Vegetation Expansion on the Tibetan Plateau and Its Relationship with Climate Change

The natural shift in land cover from non-vegetated to vegetated land is termed as vegetation expansion, which has substantial impacts on regional climate conditions and land surface energy balance. Barrens dominate the northwestern Tibetan Plateau, where vegetation is predicted to expand northwestward with the ongoing climate warming. However, rare studies have confirmed such a forecast with large-scale vegetation monitoring. In this study, we used a landcover dataset, classified according to the International Geosphere–Biosphere Program criteria, to examine previous model-based predictions and the role of climate on the expansion rate across the plateau. Our results showed that shrublands, open forests, grasslands, and water bodies expanded while evergreen and deciduous broadleaf forests, croplands and barrens shrank during the period 2001–2018. Vegetation expanded by 33,566 km2 accounting for about 1.3% of the total area of this plateau and the land cover shifting from barrens to grasslands was the primary way of vegetation expansion. Spatially, the vegetation expanded northwestward to lands with colder, drier, and more radiation in the climate. Increasing precipitation positively correlated with the vegetation expansion rate for the arid and semi-arid northwest Tibetan Plateau and warming contributed to the vegetation expanding in the semi-humid southeast Tibetan Plateau. Our results verified the predictions of models and highlighted the “greening” on barrens in recent years.

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Uncertainty and Variation of Remotely Sensed Lake Ice Phenology across the Tibetan Plateau

Remote Sensing ◽

10.3390/rs10101534 ◽

2018 ◽

Vol 10 (10) ◽

pp. 1534 ◽

Cited By ~ 8

Author(s):

Linan Guo ◽

Yanhong Wu ◽

Hongxing Zheng ◽

Bing Zhang ◽

Junsheng Li ◽

...

Keyword(s):

Tibetan Plateau ◽

Land Surface ◽

Regional Climate ◽

Local Environment ◽

Remotely Sensed ◽

The Tibetan Plateau ◽

Remotely Sensed Data ◽

Lake Ice ◽

Reflectance Data ◽

Ice Phenology

In the Tibetan Plateau (TP), the changes of lake ice phenology not only reflect regional climate change, but also impose substantial ecohydrological impacts on the local environment. Due to the limitation of ground observation, remote sensing has been used as an alternative tool to investigate recent changes of lake ice phenology. However, uncertainties exist in the remotely sensed lake ice phenology owing to both the data and methods used. In this paper, three different remotely sensed datasets are used to investigate the lake ice phenology variation in the past decade across the Tibetan Plateau, with the consideration of the underlying uncertainties. The remotely sensed data used include reflectance data, snow product, and land surface temperature (LST) data of moderate resolution imaging spectroradiometer (MODIS). The uncertainties of the three methods based on the corresponding data are assessed using the triple collocation approach. Comparatively, it is found that the method based on reflectance data outperforms the other two methods. The three methods are more consistent in determining the thawing dates rather than the freezing dates of lake ice. It is consistently shown by the three methods that the ice-covering duration in the northern part of the TP lasts longer than that in the south. Though there is no general trend of lake ice phenology across the TP for the period of 2000–2015, the warmer climate and stronger wind have led to the earlier break-up of lake ice.

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Modeling the influence of land surface flux on the regional climate of the Tibetan Plateau

Theoretical and Applied Climatology ◽

10.1007/s00704-015-1495-x ◽

2015 ◽

Vol 125 (1-2) ◽

pp. 45-52 ◽

Cited By ~ 7

Author(s):

Weiqiang Ma ◽

Yaoming Ma

Keyword(s):

Tibetan Plateau ◽

Land Surface ◽

Regional Climate ◽

Surface Flux ◽

The Tibetan Plateau

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Quantification of the relative role of land-surface processes and large-scale forcing in dynamic downscaling over the Tibetan Plateau

Climate Dynamics ◽

10.1007/s00382-016-3168-6 ◽

2016 ◽

Vol 48 (5-6) ◽

pp. 1705-1721 ◽

Cited By ~ 31

Author(s):

Yanhong Gao ◽

Linhong Xiao ◽

Deliang Chen ◽

Fei Chen ◽

Jianwei Xu ◽

...

Keyword(s):

Tibetan Plateau ◽

Land Surface ◽

Large Scale ◽

Surface Processes ◽

The Tibetan Plateau ◽

Relative Role ◽

Dynamic Downscaling ◽

Land Surface Processes

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Impact of Initialized Land Surface Temperature and Snowpack on Subseasonal to Seasonal Prediction Project, Phase I (LS4P-I): Organization and Experimental design

10.5194/gmd-2020-329 ◽

2021 ◽

Author(s):

Yongkang Xue ◽

Tandong Yao ◽

Aaron A. Boone ◽

Ismaila Diallo ◽

Ye Liu ◽

...

