Himalayan orogenic belt is the highest and largest continental collision and subduction zone on the Earth. The Himalayan orogenic belt has produced frequent large earthquakes and caused several geohazards due to landslides and housing collapse, having an impact on the safety of life and property along a length of over 2500 km. Here we took three earthquake clusters as examples, which occurred at Nepal Himalaya, eastern Himalayan syntaxis and western Himalayan syntaxis, respectively. Here we calculated the earthquake locations and fault plane solutions based on the waveform data recorded by seismic stations deployed in source areas by the Institute of Tibetan Plateau Research, Chinese Academy of Sciences. We found that at the Nepal Himalayan, the Main Himalayan Thrust is the major tectonic structure for large earthquakes to occur. At the eastern Himalayan syntaxis, most earthquakes are of the reverse or strike-slip faulting. The major tectonic feature is the combination of the NE-dipping thrust with the southeastern escape of the Tibetan plateau. At the western Himalayan syntaxis, intermediate-depth earthquakes are active. These observations reveal the geometry of the deep subduction of the continental plate with steep dipping angle.
Thermokarst lake is the most visible morphologic landscape developing during the process of permafrost degradation, and it is still an international hot topic in permafrost research. The climate warming, and the consequent degradation of the permafrost on the Qinghai-Tibet Plateau aggravate thermokarst lake development. The permafrost is normally considered as an aquiclude, and the permafrost degradation, especially when the permafrost is completely thawed by a thermokarst lake, might influence regional ground water. Therefore, a research program focusing on environmental and hydrological effects of thermokarst lakes in permafrost regions of the Qinghai-Tibet Plateau was started and supported by the National Natural Science Foundation of China. The work proposed by the application includes: To analysis the spatial and temporal distribution rule of thermokarst lakes in the Qinghai-Tibet Engineering Corridor (QTEC) under the climate change and engineering activities, and to evaluate the ecological environment effects through remote sensing and field investigation; to reveal the main factors influencing a typical thermokarst lake and its hydrothermal condition, and to elucidate the conversion relationship between the thermokarst lake and the groundwater with hydrological and isotope tracer tests; to make an analysis of the influences of different lake stage and size on regional permafrost, hydrological conditions and ecological environment through numerical simulation and statistical modelling, considering the relationships between the thermokarst lake and the ground water level. The research results will help to accurately assess regional permafrost ecological environment evolution and trend prediction, and to reasonably understand the impact factors of the permafrost hydrological evolution and its response mechanism to the ecological environment in the river source regions of the Qinghai-Tibet Plateau. In this paper, the research status analysis, the main research contents, research objectives and prospects were introduced so as to provide some references for related researchers and engineers.
Permafrost changes under natural sites along the Qinghai-Tibet Railway were investigated based on the ground temperature monitored from the year of 2006 to 2015. Among these sites, mean permafrost table was 3.54 m, with a range of 0.88 to 9.14 m. Among the sites with decreasing permafrost table, mean decreasing amplitude of permafrost table was 0.51 m, with a range of 0.05 to 2.22 m; mean decreasing rate of permafrost table was 0.07 m/a, with a range of 0.01 to 0.25 m/a. Decreasing amplitude and decreasing rate of permafrost table in high temperature regions were 0.47 m and 0.06 m/a greater than those in low temperature regions, respectively. In general, ground temperatures at permafrost table and 15 m depth presented rising tendency. Mean rising amplitude of ground temperature at permafrost table was 0.16 ℃, with a range of 0.01 to 0.60 ℃; mean rising rate of ground temperature at permafrost table was 0.018 ℃/a, with a range of 0.001 to 0.067 ℃/a. Rising amplitude and rising rate of ground temperature at permafrost table in low temperature regions were 0.12 ℃ and 0.014 ℃/a greater than those in high temperature regions, respectively. Mean rising amplitude of ground temperature at 15 m depth was 0.10 ℃, with a range of 0.01 to 0.48 ℃; mean rising rate of ground temperature at 15 m depth was 0.011 ℃/a, with a range of 0.002 to 0.054 ℃/a. Rising amplitude and rising rate of ground temperature at 15 m depth in low temperature regions were 0.11 ℃ and 0.012 ℃/a greater than those in high temperature regions, respectively. Due to the effect of local factors, increasing of permafrost table and decreasing of ground temperature were observed under several sites.
The Eastern Kunlun fault zone (EKLF) is a large left-lateral strike-slip fault, whose slip rate is meaningful to seismic hazard assessment and geodynamics of the Tibetan Plateau. Previous studies suggested that the late Quaternary average slip rate was stable and uniform (10~13 mm/a) in the central and western segment of the EKLF. But there were a few researches of accurate slip rate in the central segment on the EKLF. Therefore, we focused on an offset and well preserved alluvial fan from Xiugou basin, located in the east of Xidatan-Dongdatan, to make it clear. Moreover, we used high-resolution satellite images and digital elevation model extracted from SPOT7 stereo image pairs to restore the offset alluvial fan, and combined terrestrial cosmogenic nuclides method, including 13 quartz-rich samples from this fan surface, 1 quartz-rich sample from the main active channel bed and 1 10Be depth profile from this fan edge to eliminate the 10Be concentration of inheritance accurately, with 1 optically stimulated luminescence sample to obtain the reliable age of this alluvial fan together. Referring to field observations, this alluvial fan was offset left-laterally by (1 862±103) m, and its age is (76.55±3.20)~(106.37±3.38) ka which can be determined through the actual geologic setting and improving chi-square test. Thus, we used the Monte Carlo method to obtain a left-lateral slip rate of (20.3+3.5/-2.3) mm/a with 68% confidence envelopes since the late Pleistocene in the Xiugou basin. As a result, combining with the results of previous studies, the left-lateral slip rate indicated that the obviously decreasing activity transferred from late Pleistocene to Holocene on the central segment of the EKLF.
