scholarly journals Geophysical fluid dynamics: whence, whither and why?

2016 ◽  
Vol 472 (2192) ◽  
pp. 20160140 ◽  
Author(s):  
Geoffrey K. Vallis
Keyword(s):  
Fluid Dynamics ◽  
General Circulation ◽  
Condensed Matter ◽  
General Circulation Models ◽  
Condensed Matter Physics ◽  
Geophysical Fluid Dynamics ◽  
Emergent Phenomena ◽  
Interacting Systems ◽  
Geophysical System

This article discusses the role of geophysical fluid dynamics (GFD) in understanding the natural environment, and in particular the dynamics of atmospheres and oceans on Earth and elsewhere. GFD, as usually understood, is a branch of the geosciences that deals with fluid dynamics and that, by tradition, seeks to extract the bare essence of a phenomenon, omitting detail where possible. The geosciences in general deal with complex interacting systems and in some ways resemble condensed matter physics or aspects of biology, where we seek explanations of phenomena at a higher level than simply directly calculating the interactions of all the constituent parts. That is, we try to develop theories or make simple models of the behaviour of the system as a whole. However, these days in many geophysical systems of interest, we can also obtain information for how the system behaves by almost direct numerical simulation from the governing equations. The numerical model itself then explicitly predicts the emergent phenomena—the Gulf Stream, for example—something that is still usually impossible in biology or condensed matter physics. Such simulations, as manifested, for example, in complicated general circulation models, have in some ways been extremely successful and one may reasonably now ask whether understanding a complex geophysical system is necessary for predicting it. In what follows we discuss such issues and the roles that GFD has played in the past and will play in the future.

scholarly journals On the role of Eurasian autumn snow cover in dynamical seasonal predictions 

2021 ◽  
Author(s):  
Paolo Ruggieri ◽  
Marianna Benassi ◽  
Stefano Materia ◽  
Daniele Peano ◽  
Constantin Ardilouze ◽  
...  
Keyword(s):  
Snow Cover ◽  
Northern Hemisphere ◽  
Land Surface ◽  
General Circulation ◽  
Dominant Role ◽  
General Circulation Models ◽  
The Arctic ◽  
Seasonal Forecasts ◽  
Eurasian Snow

<p>Seasonal climate predictions leverage on many predictable or persistent components of the Earth system that can modify the state of the atmosphere and of relant weather related variable such as temprature and precipitation. With a dominant role of the ocean, the land surface provides predictability through various mechanisms, including snow cover, with particular reference to Autumn snow cover over the Eurasian continent. The snow cover alters the energy exchange between land surface and atmosphere and induces a diabatic cooling that in turn can affect the atmosphere both locally and remotely. Lagged relationships between snow cover in Eurasia and atmospheric modes of variability in the Northern Hemisphere have been investigated and documented but are deemed to be non-stationary and climate models typically do not reproduce observed relationships with consensus. The role of Autumn Eurasian snow in recent dynamical seasonal forecasts is therefore unclear. In this study we assess the role of Eurasian snow cover in a set of 5 operational seasonal forecast system characterized by a large ensemble size and a high atmospheric and oceanic resolution. Results are compemented with a set of targeted idealised simulations with atmospheric general circulation models forced by different snow cover conditions. Forecast systems reproduce realistically regional changes of the surface energy balance associated with snow cover variability. Retrospective forecasts and idealised sensitivity experiments converge in identifying a coherent change of the circulation in the Northern Hemisphere. This is compatible with a lagged but fast feedback from the snow to the Arctic Oscillation trough a tropospheric pathway.</p>

scholarly journals A Lagrangian-Based Approach for Determining Trajectories Taxonomy and Turbulence Regimes

2007 ◽  
Vol 37 (6) ◽  
pp. 1584-1609 ◽  
Author(s):  
Volfango Rupolo
Keyword(s):  
Time Scales ◽  
General Circulation ◽  
Eddy Diffusivity ◽  
General Circulation Models ◽  
Velocity Correlation ◽  
Velocity Correlation Function ◽  
Different Shapes ◽  
Surface Drifters ◽  
Current Systems

Abstract The use of the ratio between the acceleration and velocity time scales y = Ta/Tυ to separate Lagrangian trajectories in homogeneous classes is proposed. In fact, when analyzing subsurface floats data in the Atlantic Ocean and surface drifters data in the world’s ocean basins, it is observed that trajectories having different values of y are characterized by different shapes, correlation, and dispersal properties. In particular, trajectories having similar values of the acceleration and velocity time scales clearly show the influence of eddies and are characterized by an oscillating velocity correlation function. It is shown here that this trajectory screening is a useful procedure to rationalize the analysis of real Lagrangian trajectories and to avoid a mixture of different regimes, when averaging quantities. The mean statistical quantities computed averaging on quasi-homogeneous datasets put in evidence the role of the coherent structures in the dispersion properties, both in time and in the main oceanic current systems. These results are discussed in the context of the parameterization of eddy diffusivity in general circulation models.

