. To do this, the cloud overlap parameter α, which is an inverse exponential function of the cloud layer separation D and decorrelation length scale L, is calculated using CloudSat and is discussed. The parameters α and L are both widely used to characterize the transition from the maximum to random overlap assumption with increasing layer separations. For those non-adjacent layers without clear sky between them (that is, contiguous cloud layers), it is found that the overlap parameter α is sensitive to the unique thermodynamic and dynamic environment over the TP, i.e., the unstable atmospheric stratification and corresponding weak wind shear, which leads to maximum overlap (that is, greater α values). This finding agrees well with the previous studies. Finally, we parameterize the decorrelation length scale L as a function of the wind shear and atmospheric stability based on a multiple linear regression. Compared with previous parameterizations, this new scheme can improve the simulation of total cloud cover over the TP when the separations between cloud layers are greater than 1 km. This study thus suggests that the effects of both wind shear and atmospheric stability on cloud overlap should be taken into account in the parameterization of decorrelation length scale L in order to further improve the calculation of the radiative budget and the prediction of climate change over the TP in the atmospheric models.

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Simulations of the Impact of Lakes on Local and Regional Climate Over the Tibetan Plateau

ATMOSPHERE-OCEAN ◽

10.1080/07055900.2017.1401524 ◽

2017 ◽

Vol 56 (4) ◽

pp. 230-239 ◽

Cited By ~ 7

Author(s):

Lingjing Zhu ◽

Jiming Jin ◽

Xin Liu ◽

Lei Tian ◽

Qunhui Zhang

Keyword(s):

Tibetan Plateau ◽

Regional Climate ◽

The Tibetan Plateau ◽

The Impact

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The impact of atmospheric dynamics on vertical cloud overlap over the Tibetan Plateau

10.5194/acp-2017-642 ◽

2017 ◽

Author(s):

Jiming Li ◽

Qiaoyi Lv ◽

Bida Jian ◽

Min Zhang ◽

Chuanfeng Zhao ◽

...

Keyword(s):

Tibetan Plateau ◽

Wind Shear ◽

Cloud Cover ◽

Atmospheric Stability ◽

Separation Distance ◽

Atmospheric Dynamics ◽

The Tibetan Plateau ◽

Total Cloud Cover ◽

The Impact ◽

Overlap Parameter

Abstract. The accurate representation of cloud vertical overlap in atmospheric models is particularly significant for predicting the total cloud cover and for the calculations related to the radiative budget in these models. However, it has received too little attention due to the limited observation, especially over the Tibetan Plateau (TP). In this study, 4 years (2007–2010) of data from the CloudSat cloud product and collocated ERA-Interim reanalysis product were analyzed to examine the seasonal and zonal variations of cloud overlap properties over the TP region, and evaluate the effect of atmospheric dynamics on cloud overlap. Unique characteristics of cloud overlap over the TP have been found. The statistical results show that the random overlap assumption slightly underestimates the total cloud coverage for discontinuous cloud layers over the TP, whereas the overlap parameter α for continuous cloud sharply decrease from maximum to random overlap with an increase of layer distance, eventually trending towards a minimal overlap (e.g., negative α values) as the cloud layer separation distance exceeds 1.5 km. Compared with the global averaged cloud overlap characteristics, the proportion of minimal overlap over the TP is significant high (about 41 %). It may be associated with the unique topographical forcing and thermos-dynamical environment of the TP. As a result, we propose a valid scheme for quantifying the degree of cloud overlap over the TP through a linear combination of the maximum and minimum overlap, and further parameterize decorrelation length scale L as a function of wind shear and atmospheric stability. Compared with other parameterizations, the new scheme reduces the bias between predicted and observed cloud covers. These results thus indicate that effects of wind shear and atmospheric stability on cloud overlap should both be taken into account in the parameterization of overlap parameter to improve the simulation of total cloud cover in models.

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Plants and Microbes Mediate the Shift in Ecosystem Multifunctionality From Low to High Patterns Across Alpine Grasslands on the Tibetan Plateau

Frontiers in Plant Science ◽

10.3389/fpls.2021.760599 ◽

2021 ◽

Vol 12 ◽

Author(s):

Yi Wang ◽

Miao Liu ◽

Youchao Chen ◽

Tao Zeng ◽

Xuyang Lu ◽

...

