scholarly journals Spatio-Seasonal Hypoxia/Anoxia Dynamics and Sill Circulation Patterns Linked to Natural Ventilation Drivers, in a Mediterranean Landlocked Embayment: Amvrakikos Gulf, Greece

Geosciences ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 241
Author(s):  
Nikos Georgiou ◽  
Elias Fakiris ◽  
Constantin Koutsikopoulos ◽  
George Papatheodorou ◽  
Dimitris Christodoulou ◽  
...  
Keyword(s):  
Natural Ventilation ◽  
Marine Protected Area ◽  
Circulation Pattern ◽  
Water Circulation ◽  
Fish Mortality ◽  
Water Volume ◽  
Future Research ◽  
River Inflow ◽  
Circulation Patterns ◽  
Seasonal Hypoxia

Amvrakikos Gulf is a Mediterranean landlocked, fjord-like embayment and marine protected area suffering from natural, human-induced hypoxia/anoxia and massive fish mortality events. Seasonal marine geophysical and oceanographic surveys were conducted focusing on the water-circulation patterns at the sill and the spatial-seasonal distribution of dissolved oxygen (DO) in the gulf. Detailed surveys at the sill, the only communication route between the gulf and the open sea, revealed a two-layer water circulation pattern (top brackish outflow–bottom seawater inflow) and the role of the tide in the daily water exchange. Statistical analysis of the known natural drivers of DO distribution (density difference between the Ionian Sea and Amvrakikos, river inflow, wind) revealed that horizontal density gradients strongly affect anoxia reduction and seafloor oxygenation, while river inflow and wind mainly oxygenate volume/areas located above or within the pycnocline range, with DO concentrations > 2 mg/L. Complex geomorphology with well-formed internal basins contributes to the development and preservation of low DO conditions below the pycnocline. Finally, 43% of the seafloor and 36% of the gulf’s total water volume are permanently hypoxic, and reach a maximum of 70% and 62%, respectively, in September and July. This work is tailored to future ecosystem management plans, decisions, and future research on coastal ecosystems.

scholarly journals Effect of the El Niño Decaying Pace on the East Asian Summer Monsoon Circulation Pattern during Post-El Niño Summers

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 140
Author(s):  
Wenping Jiang ◽  
Gen Li ◽  
Gongjie Wang
Keyword(s):  
El Niño ◽  
Asian Monsoon ◽  
East Asian Monsoon ◽  
El Nino ◽  
East Asian ◽  
Circulation Pattern ◽  
Northwest Pacific ◽  
Monsoon Circulation ◽  
Circulation Patterns ◽  
Sst Anomalies

El Niño events vary from case to case with different decaying paces. In this study, we demonstrate that the different El Niño decaying paces have distinct impacts on the East Asian monsoon circulation pattern during post-El Niño summers. For fast decaying (FD) El Niño summers, a large-scale anomalous anticyclone dominates over East Asia and the North Pacific from subtropical to mid-latitude; whereas, the East Asian monsoon circulation display a dipole pattern with anomalous northern cyclone and southern anticyclone for slow decaying (SD) El Niño summers. The difference in anomalous East Asian monsoon circulation patterns was closely associated with the sea surface temperature (SST) anomaly patterns in the tropics. In FD El Niño summers, the cold SST anomalies in the tropical central-eastern Pacific and warm SST anomalies in the Maritime Continent induce the anticyclone anomalies over the Northwest Pacific. In contrast, the warm Kelvin wave anchored over the tropical Indian Ocean during SD El Niño summers plays a crucial role in sustaining the anticyclone anomalies over the Northwest Pacific. In particular, the opposite atmospheric circulation anomaly patterns over Northeast Asia and the mid-latitude North Pacific are mainly modulated by the stationary Rossby wave trains triggered by the opposite SST anomalies in the tropical eastern Pacific during FD and SD El Niño summers. Finally, the effect of distinct summer monsoon circulation patterns associated with the El Niño decay pace on the summer climate over East Asia are also discussed.

