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

2018 ◽  
Vol 10 (10) ◽  
pp. 1534 ◽  
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.

A Spatial and Temporal Continuum Remotely Sensed Soil Moisture Dataset of the Tibet Plateau From 2002 to 2015

2020 ◽  
Author(s):  
Yaokui Cui ◽  
Chao Zeng ◽  
Jie Zhou ◽  
Xi Chen
Keyword(s):  
Soil Moisture ◽  
Tibetan Plateau ◽  
Land Surface ◽  
European Space Agency ◽  
Remotely Sensed ◽  
General Regression Neural Network ◽  
Tibet Plateau ◽  
The Tibetan Plateau ◽  
Space Agency ◽  
Spatio Temporal

<p><strong>Abstract</strong>:</p><p>Surface soil moisture plays an important role in the exchange of water and energy between the land surface and the atmosphere, and critical to climate change study. The Tibetan Plateau (TP), known as “The third pole of the world” and “Asia’s water towers”, exerts huge influences on and sensitive to global climates. Long time series of and spatio-temporal continuum soil moisture is helpful to understand the role of TP in this situation. In this study, a dataset of 14-year (2002–2015) Spatio-temporal continuum remotely sensed soil moisture of the TP at 0.25° resolution is obtained, combining MODIS optical products and ESA (European Space Agency) ECV (Essential Climate Variable) combined soil moisture products based on General Regression Neural Network (GRNN). The validation of the dataset shows that the soil moisture is well reconstructed with R<sup>2</sup> larger than 0.65, and RMSE less than 0.08 cm<sup>3</sup> cm<sup>-3</sup> and Bias less than 0.07 cm<sup>3</sup> cm<sup>-3 </sup>at 0.25° and 1° spatial scale, compared with the in-situ measurements in the central of TP. And then, spatial and temporal characteristics and trend of SM over TP were analyzed based on this dataset.</p><p><strong>Keywords: </strong>Soil moisture; Remote Sensing; Dataset; GRNN; ECV; Tibetan Plateau</p>

scholarly journals Variations of Lake Ice Phenology on the Tibetan Plateau From 2001 to 2017 Based on MODIS Data

2019 ◽  
Vol 124 (2) ◽  
pp. 825-843 ◽  
Author(s):  
Yu Cai ◽  
Chang‐Qing Ke ◽  
Xingong Li ◽  
Guoqing Zhang ◽  
Zheng Duan ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
The Tibetan Plateau ◽  
Lake Ice ◽  
Modis Data ◽  
Ice Phenology

Detecting evapotranspiration biases in reanalyses and regional climate modeling

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

<p>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.</p><p>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.</p>

scholarly journals The Impact of Preceding Spring Antarctic Oscillation on the Variations of Lake Ice Phenology over the Tibetan Plateau

2020 ◽  
Vol 33 (2) ◽  
pp. 639-656 ◽  
Author(s):  
Yong Liu ◽  
Huopo Chen ◽  
Huixin Li ◽  
Huijun Wang
Keyword(s):  
Climate Change ◽  
Tibetan Plateau ◽  
North Atlantic ◽  
The Tibetan Plateau ◽  
Antarctic Oscillation ◽  
Lake Ice ◽  
The North ◽  
The North Atlantic ◽  
Sst Anomalies ◽  
Ice Phenology

ABSTRACTThe lake ice phenology response to climate change has been receiving growing concern in recent years. However, most studies have put emphasis on the spatial and temporal variability of lake ice phenology, and relatively few studies have been devoted to investigating the physical mechanisms of changes in lake ice phenology from the perspective of climatic dynamics. This study investigates the possible impact of the Antarctic Oscillation (AAO) on the variations in lake ice phenology over the Tibetan Plateau (TP). The results show that there is an intimate relationship between the AAO and the variations in break-up/ice duration during the period 2003–15. Further analysis indicates that the preceding boreal spring AAO-induced atmospheric circulation anomalies are favorable for generating tropical South Atlantic Ocean SST anomalies through air–sea interaction. Then the tropical SST anomalies strengthen the anomalous local-scale meridional–vertical circulation that projects into the Azores high and further induce the extratropical portion of the North Atlantic SST tripole. The anomalous warm core in the North Atlantic serves as the source of wave activity flux and stimulates a stationary wave train along the Eurasian continent to change the downstream atmospheric circulation. As a response, an abnormal cyclone and enhanced updraft are triggered over the TP, which are favorable for the formation of snowfall and then lower the surface air temperature according to the snow-albedo feedback mechanism, and thus result in the prolonged lake ice duration events. This study provides a new insight to link the AAO influence and climate over the TP and is helpful to understand the changes in lake ice phenology in response to climate change in recent years.