scholarly journals Condensed Matter Physics dalam Kulit Kacang

2018 ◽  
Author(s):  
Muhammad Gaffar
Keyword(s):  
High Energy Physics ◽  
Condensed Matter ◽  
High Energy ◽  
Condensed Matter Physics ◽  
Emergent Phenomena ◽  
Energy Physics

Condensed Matter Physics (CMP) menjadi salah satu cabang fisika yang berkembang dengan sangat cepat. Perkembangan fenomena, konsep, dan teknik semakin bercabang, dan meluas begitu deras, begitu juga dengan diversitasnya. Mungkin masih ada yang merasa kabur dan asingnya makna CMP itu sendiri, apa yang dipelajari, dan tujuannya. Di kelompok garis kanan mungkin ada yang masih meragukan karir dari ilmu CMP ini. Dan dikelompok garis kiri mungkin ada yang mempermasalahkan bahwa CMP terlalu teknis, dan tidak se-teoritis ataupun tidak se-filosofis High Energy Physics(HEP) ataupun kosmologi.Tulisan ini mungkin belum akan dapat menjawab semua penasaran tersebut. Namun saya akan mencoba mengulas tentang CMP itu sendiri—yang berhasil membuat saya banting stir ketertarikan dari HEP dan Kosmologi.Artikel ini akan mendiskusikan tentang hirarki dan paradigma dalam sains, fisika khususnya, dilanjutkan membahas paradigma dan hal yang meng-drive CMP. Lalu akan mengulas emergent phenomena lebih dalam dan konsekuensi terhadap perkembangan teknologi, yang diulas secara historikal, lalu melihat sekilas pengaruh komunitas ilmuwan di bidang ini. Diakhiri akan membahas sedikit tentang bagaimana mempersiapkan diri untuk mempelejari CMP lebih dalam, dan rekomendasi rancangan studi bagi S-1.Tulisan ini jauh dari sempurna, yang hanya ditulis oleh mahasiswa S-1 semester 6 yang sedang menjalani studi formal mengenai CMP. Tulisan ini ditulis atas keinginan dan semangat tinggi untuk memperkenalkan CMP kepada khalayak ramai, dan berbagi ketertarikan. Semoga tulisan ini bisa menjadi inspirasi bagi yang membaca. Jangan biarkan High Energy Physics dan Cosmology merebut semua kesenangan!

scholarly journals Radiative-Convective Equilibrium Model Intercomparison Project

2017 ◽  
Author(s):  
Allison A. Wing ◽  
Kevin A. Reed ◽  
Masaki Satoh ◽  
Bjorn Stevens ◽  
Sandrine Bony ◽  
...  
Keyword(s):  
General Circulation ◽  
General Circulation Models ◽  
Cloud Fraction ◽  
Model Intercomparison ◽  
Tropical Circulation ◽  
Cloud Feedbacks ◽  
Single Column ◽  
Intercomparison Project ◽  
Self Aggregation

Abstract. RCEMIP, an intercomparison of multiple types of models configured in radiative-convective equilibrium (RCE), is proposed. RCE is an idealization of the climate system in which there is a balance between radiative cooling of the atmosphere and heating by convection. The scientific objectives of RCEMIP are three-fold. First, clouds and climate sensitivity will be investigated in the RCE setting. This includes determining how cloud fraction changes with warming and the role of self-aggregation of convection. Second, RCEMIP will quantify the dependence of the degree of convective aggregation and tropical circulation regimes on temperature. Finally, by providing a common baseline, RCEMIP will allow the robustness of the RCE state, cloud feedbacks, and convective aggregation across the spectrum of models to be assessed. A novel aspect and major advantage of RCEMIP is the accessibility of the RCE framework to a variety of models, including cloud-resolving models, general circulation models, global cloud-resolving models, and single column models.

