scholarly journals Kinetic energy-conserving hyperdiffusion can improve low resolution atmospheric models

2015 ◽  
Vol 7 (3) ◽  
pp. 1117-1135 ◽  
Author(s):  
Pablo Zurita-Gotor ◽  
Isaac M. Held ◽  
Malte F. Jansen
Keyword(s):  
Kinetic Energy ◽  
Atmospheric Models ◽  
Low Resolution ◽  
Energy Conserving

scholarly journals A Parameterization of Sticking Efficiency for Collisions of Snow and Graupel with Ice Crystals: Theory and Comparison with Observations*

2015 ◽  
Vol 72 (12) ◽  
pp. 4885-4902 ◽  
Author(s):  
Vaughan T. J. Phillips ◽  
Marco Formenton ◽  
Aaron Bansemer ◽  
Innocent Kudzotsa ◽  
Barry Lienert
Keyword(s):  
Probability Distribution ◽  
Kinetic Energy ◽  
Ice Crystals ◽  
Field Observations ◽  
Laboratory Studies ◽  
Atmospheric Models ◽  
Vapor Growth ◽  
Collision Processes ◽  
Work Done ◽  
Temperature Surface

Abstract A new parameterization of sticking efficiency for aggregation of ice crystals onto snow and graupel is presented. This parameter plays a crucial role for the formation of ice precipitation and for electrification processes. The parameterization is intended to be used in atmospheric models simulating the aggregation of ice particles in glaciated clouds. It should improve the ability to forecast snow. Based on experimental results and general considerations of collision processes, dependencies of the sticking efficiency on temperature, surface area, and collision kinetic energy of impacting particles are derived. The parameters have been estimated from some laboratory observations by simulating the experiments and minimizing the squares of the errors of the prediction of observed quantities. The predictions from the new scheme are compared with other available laboratory and field observations. The comparisons show that the parameterization is able to reproduce the thermal behavior of sticking efficiency, observed in published laboratory studies, with a peak around −15°C corresponding to dendritic vapor growth of ice. Finally, a new theory of sticking efficiency is proposed. It explains the empirically derived parameterization in terms of a probability distribution of the work that would be required to separate two contacting particles colliding in all possible ways among many otherwise identical collisions of the same pair with a given initial collision kinetic energy. For each collision, if this work done would exceed the initial collision kinetic energy, then there is no separation after impact. The probability of that occurring equals the sticking efficiency.

scholarly journals A convective kinematic trajectory technique for low-resolution atmospheric models

2000 ◽  
Vol 105 (D19) ◽  
pp. 24375-24386 ◽  
Author(s):  
S. R. Freitas ◽  
M. A. F. Silva Dias ◽  
P. L. Silva Dias ◽  
K. M. Longo ◽  
P. Artaxo ◽  
...  
Keyword(s):  
Atmospheric Models ◽  
Low Resolution

scholarly journals A note on the influence of atmospheric model resolution in coupled climate–ice-sheet simulations

2017 ◽  
Author(s):  
Marcus Löfverström ◽  
Johan Liakka
Keyword(s):  
North America ◽  
General Circulation ◽  
Fundamental Problem ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Circulation Model ◽  
Atmospheric Model ◽  
Atmospheric Models ◽  
Low Resolution ◽  
Surface Mass

Abstract. Coupled climate–ice-sheet simulations have been growing in popularity in recent years. Experiments of this type are however challenging as ice sheets evolve over multi-millennial time scales, which is beyond the practical integration limit for most Earth-system models. A common method to increase model throughput is to trade resolution for computational efficiency (compromises accuracy for speed). Here, we analyze how the resolution of an atmospheric general circulation model (AGCM) influences the simulation quality of a standalone ice-sheet model. Four identical AGCM simulations of the Last Glacial Maximum (LGM) were run at different horizontal resolutions: T85 (1.4°), T42 (2.8°), T31 (3.8°), and T21 (5.6°). These simulations were subsequently used as forcing of an ice-sheet model. While the T85 climate forcing reproduces the LGM ice sheets to a high accuracy, the intermediate resolution cases (T42 and T31) fail to build the Eurasian Ice Sheet. The T21 case fails in both Eurasia and North America. Sensitivity experiments using different surface mass balance parameterizations improve the simulations of the Eurasian ice-sheet in the T42 case, but the compromise is a substantial ice buildup in Siberia. The T31 and T21 cases are not improving in the same way in Eurasia, though the latter simulates the continent-wide Laurentide Ice Sheet in North America. The difficulty to reproduce the LGM ice sheets in the T21 case is in broad agreement with previous studies using low-resolution atmospheric models, and is caused by a deterioration of the atmospheric climate between the T31 and T21 resolutions. It is speculated that this deficiency may demonstrate a fundamental problem using low-resolution atmospheric models in these types of experiments.

The 2009 Wesley impact: Asteroidal or Cometary?