It is important to investigate the soil organic carbon reserves of the northern Tibetan Plateau for understanding the global carbon cycle. The surface soil carbon storage is 1.27×108 t, and the surface topsoil organic carbon density is 4.96×103 t/km2 in the study area. Compared with the results of the second National Soil Census, the distribution of organic carbon reserves of chestnut soil, sierozem, alpine steppe soil, swamp soil, sandy soil and ustic cambisols increased gradually, which are mainly distributed in savanes of the northern Qinghai Lake and woodland in middle-high mountain areas of the eastern Qinghai Lake; savanes and woodland are classified as the carbon sink area because this area’s carbon sequestration is greater than the release quantity. By contrast, the distribution of organic carbon reserves of mountain meadow soil, alpine meadow soil, grey cinnamon soil, chernozem and anthropogenic-alluvial soil decreased gradually, which are mainly distributed in the farming areas of eastern Qinghai Province. This area’s carbon sequestration is less than the release quantity because of cultivation effect, and is classified as the carbon source area. The 97.5% of organic carbon storage cumulative frequency is closed to the threshold value of the organic carbon saturation. The carbon sequestration potential of the study area is 241.57×106 t. Take the widely distributed chestnut soil as a case, it will take 18.66 years to reach saturation for the soil organic carbon reserves of chestnut soil.
Various three-dimensional (3D) geophysical and geological data are increasingly available with the advanced technology in the recent years. New challenges emerge frequently in visualizing 3D data due to data variety and the specific display requirement. In this study, we presented a solution of the data assimilation and visualization of lithospheric structures in the eastern margin of the Tibetan Plateau. Three typical datasets were assimilated in the model: ①seismic velocity to the depth of 100 km, ②fault geometry in the upper-and mid-crust and ③topographical data on the surface. The S and P wave velocities in the study area obtained from a high-density portable seismic array were interpolated into regular blocks of the size of 1 km×1 km×2 km and written in RAW format. The major active faults were digitalized and their 3D geometry was generalized by using striking and trending angles, and then organized into unstructured VTK format. The surface topographical DEM data were also converted into unstructured VTK format. In order to integrate and visualize the data, an open source multi-platform software package Paraview was used. It offered various visualization schemes; in particular, volume rendering technique provided stunning static/dynamic images of the structures and highlighted the anomalies in the 3D space. This solution can be applied to other types of 3D geophysical and geological data.
The Tibetan Plateau Shear Line (TPSL) is usually accompanied by the Tibetan Plateau Vortex (TPV) and this phenomenon is one of the assembled weather systems over the Tibetan Plateau (TP) and its surrounding areas. This assembled system plays a very important role in the high impact weather process in the TP and East China. We reviewed the research history and progress of TPVs and TPSLs, and mainly discussed the relationship and interaction mechanism of them. According to the latest research achievement of TPSLs and its relationship with TPVs, the development and application trends of related theory and methods, we proposed several notable new research directions in the field of this study. It is not clear for the relationship and the physical mechanism of the interaction between TPSLs and TPVs as well as some high impact weather initiated by them currently. Therefore, this research work is really quite important for theoretical development of weather dynamics of the TP, and is expected to provide a theoretical guide for severe weather analysis and forecast over the TP and its neighborhood.
Mercury (Hg) is a global pollutant. As one of the significant cryospheric environmental matrix, snow-ice plays a unique role in Hg biogeochemical cycling, which has drawn a wide attention of scientists. Besides polar regions, a large aggregate of glaciers are distributed in the high elevation of mid-high latitude areas. These alpine glaciers are proximate to human residence and are sensitive to the climate change, which would readily impact the human society, water resource security and water quality. Consequently, investigating the behavior and environmental effects of Hg relevant to the melt of alpine glaciers represents significant scientific and social importance. The deposition and storage of Hg in alpine glacier areas were outlined and the removal characteristics and transformation of Hg during glacier melt process and transport of Hg in glacier-fed river were summarized. Based on this study, we suggested that glacier be one of the potential sources of Hg to the downstream areas. Moreover, it was worth concerning the fate and environmental effects of Hg in the ecosystem fed by the glacier runoff. Eventually, we proposed prospects of the process of Hg release during glacier melt and the hot issues of Hg transport in glacier runoff.