scholarly journals Synthesis method for simulating snow distribution utilizing remotely sensed data for the Tibetan Plateau

2014 ◽  
Vol 8 (1) ◽  
pp. 084696 ◽  
Author(s):  
Hongyi Li ◽  
Zhiguang Tang ◽  
Jian Wang ◽  
Tao Che ◽  
Xiaoduo Pan ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Synthesis Method ◽  
Remotely Sensed ◽  
The Tibetan Plateau ◽  
Remotely Sensed Data ◽  
Snow Distribution

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

2020 ◽  
Vol 12 (24) ◽  
pp. 4150
Author(s):  
Zhipeng Wang ◽  
Jianshuang Wu ◽  
Ben Niu ◽  
Yongtao He ◽  
Jiaxing Zu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Land Cover ◽  
Land Surface ◽  
Large Scale ◽  
Regional Climate ◽  
Expansion Rate ◽  
The Tibetan Plateau ◽  
Vegetation Monitoring ◽  
Climate Conditions ◽  
Vegetation Expansion

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.

Evaluation of Winter Precipitation Products over the Tibetan Plateau with the Sublimation derived from Remotely Sensed Snow Cover Data

2020 ◽  
Author(s):  
Hui Lu ◽  
Junhua Zhou ◽  
Kun Yang
Keyword(s):  
Tibetan Plateau ◽  
Snow Cover ◽  
Land Surface ◽  
Remotely Sensed ◽  
Winter Precipitation ◽  
Area Ratio ◽  
Observation Data ◽  
The Tibetan Plateau ◽  
China Meteorological Administration ◽  
Statistical Area

<p>Many model results showed obvious wet biases during winter while the simulation was good during summer over the Tibetan Plateau (TP). Low gauge density and the limited capacity of snowfall may introduce dry biases into the observation and then exaggerate the overestimation of winter precipitation. To evaluate the winter precipitation products over the TP, we compared six precipitation products, including TRMM, ERA5, ERA-Interim, GLDAS, HAR, and the observation provided by China Meteorological Administration (CMA), against a sublimation dataset derived from remotely sensed snow cover data. The Kuzmin formula constrained with IMS snow cover product and land surface temperature was used to estimate sublimation. To ensure the reliability of the sublimation value, the accuracy of the simulated sublimation value was verified by the sublimation value observed at the pass area of Dadongshu Station and the consistency of two snow cover products was verified by using MODIS daily cloud-free snow cover products over the Tibetan Plateau.</p><p>The comparison revealed that the average underestimated area ratio of CMA on the TP and the Inner TP respectively were about 60% and 90%. CMA has an obvious underestimation (80% region showed underestimation and precipitation underestimation ratio mostly more than 100%) in the west of TP where lack of observation site. However, there was not obvious underestimation in East TP because of the dense stations available. It implies that the observation data has considerable dry biases (~200%) in winter precipitation over the Western TP where more ground stations are needed to get a reliable precipitation observation. For other precipitation products, HAR showed the smallest underestimation with a 12% region of precipitation underestimation. ERA5 and ERA-Interim are close behind HAR, but the underestimation area ratio of ERA5 was about 15% smaller than ERA-Interim in each statistical area of TP. TRMM and GLDAS show comparable underestimation and both are more apparent than ERA-interim. The underestimation phenomenon of TRMM shows little difference in the western and eastern TP and the underestimated area ratio of TRMM was 64.68% on the TP.</p>

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