| 1. |
- Wu, Xiao-Ling, et al.
(författare)
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Coupled Hydraulic and Kalman Filter Model for Real-Time Correction of Flood Forecast in the Three Gorges Interzone of Yangtze River, China
- 2013
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Ingår i: Journal of hydrologic engineering. - 1084-0699 .- 1943-5584. ; 18:11, s. 1416-1425
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Tidskriftsartikel (refereegranskat)abstract
- The Three Gorges Project along the Yangtze River in China, as one of the biggest hydropower-complex projects in the world, plays a significant role in the economic development of the area even of the whole nation. An accurate and reliable flood forecast modeling system is of significant importance for flood control, flood warning, and operation of larger reservoirs. Kalman filter coupling with hydrological models or hydraulic models is one of the efficient methods to adjust real-time flood series for reducing errors from model structure, input data, and calibrated parameters. However, the coupling model is time consuming in computation because the state vectors in this kind of Kalman filter including both water stage and discharge are solved simultaneously. In this study, an alternative coupling method was developed, which separates system state equations and measurement equations allowing the water stage and discharge to be computed alternately. The new method was applied for real-time flood forecasting in the Three Gorges interzone of Yangtze River. The hydraulic model is calibrated and verified against the observed flood stage and discharge before and during Three Gorges Dam construction periods. Study results demonstrate that the new model is efficient in real-time flood forecasting. A comparative study shows that the newly developed approach outperforms the conventional methods in terms of modeling efficiency, root mean square error, as well as the forecasting errors in the maximum water stage and peak flow.
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| 2. |
- Yao, Tandong, et al.
(författare)
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Recent Third Pole’s rapid warming accompanies cryospheric melt and water cycle intensification and interactions between monsoon and environment: multi-disciplinary approach with observation, modeling and analysis
- 2019
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Ingår i: Bulletin of The American Meteorological Society. - 0003-0007 .- 1520-0477. ; :March, s. 423-444
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Tidskriftsartikel (refereegranskat)abstract
- The Third Pole (TP) is experiencing rapid warming and is currently in its warmest period in the past 2,000 years. This paper reviews the latest development in multidisciplinary TP research associated with this warming. The rapid warming facilitates intense and broad glacier melt over most of the TP, although some glaciers in the northwest are advancing. By heating the atmosphere and reducing snow/ice albedo, aerosols also contribute to the glaciers melting. Glacier melt is accompanied by lake expansion and intensification of the water cycle over the TP. Precipitation has increased over the eastern and northwestern TP. Meanwhile, the TP is greening and most regions are experiencing advancing phenological trends, although over the southwest there is a spring phenological delay mainly in response to the recent decline in spring precipitation. Atmospheric and terrestrial thermal and dynamical processes over the TP affect the Asian monsoon at different scales. Recent evidence indicates substantial roles that mesoscale convective systems play in the TP’s precipitation as well as an association between soil moisture anomalies in the TP and the Indian monsoon. Moreover, an increase in geohazard events has been associated with recent environmental changes, some of which have had catastrophic consequences caused by glacial lake outbursts and landslides. Active debris flows are growing in both frequency of occurrences and spatial scale. Meanwhile, new types of disasters, such as the twin ice avalanches in Ali in 2016, are now appearing in the region. Adaptation and mitigation measures should be taken to help societies’ preparation for future environmental challenges. Some key issues for future TP studies are also discussed.
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| 3. |
- Chen, Peng, et al.
(författare)
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Holocene monsoon dynamics at Kunlun Pass on the northeastern Qinghai-Tibet Plateau
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 771
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Tidskriftsartikel (refereegranskat)abstract
- Various proxy records have been used for the understanding of environmental and climate variations during the Holocene. Here, for the first time, we use meteoric Be-10 isotope measurements performed on sediments from a drill core collected at the Kunlun Pass (KP) on the northeastern Qinghai-Tibet Plateau (NETP) to investigate hydroclimate changes during the Holocene. The Be-10 flux suggests relative low levels in the Early Holocene, followed by a sharp increase to high values at around 4 ka BP (4 ka BP - 4000 years before present). Afterwards, the Be-10 flux remains on a high level during the Late Holocene, but decreases slightly towards today. These Be-10 deposition patterns are compared to moisture changes in regions dominated by the Indian Summer Monsoon (ISM), East Asian Summer Monsoon (EASM), and the Westerlies. Different from the gradual changes in monsoon patterns, the Be-10 data reveal low levels during the Early Holocene until similar to 4 ka BP when an obvious increase is indicated and a relative high level continues to this day, which is relatively more in agreement with patterns of the Westerlies. This finding provides a new evidence fora shift in the dominant pattern of atmospheric circulation the KP region from a more monsoonal one to one dominated by the Westerlies. Our results improve the understanding of non-stationary interactions and spatial relevance of the EASM, the ISM and the Westerlies on the Qinghai-Tibet Plateau.