The Qinghai-Tibet Engineering Corridor (QTEC) is a strategic passage between Tibet and central China. In the past half century, several major projects have been built in this narrow corridor with vulnerable geoenvironment. Along with a new round of economic development of the Tibet autonomous region, some major linear projects including expressway, double-tracking railway, high voltage power transmission line have been incorporated into the national development planning within the corridor, and especially the expressway construction is imminent now. In the QTEC, permafrost is a controlling factor of geological environment, which will impose great restrictions on engineering construction. In turn, engineering construction will induce significant effects on permafrost geological environment. With more and more linear infrastructures crowding into the QTEC, the thermal interaction among permafrost engineering and engineering disturbance on permafrost thermal-mechanical regime will be more significant. With respect to this issue, a research program focusing on thermal-mechanical influences and environmental effects of expressway construction on the Qinghai-Tibet permafrost engineering corridor was started and supported by the National Natural Science Foundation of China. In this paper, the research significance, key scientific issues, main research contents and goals of the program are introduced so as to provide some references for related researchers and engineers.
The origin and formation time of the first bend are important scientific problems in the Yangtze River system and the evolution of the river system, even tectonic research around the southeastern margin of the Qinghai-Tibet Plateau. These problems have attracted the attention of many domestic and international scholars and they hold two different opinions. one is river capture hypothesis; another hypothesis is river natural adaptation to terrain. It is necessary to get reliable geological evidences and chronological data in order to reconstruct the evolution history of the Yangtze River. In the recent years, much work has been done to study the evolution history of the Yangtze River. Thus, it is possible now to integrate all the relevant chronological data and geological evidences to understand the evolution of Yangtze River.
The tectonogeomorphology is regarded as the key to understanding the uplift history of the Tibetan Plateau. But its research is blocked by the poor constrains of chronology. The low temperature thermochronology, the most fashions are the zircon and apatite fission-track and (U-Th)/He thermochronology (ZFT, AFT, ZHe and AHe), has thoroughly developed recently, become a sensitive and precise tool for this kind study, and was suggested in this paper. A metasynthesis study of the multiple low temperature thermochronology was proposed, including the bedrocks of high altitude mountains, on which low-relief and layered landscapes has developed and relicted, as well as the synorogenic deposits, such as the Cenozoic sediments, river terraces and modern river deposits. Thus, mutual compensation of advantages among ZFT, AFT, ZHe and AHe could be achieved to yield a whole exhumation and evolution history of regional tectonogeomorphology during the Cenozic. Accordingly, several conceptual growth models of the tectonogeomorphology terrane can be yielded. However, issues as pointed out in this study are still exist when conducting the relevant researches, and should be carefully addressed.
Volcanic eruptions can significantly cool the global troposphere on the time scales from several months up to a decade due to reflection of solar radiation by sulfate aerosols and feedback mechanisms in the climate system. The impact of volcanic eruptions on global climate are discussed in many studies. However, few studies have been done on the impact of volcanic eruption on climate change in China in the past millennium. The 1300-year and 600-year temperature series were reconstructed based on the six tree-ring temperature proxy data in northeastern and southeastern Tibetan Plateau, respectively. Three warm periods occurred in 670-920,1000-1310 and 1590-1930, and three cold periods happened at 920-1000,1310-1590 and 1930-2000 in the northeastern Tibetan Plateau. There were two obviously warm periods (1385-1450 and 1570-1820) and two cold periods (1450-1570 and 1820-2000) in southeastern Tibetan Plateau. Contrasting with volcanic eruption chronology, we analyzed the relationship between volcanic activity and temperature variation in the eastern Tibetan plateau during the past millennium using Superposed Epoch Analysis (SEA) method. The results indicated that the temperature decreased one year after large volcanic eruptions located beteen 10°S and 10°N in latitude in northeastern Tibetan Plateau and two years in southeastern Tibetan Plateau. The volcanic eruptions occurred at different latitudes have different impacts on the temperature variations, which may be caused by regional difference, the nature of the eruption, the magnitude of the resulting change in incoming solar radiation, prevailing background climate and internal variability, season, latitude, and other considerations.
Tibetan Plateau, with its unique characteristics and its impact on the global environment, ecology and climate, is an important research region of the international scientific community. The development of international cooperation in the field of Tibetan Plateau was reviewed and the quantitative statistics and data in accordance with the SCI papers of international cooperation in the field of Tibetan Plateau were analyzed during the 35 years of 1980-2014. The experience of international cooperative research in the field of Tibetan Plateau from starting stage to rapid development to tend to mature stage of development was summarized. International cooperative research has become the main organization of research in the field of Tibetan Plateau. Tibet Plateau international collaboration changing from single academic discipline to multi academic disciplines was analized. Changes in major countries of international cooperation research and independent research in the field of Tibetan Plateau were compared and suggestions for strengthening international cooperative research in the field of Tibetan Plateau for China in the future were put forward.