Improving the Prediction of Winter Precipitation and Temperature over the Continental United States: Role of the ENSO State in Developing Multimodel Combinations

2010 ◽  
Vol 138 (6) ◽  
pp. 2447-2468 ◽  
Author(s):  
Naresh Devineni ◽  
A. Sankarasubramanian
Keyword(s):  
General Circulation ◽  
General Circulation Models ◽  
Winter Precipitation ◽  
Skill Levels ◽  
Higher Weights ◽  
Atmospheric General Circulation Models ◽  
Multimodel Ensembles ◽  
Precipitation And Temperature

Abstract Recent research into seasonal climate prediction has focused on combining multiple atmospheric general circulation models (GCMs) to develop multimodel ensembles. A new approach to combining multiple GCMs is proposed by analyzing the skill levels of candidate models contingent on the relevant predictor(s) state. To demonstrate this approach, historical simulations of winter (December–February, DJF) precipitation and temperature from seven GCMs were combined by evaluating their skill—represented by mean square error (MSE)—over similar predictor (DJF Niño-3.4) conditions. The MSE estimates are converted into weights for each GCM for developing multimodel tercile probabilities. A total of six multimodel schemes are considered that include combinations based on pooling of ensembles as well as on the long-term skill of the models. To ensure the improved skill exhibited by the multimodel scheme is statistically significant, rigorous hypothesis tests were performed comparing the skill of multimodels with each individual model’s skill. The multimodel combination contingent on Niño-3.4 shows improved skill particularly for regions whose winter precipitation and temperature exhibit significant correlation with Niño-3.4. Analyses of these weights also show that the proposed multimodel combination methodology assigns higher weights for GCMs and lesser weights for climatology during El Niño and La Niña conditions. On the other hand, because of the limited skill of GCMs during neutral Niño-3.4 conditions, the methodology assigns higher weights for climatology resulting in improved skill from the multimodel combinations. Thus, analyzing GCMs’ skill contingent on the relevant predictor state provides an alternate approach for multimodel combinations such that years with limited skill could be replaced with climatology.

scholarly journals Fog and rain in the Amazon

2015 ◽  
Vol 112 (37) ◽  
pp. 11473-11477 ◽  
Author(s):  
Usama Anber ◽  
Pierre Gentine ◽  
Shuguang Wang ◽  
Adam H. Sobel
Keyword(s):  
General Circulation ◽  
Large Scale ◽  
General Circulation Models ◽  
Surface Energy Budget ◽  
Wet Season ◽  
Large Scale Circulation ◽  
Cloud Albedo ◽  
The Difference ◽  
Hydrological Cycles

The diurnal and seasonal water cycles in the Amazon remain poorly simulated in general circulation models, exhibiting peak evapotranspiration in the wrong season and rain too early in the day. We show that those biases are not present in cloud-resolving simulations with parameterized large-scale circulation. The difference is attributed to the representation of the morning fog layer, and to more accurate characterization of convection and its coupling with large-scale circulation. The morning fog layer, present in the wet season but absent in the dry season, dramatically increases cloud albedo, which reduces evapotranspiration through its modulation of the surface energy budget. These results highlight the importance of the coupling between the energy and hydrological cycles and the key role of cloud albedo feedback for climates over tropical continents.

scholarly journals Impact of Stochastic Physics and Model Resolution on the Simulation of Tropical Cyclones in Climate GCMs

2021 ◽  
Vol 34 (11) ◽  
pp. 4315-4341
Author(s):  
Pier Luigi Vidale ◽  
Kevin Hodges ◽  
Benoit Vannière ◽  
Paolo Davini ◽  
Malcolm J. Roberts ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Seasonal Cycle ◽  
General Circulation ◽  
Dynamic Environment ◽  
General Circulation Models ◽  
Model Resolution ◽  
Grid Spacing ◽  
The Cost ◽  
Stochastic Physics

AbstractThe role of model resolution in simulating geophysical vortices with the characteristics of realistic tropical cyclones (TCs) is well established. The push for increasing resolution continues, with general circulation models (GCMs) starting to use sub-10-km grid spacing. In the same context it has been suggested that the use of stochastic physics (SP) may act as a surrogate for high resolution, providing some of the benefits at a fraction of the cost. Either technique can reduce model uncertainty, and enhance reliability, by providing a more dynamic environment for initial synoptic disturbances to be spawned and to grow into TCs. We present results from a systematic comparison of the role of model resolution and SP in the simulation of TCs, using EC-Earth simulations from project Climate-SPHINX, in large ensemble mode, spanning five different resolutions. All tropical cyclonic systems, including TCs, were tracked explicitly. As in previous studies, the number of simulated TCs increases with the use of higher resolution, but SP further enhances TC frequencies by ~30%, in a strikingly similar way. The use of SP is beneficial for removing systematic climate biases, albeit not consistently so for interannual variability; conversely, the use of SP improves the simulation of the seasonal cycle of TC frequency. An investigation of the mechanisms behind this response indicates that SP generates both higher TC (and TC seed) genesis rates, and more suitable environmental conditions, enabling a more efficient transition of TC seeds into TCs. These results were confirmed by the use of equivalent simulations with the HadGEM3-GC31 GCM.

Sign in / Sign up

Export Citation Format

Share Document