Summer circulation patterns related to the upper tropospheric vortices over the Tropical South Atlantic

1997 ◽  
Vol 64 (3-4) ◽  
pp. 203-213 ◽  
Author(s):  
M. T. Kayano ◽  
N. J. Ferreira ◽  
M. C. V. Ram�rez
Keyword(s):  
South Atlantic ◽  
Summer Circulation ◽  
Circulation Patterns

USING NEODYMIUM ISOTOPES TO DECIPHER COMPLEX CIRCULATION PATTERNS IN THE SOUTH ATLANTIC AT THE END OF THE CRETACEOUS

2020 ◽  
Author(s):  
Shannon J. Haynes ◽  
◽  
Kenneth G. MacLeod ◽  
Jean-Baptiste Ladant ◽  
Christopher J. Poulsen ◽  
...  
Keyword(s):  
South Atlantic ◽  
The South ◽  
Neodymium Isotopes ◽  
Circulation Patterns

scholarly journals The Role of Synoptic Cyclones for the Formation of Arctic Summer Circulation Patterns as Clustered by Self-Organizing Maps

Atmosphere ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 474 ◽  
Author(s):  
Min-Hee Lee ◽  
Joo-Hong Kim
Keyword(s):  
Arctic Ocean ◽  
Large Scale ◽  
The Arctic ◽  
Cyclone Activity ◽  
Summer Circulation ◽  
Self Organizing Maps ◽  
Weather Patterns ◽  
Atmospheric Circulation Patterns ◽  
Circulation Patterns ◽  
Self Organizing

Contribution of extra-tropical synoptic cyclones to the formation of mean summer atmospheric circulation patterns in the Arctic domain (≥60° N) was investigated by clustering dominant Arctic circulation patterns based on daily mean sea-level pressure using self-organizing maps (SOMs). Three SOM patterns were identified; one pattern had prevalent low-pressure anomalies in the Arctic Circle (SOM1), while two exhibited opposite dipoles with primary high-pressure anomalies covering the Arctic Ocean (SOM2 and SOM3). The time series of their occurrence frequencies demonstrated the largest inter-annual variation in SOM1, a slight decreasing trend in SOM2, and the abrupt upswing after 2007 in SOM3. Analyses of synoptic cyclone activity using the cyclone track data confirmed the vital contribution of synoptic cyclones to the formation of large-scale patterns. Arctic cyclone activity was enhanced in the SOM1, which was consistent with the meridional temperature gradient increases over the land–Arctic ocean boundaries co-located with major cyclone pathways. The composite daily synoptic evolution of each SOM revealed that all three SOMs persisted for less than five days on average. These evolutionary short-term weather patterns have substantial variability at inter-annual and longer timescales. Therefore, the synoptic-scale activity is central to forming the seasonal-mean climate of the Arctic.

Late cretaceous ocean circulation in the south Atlantic and Pacific oceans

2019 ◽  
Author(s):  
◽  
Shannon Haynes
Keyword(s):  
Indian Ocean ◽  
Ocean Circulation ◽  
Late Cretaceous ◽  
North Atlantic ◽  
High Latitude ◽  
Climate Model ◽  
South Atlantic ◽  
Regional Studies ◽  
Circulation Patterns ◽  
Insight Into

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Cooling during the last 15 million years of the Cretaceous is widely believed to have resulted in a reorganization of ocean circulation, with cooler periods being associated with deep ocean convection in high latitude regions (e.g., Robinson et al., 2010; MacLeod et al., 2011; Robinson and Vance, 2012; Jung et al., 2013). Understanding the relationship between climate change and sub-surface ocean circulation patterns, and gaining further insight into how circulation dynamics were influenced by the unique Cretaceous paleobathymetry is crucial to furthering our understanding of global climate dynamics during the Late Cretaceous. To provide further insight into Late Cretaceous ocean circulation we used neodymium isotopes as a tool to infer past ocean circulation patterns. Neodymium was extracted from fossilized fish teeth and bone fragments from bulk rock samples at 26 different sites (4 Pacific, 12 South Atlantic, 3 North Atlantic, 3 proto-Indian Ocean). We present two regional studies that focus on Campanian (84-72 Ma) and Maastrichtian (72-66 Ma) circulation patterns in the Pacific (Chapter 2) and South Atlantic (Chapter 3) Oceans. These chapters argue that, by the end of the Cretaceous, climate had cooled enough to support high latitude convection but also that circulation patterns were tightly controlled by bathymetry. To investigate the global implications of these two regional studies we also present preliminary neodymium isotopic data from several sites in the North Atlantic and proto-Indian Ocean (Chapter 4). Further, neodymium isotopic trends were compared to climate model simulations as well as to previously published neodymium, carbon, and oxygen isotopic records.

scholarly journals Evaluating Boreal Summer Circulation Patterns of CMIP6 Climate Models Over The Asian Region

2021 ◽  
Author(s):  
Lulei Bu ◽  
Zhiyan Zuo ◽  
Ning An
Keyword(s):  
Extreme Events ◽  
Climate Models ◽  
Model Performance ◽  
Coupled Model ◽  
Boreal Summer ◽  
Self Organizing Map ◽  
Summer Circulation ◽  
Circulation Patterns ◽  
Daily Scale ◽  
Intercomparison Project

Abstract Our confidence in future climate projection depends on the ability of climate models to simulate the current climate, and model performance in simulating atmospheric circulation affects the ability to simulate extreme events. This study uses the self-organizing map (SOM) method to evaluate the frequency, persistence, and transition characteristics of models in the Coupled Model Intercomparison Project Phase 6 (CMIP6) for different ensembles of the 500 hPa daily geopotential height (Z500) in Asia, and then ranks all ensembles according to a comprehensive ranking metric (MR). Our results show that the SOM method is a powerful tool for assessing the daily-scale circulation simulation skills in Asia, and the results are not significantly affected by different map sizes. Positive associations between the performance of ensembles for any two of frequency, persistence, and transition were found, indicating that an ensemble that performs well for one metric is good for the others. The results of the MR ranking show that the r10i1p1f1 ensemble of CanESM5 gives the best overall simulation of 500 hPa circulation in Asia, and this is also the ensemble that best simulates frequency characteristics. The MR simulation skills of the 10 best ensembles for the position of the Western North Pacific Subtropical High (WNPSH) are far better than those of the 10 worst. Such differences may lead to errors in the simulation of extreme events. This study will help future studies in the choice of ensembles with higher circulation simulation skills to improve the credibility of their conclusions.

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