Based on the NCEP/NCAR daily reanalysis data and the daily rainfall data of ground observation at 164 weather stations in the middle and lower reaches of the Yangtze River from 1960 to 2013, the relationship between South Asia high low frequency oscillation and the drought and flood in the middle and lower reaches of the Yangtze River were analyzed using a composite analysis, wavelet analysis and band-pass filtering analysis method. The results indicated that in the typical drought and flood years, the Qinghai-Tibet Plateau 200 hPa atmosphere u, v low-frequency primary cycle and the summer rainfall cycle over the middle and lower reaches of the Yangtze River were the same. In more summer rainfall, from the Qinghai-Tibet Plateau to east China and west Pacific coast, there existed a cycle-anticyclone-cycle low frequency wave train. Low-frequency anticyclone controlled eastern China and the low-frequency cyclone controlled the northern Qinghai-Tibet Plateau. In drought years, results were opposite. In flood years, the precipitation of low frequency over the middle and lower reaches of the Yangtze River and that of 200 hPa atmospheric low frequency change of the Qinghai-Tibet Plateau was closely related. When the northerly wind in the northeast part of the the Qinghai-Tibet Plateau and in the middle and lower reaches of the Yangtze River was strong, and Lake Baikal southerly wind was strong, there was more precipitation. On the contrary, precipitation was less. The low frequency oscillation wave train was mainly spread from the northeast of China and Japan's southern to China’s southwest. However, in drought years, the relationship between them was not clear and needed to be further studied.
In the Gyirong and Nyalam areas, a massive amount of augen gneisses are extensively exposed in the middle Himalayan orogen. They consist of quartz, K-feldspar, plagioclase, biotite and minor muscovite. Zircons from augen gneisses have magmatic rims indicated by concentric oscillatory zoning. LA-ICP-MS zircon U-Pb dating gave weighted mean ages of (488.5±1.1) Ma (MSWD=0.6)、(475.1±0.7) Ma (MSWD=1.5) and (468.1±2.5) Ma (MSWD=4.2), hinting early Paleozoic magmatism in the Greater Himalayan Crystalline complex (GHC). The data in this study and other published geochronological results of Cambrian-Ordovician magmatites demonstrated that early Paleozoic orogenesis existed in the Himalayas. Early Paleozoic tectonic events preserved in Himalayas are well compared with the contemporaneous ones in the Lhasa terrane, Qiangtang terrane, Baoshan terrane and Tengchong terrane located in the south and southeast of Tibet Plateau. Integrating previous studies, we suggested an Andean-type orogeny corresponding to dynamic adjusting of the plates by subduction of the Proto-Tethys Ocean lithosphere along the northern margin of Gondwana, instead of Pan-African orogeny that was characterized by the continent-continent collisions during Gondwana assembly.
Studying climate changes over the past 2 000 years has important scientific significance in exploring climate variability on decadal to centennial timescales, assessing the natural and anthropogenic contribution to the climate warming, and understanding the effects of human activities in the past and future climate changes. Due to the scarcity of observation and uncertainty of reconstruction in this period, climate model is developed as a useful tool for studying paleoclimate.The Community Earth System Model (CESM) is one of the state-of-the-art climate models, but its performance in simulating the temperature in China has not been examined.The temperature datasets of observation/reanalysis (GHCN_CAMS) and reconstructions during the past 2000 years in China were used to examine the performance of CESM. The comparison between the annual average temperatures of GHCN_CAMS reanalysis and simulation showed that the model well reproduced the spatial distributions and upward trend of the annual average temperature in China, and the comparison with reconstructions in five sub-regions of China indicated that the simulation were in good consistent with the average temperature changes of reconstructionson decadal time scales. On the centennial time scale, the average temperature fluctuations of simulation in the regions of China were in accord with reconstructions generally except for Central East and Tibet.There existed three warm periods of simulated temperature variation in China over the past 2000 years, including 0-540AD, 800-1250AD and 1901-2000AD, and two cold periods involving the 551-721AD and 1400-1850AD, which had some discrepancies with reconstructions. And the discrepancies between simulation and reconstructions might be related to uncertainties of the resolution, external forcing and parameterization of the subgrid-scale process in the model.
The distribution curve of the Ratios of the Average Horizontal Geostress and the Vertical Geostresses(RAHVG) varying with depth and regression equation were obtained in Qinghai-Tibet area of China for the first time by collecting and analyzing 200 in-situ measured geostress results based on the analysis of distribution rule of geostress in China. Then the geostress distribution rule and the characteristics were analyzed, and it is found that the geostress in Qinghai-Tibet area conforms to the geostress distribution rule in China, but the geostress in Qinghai-Tibet area is significantly subjected to tectonic squeezing and the tectonic geostress is very obvious in magmatic rock. The RAHVG of the magmatic rock varying with depth in Qinghai-Tibet area is significantly greater than that in China between the depth of 100 m and 800 m. It shows that the stress of the magmatic rock in Qinghai-Tibet area is significantly subjected to squeezing tectonic. The RAHVG of the sedimentary rock varying with depth in Qinghai-Tibet area is basically consistent with that in China, but the value in Qinghai-Tibet area is greater. It shows that the stress of the sedimentary rock in Qinghai-Tibet area is not significantly subjected to squeezing tectonic. The RAHVG of the metamorphic rock varying with depth in Qinghai-Tibet area is significantly greater than that in China. It shows that the stress of the metamorphic rock in Qinghai-Tibet area is subjected to squeezing tectonic in some degree. This study can provide references to the study of distribution characteristics of geostress in Qinghai-Tibet area. It also has important practical value for underground engineering survey, design, structural analysis and construction in Qinghai-Tibet area.