2021 ◽  
Author(s):  
James Sinclair ◽  
Glenn Orton ◽  
Meera Krishnamoorty ◽  
Leigh Fletcher ◽  
Joseph Hora ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Radiative Transfer ◽  
Heterogeneous Population ◽  
Atmospheric Response ◽  
Atmospheric Models ◽  
Low Resolution ◽  
Impact Site ◽  
Long Time ◽  
The Impact ◽  
Unknown Object

<p>We present Earth-based observations of Jupiter from 1994 and 2009, which respectively capture the effects on Jupiter’s atmosphere by the impacts of Comet D/Shoemaker-Levy 9 (SL9) and the impact by an unknown object whose visible impression on Jupiter’s appearance was discovered by Anthony Wesley.  Previous studies have suggested the 2009 impactor was by an asteroid on the basis of differences in Jupiter’s atmospheric response compared to the 1994 impact by SL9.  These differences include detections of 9.1-μm silicate features in the 2009 impact site (Orton et al., 2010, Icarus 211, 587-602) and the fact the 2009 debris field shrank faster (Hammel et al., 2010, ApJL 715, L150-L154), both of which suggest the 2009 impactor was more rocky/refractory in composition.  However, Schenk <em>et al.</em> 2004 (Jupiter: The Planet, Satellites and Magnetosphere, Bagenal, Dowling, McKinnon, 427-456) state that comets are orders of magnitude more likely to impact Jupiter than asteroids since Jupiter should have cleared its orbit a long time ago. Thus, either (1) the 2009 impact was caused by an asteroid and therefore a statistical fluke, (2) Jupiter-Family Comets (JFCs) are a highly heterogeneous population, with some containing rocky/refractory interiors hidden from remote-sensing, or (3) there is a population of asteroids among bodies classified as JFCs. In order to explore these hypotheses, we performed a comparative spectral re-analysis of broadband imaging and low-resolution spectra measured during/after the 1994 and 2009 impacts. The comparison used consistent procedures for reduction and calibration of the data, atmospheric models, radiative-transfer software and spectroscopic line data in order to facilitate direct comparisons between 1994 and 2009 events.  </p>

scholarly journals Stability Analysis of Geostrophic Adjustment on Hexagonal Grids for Regions with Variable Depth

2005 ◽  
Vol 133 (11) ◽  
pp. 3335-3344 ◽  
Author(s):  
Tomas Torsvik ◽  
Øyvind Thiem ◽  
Jarle Berntsen
Keyword(s):  
Ocean Circulation ◽  
Numerical Solutions ◽  
Ocean Basin ◽  
Paper Analysis ◽  
Variable Depth ◽  
Atmospheric Models ◽  
Numerical Studies ◽  
Energy Conserving ◽  
Hexagonal Grids ◽  
Ocean Models

Abstract Hexagonal grids have been used in a number of numerical studies, and especially in relation to atmospheric models. Recent studies have suggested that ocean circulation models may also benefit from the use of hexagonal grids. These grids tend to induce less systematic errors and have better horizontal isotropy properties than traditional square grid schemes. If hexagonal grids are to be applied in ocean models, a number of features that are characteristic of ocean circulation problems need to be attended to. The topography of the ocean basin is an important feature in most ocean models. Ocean modelers can experience instabilities due to depth variations. In the present paper, analysis of the propagation matrix for the spatially discretized system is used to explain unphysical growth of the numerical solutions of the linear shallow water equations when using hexagonal grids over domains with variable depth. It is shown that a suitable weighting of the Coriolis terms may give an energy-conserving and stable numerical scheme.

scholarly journals The influence of atmospheric grid resolution in a climate model-forced ice sheet simulation

2018 ◽  
Vol 12 (4) ◽  
pp. 1499-1510 ◽  
Author(s):  
Marcus Lofverstrom ◽  
Johan Liakka
Keyword(s):  
North America ◽  
General Circulation ◽  
Climate Model ◽  
Fundamental Problem ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Circulation Model ◽  
Atmospheric Models ◽  
Low Resolution ◽  
Surface Mass

Abstract. Coupled climate–ice sheet simulations have been growing in popularity in recent years. Experiments of this type are however challenging as ice sheets evolve over multi-millennial timescales, which is beyond the practical integration limit of most Earth system models. A common method to increase model throughput is to trade resolution for computational efficiency (compromise accuracy for speed). Here we analyze how the resolution of an atmospheric general circulation model (AGCM) influences the simulation quality in a stand-alone ice sheet model. Four identical AGCM simulations of the Last Glacial Maximum (LGM) were run at different horizontal resolutions: T85 (1.4∘), T42 (2.8∘), T31 (3.8∘), and T21 (5.6∘). These simulations were subsequently used as forcing of an ice sheet model. While the T85 climate forcing reproduces the LGM ice sheets to a high accuracy, the intermediate resolution cases (T42 and T31) fail to build the Eurasian ice sheet. The T21 case fails in both Eurasia and North America. Sensitivity experiments using different surface mass balance parameterizations improve the simulations of the Eurasian ice sheet in the T42 case, but the compromise is a substantial ice buildup in Siberia. The T31 and T21 cases do not improve in the same way in Eurasia, though the latter simulates the continent-wide Laurentide ice sheet in North America. The difficulty to reproduce the LGM ice sheets in the T21 case is in broad agreement with previous studies using low-resolution atmospheric models, and is caused by a substantial deterioration of the model climate between the T31 and T21 resolutions. It is speculated that this deficiency may demonstrate a fundamental problem with using low-resolution atmospheric models in these types of experiments.

scholarly journals Kinetic energy conserving integrators for Gaussian thermostatted SLLOD

1999 ◽  
Vol 111 (1) ◽  
pp. 18-26 ◽  
Author(s):  
Fei Zhang ◽  
Debra J. Searles ◽  
Denis J. Evans ◽  
Jan S. den Toom Hansen ◽  
Dennis J. Isbister
Keyword(s):  
Kinetic Energy ◽  
Energy Conserving
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