scholarly journals Climate model boundary conditions for four Cretaceous time slices

2007 ◽  
Vol 3 (4) ◽  
pp. 647-657 ◽  
Author(s):  
J. O. Sewall ◽  
R. S. W. van de Wal ◽  
K. van der Zwan ◽  
C. van Oosterhout ◽  
H. A. Dijkstra ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
General Circulation ◽  
Climate Model ◽  
General Circulation Models ◽  
Lead Author ◽  
Published Data ◽  
Surface Boundary ◽  
Surface Boundary Conditions ◽  
Digital Elevation ◽  
Earth’S Climate

Abstract. General circulation models (GCMs) are useful tools for investigating the characteristics and dynamics of past climates. Understanding of past climates contributes significantly to our overall understanding of Earth's climate system. One of the most time consuming, and often daunting, tasks facing the paleoclimate modeler, particularly those without a geological background, is the production of surface boundary conditions for past time periods. These boundary conditions consist of, at a minimum, continental configurations derived from plate tectonic modeling, topography, bathymetry, and a vegetation distribution. Typically, each researcher develops a unique set of boundary conditions for use in their simulations. Thus, unlike simulations of modern climate, basic assumptions in paleo surface boundary conditions can vary from researcher to researcher. This makes comparisons between results from multiple researchers difficult and, thus, hinders the integration of studies across the broader community. Unless special changes to surface conditions are warranted, researcher dependent boundary conditions are not the most efficient way to proceed in paleoclimate investigations. Here we present surface boundary conditions (land-sea distribution, paleotopography, paleobathymetry, and paleovegetation distribution) for four Cretaceous time slices (120 Ma, 110 Ma, 90 Ma, and 70 Ma). These boundary conditions are modified from base datasets to be appropriate for incorporation into numerical studies of Earth's climate and are available in NetCDF format upon request from the lead author. The land-sea distribution, bathymetry, and topography are based on the 1°×1° (latitude × longitude) paleo Digital Elevation Models (paleoDEMs) of Christopher Scotese. Those paleoDEMs were adjusted using the paleogeographical reconstructions of Ronald Blakey (Northern Arizona University) and published literature and were then modified for use in GCMs. The paleovegetation distribution is based on published data and reconstructions and consultation with members of the paleobotanical community and is represented as generalized biomes that should be easily translatable to many vegetation-modeling schemes.

scholarly journals Climate model boundary conditions for four Cretaceous time slices

2007 ◽  
Vol 3 (3) ◽  
pp. 791-810 ◽  
Author(s):  
J. O. Sewall ◽  
R. S. W. van de Wal ◽  
K. van der Zwan ◽  
C. van Ooosterhout ◽  
H. A. Dijkstra ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
General Circulation ◽  
Climate Model ◽  
General Circulation Models ◽  
Lead Author ◽  
Published Data ◽  
Surface Boundary ◽  
Surface Boundary Conditions ◽  
Digital Elevation ◽  
Earth’S Climate

Abstract. General circulation models (GCMs) are useful tools for investigating the characteristics and dynamics of past climates. Understanding of past climates contributes significantly to our overall understanding of Earth's climate system. One of the most time consuming, and often daunting, tasks facing the paleoclimate modeler, particularly those without a geological background, is the production of surface boundary conditions for past time periods. These boundary conditions consist of, at a minimum, continental configurations derived from plate tectonic modeling, topography, bathymetry, and a vegetation distribution. Typically, each researcher develops a unique set of boundary conditions for use in their simulations. Thus, unlike simulations of modern climate, basic assumptions in paleo surface boundary conditions can vary from researcher to researcher. This makes comparisons between results from multiple researchers difficult and, thus, hinders the integration of studies across the broader community. Unless special changes to surface conditions are warranted, researcher dependent boundary conditions are not the most efficient way to proceed in paleoclimate investigations. Here we present surface boundary conditions (land-sea distribution, paleotopography, paleobathymetry, and paleovegetation distribution) for four Cretaceous time slices (120 Ma, 110 Ma, 90 Ma, and 70 Ma). These boundary conditions are modified from base datasets to be appropriate for incorporation into numerical studies of Earth's climate and are available in NetCDF format upon request from the lead author. The land-sea distribution, bathymetry, and topography are based on the 1°×1° (latitude x longitude) paleo Digital Elevation Models (paleoDEMs) of Christopher Scotese. Those paleoDEMs were adjusted using the paleogeographical reconstructions of Ronald Blakey (Northern Arizona University) and published literature and were then modified for use in GCMs. The paleovegetation distribution is based on published data and reconstructions and consultation with members of the paleobotanical community and is represented as generalized biomes that should be easily translatable to many vegetation-modeling schemes.