The origin, radiation, dispersal, and extinction of the Neogene mammals provide important insights in our understanding of mammalian geographical distribution and regional differentiations, and such an evolutionary history can, in turn, reflect significant changes in climate and environments. Mammals are very sensitive to climatic and environmental changes, and their distribution is closely related to their natural habitats. Throughout the late Cenozoic, the formation of the Tibetan Plateau also had a profound influence on the evolution of mammals in East Asia. The uplifting plateau was a major drive in changes of natural environments, which have a direct impact on the differentiation of the faunal composition and distribution. The Chinese Neogene mammalian fossil records are unparalleled in the world, and with its unique zoogeographical position, such a record of faunal compositions is sensitive to regional differentiations. Furthermore, China was a center of origin and dispersal for many representative mammalian groups, and also a key intersection for intercontinental migrations. Most taxa of the distinctive modern mammalian fauna of the Tibetan Plateau have long life history in this plateau, which indicate that they have long-term adaptation procedures within the high-elevation plateau. The late Neogene mammalian fossils from the Tibetan Plateau suggest that some Quaternary mammals first evolved in Tibet before the beginning of the Ice Age. The cold winters in high Tibet served as a habituation ground for the members of the megafauna, which became pre-adapted for the Ice Age, successfully expanding to the Eurasian mammoth steppe. As a result, the research on the Neogene mammalian faunas of the Tibetan Plateau will be focused, because these cold-adapted mammals were dominant in the subsequent Quaternary Ice Age, and become the basis of the modern mammalian zoogeographical patterns and biodiversities. Taking advantage of the above favorable conditions, the response of the Neogene zoogeographical regionalism to the major climatic events and more accurately judge the influence of the Tibetan Plateau uplift to the terrestrial ecosystem can be more accurately judged.
Quantitative estimation of paleoelevation is crucial to constrain uplift history of the Tibetan Plateau. So far, there are four kinds of paleoaltimeter used to reveal Cenozoic paleoelevation of the Tibetan Plateau, including oxygen-isotope paleoaltimeter, △47 paleotemperaturepaleoaltimeter, Hydrogen-isotope paleoaltimeter, Paleobotanic paleoaltimeter, and Analysis of paleoenvironment. The oxygen-isotope paleoaltimeter, which is based on the relationship between the oxygen isotope value (18O) of surface water and elevation, includes empirical relationship equation and model relationship equation. △47 paleotemperature-paleoaltimeter is a new approach to reconstruct paleoelevation, which has been used in just one position in Tibet. Paleobotanic paleoaltimeter contains co-existence analysis and leaf physiognomic approach, and Analysis of paleoenvironment is a semi-quantitative method. Through detailed comparison of various principles, application condition, influencing factors, and pros-cons of the different paleoaltimeters, we focused on summarizing achievements and problems of these research methods, and further discussed their application potential and prospects. In the future work, we need to pay more attention to obtain new modern data to improve the above paleoaltimeters and introduce new paleoaltimeters.
3D laser scanning has been a new technology in measurement of spatial information in recent years. In this paper, this technology was applied tentatively to the efficiency evaluation of the protective system of sand drift control engineering along Qinghai-Tibet Railway. The sand control efficiency of the system was evaluated by accurately measuring the morphology of sand deposition over the typical sand drift control measures, aeolian erosion and deposition profiles of the cross-section and quantities of erosion and deposition using the 3D laser scanning technology. The concave surface of rocky checkerboard sand barriers easily formed along the perpendicularly direction to the railway. Sand accumulation occured more on the sides of rocky checkerboard than its center. The effective distance of sand fences was about 12 H and sand-blocking volume was 14.93 m3 per 1 m width. Therefore, the space of sand fences should remain 9~12 H in the construction of protective systems. The objective of this study is to extend this technology to the measurement of sand disaster threatening other railways, buildings and engineering measures and to the evaluation of the protective efficiency of their control systems, thus eventually providing technical support to the measure selection, structure optimization and rational distribution of the integrative sand drift control system.
This paper describes the current status and perspective for the hydrological modelling over the Tibetan Plateau (TP). Hydrological models, as primary tools to study hydrological processes, can provide theoretical and decision support for water resources management as well as disaster prevention and mitigation in river basins. As is known, the first-generation hydrological models are “lumped”, and the second-generation hydrological models are “distributed”. However, most of the above models mainly describe the “precipitation-to runoff” water transport processes (“hydrosphere”) without carefully addressing the special role of vegetation in the water and energy exchanges in the landatmosphere interactions (“biosphere-atmosphere”). Over the past decade, in the context of climate change, with the vibrant developments of atmospheric science and ecology, distributed hydrological models began to describe the biosphereatmosphere interactions by improving the water and energy cycle formulations between the land and atmosphere, as well as enhancing the descriptions of physiological processes of vegetation. Up to now, a comprehensive description of hydrosphere-biosphere-atmosphere interactions in river basins has been realized by the hydrological community. However, regarding TP with a large portion of cryosphere land cover, the detailed cryospheric processes are of essence to be further considered in the multi-sphere hydrological modeling over TP. This will largely contribute to studies of the interaction mechanism among the cryosphere and other spheres (hydrosphere /biosphere /atmosphere), and thus improve the predictive ability of the region’s water resources and water-related disasters.
