The Experts below are selected from a list of 29553 Experts worldwide ranked by ideXlab platform
Ning Zeng - One of the best experts on this subject based on the ideXlab platform.
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the Hydrological Cycle in the mediterranean region and implications for the water budget of the mediterranean sea
Journal of Climate, 2002Co-Authors: Annarita Mariotti, M V Struglia, Ning ZengAbstract:Abstract The Hydrological Cycle in the Mediterranean region is analyzed focusing on climatology and interannual to interdecadal variability, in particular long-term changes related to the well-established North Atlantic Oscillation (NAO) teleconnection. Recent atmospheric reanalyses and observational datasets are used: precipitation, evaporation, and moisture flux from 50 yr of NCEP's and 15 yr of ECMWF's reanalyses; precipitation from the Climate Prediction Center Merged Analysis of Precipitation (CMAP) and the East Anglia University Climate Research Unit (CRU) datasets; and evaporation from the University of Wisconsin—Milwaukee (UWM) Comprehensive Ocean–Atmosphere Data Set (COADS). A budget analysis is performed to study contributions to the freshwater flux into the Mediterranean Sea, including atmospheric as well as river discharge inputs. The total river discharge is derived using historical time series from Mediterranean Hydrological Cycle Observing System (MED-HYCOS) and Global Runoff Data Center (G...
Hongxing Zheng - One of the best experts on this subject based on the ideXlab platform.
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changes in components of the Hydrological Cycle in the yellow river basin during the second half of the 20th century
Hydrological Processes, 2004Co-Authors: Hongxing ZhengAbstract:The Yellow River basin of China, located in the semi-humid, semi-arid and and climatic zones, is now confronted with serious problems of water deficit. With regard to intensified human activities and climatic change, knowledge about changes in the regional Hydrological Cycle should be seen as a key requirement in searching for an adaptation strategy in water resource use. This paper attempts to detect trends associated with Hydrological Cycle components in the region. The Hydrological Cycle components are derived from monthly precipitation and runoff date, based on the schemes proposed herein. Two methods, including linear regression and Mann-Kendall, have been applied to the detection of trends in the Hydrological Cycle components. For the Lanzhou station, only surface runoff showed a decreasing trend. As for Huayuankou station, the results have shown that natural runoff, surface runoff and groundwater runoff all have significant decreasing trends, whereas the decreasing trend of the other components is not significant. Impacts of human activities, climatic change and annual runoff coefficient change on the Hydrological Cycle components are also discussed. The study suggests that increasing water resources development and utilization is the most important factor in causing the frequent drying-up in the main course of the Yellow River. Moreover, the similarities of the trends in precipitation and natural runoff suggest a linkage between climatic change and Hydrological Cycle change. Copyright (C) 2004 John Wiley Sons, Ltd.
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Hydrological Cycle changes in China’s large river basin: The Yellow River drained dry
Advances in Global Change Research, 2002Co-Authors: Hongxing ZhengAbstract:The Yellow River is one of the most important rivers in China. In the recent years, the Hydrological Cycle of the basin have changed greatly. Particularly, the main course of the lower reaches has been drying up which has caused a series of ecological, environmental and socioeconomical problems. In this paper, we have tried to explain the reasons for the Hydrological Cycle changes regarding the physical aspects and human activities. On the basis of the research on the characteristics of Hydrological Cycle and water resources in the basin, we find that the climate change impact may be one of the reasons. However, the prevailing impacts on the water resources were from human activities associated with land use and land cover change in the river basin. According to the research, some major countermeasures were suggested to enhance water management as the adaptive approach. Finally the authors addressed the highlights of Hydrological Cycle regarding water resources development and major conclusion remarks.
Tajdarul H Syed - One of the best experts on this subject based on the ideXlab platform.
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analysis of process controls in land surface Hydrological Cycle over the continental united states
Journal of Geophysical Research, 2004Co-Authors: Tajdarul H Syed, Venkat Lakshmi, Evan K Paleologos, Dag Lohmann, Kenneth E Mitchell, James S FamigliettiAbstract:The paper uses two years (1997–1999) of data from the North American Land Data Assimilation System at National Centers for Environmental Prediction to analyze the variability of physical variables contributing to the Hydrological Cycle over the conterminous United States. The five Hydrological variables considered in this study are precipitation, top layer soil moisture (0–10 cm), total soil moisture (0–200 cm), runoff, and potential evaporation. There are two specific analyses carried out in this paper. In the first case the principal components of the Hydrological Cycle are examined with respect to the loadings of the individual variables. This helps to ascertain the contribution of physical variables to the Hydrological process in decreasing order of process importance. The results from this part of the study had revealed that both in annual and seasonal timescales the first two principal components account for 70–80% of the variance and that precipitation dominated the first principal component, the most dominant mode of spatial variability. It was followed by the potential evaporation as the secondmost dominant process controlling the spatial variability of the hydrologic Cycle over the continental United States. In the second case each Hydrological variable was examined individually to determine the temporal evolution of its spatial variability. The results showed the presence of heterogeneity in the spatial variability of hydrologic variables and the way these patterns of variance change with time. It has also been found that the temporal evolution of the spatial patterns did not resemble white noise; the time series of the scores of the principal components showed proper cyclicity at seasonal to annual timescales. The northwestern and the southeastern parts of the United States had been found to have contributed significantly toward the overall variability of potential evaporation and soil moisture over the United States. This helps in determining the spatial patterns expected from Hydrological variability. More importantly, in the case of modeling as well as designing observing systems, these studies will lead to the creation of efficient and accurate land surface measurement and parameterization schemes.