Keyword(s):

Tibetan Plateau ◽

Surface Temperature ◽

Land Surface Temperature ◽

Land Surface ◽

Large Scale ◽

Initial Conditions ◽

Yangtze River Basin ◽

Seasonal Prediction ◽

High Mountain ◽

The Tibetan Plateau

Abstract. Sub-seasonal to seasonal (S2S) prediction, especially the prediction of extreme hydroclimate events such as droughts and floods, is not only scientifically challenging but has substantial societal impacts. Motivated by preliminary studies, the Global Energy and Water Exchanges (GEWEX)/Global Atmospheric System Study (GASS) has launched a new initiative called Impact of initialized Land Surface temperature and Snowpack on Sub-seasonal to Seasonal Prediction (LS4P), as the first international grass-root effort to introduce spring land surface temperature (LST)/subsurface temperature (SUBT) anomalies over high mountain areas as a crucial factor that can lead to significant improvement in precipitation prediction through the remote effects of land/atmosphere interactions. LS4P focuses on process understanding and predictability, hence it is different from, and complements, other international projects that focus on the operational S2S prediction. More than forty groups worldwide have participated in this effort, including 21 Earth System Models, 9 regional climate models, and 7 data groups. This paper overviews the history and objectives of LS4P, provides the first phase experimental protocol (LS4P-I) which focuses on the remote effect of the Tibetan Plateau, discusses the LST/SUBT initialization, and presents the preliminary results. Multi-model ensemble experiments and analyses of observational data have revealed that the hydroclimatic effect of the spring LST in the Tibetan Plateau is not limited to the Yangtze River basin but may have a significant large-scale impact on summer precipitation and its S2S prediction. LS4P models are unable to preserve the initialized LST anomalies in producing the observed anomalies largely for two main reasons: i) inadequacies in the land models arising from total soil depths which are too shallow and the use of simplified parameterizations which both tend to limit the soil memory; and ii) reanalysis data, that are used for initial conditions, have large discrepancies from the observed mean state and anomalies of LST over the Tibetan Plateau. Innovative approaches have been developed to largely overcome these problems.

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Detecting evapotranspiration biases in reanalyses and regional climate modeling

10.5194/egusphere-egu21-7076 ◽

2021 ◽

Author(s):

Jingyu Dan ◽

Yanhong Gao

Keyword(s):

Tibetan Plateau ◽

Land Surface ◽

Water Cycle ◽

Climate Modeling ◽

Global Climate ◽

Monsoon Season ◽

Regional Climate ◽

Horizontal Resolution ◽

The Tibetan Plateau ◽

Free Atmosphere

As the highest plateau in the world, the Tibetan Plateau (TP) exerts great impacts on regional and global climate and water cycle through interactions between land and free atmosphere. Terrestrial evapotranspiration is a critical component of the Earth's water cycle. To better understand the heterogeneity of the evapotranspiration over the Tibetan Plateau and its influences, we conducted a whole year dynamical downscale modelling (DDM) with the horizontal resolution at 28km and a convection permitting modelling (CPM) at 4km for 2014. DDM and CPM simulation results are compared with an satellite retrieving dataset, which is referred as OBS in the following, the global land surface data assimilation system (GLDAS) and two commonly used reanalyses ERA-Interim and ERA5, as well. The annual and seasonal means and seasonal variabilities are inter-compared. The evapotranspiration over ten dominant land use types are investigated based on six datasets. Differences with the satellite dataset are illustrated and relationships with soil moisture and temperature, precipitation and radiation are explored. The followings are obtained. GLDAS generally reproduces magnitude and pattern of the OBS; reanalyses overestimate, DDM and CPM underestimate compared to the OBS and GLDAS.The overestimations in reanalyses occur in the monsoon season and the underestimations in DDM and CPM occur in the non-monsoon season. Large evapotranspiration biases exist over the vegetated ground which exert large impacts on the TP-average biases for growing season.

