Precipitation Simulation in Global Climate Models: Impact of Horizontal Resolution and Improved Land Surface Scheme (PHD). PDF Download
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Author: Muhammad Javed Shaikh
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Category :
Languages : en
Pages : 0
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Author: Muhammad Javed Shaikh
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Category :
Languages : en
Pages : 0
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Author: Singh, Shweta
Publisher: KIT Scientific Publishing
ISBN: 3731510685
Category : Science
Languages : en
Pages : 198
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The impact of land-surface properties like vegetation, soil type, soil moisture, and the orography on the atmosphere is manifold. These features determine the evolution of the atmospheric boundary layer, convective conditions, cloud evolution and precipitation. The impact of model grid spacing and land-surface resolution on convective precipitation over heterogeneous surfaces is investigated using ICOsahedral Nonhydrostatic (ICON) simulations within the framework of the HD(CP)2 project.
Author:
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Category : Atmospheric chemistry
Languages : en
Pages : 406
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Category : Dissertations, Academic
Languages : en
Pages : 994
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Author: Martin Beniston
Publisher: Springer Science & Business Media
ISBN: 0306479834
Category : Science
Languages : en
Pages : 507
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year simulations in order to separate noise in the system from the climate change signal. Several contributing papers focused on case studies using Regional Climate Models (RCMs) linked to hydrological models, applied to the analysis of runoff under conditions of convective activity and extreme precipitation, in regions of complex topography, or stakeholder-driven investigations such as water runoff simulations in Quebec undertaken for a major utility. Thorough analyses of GCM results for the Century were reported at the Workshop, in order to illustrate the improvements in model results which have taken place in recent years, and the increasing confidence with which the models can be used for projecting climatic change in coming decades. However, there is still much room for improvement; there is also a need to address more fully the manner in which climate and impacts models (e. g. , hydrological models) can be linked, in terms of consistency and the overlap between different scales, the underlying physical assumptions, and the parameterizations used. Session 2 was devoted to the two extremes of water resources, namely floods and droughts, the focus here being to identify the climate change component in river floods. These have significant economic implications, as was shown by several scientists from Western and Central Europe. Many long time series have been studied worldwide with the aim of detection of nonstationarities, yet there is no conclusive evidence of climate-related changes in flow records, in general.
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Category :
Languages : en
Pages : 5
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In order to evaluate the consequences of climate change for agriculture and the economy we need to develop climate models capable of correctly simulating regional precipitation patterns. The deficiency of global climate models in the simulation of orographic precipitation may be related to the crudeness of model topography. Inadequacies in the parameterizations of physical processes cause additional errors in the calculation of orographic as well as frontal precipitation. In this study, we have investigated the role of model resolution in simulating the geographical distribution of precipitation over China. Comparisons are made between observations and the calculated precipitation fields in a seasonal run with climatological sea surface temperatures. This study describes results for June and July from 12 month simulations of the ECMWF model at the following four resolutions: T21 (5 x 5 degree), T42 (3 x 3 degree), T63 (2 x 2 degree) and T106 (1 x 1 degree). A description of this model is given by Simmons et. al. (1988). The various resolutions of the ECMWF model are virtually identical with the exception of the gravity wave drag (Palmer et al. 1986), vertical diffusion coefficients and orography. The T21 resolution lacks gravity wave drag completely.
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Category : Dissertation abstracts
Languages : en
Pages : 896
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Category :
Languages : en
Pages :
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One key question regarding current climate models is whether the projection of climate extremes converges to a realistic representation as the spatial and temporal resolutions of the model are increased. Ideally the model extreme statistics should approach a fixed distribution once the resolutions are commensurate with the characteristic length and time scales of the processes governing the formation of the extreme phenomena of interest. In this study, a series of AGCM runs with idealized 'aquaplanet-steady-state' boundary conditions have been performed with the Community Atmosphere Model CAM3 to investigate the effect of horizontal resolution on climate extreme simulations. The use of the aquaplanet framework highlights the roles of model physics and dynamics and removes any apparent convergence in extreme statistics due to better resolution of surface boundary conditions and other external inputs. Assessed at a same large spatial scale, the results show that the horizontal resolution and time step have strong effects on the simulations of precipitation extremes. The horizontal resolution has a much stronger impact on precipitation extremes than on mean precipitation. Updrafts are strongly correlated with extreme precipitation at tropics at all the resolutions, while positive low-tropospheric temperature anomalies are associated with extreme precipitation at mid-latitudes.