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| 4. |
- Chen, Peng, et al.
(författare)
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Relationship between precipitation and Be-10 and impacts on soil dynamics
- 2020
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Ingår i: Catena (Cremlingen. Print). - : Elsevier BV. - 0341-8162 .- 1872-6887. ; 195
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Tidskriftsartikel (refereegranskat)abstract
- Meteoric beryllium-10 (Be-10) is commonly used as a proxy of landscape dynamics (erosion and sedimentation rates) and soil development. Soil represents the first-stage reservoir of meteoric Be-10, and variability in the concentration of the isotope in soils may be affected by soil properties and atmospheric deposition. Although many investigations have targeted this issue, there are still problems in estimating the atmospheric input of the isotope in different soil environments. Here, we used Be-10 data measured in soils distributed across China to explore the potential influence of meteorological and pedological conditions on the isotope concentration and related applications. In addition, to determine the mechanisms controlling Be-10 concentrations in topsoil on a regional scale, the soil samples were sub-divided into 18 different catchments according to fluvial systems. The results indicated that there were significant negative correlations between precipitation and the soil Be-10 concentration in high-precipitation regions (> 1200 mm.y(-1)) and significant positive correlations for soils in low precipitation regions (< 1200 mm.y(-1)). The data also revealed that precipitation is the most important variable controlling the Be-10 concentration in soils of China when compared with the effects of soil properties such as grain size, mineralogy, pH, and cation exchange capacity. Land use and soil erosion may have limited impacts on the distribution of Be-10 in soils.
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| 5. |
- Chen, Peng, et al.
(författare)
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Tendency of soil erosion dynamics by coupling radioisotopes and RUSLE model on the Southeastern Tibetan Plateau in response to climate warming and human activity
- 2023
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Ingår i: Catena. - : Elsevier BV. - 0341-8162. ; 223
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Tidskriftsartikel (refereegranskat)abstract
- Soil erosion has created landscape problems in many parts of the world and in particular in cold regions where the sensitive permafrost conditions have changed due to climate warming. Such a case occurred in the Tibetan Plateau (TP), which has been strongly affected by global warming and human activities. Monitoring technologies, like remote sensing and field surveys were used to explore soil erosion rates in the TP, but they were limited by the resolution and meteorological disturbance factors or the spatial and time scales. Here, we present for the first time 210Pbex (excess lead-210) and 137Cs (caesium-137) data of soils from the southeastern TP (SETP) covering an area of 640,000 km2. In the permafrost-dominant areas, the results show mean soil-erosion rates in the last 56–100 years that were relatively higher (1891 t·km−2·a-1) based on 210Pbex than those based on 137Cs (1623 t·km−2·a-1). Modelling results from the Revised Universal Soil Loss Equation (RUSLE) indicate relatively high mean soil erosion rates of 4363 and 4394 t·km−2·a-1 using a period covering the last 40 or 10 years respectively. Our data suggest accelerating erosion rates on the SETP that are linked to permafrost degradation, and glacier and snow melting due to accelerating global climate warming. The increase in ground surface temperature of ∼2 °C in the last four decades has further shifted the regional hydrology, affecting the degeneration of vegetation cover and a further increase in soil-erosion rates. However, our radionuclides data also expose low erosion rates in the seasonally frozen ground at some sampling sites which indicates the complex nature of erosion trends in cold regions that require careful adaptation of soil management.
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| 6. |
- Chen, Peng, et al.
(författare)
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Use of Be-10 isotope to predict landscape development in the source area of the Yellow River (SAYR), northeastern Qinghai-Tibet Plateau
- 2019
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Ingår i: Journal of Environmental Radioactivity. - : ELSEVIER SCI LTD. - 0265-931X .- 1879-1700. ; 203, s. 187-199
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Tidskriftsartikel (refereegranskat)abstract
- The magnitude of soil and sediment erosion and accumulation processes can profoundly affect landscape development and hamper efficient management of natural resources. Consequently, estimating the rates and causes of these processes is essential, particularly in remote regions, for prediction of changes in landform and river evolution and protection of local ecosystem. We here present the results of a soil and sediment erosion investigation in the Source Area of the Yellow River (SAYR), northeast Qinghai-Tibet Plateau based on a combined analysis of Be-10 cosmogenic isotope and Soil and Water Assessment Tool (SWAT) simulation modelling. The data reveal variable soil erosion trends that range between 103 and 830 t km(-2) a(-1). The low values occur in the western part of the basin that are associated with low sediment yield, while the high values appear in the dominant sediment export part of the basin along the main stream of the Yellow River in the east. Generally, soil and sediment accumulation is characterized by high Be-10 concentration in the western part and the northwest of Ngoring Lake. The style of landform development by the erosion/accumulation processes is closely linked to the distribution and degradation extent of the permafrost in the study region. Soil surface erosion increases with more permafrost degradation from the western to the eastern part of the basin, and surface soil particles are dominantly removed from the surface rather than deeper layers.
