Model-data comparison of the parabolic equation approximation for long-range propagation, time spreading, and channel bandwidth estimation

2019 ◽  
Vol 146 (4) ◽  
pp. 3036-3036
Author(s):  
Paul C. Hines ◽  
Terry Deveau ◽  
Elizabeth Kusel ◽  
David R. Barclay ◽  
Dainis Nams ◽  
...  
Keyword(s):  
Parabolic Equation ◽  
Long Range ◽  
Propagation Time ◽  
Bandwidth Estimation ◽  
Model Data ◽  
Data Comparison ◽  
Channel Bandwidth

Ray Theory versus the Parabolic Equation in a Long Range Ducted Environment

1983 ◽  
Author(s):  
A. Tolstoy ◽  
E. R. Franchi ◽  
K. R. Nicolas
Keyword(s):  
Parabolic Equation ◽  
Long Range ◽  
Ray Theory ◽  
Theory Versus

scholarly journals The Last Glacial Maximum and Heinrich Event 1 in terms of climate and vegetation around the Alboran Sea: a preliminary model-data comparison

2005 ◽  
Vol 337 (10-11) ◽  
pp. 983-992 ◽  
Author(s):  
Masa Kageyama ◽  
Nathalie Combourieu Nebout ◽  
Pierre Sepulchre ◽  
Odile Peyron ◽  
Gerhard Krinner ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Glacial Maximum ◽  
Model Data ◽  
Last Glacial ◽  
Data Comparison ◽  
Heinrich Event ◽  
Preliminary Model ◽  
The Last Glacial Maximum ◽  
Heinrich Event 1 ◽  
The Last Glacial

Weichselian Late Pleniglacial surface winds over northwest and central Europe: a model–data comparison

2007 ◽  
Vol 22 (3) ◽  
pp. 281-293 ◽  
Author(s):  
H. Renssen ◽  
C. Kasse ◽  
J. Vandenberghe ◽  
S. J. Lorenz
Keyword(s):  
Central Europe ◽  
Surface Winds ◽  
Model Data ◽  
Data Comparison

Probing based wireless channel bandwidth estimation and its application to video streaming over wireless networks

2008 ◽  
Author(s):  
Hyeong-Min Nam ◽  
Kyung-Seok Shin ◽  
Jae-Yun Jeong ◽  
Seong-Jun Bae ◽  
Sung-Jea Ko
Keyword(s):  
Wireless Networks ◽  
Video Streaming ◽  
Wireless Channel ◽  
Bandwidth Estimation ◽  
Channel Bandwidth

scholarly journals The relative roles of CO<sub>2</sub> and palaeogeography in determining Late Miocene climate: results from a terrestrial model-data comparison

2012 ◽  
Vol 8 (2) ◽  
pp. 715-786 ◽  
Author(s):  
C. D. Bradshaw ◽  
D. J. Lunt ◽  
R. Flecker ◽  
U. Salzmann ◽  
M. J. Pound ◽  
...  
Keyword(s):  
Late Miocene ◽  
Ice Sheet ◽  
Co2 Concentration ◽  
Model Data ◽  
Data Comparison ◽  
Fully Coupled

Abstract. The Late Miocene (∼11.6–5.3 Ma) palaeorecord provides evidence for a warmer and wetter climate than that of today and there is uncertainty in the palaeo-CO2 record of at least 150 ppmv. We present results from fully coupled atmosphere-ocean-vegetation simulations for the Late Miocene that examine the relative roles of palaeogeography (topography and ice sheet geometry) and CO2 concentration in the determination of Late Miocene climate through comprehensive terrestrial model-data comparisons. Assuming that the data accurately reflects the Late Miocene climate, and that the Late Miocene palaeogeographic reconstruction used in the model is robust, then results indicate that the proxy-derived precipitation differences between the Late Miocene and modern can be largely accounted for by the palaeogeographic changes alone. However, the proxy-derived temperatures differences between the Late Miocene and modern can only begin to be accounted for if we assume a palaeo-CO2 concentration towards the higher end of the range of estimates.

Towards model-data comparison of the deglacial temperature evolution in space and time

2021 ◽  
Author(s):  
Nils Weitzel ◽  
Heather Andres ◽  
Jean-Philippe Baudouin ◽  
Oliver Bothe ◽  
Andrew Dolman ◽  
...  
Keyword(s):  
Earth System ◽  
Sources Of Information ◽  
Last Deglaciation ◽  
Model Data ◽  
Glacial Cycle ◽  
Data Comparison ◽  
Space And Time ◽  
Proxy Records ◽  
Scale Temperature ◽  
The Last Deglaciation