Keyword(s):

Tibetan Plateau ◽

Correlation Coefficients ◽

Terrestrial Ecosystems ◽

Alpine Grassland ◽

Future Climate Change ◽

The Tibetan Plateau ◽

Grassland Ecosystem ◽

The Impact ◽

Ecosystem Multifunctionality ◽

Alpine Grassland Ecosystem

Both plant communities and soil microbes have been reported to be correlated with ecosystem multifunctionality (EMF) in terrestrial ecosystems. However, the process and mechanism of aboveground and belowground communities on different EMF patterns are not clear. In order to explore different response patterns and mechanisms of EMF, we divided EMF into low (<0) and high patterns (>0). We found that there were contrasting patterns of low and high EMF in the alpine grassland ecosystem on the Tibetan Plateau. Specifically, compared with low EMF, environmental factors showed higher sensitivity to high EMF. Soil properties are critical factors that mediate the impact of community functions on low EMF based on the change of partial correlation coefficients from 0 to 0.24. In addition, plant community functions and microbial biomass may mediate the shift of EMF from low to high patterns through the driving role of climate across the alpine grassland ecosystem. Our findings will be vital to clarify the mechanism for the stability properties of grassland communities and ecosystems under ongoing and future climate change.

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Characteristics of Deep Convective Systems and Initiation during Warm Seasons over China and Its Vicinity

Remote Sensing ◽

10.3390/rs13214289 ◽

2021 ◽

Vol 13 (21) ◽

pp. 4289

Author(s):

Yang Li ◽

Yubao Liu ◽

Yun Chen ◽

Baojun Chen ◽

Xin Zhang ◽

...

Keyword(s):

Tibetan Plateau ◽

South China ◽

Warm Season ◽

Statistical Characteristics ◽

The Tibetan Plateau ◽

Spatiotemporal Resolution ◽

Convective Systems ◽

Seasonal And Diurnal Variations ◽

Deep Convective Systems ◽

Guizhou Plateau

The spatiotemporal statistical characteristics of warm-season deep convective systems, particularly deep convective systems initiation (DCSI), over China and its vicinity are investigated using Himawari-8 geostationary satellite measurements collected during April-September from 2016 to 2020. Based on a satellite brightness temperature multiple-threshold convection identification and tracking method, a total of 47593 deep convective systems with lifetimes of at least 3 h were identified in the region. There are three outstanding local maxima in the region, located in the southwestern, central and eastern Tibetan Plateau and Yunnan-Guizhou Plateau, followed by a region of high convective activities in South China. Most convective systems are developed over the Tibetan Plateau, predominantly eastward-moving, while those developed in Yunnan-Guizhou Plateau and South China mostly move westward and southwestward. The DSCI occurrences become extremely active after the onset of the summer monsoon and tend to reach a maximum in July and August, with a diurnal peak at 11–13 LST in response to the enhanced solar heating and monsoon flows. Several DCSI hotspots are identified in the regions of inland mountains, tropical islands and coastal mountains during daytime, but in basins, plains and coastal areas during nighttime. DCSI over land and oceans exhibits significantly different sub-seasonal and diurnal variations. Oceanic DCSI has an ambiguous diurnal variation, although its sub-seasonal variation is similar to that over land. It is demonstrated that the high spatiotemporal resolution satellite dataset provides rich information for understanding the convective systems over China and vicinity, particularly the complex terrain and oceans where radar observations are sparse or none, which will help to improve the convective systems and initiation nowcasting.

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The South Asia Monsoon Break Promotes Grass Growth on the Tibetan Plateau

10.5194/egusphere-egu21-5776 ◽

2021 ◽

Author(s):

Yanghang Ren ◽

Kun Yang ◽

Han Wang

Keyword(s):

Soil Moisture ◽

Tibetan Plateau ◽

Solar Radiation ◽

Climate Variability ◽

South Asia ◽

The Tibetan Plateau ◽

The South ◽

Central Eastern ◽

Grass Growth ◽

The Impact

<p>As region that is highly sensitive to global climate change, the Tibetan Plateau (TP) experiences an intra-seasonal soil water deficient due to the reduced precipitation during the South Asia monsoon (SAM) break. Few studies have investigated the impact of the SAM break on TP ecological processes, although a number of studies have explored the effects of inter-annual and decadal climate variability. In this study, the response of vegetation activity to the SAM break was investigated. The data used are: (1) soil moisture from in situ, satellite remote sensing and data assimilation; and (2) the Normalized Difference Vegetation Index (NDVI) and Solar-Induced chlorophyll Fluorescence&#160;(SIF). We found that in the region impacted by SAM break, which is distributed in the central-eastern part of TP, photosynthesis become more active during the SAM break. And temporal variability in the photosynthesis of this region is controlled mainly by solar radiation variability and has little sensitivity to soil moisture. We adopted a diagnostic process-based modeling approach to examine the causes of enhanced plant activity during the SAM break on the central-eastern TP. Our analysis indicates that active photosynthetic behavior in the reduced precipitation is stimulated by increases in solar radiation absorbed and temperature. This study highlights the importance of sub-seasonal climate variability for characterizing the relationship between vegetation and climate.</p>

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<sup>10</sup>Be systematics in the Tsangpo-Brahmaputra catchment: the cosmogenic nuclide legacy of the eastern Himalayan syntaxis

10.5194/esurf-2017-18 ◽

2017 ◽

Author(s):

Maarten Lupker ◽

Jérôme Lavé ◽

Christian France-Lanord ◽

Marcus Christl ◽

Didier Bourlès ◽

...