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Sensitivity of regional climate simulations to land-surface schemes on the Tibetan Plateau

Climate Research ◽

10.3354/cr01262 ◽

2014 ◽

Vol 62 (1) ◽

pp. 25-43 ◽

Cited By ~ 10

Author(s):

X Wang ◽

M Yang ◽

G Pang

Keyword(s):

Tibetan Plateau ◽

Land Surface ◽

Regional Climate ◽

The Tibetan Plateau ◽

Climate Simulations

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Impacts of the Westerlies on Planetary Boundary Layer Growth Over a Valley on the North Side of the Central Himalayas

10.5194/ems2021-435 ◽

2021 ◽

Author(s):

Xuelong Chen

Keyword(s):

Tibetan Plateau ◽

Wind Direction ◽

Land Surface ◽

Large Scale ◽

Vertical Structure ◽

Surface Wind ◽

The Tibetan Plateau ◽

The North ◽

Synoptic Wind ◽

Synoptic Circulation

The spatial-temporal structure of the Planetary Boundary Layer (PBL) over mountainous areas can be strongly modified by topography. The PBL over the mountainous terrain of the Tibetan Plateau (TP) is more complex than that observed over its flat areas. To date, there have been no detailed analyses which have taken into account the topography effects exerted on PBL growth over the Tibetan Plateau (TP). A clear understanding of the processes involved in the PBL growth and depth over the TP&#8217;s mountainous areas is therefore long overdue.The PBL in the Himalayan region of the Tibetan Plateau (TP) is important to the study of interaction between the area&#8217;s topography and synoptic circulation.This study used radiosonde, in-situ measurements, ERA5 reanalysis dataset and numerical model to investigate the vertical structure of the PBL and the land surface energy balance in the Rongbuk Valley on the north of the central Himalaya, and their association with the Westerlies, which control the climate of the Himalaya in winters. Two sunny November days in 2014 with different synoptic conditions in terms of large-scale wind direction and speed were selected to investigate the ways in which large-scale synoptic forcing affected the vertical structure of the PBL, atmospheric stability, surface wind field, and land surface energy fluxes. The results revealed that the valley winds and PBL growth were strongly influenced by the variations of the westerlies. When the synoptic wind direction at the height of the mountain ridges was parallel to the axis of the valley, the downward transmission of the westerlies to the valley floor (DTWTV) was strong and cause high near-surface wind speeds and sensible heat flux value, then produced an extremely deep PBL (9 km above sea level) in the early afternoon of November 23. When the synoptic wind direction at the ridge height intersected the axis of the valley and was weak, the DTWTV was weak, and the PBL became relatively low on November 28. These results demonstrate that the interaction between the topography and synoptic circulation plays a critical role in PBL growth.

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Impact of Initialized Land Surface Temperature and Snowpack on Subseasonal to Seasonal Prediction Project, Phase I (LS4P-I): organization and experimental design

Geoscientific Model Development ◽

10.5194/gmd-14-4465-2021 ◽

2021 ◽

Vol 14 (7) ◽

pp. 4465-4494

Author(s):

Yongkang Xue ◽

Tandong Yao ◽

Aaron A. Boone ◽

Ismaila Diallo ◽

Ye Liu ◽

...

Keyword(s):

Tibetan Plateau ◽

Surface Temperature ◽

Land Surface Temperature ◽

Land Surface ◽

Large Scale ◽

Initial Conditions ◽

Yangtze River Basin ◽

Seasonal Prediction ◽

High Mountain ◽

The Tibetan Plateau

Abstract. Subseasonal-to-seasonal (S2S) prediction, especially the prediction of extreme hydroclimate events such as droughts and floods, is not only scientifically challenging, but also has substantial societal impacts. Motivated by preliminary studies, the Global Energy and Water Exchanges (GEWEX)/Global Atmospheric System Study (GASS) has launched a new initiative called “Impact of Initialized Land Surface Temperature and Snowpack on Subseasonal to Seasonal Prediction” (LS4P) as the first international grass-roots effort to introduce spring land surface temperature (LST)/subsurface temperature (SUBT) anomalies over high mountain areas as a crucial factor that can lead to significant improvement in precipitation prediction through the remote effects of land–atmosphere interactions. LS4P focuses on process understanding and predictability, and hence it is different from, and complements, other international projects that focus on the operational S2S prediction. More than 40 groups worldwide have participated in this effort, including 21 Earth system models, 9 regional climate models, and 7 data groups. This paper provides an overview of the history and objectives of LS4P, provides the first-phase experimental protocol (LS4P-I) which focuses on the remote effect of the Tibetan Plateau, discusses the LST/SUBT initialization, and presents the preliminary results. Multi-model ensemble experiments and analyses of observational data have revealed that the hydroclimatic effect of the spring LST on the Tibetan Plateau is not limited to the Yangtze River basin but may have a significant large-scale impact on summer precipitation beyond East Asia and its S2S prediction. Preliminary studies and analysis have also shown that LS4P models are unable to preserve the initialized LST anomalies in producing the observed anomalies largely for two main reasons: (i) inadequacies in the land models arising from total soil depths which are too shallow and the use of simplified parameterizations, which both tend to limit the soil memory; (ii) reanalysis data, which are used for initial conditions, have large discrepancies from the observed mean state and anomalies of LST over the Tibetan Plateau. Innovative approaches have been developed to largely overcome these problems.

Download Full-text