Based on the change law of solar radiation intensity and shadow of land bridge variation with time, the mathematical model expressing of the relationship among time, solar radiation intensity,solar position and shadow track was established. The effects of the sunshine-shield of land bridge floor were studied using the model. Direct rate concept was proposed to define the proportion of solar direct radiation energy of the surrounding permafrost. The results show that height, direction and width of land bridge are the major influence factors on the solar radiation of underbridge and surrounding permafrost. With the increase of the height, shading scope and direct rate of sunshade center also increase; with the increase of the width, direct rate of the surrounding permafrost decrease; there was obvious asymmetry distribution of permafrost surface direct rate, especially for the east-west bridge. Sunshine-shield of land bridge can effectively reduce the sun radiation heat of the surrounding permafrost and also cause non-uniform distribution of solar radiation on permafrost surface around piles, which should be concerned in the stability estimation of land bridge.
The interaction between atmosphere, hydrosphere, cryosphere and biosphere of the Tibetan Plateau (TP) significantly affects not only climate pattern and climate change in local and surrounding area, but also the Asian monsoon process and the global atmospheric circulation. The study of the #cod#x0201c;Tibet Plateau climate system change and mechanism of its impact on East Asia#cod#x0201d;, a project of the National Key Scientific Research Program of China for Global Change Study, was initiated in September of 2010. It aimed at performing integrated research on the Tibetan Plateau climate system responding to global change and its impact on surrounding areas, collaborating on major scientific issues to achieve breakthrough in scientific research on the Tibet Plateau climate system change and mechanism of its impact on East Asia, proposing prospective strategy coping with abnormal climate change to reduce regional natural disaster losses. A simultaneous and coordinated experiment of airborne remote sensing and groundbased observation was carried out in TP for the first time. And a series of research results have been achieved in the past three years of project implementation. The results include determination of regional distributions and seasonal variations of land surface heat fluxes in whole TP region, behavior of the tropopause folding events over the west TP, definition of plateau monsoon and its association with general circulation anomalies, decrements of solar radiation and wind speed across China and TP area in recent decades and their possible causes, weaken trend of sensible heat source in the spring over TP and its impact on the Asian summer monsoon, and classification of land cover in high altitude region of Mount Qomolangma, etc.
The occurrence of thermokarst lake is an indicator implying the permafrost warming. A study of thermokarst lake and their thermal effect will become an important basic work that responds to the permafrost hazards induced by the climate changes and the anthropogenic activities on the QinghaiTibet Plateau. Based on SPOT-5 satellite image data, we interpreted and obtained the area and quantity of thermokarst lakes from Chumaerhe to Fenghuoshan Mountain section along the Qinghai-Tibet Highway under the ArcGIS platform in this paper. The result shows that these thermokarst lakes have mainly spread in Chumaerhe High Plains and Beiluhe Basin and approximately 80% lakes have been developing in rich-ice permafrost regions. The thermokarst lake influences the permafrost through downward and lateral heat transfer. The downward heat transfer accelerates the thawing of permafrost and the formation of an open-talik, the lateral heat erosion will cause the permafrost warming at lakeshore and expand the scope of the heat-affected. The modeled result of a typical thermokarst lake in Beiluhe Basin shows that the lake has always released the heat to lakeshore in a whole year. If the thermokarst lake is close to the roadbed, it will cause influence on the stability of roadbed, especially the lateral thermal erosion often leads to the temperature increases of frozen soil subgrade and induces the embankment disease.
The climatic change since the Last Glacial Maximum (LGM) period was reconstructed based on the analysis of geochemical characteristics of the aeolian deposits in Gonghe Basin, northeastern Qinghai-Tibetan Plateau, coupled with the 14C and OSL chronology. The cold and wet climate dominated the region before 21 ka BP, and the climate became very cold and dry in 21~15.82 ka BP, corresponding to the LGM period. From 15.82 to 9.5 ka BP, the regional climate tended to be warm and dry in general. During this period, the cold and dry condition occurred in 14.5~13.6 ka BP and 11.9-9.5 ka BP, implying the Oldest Dryas and Younger Dryas phases, while the relatively warm climate was found in 15.82~14.5 ka BP and 13.6~11.9 ka BP (BøllingAllerød period, B/A period). The warm and humid degree obviously increased between 9.5 and 7.2 ka BP, marking the relatively warm and wet condition. The cold-dry and warm-humid climate fluctuated in 7.2~5.1 ka BP. In 5.1~2.7 ka BP, the degree of warm and wet is relatively stable but it tended to be cold with high moisture since 2.7 ka BP. These changes are coincident with the paleoclimatic records in Qinghai-Tibetan Plateau, reflecting higher consistency in climatic change between Gonghe Basin and Qinghai-Tibetan Plateau.
