scholarly journals GCM simulations of Uranus and Neptune: general circulation and eddy activity

2021 ◽  
Author(s):  
Gwenaël Milcareck ◽  
Sandrine Guerlet ◽  
Aymeric Spiga ◽  
Jérémy Leconte ◽  
Déborah Bardet ◽  
...  
Keyword(s):  
General Circulation ◽  
Eddy Activity

The Effect of a Strong Zonal Jet Stream on the Temporal Evolution of Baroclinic Eddies

2020 ◽  
Author(s):  
Or Hadas ◽  
Yohai Kaspi
Keyword(s):  
General Circulation ◽  
Baroclinic Instability ◽  
Storm Track ◽  
Storm Tracks ◽  
Jet Stream ◽  
Similar Response ◽  
Jet Streams ◽  
Eddy Activity ◽  
Zonal Jets ◽  
The Pacific

<p>The midlatitude storm tracks are one of the most prominent features of the extratropical climate. Much of our understanding of what controls the storm tracks comes from linear theory of baroclinic instability, which explains generally most of the observed response of storms to the general circulation. One example to where this approach is lacking is the Pacific midwinter minimum, a decrease in the eddy activity over the Pacific storm track during midwinter when baroclinicity is at its peak due to extremely strong zonal jets. A similar response was found recently for the Atlantic storm track<strong>,</strong> in correlation to periods of strong zonal jets. Following on these findings we study the effect of strong zonal jet streams on eddy activity in the midlatitudes. In order to isolate the effect of the jet strength we used several idealized GCM experiments with different jet strengths, and analyze the formed storm track from a Lagrangian perspective by using a storm tracking algorithm. In both the Eulerian analysis and analysis of the tracks a strong reduction of high level eddy activity is prominent, as well as a modest weakening of the low-level activity. The observed response is then further analyzed by studying the connection between the upper and lower wave and how it changes with jet-stream intensity. </p><p> </p>

scholarly journals Effects of the Mean Flow on Martian Transient Eddy Activity: Studies with an Idealized General Circulation Model

2019 ◽  
Vol 76 (8) ◽  
pp. 2375-2397
Author(s):  
Todd A. Mooring ◽  
Isaac M. Held ◽  
R. John Wilson
Keyword(s):  
General Circulation Model ◽  
Spatial Patterns ◽  
General Circulation ◽  
Circulation Model ◽  
Transient Eddy ◽  
Mean Flow ◽  
Eddy Activity ◽  
Idealized Model ◽  
Zonal Wavenumber ◽  
The Mean

Abstract The extent to which the eddy statistics of the Martian atmosphere can be inferred from the mean state and highly simplified assumptions about diabatic and frictional processes is investigated using an idealized general circulation model (GCM) with Newtonian relaxation thermal forcing. An iterative technique, adapted from previous terrestrial studies, is used to generate radiative equilibrium temperatures such that the three-dimensional time-mean temperature fields of the idealized model match means computed from the Mars Analysis Correction Data Assimilation (MACDA). Focusing on a period of strong Northern Hemisphere eddy activity prior to winter solstice, it is found that the idealized model reproduces some key features of the spatial patterns of the MACDA eddy temperature variance and kinetic energy fields. The idealized model can also simulate aspects of MACDA’s seasonal cycle of spatial patterns of low-level eddy meridional wind and temperature variances. The most notable weakness of the model is its eddy amplitudes—both their absolute values and seasonal variations are quite unrealistic, for reasons unclear. The idealized model was also run with a mean flow based on output from the Geophysical Fluid Dynamics Laboratory (GFDL) full-physics Mars GCM. The idealized model captures the difference in mean flows between MACDA and the GFDL Mars GCM and reproduces a bias in the more complex model’s eddy zonal wavenumber distribution. This implies that the mean flow is an important influence on transient eddy wavenumbers and that improving the GFDL Mars GCM’s mean flow would make its eddy scales more realistic.

Downstream Suppression of Baroclinic Waves

2021 ◽  
Vol 34 (3) ◽  
pp. 919-930
Author(s):  
Lina Boljka ◽  
David W. J. Thompson ◽  
Ying Li
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
General Circulation ◽  
Wave Packets ◽  
Storm Track ◽  
Eddy Activity ◽  
Baroclinic Waves ◽  
The North ◽  
The North Pacific ◽  
Downstream Development

AbstractBaroclinic waves drive both regional variations in weather and large-scale variability in the extratropical general circulation. They generally do not exist in isolation, but rather often form into coherent wave packets that propagate to the east via a mechanism called downstream development. Downstream development has been widely documented and explored. Here we document a novel but also key aspect of baroclinic waves: the downstream suppression of baroclinic activity that occurs in the wake of eastward propagating disturbances. Downstream suppression is apparent not only in the Southern Hemisphere storm track as shown in previous work, but also in the North Pacific and North Atlantic storm tracks. It plays an essential role in driving subseasonal periodicity in extratropical eddy activity in both hemispheres, and gives rise to the observed quiescence of the North Atlantic storm track 1–2 weeks following pronounced eddy activity in the North Pacific sector. It is argued that downstream suppression results from the anomalously low baroclinicity that arises as eastward propagating wave packets convert potential to kinetic energy. In contrast to baroclinic wave packets, which propagate to the east at roughly the group velocity in the upper troposphere, the suppression of baroclinic activity propagates eastward at a slower rate that is comparable to that of the lower to midtropospheric flow. The results have implications for understanding subseasonal variability in the extratropical troposphere of both hemispheres.

scholarly journals Was the North Pacific Wintertime Climate Less Stormy during the Mid-Holocene?