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| 7. |
- Chen, Xuegao, et al.
(författare)
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Distribution of I-129 in terrestrial surface water environments
- 2015
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; 361, s. 604-608
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Tidskriftsartikel (refereegranskat)abstract
- The global distribution of the radioactive isotope iodine-129 in surface waters (lakes and rivers) is presented here and compared with the atmospheric deposition and distribution in surface marine waters. The results indicate relatively high concentrations in surface water systems in close vicinity of the anthropogenic release sources as well as in parts of Western Europe, North America and Central Asia. I-129 level is generally higher in the terrestrial surface water of the Northern hemisphere compared to the southern hemisphere. The highest values of I-129 appear around 50 degrees N and 40 degrees S in the northern and southern hemisphere, separately. Direct gaseous and marine atmospheric emissions are the most likely avenues for the transport of 1291 from the sources to the terrestrial surface waters. To apply iodine-129 as process tracer in terrestrial surface water environment, more data are needed on I-129 distribution patterns both locally and globally.
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| 8. |
- Chen, Xuegao, et al.
(författare)
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Estimation of I-129 inventory in the oceans
- 2016
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 308:1, s. 59-65
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Tidskriftsartikel (refereegranskat)abstract
- Spatial distribution of oceanic I-129 inventory presented here is based on collection of data from published literatures coupled with model calculation using ArcGIS software tools. A total of 363 thiessen polygons were created for the oceans in order to cover the tremendous variability in distribution of I-129 data range. The results indicate that total I-129 oceanic inventory is approximately 7310 kg, which is mainly stored in the region of the North Atlantic and the Arctic Oceans. The concentrations of I-129 in the oceans are 3-4 orders of magnitude higher than the pre-anthropogenic level reflecting effects of post 1945 anthropogenic activities.
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| 9. |
- Jiang, Peng, et al.
(författare)
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Changes of storm properties in the United States : Observations and multimodel ensemble projections
- 2016
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Ingår i: Global and Planetary Change. - : Elsevier BV. - 0921-8181. ; 142, s. 41-52
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Tidskriftsartikel (refereegranskat)abstract
- Changes in climate are likely to induce changes in precipitation characteristics including intensity, frequency, duration and patterns of events. In this paper, we evaluate the performance of multiple regional climate models (RCMs) in the North American Regional Climate Change Assessment Program (NARCCAP) to simulate storm properties including storm duration, inter-storm period, storm intensity, and within-storm patterns at eight locations in the continental US. We also investigate the future projections of them based on precipitation from NARCCAP historic runs and future runs. Results illustrate that NARCCAP RCMs are consistent with observed precipitation in the seasonal variation of storm duration and inter-storm period, but fail to simulate the magnitude. The ability to simulate the seasonal trend of average storm intensity varies among locations. Within-storm patterns from RCMs exhibit greater variability than from observed records. Comparisons between RCM-historic simulations and RCM projections indicate that there is a large variation in the future changes in storm properties. However, multi-model ensembles of the storm properties suggest that most regions of the United States will experience future changes in storm properties that includes shorter storm duration, longer inter-storm period, and larger average storm intensity.
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| 10. |
- Yi, Peng, et al.
(författare)
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Evaluation of groundwater discharge into surface water by using Radon-222 in the Source Area of the Yellow River, Qinghai-Tibet Plateau
- 2018
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Ingår i: Journal of Environmental Radioactivity. - : Elsevier BV. - 0265-931X. ; 192, s. 257-266
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Tidskriftsartikel (refereegranskat)abstract
- Understanding hydrological processes in the Source Area of the Yellow River (SAYR), Qinghai-Tibet Plateau, is vital for protection and management of groundwater and surface water resources in the region. In situ water measurements of exchange rates between surface water and groundwater are, however, hard to conduct because of the harsh natural conditions of the SAYR. We here present an indirect method using in situ 222Rn measurements to estimate groundwater discharge into rivers and lakes in the SAYR. 222Rn was measured in rivers, lakes, groundwater and springs during three sampling periods (2014–2016), and the results indicate large variability in the concentration of the isotope. The data also indicate decreasing 222Rn trends in groundwater in the cold season (the Feb-2015 sampling period) which may be linked to frequency of capturing 222Rn in the frozen ground caused by geocryogenic processes. In addition, permafrost spatial extent and freeze-thaw processes have strongly affected the hydrological conditions in the region.
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