The observation data collected by Atmospheric and Environmental Comprehensive Observation and Research Station on Mt. Qomolangma, Chinese Academy of Sciences (AECORSQ,CAS) and the AIRS(Atmospheric Infrared Sounder) satellite data obtained during the period of from March to May of 2008 are employed to analyze the diurnal changes and the vertical features of atmosphere over the northern region of the Himalayas in spring. The results show that the diurnal mean variation of surface air temperature has one-peak-one-vale pattern. The highest temperature occurred around 18:00 Beijing local time and the lowest was between 7:00 to 9:00 Beijing local time.The diurnal mean variation of wind speed has onepeak pattern, and the air pressure has two-peaks-two-vales pattern while the lowest occurred at 19:00 Beijing local time. The diurnal mean variations of sensible heat flux and latent heat flux were consistent with the diurnal change of air temperature. The pattern looks like the net radiation diurnal pattern, but the peak time appears about 2 hours later. The sensible heating flux is stronger than latent heating flux over the Tibetan Plateau in spring. There are two main reasons which caused the remarkable diurnal variation of air temperature over the Tibetan Plateau while the mass of the atmosphere over the plateau is much less than the mass of atmosphere over other regions, and it can gain more solar shortwave radiation and less shortwave radiation while the optical depth over this region is smaller.
Based on the simulative research on the characteristics of wind speed, sand-fixed rate of rocky checkerboard sand barriers along Qinghai-Tibet Railway in wind tunnel, several conclusions were drawn as follows. Horizontal wind speed rapidly decreases when it flows to the fringe of rocky checkerboard sand barriers. Weaken efficiency of rocky checkerboard sand barrier on airflow is distinct, with about 50%. Wind speed changes little over rocky checkerboard sand barrier. In contrast, although the wind speed decreases from rocky checkerboard sand barrier to its lower reach, its magnitude is very small. Wind speed varies logarithmically with height. Variation of wind speed is similar among rocky checkerboard sand barriers as height increases. Roughness is about 5.2 mm and drag velocity is 2.4 cm/s for rocky checkerboard sand barrier. Sand-fixing mass increased with inlet wind speed. For a given wind speed, sand-fixing mass increased exponentially with distance to sand sources.
The processes of energy and water cycle over the Tibetan Plateau have shown that the giant prominence exerts thermal effects on the atmosphere, thus greatly influencing atmospheric circulations over China, Asia and even the globle. Focusing on this issue, the intensive observation period (IOP) and long-term observation of the GEWEX (Global Energy and Water cycle Experiment) Asian Monsoon Experiment on the Tibetan Plateau ( GAME/Tibet ) and CEOP (Coordinated Enhanced Observing Period) Asia Australia Monsoon Project (CAMP) on the Tibetan Plateau (CAMP/ Tibet ) have been carried out successfully from the beginning of 1996 under the support of National Natural Science Foundation of China (NSFC), the Chinese Academy of Sciences(CAS), the China Meteorological Administration(CMA) and the Japanese government etc. A large number of data has been collected, which is the best data set so far for the study of energy and water cycle over the Tibetan Plateau. Great progress has been made in the study of energy and water cycle over the Tibetan Plateau through the in-situ data analysis, satellite remote sensing parameterization and the numerical modeling, etc. The progresses of the study of energy and water cycle over the Tibetan Plateau and the role of the international cooperation in the projects will be introduced in detail. The role of the international cooperation in getting the research found from abroad and in training young scientists and students is also mentioned. The existing problems in the international cooperation and the solving ways are presented in the paper at the same time.
The frozen soil region of many years located in the Qinghai-Tibet Plain hinterland, Changing of the Water content of soil during freeze-thaw process, intensely responds to climate change and brings remarkable change on land energy-water balance, then has the large feedback function to the global climate. In order to reveal this kind of change, we used the observation data from the wind volcano testing field system, selected water-heat coupling model SHAW as dynamics restraint frame, which consider the influence of snow cover & the vegetation cover & the forest flooring to the soil freezing and thawing, and improved SHAW forecast capacity to the soil moisture content and the frozen soil depth by Ensemble Kalman Filter of data simulation method. The analysis based on data assimilation theory indicate that the data assimilation method may remarkably enhance the forecasting ability of water-heat coupling model to state variables, and provide theory basis for monitor utilizing multiple source information in frozen soil area.
Analysis of the vegetation coverage changing with the time in the last 21 years is the purpose of this paper to study the regularity of the regional eco-environment in the Tibetan plateau. Based on the remote sensing data GIMMS NDVI, statistical processing and analysis, also calculation, the paper gives quantitative analyses and evaluations of the variability of vegetated rate of the Tibetan plateau. In the last 21 years, the regional vegetation coverage has been on the slow increase at the rate of 3 961.9 km2/a as a whole, except for some place degradation, and also the human have not done damage to the eco-environment. From 1982 to 1991, the vegetation coverage of the whole region increased, except for degrading region at the middle and the west of the area. The value increased is decreasing from the south and the east to the north and the west. The induction, the climate benefiting the vegetation growing, changing with degree of longitude and latitude, can be worked out. It's the main period from 1992 to 2002 that the vegetation degrade, those deteriorated regions are located in the resource regions of the Yangtze river, the Yellow river, the Lancangjiang river and the Nujiang river, which indicates the changing climate would be adverse to the vegetation. The NDVI also has two significant periods of 7 years and 3.5 years, caused by the same significant periods of the temperature, and that indicates that the plateau plant is more senstive to the temperature than to the precipitation. Over 21 years, there are 7 from 8 types vegetation coverage which are raising unstably including clod-arid-region plant with vulnerability and difficult recovery.