Author: Elizabeth A. Maroon
Publisher:
ISBN:
Category :
Languages : en
Pages : 133
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In this thesis, coupled and atmosphere-only global climate models are used to examine two large-scale climate asymmetries: the zonal asymmetry of tropical precipitation about the equator and the preference for sinking in the North Atlantic Ocean, but not in the North Pacific Ocean. The examination of these two climate asymmetries is performed using models of differing complexity. The first half of this dissertation discusses the influence of land on the distribution of tropical precipitation in idealized geometry models. A continent is added to the Northern Hemisphere subtropics of two aquaplanet models; annual mean insolation is prescribed and the albedo and longitudinal extent of the continent are varied. One of the models, GRaM, has gray-radiation physics with moist dynamics, while the other model, GFDL's AM2.1, has comprehensive physics. In the GRaM model, the pattern of the precipitation response is mostly related to decreased evaporation due to the now unsaturated surface. As the albedo of land is increased, precipitation shifts southward away from the hemisphere with less absorbed energy. In the AM2.1 model, there is a zonally-varying response in tropical precipitation due to the addition of land, but this response is not rubust in simulations that include a seasonal cycle of insolation. As albedo over land is increased, precipitation shifts southward zonally, just as in GRaM. When the width of the continent is increased, tropical precipitation shifts toward the continent, which indicates that continental width plays an important role in setting the distribution of tropical atmospheric overturning circulations. The second half of this dissertation examines the influence of Rocky Mountain orography on the location of Northern Hemisphere sinking of the oceanic meridional overturning circulation (MOC). Warren (1983) found that there is greater transport of salt into the high latitude North Atlantic than into the North Pacific, allowing water to sink in the winter as the downward branch of the Atlantic MOC (AMOC). The southwest-to-northeast tilt of the boundary between the North Atlantic subtropical and subpolar gyres, which is forced by the winds, accomplishes this northward salt transport. Because the Rocky Mountains influence the distribution of wind stress curl in the midlatitude North Atlantic, the presence of the Rockies may be the reason why water sinks in the North Atlantic (Warren, 1983). To test Warren's hypothesis, we remove the Rocky Mountains in a coarse resolution version of GFDL's CM2.1 model that has realistic boundary conditions. In this simulation, the removal of the Rockies causes the strength of the AMOC to decrease by 7 Sv and a Pacific MOC (PMOC) starts. Additional coupled simulations are performed that re-route western North American rivers from the North Pacific to the North Atlantic while retaining the Rocky Mountains. In all of the simulations, decreased runoff to the North Pacific is responsible for the increase in salinity that initiates the sinking in the PMOC. A salinity-advection feedback amplifies the initial density anomaly in the region of Pacific sinking. Similarly, increased runoff to the North Atlantic, not altered wind stress, is responsible for the decrease in AMOC strength, but the AMOC still exists after the Rocky Mountains are removed. Atmosphere-only simulations are used to isolate the changes in surface wind due to the mechanical (orographic) and thermodynamical (buoyancy) impacts of the Rockies on the MOC. We find that the changes in wind stress curl that are responsible for the North Atlantic gyre circulations are strongly affected by the Rocky Mountain orography through its impact on the atmospheric stationary wave (as is well known). Nonetheless, the preference for sinking in the North Atlantic is not affected by changes in the pattern of wind stress that result from the presence of the Rockies.
Author: Matthew Collins
Publisher: Frontiers Media SA
ISBN: 2889741397
Category : Science
Languages : en
Pages : 178
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