Annarita Mariotti - One of the best experts on this subject based on the ideXlab platform.
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the Hydrological Cycle in the mediterranean region and implications for the water budget of the mediterranean sea
Journal of Climate, 2002Co-Authors: Annarita Mariotti, M V Struglia, Ning ZengAbstract:Abstract The Hydrological Cycle in the Mediterranean region is analyzed focusing on climatology and interannual to interdecadal variability, in particular long-term changes related to the well-established North Atlantic Oscillation (NAO) teleconnection. Recent atmospheric reanalyses and observational datasets are used: precipitation, evaporation, and moisture flux from 50 yr of NCEP's and 15 yr of ECMWF's reanalyses; precipitation from the Climate Prediction Center Merged Analysis of Precipitation (CMAP) and the East Anglia University Climate Research Unit (CRU) datasets; and evaporation from the University of Wisconsin—Milwaukee (UWM) Comprehensive Ocean–Atmosphere Data Set (COADS). A budget analysis is performed to study contributions to the freshwater flux into the Mediterranean Sea, including atmospheric as well as river discharge inputs. The total river discharge is derived using historical time series from Mediterranean Hydrological Cycle Observing System (MED-HYCOS) and Global Runoff Data Center (G...
Martin Wild - One of the best experts on this subject based on the ideXlab platform.
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the sensitivity of the modeled energy budget and Hydrological Cycle to co 2 and solar forcing
Earth System Dynamics Discussions, 2013Co-Authors: Nathalie Schaller, Martin Wild, Jan Cermak, Reto KnuttiAbstract:Abstract. The transient responses of the energy budget and the Hydrological Cycle to CO2 and solar forcings of the same magnitude in a global climate model are quantified in this study. Idealized simulations are designed to test the assumption that the responses to forcings are linearly additive, i.e. whether the response to individual forcings can be added to estimate the responses to the combined forcing, and to understand the physical processes occurring as a response to a surface warming caused by CO2 or solar forcing increases of the same magnitude. For the global climate model considered, the responses of most variables of the energy budget and Hydrological Cycle, including surface temperature, do not add linearly. A separation of the response into a forcing and a feedback term shows that for precipitation, this non-linearity arises from the feedback term, i.e. from the non-linearity of the temperature response and the changes in the water Cycle resulting from it. Further, changes in the energy budget show that less energy is available at the surface for global annual mean latent heat flux, and hence global annual mean precipitation, in simulations of transient CO2 concentration increase compared to simulations with an equivalent transient increase in the solar constant. On the other hand, lower tropospheric water vapor increase is similar between simulations with CO2 and solar forcing increase of the same magnitude. The response in precipitation is therefore more muted compared to the response in water vapor in CO2 forcing simulations, leading to a larger increase in residence time of water vapor in the atmosphere compared to solar forcing simulations. Finally, energy budget calculations show that poleward atmospheric energy transport increases more in solar forcing compared to equivalent CO2 forcing simulations, which is in line with the identified strong increase in large-scale precipitation in solar forcing scenarios.
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combined surface solar brightening and increasing greenhouse effect support recent intensification of the global land based Hydrological Cycle
Geophysical Research Letters, 2008Co-Authors: Martin Wild, Jurgen Grieser, Christoph ScharAbstract:[1] The surface net radiation (surface radiation balance) is the key driver behind the global Hydrological Cycle. Here we present a first-order trend estimate for the 15-year period 1986–2000, which suggests that surface net radiation over land has rapidly increased by about 2 Wm−2 per decade, after several decades with no evidence for an increase. This recent increase is caused by increases in both downward solar radiation (due to a more transparent atmosphere) and downward thermal radiation (due to enhanced concentrations of atmospheric greenhouse-gases). The positive trend in surface net radiation is consistent with the observed increase in land precipitation (3.5 mmy−1 per decade between 1986 and 2000) and the associated intensification of the land-based Hydrological Cycle. The concurrent changes in surface net radiation and Hydrological Cycle were particularly pronounced in the recovery phase following the Mount Pinatubo volcanic eruption, but remain evident even when discarding the Pinatubo-affected years.
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is the Hydrological Cycle accelerating
Science, 2002Co-Authors: Atsumu Ohmura, Martin WildAbstract:As global climate warms, most atmospheric scientists believe that evaporation will increase and as a result, the Hydrological Cycle will accelerate. But results from a network of water-filled pans used to monitor evaporation suggest that the opposite may be happening. In this Perspective, Ohmura and Wild review the evidence for and against an accelerated Hydrological Cycle. They highlight a new explanation for the pan evaporation data by Roderick and Farquhar, but warns that the issue is far from resolved.