The exchange of heat fluxes between land surface and atmosphere over the Tibetan plateau area plays an important role in the Asian monsoon system, which in turn is a major component of both the energy and water cycles of the global climate system. It was also regarded as the main task in the GEWEX (Global Energy and Water Cycle Experiment) Asian Monsoon Experiment on the Tibetan plateau (GAME/Tibet, 1996-2000) and CEOP (Coordinated Enhanced Observing Period) Asia-Australia Monsoon Project (CAMP) on the Tibetan plateau (CAMP/Tibet, 2001-2006). Firstly, the field experiments of the GAME/Tibet and the CAMP/Tibet are introduced and some results on the local energy partitioning (the diurnal variations and intermonthly variations of radiation energy budget and land surface energy budget) are presented in this study. The study of the regional distribution of land surface heat fluxes of paramount importance over heterogeneous landscape of the Tibetan Plateau is also one of the main scientific objectives of the GAME/Tibet and the CAMP/Tibet. Therefore, the regional distributions and their inter-monthly variations of surface heat fluxes (net radiation flux, soil heat flux, sensible heat flux and latent heat flux) are also presented here by combining five Landsat-7 ETM images with the field observations. The derived results were validated by using the “ground truth”, and it shows that the derived regional distributions and their inter-monthly variations of land surface heat fluxes are reasonable. In order to upscale the land surface heat fluxes to the whole Tibetan Plateau area, the Institute of Tibetan Plateau Research (ITP) of the Chinese Academy of Sciences (CAS) is establishing a monitoring and Research Platform (MORP) for land surface and atmospheric processes on the Tibetan plateau. The establishing and monitoring plan of longterm scale (5-10 years) of the MORP, three new comprehensive observation and study stations (Mt. Qomolangma?Mt. Everest, Nam Cuo and Linzhi) and the up-scaling way were also introduced in this paper.
This contribution presents an overview and an outlook of studies on energy and water cycle over the Tibetan plateau with focuses on the estimation of energy balance terms and turbulent heat fluxes. On the basis of the surface energy balance calculations, we show that the phenomena of the energy imbalance exist in GAME/Tibet experiment data, although the explanations for the reasons are debated now and not resolved yet. We found that the derived latent heat flux is much higher than the measurements. However, the corrected-measurements, which are calculated according to the hypothesis of the energy balance, compare very well with the estimation of SEBS. On this basis it is concluded that the deviation is caused by the energy imbalance of ground measurements in GAME/Tibet experiment area. The latent heat fluxes were likely under-observed.
The Ev-K2-CNR SHARE-Asia Project aims to create a monitoring network along the Himalayas-Karakorum range for studying meteorological and climate parameters with particular attention paid to monsoon variability, atmospheric chemistry, glaciology and high altitude limnology and paleolimnology, as well as for precise determination of the Earth surface coordinates. Specific objectives of SHARE-Asia are: development of an integrated system of measurements for increasing knowledge on environmental and earth sciences; and activation of local technology transfer and capacity building processes. SHARE-Asia meteorological-climate and atmospheric chemistry monitoring stations are already part of important international scientific projects, such as WMO-CEOP and UNEP-ABC.
Climate variability has a large impact on the vegetation dynamics. To quantify this impact in the Tibetan plateau a study was carried out using time-series of MODIS fAPAR satellite data products and NCEP net radiation and rainfall re-analysis data. The data set spanned over the years between 2000 and 2005. The NCEP data are used to construct a time series of a radiational indicator of drought: daily net radiation and rainfall data for each NCEP grid are integrated over a period of eight days to match the temporal sampling interval of MODIS data products. The ratio of net radiation over rainfall for a given period of time is a measure of excess energy relative to available water and is therefore a measure of drought hazard. Fourier analysis of time series of the MODIS fAPAR provides two indicators of the response of vegetation photosynthetic activity to drought, as measured by the indicator just described. The two indicators used in this study are the mean yearly fAPAR value and its annual amplitude. The algorithm used (HANTS) fits iteratively a Fourier series to a set of irregularly spaced observations, after elimination of outliers, such as due to cloud-contaminated observations. The relationships between photosynthetic activity of vegetation and the radiational drought hazard indicator are determined and quantified spatially and temporally. The response during the wettest respectively driest year during the period covered by available observations was compared. The drier areas prove to be the most sensitive to climate impact. The analysis should be extended over a longer period of time to obtain a more robust assessment of climate impact on vegetation dynamics, particularly as regards the response of vegetation to temporal respectively spatial variability of climate.
A quality analysis including footprint modelling has revealed spatial and temporal structures in the quality of Eddy Covariance measurements for two highland sites located on the Tibetan plateau. Fetch analysis has shown, that up to 1/3 of the measurements do not fulfill assumptions necessary for a physically correct data processing. Despite this fact, measurements of latent heat-, CO2- and momentum flux in general fulfill the quality test criteria to an extend that the results can be regarded as suitable for fundamental research, whereby usually certain wind sectors have been found violating basic assumptions. Measurements of the sensible heat flux allow for the usage in continuously running measurement, while still few indications of the quality assessment can not be explained due to local topography, but indicate organized structures and lead to the hypothesis of mesoscale flow patterns in the boundary layer.