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Author: Ashish Sharma
Publisher:
ISBN:
Category : Arid regions climate
Languages : en
Pages : 130
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Book Description
This study performs numerical modeling for the climate of semi-arid regions by running a high-resolution atmospheric model constrained by large-scale climatic boundary conditions, a practice commonly called climate downscaling. These investigations focus especially on precipitation and temperature, quantities that are critical to life in semi-arid regions. Using the Weather Research and Forecast (WRF) model, a non-hydrostatic geophysical fluid dynamical model with a full suite of physical parameterization, a series of numerical sensitivity experiments are conducted to test how the intensity and spatial/temporal distribution of precipitation change with grid resolution, time step size, the resolution of lower boundary topography and surface characteristics. Two regions, Arizona in U.S. and Aral Sea region in central Asia, are chosen as the test-beds for the numerical experiments: The former for its complex terrain and the latter for the dramatic man-made changes in its lower boundary conditions (the shrinkage of Aral Sea). Sensitivity tests show that the parameterization schemes for rainfall are not resolution-independent, thus a refinement of resolution is no guarantee of a better result. But, simulations (at all resolutions) do capture the inter-annual variability of rainfall over Arizona. Nevertheless, temperature is simulated more accurately with refinement in resolution. Results show that both seasonal mean rainfall and frequency of extreme rainfall events increase with resolution. For Aral Sea, sensitivity tests indicate that while the shrinkage of Aral Sea has a dramatic impact on the precipitation over the confine of (former) Aral Sea itself, its effect on the precipitation over greater central Asia is not necessarily greater than the inter-annual variability induced by the lateral boundary conditions in the model and large scale warming in the region. The numerical simulations in the study are cross validated with observations to address the realism of the regional climate model. The findings of this sensitivity study are useful for water resource management in semi-arid regions. Such high spatio-temporal resolution gridded-data can be used as an input for hydrological models for regions such as Arizona with complex terrain and sparse observations. Results from simulations of Aral Sea region are expected to contribute to ecosystems management for Central Asia.
Author: Ashish Sharma
Publisher:
ISBN:
Category : Arid regions climate
Languages : en
Pages : 130
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Book Description
This study performs numerical modeling for the climate of semi-arid regions by running a high-resolution atmospheric model constrained by large-scale climatic boundary conditions, a practice commonly called climate downscaling. These investigations focus especially on precipitation and temperature, quantities that are critical to life in semi-arid regions. Using the Weather Research and Forecast (WRF) model, a non-hydrostatic geophysical fluid dynamical model with a full suite of physical parameterization, a series of numerical sensitivity experiments are conducted to test how the intensity and spatial/temporal distribution of precipitation change with grid resolution, time step size, the resolution of lower boundary topography and surface characteristics. Two regions, Arizona in U.S. and Aral Sea region in central Asia, are chosen as the test-beds for the numerical experiments: The former for its complex terrain and the latter for the dramatic man-made changes in its lower boundary conditions (the shrinkage of Aral Sea). Sensitivity tests show that the parameterization schemes for rainfall are not resolution-independent, thus a refinement of resolution is no guarantee of a better result. But, simulations (at all resolutions) do capture the inter-annual variability of rainfall over Arizona. Nevertheless, temperature is simulated more accurately with refinement in resolution. Results show that both seasonal mean rainfall and frequency of extreme rainfall events increase with resolution. For Aral Sea, sensitivity tests indicate that while the shrinkage of Aral Sea has a dramatic impact on the precipitation over the confine of (former) Aral Sea itself, its effect on the precipitation over greater central Asia is not necessarily greater than the inter-annual variability induced by the lateral boundary conditions in the model and large scale warming in the region. The numerical simulations in the study are cross validated with observations to address the realism of the regional climate model. The findings of this sensitivity study are useful for water resource management in semi-arid regions. Such high spatio-temporal resolution gridded-data can be used as an input for hydrological models for regions such as Arizona with complex terrain and sparse observations. Results from simulations of Aral Sea region are expected to contribute to ecosystems management for Central Asia.
Author: Tsou Chun Jaw
Publisher:
ISBN: 9781267132352
Category :
Languages : en
Pages : 168
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Book Description
Twentieth century climate change induced by anthropogenic forcings has been recognized as one of the most serious issues affecting the development of mankind. Impacts of climate change on hydrologic processes are highly relevant to human activities and draw a great deal of scientific attention. In particular, semi-arid hydrology and water resources, which are encountering significant challenges in present climate, are projected to be more vulnerable to the future climate. While relevant studies emphasize large-scale impacts on hydrological processes due to climate changes, investigations of the impacts of climate changes on regional, even basin-scale hydrology are relatively limited. The main objective of this dissertation is to assess the potential hydrologic impacts of climate change over a semi-arid region by means of hydrologic modeling driven by high-resolution meteorological forcings. While GCMs are considered as powerful tools to simulate large-scale climate changes in the Earth system, climate information derived from GCMs needs to be further downscaled to meet the requirements of assessing the impact of regional climate and hydrology on global climate change. In this study, dynamical downscaling implementing a Regional Climate Model (RCM) to derive finer-resolution climate data is conducted, and three GCMs (BCCR, CCSM3, and ECHAM5) are adopted as the forcing data sets of the dynamical downscaling to evaluate regional climate and its hydrologic impacts over the semi-arid Morocco under the present-day and future climate scenarios. Downscaled precipitation analyses indicate that, systematically, biases are present. Directly using biased RCM output for hydrologic assessments would lead to unrealistic results. Therefore, effective bias correction approaches for the meteorological forcings required in the hydrologic modeling are adopted. While dynamically-downscaled GCMs show varying biases, downscaled ECHAM5 runs are more realistic in reproducing the historical climate patterns. Furthermore, proposed bias corrections (QM, EDCDF, and MovingCDF) significantly reduce the biases both in the meteorological forcings and their hydrologic responses. Among the correction approaches, MovingCDF accounts for the nonstationarity within the projection period and displays the best performance in forcing correction. Hydrologic simulation runs forced by the corrected forcings are significantly improved in the historical period in comparison with the results directly forced by RCM output. For future hydrologic assessments, hydrologic simulations driven by bias-corrected climate forcings exhibit a more consistent agreement. A drier hydrologic condition in the study region is expected in the near future (2036-2065). However, the degrees of the hydrologic impact, are highly dependent on the behaviors of large-scale GCM forcings.