2010 ◽  
Vol 23 (14) ◽  
pp. 4025-4037 ◽  
Author(s):  
John C. H. Chiang ◽  
Yue Fang
Keyword(s):  
North Pacific ◽  
General Circulation ◽  
Climate Changes ◽  
South Pacific Convergence Zone ◽  
Transient Eddy ◽  
Holocene Climate ◽  
Coupled Models ◽  
Eddy Activity ◽  
Simple Physical Interpretation ◽  
Midwinter Suppression

Abstract Model evidence is presented to make the case that the midlatitude North Pacific wintertime transient eddy activity may have been significantly weaker during the mid-Holocene (∼6000 yr BP). A simulation of the mid-Holocene climate in an atmospheric general circulation model coupled to a reduced gravity ocean model showed significant reduction to transient eddy activity, up to 30% in the main storm-track region. The reduced baroclinic eddy activity is associated with basinwide climate changes over the northern and tropical Pacific, including a deepening of the Aleutian low, colder SSTs in the western and central North Pacific, a strengthening and southward shift of the subtropical jet, and a strengthened South Pacific convergence zone. These associated climate changes are consistently simulated across a range of Paleoclimate Modeling Intercomparison Project Phase II (PMIP2) coupled models forced with mid-Holocene climate forcings, suggesting they are a robust response to mid-Holocene orbital forcing. The authors link the mid-Holocene climate changes to two related modern-day analogs: (i) interannual variations in wintertime North Pacific storminess and (ii) the phenomenon of midwinter suppression whereby North Pacific transient eddy activity in today’s climate is reduced in midwinter. In both instances, the associated North Pacific climate conditions resemble those seen in the mid-Holocene simulations. While it remains to be seen which analog is dynamically more appropriate, the latter link—midwinter suppression—offers the simple physical interpretation that the mid-Holocene reduction in storminess is a consequence of a “more winterlike” climate resulting from the mid-Holocene precessional forcing.

ON EVALUATION OF THE ROLE OF THERMAL AND WIND FACTORS FOR A PHYSICAL MODEL OF THE WORLD OCEAN GENERAL CIRCULATION SYSTEM

2019 ◽  
Vol 47 (3) ◽  
pp. 80-91
Author(s):  
V. G. Neiman
Keyword(s):  
Physical Model ◽  
Ocean Circulation ◽  
General Circulation ◽  
World Ocean ◽  
Circulation System ◽  
The Public ◽  
The World ◽  
Almost All ◽  
Conceptual Foundations

The main content of the work consists of certain systematization and addition of longexisting, but eventually deformed and partly lost qualitative ideas about the role of thermal and wind factors that determine the physical mechanism of the World Ocean’s General Circulation System (OGCS). It is noted that the conceptual foundations of the theory of the OGCS in one form or another are contained in the works of many well-known hydrophysicists of the last century, but the aggregate, logically coherent description of the key factors determining the physical model of the OGCS in the public literature is not so easy to find. An attempt is made to clarify and concretize some general ideas about the two key blocks that form the basis of an adequate physical model of the system of oceanic water masses motion in a climatic scale. Attention is drawn to the fact that when analyzing the OGCS it is necessary to take into account not only immediate but also indirect effects of thermal and wind factors on the ocean surface. In conclusion, it is noted that, in the end, by the uneven flow of heat to the surface of the ocean can be explained the nature of both external and almost all internal factors, in one way or another contributing to the excitation of the general, or climatic, ocean circulation.

Pemanfaatan CFSRv2 untuk Statistical Downscaling menggunakan Principal Component Regression dan Partial Least Square

2019 ◽  
Vol 8 (1) ◽  
Author(s):  
Khairunnisa Khairunnisa ◽  
Rizka Pitri ◽  
Victor P Butar-Butar ◽  
Agus M Soleh
Keyword(s):  
Statistical Downscaling ◽  
General Circulation ◽  
Principal Component Regression ◽  
Circulation Model ◽  
Principal Component ◽  
Meteorological Station ◽  
Grid Size ◽  
Partial Least Square ◽  
Least Square ◽  
Output Data

This research used CFSRv2 data as output data general circulation model. CFSRv2 involves some variables data with high correlation, so in this research is using principal component regression (PCR) and partial least square (PLS) to solve the multicollinearity occurring in CFSRv2 data. This research aims to determine the best model between PCR and PLS to estimate rainfall at Bandung geophysical station, Bogor climatology station, Citeko meteorological station, and Jatiwangi meteorological station by comparing RMSEP value and correlation value. Size used was 3×3, 4×4, 5×5, 6×6, 7×7, 8×8, 9×9, and 11×11 that was located between (-40) N - (-90) S and 1050 E -1100 E with a grid size of 0.5×0.5 The PLS model was the best model used in stastistical downscaling in this research than PCR model because of the PLS model obtained the lower RMSEP value and the higher correlation value. The best domain and RMSEP value for Bandung geophysical station, Bogor climatology station, Citeko meteorological station, and Jatiwangi meteorological station is 9 × 9 with 100.06, 6 × 6 with 194.3, 8 × 8 with 117.6, and 6 × 6 with 108.2, respectively.

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