Keyword(s):

Tibetan Plateau ◽

Sediment Flux ◽

Coarse Grained ◽

The Tibetan Plateau ◽

Data Set ◽

Denudation Rate ◽

Cosmogenic Nuclide ◽

Denudation Rates ◽

The Impact ◽

Eastern Himalayan Syntaxis

Abstract. The Tsangpo-Brahmaputra River drains the eastern part of the Himalayan range, flowing from the Tibetan Plateau through the eastern Himalayan syntaxis and downstream to the Indo-Gangetic floodplain. As such it is a unique natural laboratory to study how denudation and sediment production processes are transferred to river detrital signals. In this study, we present a new 10Be data set to constrain denudation rates across the catchment and to quantify the impact of rapid erosion within the syntaxis region on cosmogenic nuclide budgets and signals. 10Be denudation rates span around two orders of magnitude across the catchments (ranging from 0.03 mm/yr to > 4 mm/yr) and sharply increase as the Tsangpo-Brahmaputra flows across the eastern Himalaya. The increase in denudation rates however occurs ~ 150 km downstream of the Namche Barwa-Gyala Peri massif (NBGPm), an area which has been previously characterized by extremely high erosion and exhumation rates. We suggest that this downstream lag is mainly due to the physical abrasion of coarse grained, low 10Be concentration, landslide material produced within the syntaxis that dilutes the upstream high concentration 10Be flux from the Tibetan Plateau only after abrasion has transferred sediment to the studied sand fraction. A simple abrasion model produces typical lag distances of 50 to 150 km compatible with our observations. Abrasion effects reduce the spatial resolution over which denudation can be constrained in the eastern Himalayan syntaxis. In addition, we also highlight that denudation rate estimates are dependent on the sediment connectivity, storage and quartz content of the upstream Tibetan Plateau part of the catchment which tends to lead to an overestimation of downstream denudations rates. Taking these effects into account we estimate a denudation rates of ca. 2 to 5 mm/yr for the entire syntaxis and ca. 4 to 28 mm/yr for the NBGPm, which is significantly higher than other to other large catchments. Overall, 10Be concentrations measured at the outlet of the Tsangpo-Brahmaputra in Bangladesh suggest a sediment flux between 780 and 1430 Mt/yr equivalent to a denudation rate between 0.7 and 1.2 mm/yr for the entire catchment.

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Evaluation of Noah-MP Land-Model Uncertainties over Sparsely Vegetated Sites on the Tibet Plateau

Atmosphere ◽

10.3390/atmos11050458 ◽

2020 ◽

Vol 11 (5) ◽

pp. 458

Author(s):

Guo Zhang ◽

Fei Chen ◽

Yueli Chen ◽

Jianduo Li ◽

Xindong Peng

Keyword(s):

Heat Flux ◽

Organic Matter ◽

Soil Organic Matter ◽

Tibetan Plateau ◽

Sensible Heat Flux ◽

Limiting Factors ◽

Tibet Plateau ◽

The Tibetan Plateau ◽

Annual Total ◽

The Impact

The water budget and energy exchange over the Tibetan Plateau (TP) region play an important role on the Asian monsoon. However, it is not well presented in the current land surface models (LSMs). In this study, uncertainties in the Noah with multiparameterization (Noah-MP) LSM are assessed through physics ensemble simulations in three sparsely vegetated sites located in the central TP. The impact of soil organic matter on energy flux and water cycles, along with the influence of uncertainties in precipitation are explored using observations at those sites during the third Tibetan Plateau Experiment from 1August2014 to31July2015. The greatest uncertainties are in the subprocesses of the canopy resistance, soil moisture limiting factors for evaporation, runoff (RNF) and ground water, and surface-layer parameterization. These uncertain subprocesses do not change across the different precipitation datasets. More precipitation can increase the annual total net radiation (Rn), latent heat flux (LH) and RNF, but decrease sensible heat flux (SH). Soil organic matter enlarges the annual total LH by ~26% but lessens the annual total Rn, SH, and RNF by ~7%, 7%, and 39%, respectively. Its effect on the LH and RNF at the Nagqu site, which has a sand soil texture type, is greater than that at the other two sites with sandy loam. This study highlights the importance of precipitation uncertainties and the effect of soil organic matter on the Noah-MP land-model simulations. It provides a guidance to improve the Noah-MP LSM further and hence the land-atmosphere interactions simulated by weather and climate models over the TP region.

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