Author: Rao Kotamarthi
Publisher: Cambridge University Press
ISBN: 110847375X
Category : Nature
Languages : en
Pages : 213
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Book Description
A practical guide to understanding, using and producing downscaled climate data, for researchers, graduate students, policy makers and practitioners.
Author: Douglas Maraun
Publisher: Cambridge University Press
ISBN: 1108340644
Category : Science
Languages : en
Pages : 366
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Book Description
Statistical downscaling and bias correction are becoming standard tools in climate impact studies. This book provides a comprehensive reference to widely-used approaches, and additionally covers the relevant user context and technical background, as well as a synthesis and guidelines for practitioners. It presents the main approaches including statistical downscaling, bias correction and weather generators, along with their underlying assumptions, skill and limitations. Relevant background information on user needs and observational and climate model uncertainties is complemented by concise introductions to the most important concepts in statistical and dynamical modelling. A substantial part is dedicated to the evaluation of regional climate projections and their value in different user contexts. Detailed guidelines for the application of downscaling and the use of downscaled information in practice complete the volume. Its modular approach makes the book accessible for developers and practitioners, graduate students and experienced researchers, as well as impact modellers and decision makers.
Author: Benestad Rasmus E
Publisher: World Scientific Publishing Company
ISBN: 9813107294
Category : Science
Languages : en
Pages : 228
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Book Description
Empirical-statistical downscaling (ESD) is a method for estimating how local climatic variables are affected by large-scale climatic conditions. ESD has been applied to local climate/weather studies for years, but there are few — if any — textbooks on the subject. It is also anticipated that ESD will become more important and commonplace in the future, as anthropogenic global warming proceeds. Thus, a textbook on ESD will be important for next-generation climate scientists.
Author: Taesam Lee
Publisher: CRC Press
ISBN: 0429861141
Category : Science
Languages : en
Pages : 163
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Book Description
Global climate change is typically understood and modeled using global climate models (GCMs), but the outputs of these models in terms of hydrological variables are only available on coarse or large spatial and time scales, while finer spatial and temporal resolutions are needed to reliably assess the hydro-environmental impacts of climate change. To reliably obtain the required resolutions of hydrological variables, statistical downscaling is typically employed. Statistical Downscaling for Hydrological and Environmental Applications presents statistical downscaling techniques in a practical manner so that both students and practitioners can readily utilize them. Numerous methods are presented, and all are illustrated with practical examples. The book is written so that no prior background in statistics is needed, and it will be useful to graduate students, college faculty, and researchers in hydrology, hydroclimatology, agricultural and environmental sciences, and watershed management. It will also be of interest to environmental policymakers at the local, state, and national levels, as well as readers interested in climate change and its related hydrologic impacts. Features: Examines how to model hydrological events such as extreme rainfall, floods, and droughts at the local, watershed level. Explains how to properly correct for significant biases with the observational data normally found in current Global Climate Models (GCMs). Presents temporal downscaling from daily to hourly with a nonparametric approach. Discusses the myriad effects of climate change on hydrological processes.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309492432
Category : Science
Languages : en
Pages : 29
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Book Description
We live on a dynamic Earth shaped by both natural processes and the impacts of humans on their environment. It is in our collective interest to observe and understand our planet, and to predict future behavior to the extent possible, in order to effectively manage resources, successfully respond to threats from natural and human-induced environmental change, and capitalize on the opportunities â€" social, economic, security, and more â€" that such knowledge can bring. By continuously monitoring and exploring Earth, developing a deep understanding of its evolving behavior, and characterizing the processes that shape and reshape the environment in which we live, we not only advance knowledge and basic discovery about our planet, but we further develop the foundation upon which benefits to society are built. Thriving on Our Changing Planet: A Decadal Strategy for Earth Observation from Space (National Academies Press, 2018) provides detailed guidance on how relevant federal agencies can ensure that the United States receives the maximum benefit from its investments in Earth observations from space, while operating within realistic cost constraints. This short booklet, designed to be accessible to the general public, provides a summary of the key ideas and recommendations from the full decadal survey report.
Author: Howard Wheater
Publisher: Cambridge University Press
ISBN: 1139468081
Category : Science
Languages : en
Pages : 222
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Book Description
Arid and semi-arid regions are defined as areas where water is at its most scarce. The hydrological regime in these areas is extreme and highly variable, and they face great pressures to deliver and manage freshwater resources. However, there is no guidance on the decision support tools that are needed to underpin flood and water resource management in arid areas. UNESCO initiated the Global network for Water and Development Information for arid lands (GWADI), and arranged a workshop of the world's leading experts to discuss these issues. This book presents chapters from contributors to the workshop, and includes case studies from the world's major arid regions to demonstrate model applications, and web links to tutorials and state-of-the-art modelling software. This volume is a valuable reference for researchers and engineers working on the water resources of arid and semi-arid regions.
Author: Bijaya Prakash Shrestha
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