The Kinematics Of Paleo Landforms

1994 ◽  
Author(s):  
R.G. Craig
Keyword(s):  
Boundary Conditions ◽  
General Circulation ◽  
Initial Conditions ◽  
General Circulation Models ◽  
Quaternary Geology ◽  
Current Form ◽  
Digital Elevation ◽  
Challenges And Opportunities ◽  
Simplifying Assumptions ◽  
Increasing Demand

Reconstructions of past, climates and other applications of global models require specification of landforms arid geomorphic systems as boundary conditions. As general circulation models become more sophisticated and comprehensive and the range of applications for reconstructions grows, there will be an increasing demand for valid geomorphic boundary conditions throughout the Phanerozoic. Geomorphologists have not yet, developed the tools and expertise needed to produce reconstructions, so a major gap in understanding of global change now exists. A strategy to fill that gap is presented here. If geomorphology is the study of the form of the land, and if the form of the land can be described by a set of numbers (digital elevation models), then whither geomorphology? Do we become numericists, mathematicians, and statisticians? If geomorphology is the study of the processes shaping the land, and if the form is completely explained by a set of processes and an initial condition (i.e., landform at some earlier time), then two "knowns," current form and current processes, are essential. But if processes themselves change through time and there is an infinite set, of initial conditions, one set for each point in time, then the job becomes overwhelmingly complex. As the geomorphic community has become painfully aware of the difficulties of deep reconstructions, we have withdrawn into the Quaternary, a period during which many simplifying assumptions can be made which allow solution of geomorphic problems. Hence the Geological Society of America lumps "Quaternary Geology" and "Geomorphology" into one division. We have become so comfortable with the notion that, geomorphology and Quaternary geology are synonymous that we have lost sight of the goals of founders of the science such as William Morris Davis and John Wesley Powell who strove to unearth the landforms of the distant past. Of course there is plenty to keep us busy in the good ol’ Quaternary; but we shouldn't ignore the enormous challenges and opportunities that await those who would reconstruct landforms of earlier times.

scholarly journals Upward Shift of the Atmospheric General Circulation under Global Warming: Theory and Simulations

2012 ◽  
Vol 25 (23) ◽  
pp. 8259-8276 ◽  
Author(s):  
Martin S. Singh ◽  
Paul A. O’Gorman
Keyword(s):  
Climate Change ◽  
General Circulation ◽  
General Circulation Models ◽  
Meridional Wind ◽  
Lapse Rate ◽  
Surface Boundary ◽  
Upper Troposphere ◽  
Zonal Winds ◽  
Upward Shift ◽  
Surface Boundary Conditions

Abstract Many features of the general circulation of the atmosphere shift upward in response to warming in simulations of climate change with both general circulation models (GCMs) and cloud-system-resolving models. The importance of the upward shift is well known, but its physical basis and the extent to which it occurs coherently across variables are not well understood. A transformation is derived here that shows how an upward shift of a solution to the moist primitive equations gives a new approximate solution with higher tropospheric temperatures. According to the transformation, all variables shift upward with warming but with an additional modification to the temperature and a general weakening of the pressure velocity. The applicability of the vertical-shift transformation is explored using a hierarchy of models from adiabatic parcel ascents to comprehensive GCMs. The transformation is found to capture many features of the response to climate change in simulations with an idealized GCM, including the mid- and upper-tropospheric changes in lapse rate, relative humidity, and meridional wind. The transformation is less accurate when applied to simulations with more realistic GCMs, but it nonetheless captures some important features. Deviations from the simulated response are primarily due to the surface boundary conditions, which do not necessarily conform to the transformation, especially in the case of the zonal winds. The results allow for a physical interpretation of the upward shift in terms of the governing equations and suggest that it may be thought of as a coherent response of the general circulation of the mid- and upper troposphere.

Using Clustered Climate Regimes to Analyze and Compare Predictions from Fully Coupled General Circulation Models

2005 ◽  
Vol 9 (10) ◽  
pp. 1-27 ◽  
Author(s):  
Forrest M. Hoffman ◽  
William W. Hargrove ◽  
David J. Erickson ◽  
Robert J. Oglesby
Keyword(s):  
Time Series ◽  
General Circulation ◽  
Climate Model ◽  
Circulation Model ◽  
Terrestrial Ecosystems ◽  
General Circulation Models ◽  
Transient Simulations ◽  
Spatio Temporal ◽  
Earth’S Climate ◽  
Fully Coupled