&lt;div&gt; &lt;p&gt;The increasing number of Earth system model simulations that try to simulate the climate during the last deglaciation (ca 20 to 10 thousand years ago) creates a demand for benchmarking against environmental proxy records synthesized for the same time period. Comparing these two data sources over a period with changing background conditions requires new methods for model-data comparison that incorporate multiple types and sources of uncertainty.&lt;/p&gt; &lt;p&gt;Natural archives of past reality are distributed sparsely and non-uniformly in space and time. Signals that can be obtained are in addition perturbed by uncertainties related to dating, the relationship between the proxy sensor and environmental fields, the archive build-up, and measurement. On the other hand, paleoclimate simulations are four-dimensional, complete, and physically consistent representations of the climate. However, they are subject to errors due to model inadequacies and sensitivity to the forcing protocol, and will not reproduce any particular history of unforced variability.&amp;#160;&lt;/p&gt; &lt;/div&gt;&lt;div&gt; &lt;p&gt;We present a method for probabilistic, multivariate quantification of the deviation between paleo-data and paleoclimate simulations that draws on the strengths of both sources of information and accounts for the aforementioned uncertainties. We compare the shape and magnitude of orbital- and millennial-scale temperature fluctuations during the last deglaciation and compute metrics of regional and global model-data mismatches. We test our algorithm with an ensemble of published simulations of the deglaciation and simulations from the ongoing PalMod project, which aims at the simulation of the last glacial cycle with comprehensive Earth system models. These are evaluated against a compilation of temperature reconstructions from multiple archives. Our work aims for a standardized model-data comparison workflow that will be used in PalMod. This workflow can be extended subsequently with additional proxy data, new simulations, and improved representations of proxy uncertainties.&amp;#160;&lt;/p&gt; &lt;/div&gt;

Model-data comparison in a strongly eddying Eocene ocean

2021 ◽  
Author(s):  
Peter Nooteboom ◽  
Michiel Baatsen ◽  
Peter Bijl ◽  
Erik van Sebille ◽  
Appy Sluijs ◽  
...  
Keyword(s):  
General Circulation ◽  
General Circulation Models ◽  
Horizontal Resolution ◽  
Late Eocene ◽  
Ocean Modeling ◽  
Equilibration Time ◽  
Model Data ◽  
Proxy Data ◽  
Biogeographic Patterns ◽  
Data Comparison

&lt;p&gt;Simulations of the geological past using General Circulation Models (GCMs) are computationally expensive. Mainly because of the long equilibration time scales, most of these GCMs have ocean components with a horizontal resolution of 1&amp;#176; or coarser. Such models are non-eddying and the effects of mesoscale ocean eddies on the transport of heat and salt are parameterized. However, from present-day ocean modeling studies, it is known that eddying ocean models better represent regional and time-mean ocean flows compared to non-eddying models. At the same time, proxy data from sediment sample sites represent climate at specific locations. Hence, the coarse ocean resolution of typical palaeo-GCMs lead to a challenge for model-data comparison in past climates.&lt;/p&gt;&lt;p&gt;Here we present the first simulations of a global eddying Eocene ocean with a 0.1&amp;#176; (horizontal) resolution model, which are initialized and forced with data from a coarser resolution (1&amp;#176; horizontally) equilibrated coupled ocean-atmosphere GCM. We investigate the response of the model equilibrium state to the change in ocean resolution and the consequences this has for model-data comparison in the middle-late Eocene (38Ma). We find that, compared to the non-eddying model, the eddying ocean resolution of palaeomodels reduce the biases in both sea surface temperatures and biogeographic patterns which are derived from proxy data.&lt;/p&gt;

scholarly journals How cold was Europe at the Last Glacial Maximum? A synthesis of the progress achieved since the first PMIP model-data comparison

2007 ◽  
Vol 3 (2) ◽  
pp. 331-339 ◽  
Author(s):  
G. Ramstein ◽  
M. Kageyama ◽  
J. Guiot ◽  
H. Wu ◽  
C. Hély ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
General Circulation ◽  
General Circulation Models ◽  
Glacial Maximum ◽  
Model Data ◽  
Last Glacial ◽  
Data Comparison ◽  
The Last Glacial Maximum ◽  
Winter Cooling ◽  
The Last Glacial

Abstract. The Last Glacial Maximum has been one of the first foci of the Paleoclimate Modelling Intercomparison Project (PMIP). During its first phase, the results of 17 atmosphere general circulation models were compared to paleoclimate reconstructions. One of the largest discrepancies in the simulations was the systematic underestimation, by at least 10°C, of the winter cooling over Europe and the Mediterranean region observed in the pollen-based reconstructions. In this paper, we investigate the progress achieved to reduce this inconsistency through a large modelling effort and improved temperature reconstructions. We show that increased model spatial resolution does not significantly increase the simulated LGM winter cooling. Further, neither the inclusion of a vegetation cover compatible with the LGM climate, nor the interactions with the oceans simulated by the atmosphere-ocean general circulation models run in the second phase of PMIP result in a better agreement between models and data. Accounting for changes in interannual variability in the interpretation of the pollen data does not result in a reduction of the reconstructed cooling. The largest recent improvement in the model-data comparison has instead arisen from a new climate reconstruction based on inverse vegetation modelling, which explicitly accounts for the CO2 decrease at LGM and which substantially reduces the LGM winter cooling reconstructed from pollen assemblages. As a result, the simulated and observed LGM winter cooling over Western Europe and the Mediterranean area are now in much better agreement.

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