Abstract Changes in Earth’s climate in response to atmospheric greenhouse gas buildup impact the health of terrestrial ecosystems and the hydrologic cycle. The environmental conditions influential to plant and animal life are often mapped as ecoregions, which are land areas having similar combinations of environmental characteristics. This idea is extended to establish regions of similarity with respect to climatic characteristics that evolve through time using a quantitative statistical clustering technique called Multivariate Spatio-Temporal Clustering (MSTC). MSTC was applied to the monthly time series output from a fully coupled general circulation model (GCM) called the Parallel Climate Model (PCM). Results from an ensemble of five 99-yr Business-As-Usual (BAU) transient simulations from 2000 to 2098 were analyzed. MSTC establishes an exhaustive set of recurring climate regimes that form a “skeleton” through the “observations” (model output) throughout the occupied portion of the climate phase space formed by the characteristics being considered. MSTC facilitates direct comparison of ensemble members and ensemble and temporal averages since the derived climate regimes provide a basis for comparison. Moreover, by mapping all land cells to discrete climate states, the dynamic behavior of any part of the system can be studied by its time-varying sequence of climate state occupancy. MSTC is a powerful tool for model developers and environmental decision makers who wish to understand long, complex time series predictions of models. Strong predicted interannual trends were revealed in this analysis, including an increase in global desertification; a decrease in the cold, dry high-latitude conditions typical of North American and Asian winters; and significant warming in Antarctica and western Greenland.

The Role of SST Structure in Convectively Coupled Kelvin–Rossby Waves and Its Implications for MJO Formation

2013 ◽  
Vol 26 (16) ◽  
pp. 5915-5930 ◽  
Author(s):  
In-Sik Kang ◽  
Fei Liu ◽  
Min-Seop Ahn ◽  
Young-Min Yang ◽  
Bin Wang
Keyword(s):  
Boundary Layer ◽  
Boundary Conditions ◽  
Planetary Boundary Layer ◽  
General Circulation ◽  
Rossby Waves ◽  
Circulation Model ◽  
Moisture Convergence ◽  
Control Factor ◽  
Surface Boundary ◽  
Surface Boundary Conditions

Abstract The dynamics of the Madden–Julian oscillation (MJO) are investigated using an aqua-planet general circulation model (GCM) and a simple one-and-a-half-layer model with a first-baroclinic mode and a planetary boundary layer. The aqua-planet GCM with zonally symmetric SST conditions simulates tropical intraseasonal disturbances with a dominant time scale of about 20 days, which is much faster than that of the observed MJO, although the GCM with realistic surface boundary conditions is shown to reproduce the observed MJO reasonably well. The SST with a broader meridional structure slows down the propagation speed. Several experiments done with various zonally symmetric surface boundary conditions showed that the meridional structure of the SST in fact is a control factor for the propagation characteristics of the MJO. With a simple theoretical model for the MJO, it is shown that the instability of the moist coupled Kelvin–Rossby waves depends on the SST structure, which determines the lower-level moisture field. The SST with a narrow meridional structure prefers to enhance only the fast eastward Kelvin wave, while the broader SST provides enough off-equatorial moisture for the growth of the Rossby component, which couples strongly with the Kelvin component and slows down the eastward modes. The SST influences the coupled Kelvin–Rossby waves through changes in the moist static stability of the free atmosphere and the frictional moisture convergence in the planetary boundary layer. The present results suggest that the essential dynamics of the MJO are rooted in a convectively coupled Kelvin–Rossby wave packet with frictional moisture convergence.

Surface Boundary Conditions for Mesoscale Regional Climate Models

2005 ◽  
Vol 9 (18) ◽  
pp. 1-28 ◽  
Author(s):  
Xin-Zhong Liang ◽  
Hyun I. Choi ◽  
Kenneth E. Kunkel ◽  
Yongjiu Dai ◽  
Everette Joseph ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
Climate Models ◽  
Climate Model ◽  
Regional Climate ◽  
Clay Fraction ◽  
Value Added ◽  
Quality Data ◽  
Surface Boundary ◽  
Surface Boundary Conditions ◽  
Vegetation Characteristic

Abstract This paper utilizes the best available quality data from multiple sources to develop consistent surface boundary conditions (SBCs) for mesoscale regional climate model (RCM) applications. The primary SBCs include 1) fields of soil characteristic (bedrock depth, and sand and clay fraction profiles), which for the first time have been consistently introduced to define 3D soil properties; 2) fields of vegetation characteristic fields (land-cover category, and static fractional vegetation cover and varying leaf-plus-stem-area indices) to represent spatial and temporal variations of vegetation with improved data coherence and physical realism; and 3) daily sea surface temperature variations based on the most appropriate data currently available or other value-added alternatives. For each field, multiple data sources are compared to quantify uncertainties for selecting the best one or merged to create a consistent and complete spatial and temporal coverage. The SBCs so developed can be readily incorporated into any RCM suitable for U.S. climate and hydrology modeling studies, while the data processing and validation procedures can be more generally applied to construct SBCs for any specific domain over the globe.

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