Six-fold increase in historical Northern Hemisphere concurrent large heatwaves driven by warming and changing atmospheric circulations

2021 ◽  
pp. 1-39
Author(s):  
Cassandra D.W. Rogers ◽  
Kai Kornhuber ◽  
Sarah E. Perkins-Kirkpatrick ◽  
Paul C. Loikith ◽  
Deepti Singh
Keyword(s):  
Northern Hemisphere ◽  
Large Scale ◽  
Warm Season ◽  
Fold Increase ◽  
Circulation Pattern ◽  
Positive Influence ◽  
Climate Risks ◽  
Circulation Patterns ◽  
Multiple Regions ◽  
Barents And Kara Seas

AbstractSimultaneous heatwaves affecting multiple regions (referred to as concurrent heatwaves), pose compounding threats to various natural and societal systems, including global food chains, emergency response systems, and reinsurance industries. While anthropogenic climate change is increasing heatwave risks across most regions, the interactions between warming and circulation changes that yield concurrent heatwaves remain understudied. Here, we quantify historical (1979-2019) trends in concurrent heatwaves during the warm-season (May-September, MJJAS) across the Northern Hemisphere mid- to high-latitudes. We find a significant increase of ~46% in the mean spatial extent of concurrent heatwaves, ~17% increase in their maximum intensity, and ~6-fold increase in their frequency. Using Self-Organising Maps, we identify large-scale circulation patterns (300 hPa) associated with specific concurrent heatwave configurations across Northern Hemisphere regions. We show that observed changes in the frequency of specific circulation patterns preferentially increase the risk of concurrent heatwaves across particular regions. Patterns linking concurrent heatwaves across eastern North America, eastern and northern Europe, parts of Asia, and the Barents and Kara Seas, show the largest increases in frequency (~5.9 additional days per decade). We also quantify the relative contributions of circulation pattern changes and warming to overall observed concurrent heatwave day frequency trends. While warming has a predominant and positive influence on increasing concurrent heatwaves, circulation pattern changes have a varying influence and account for up to 0.8 additional concurrent heatwave days per decade. Identifying regions with an elevated risk of concurrent heatwaves and understanding their drivers is indispensable for evaluating projected climate risks on interconnected societal systems and fostering regional preparedness in a changing climate.

scholarly journals Flooding Dynamics Within an Amazonian Floodplain: Water Circulation Patterns and Inundation Duration

2020 ◽  
Vol 56 (1) ◽  
Author(s):  
Sebastien Pinel ◽  
Marie‐Paule Bonnet ◽  
Joecila S. Da Silva ◽  
Tania C. Sampaio ◽  
Jérémie Garnier ◽  
...  
Keyword(s):  
Water Circulation ◽  
Circulation Patterns ◽  
Inundation Duration

scholarly journals Spring Extreme Precipitation Days in North China and Their Reliance on Atmospheric Circulation Patterns During 1979–2019

2022 ◽  
pp. 1-41
Keyword(s):  
Climate Variability ◽  
Atmospheric Circulation ◽  
Extreme Precipitation ◽  
Interannual Variation ◽  
North China ◽  
Circulation Pattern ◽  
Southerly Wind ◽  
Atmospheric Circulation Patterns ◽  
Rain Gauges ◽  
Circulation Patterns

Abstract The interannual variation of springtime extreme precipitation (SEP) days in North China (NC) and their reliance on atmospheric circulation patterns are studied by using the continuous daily record of 396 rain gauges and the fifth generation of the European Centre for Medium-Range Weather Forecasts atmospheric reanalysis during 1979–2019. The SEP days are defined as the days when at least 10% of rain gauges in NC record daily precipitation no less than 10.5 mm. Results show that the number of SEP days shows large interannual variability but no significant trend in the study period. Using the objective classification method of the obliquely rotated principal analysis in T-mode, we classify the atmospheric circulation into five different patterns based on the geopotential height at 700 hPa. Three circulation patterns all have fronts and are associated with strong southerly wind, leading to 88% of SEP days in NC. The strong southerly wind may provide moisture and dynamic forcing for the frontal precipitation. The interannual variation of SEP days is related with the number of the three above-mentioned dominant circulation patterns. Further analysis shows that the West Pacific pattern could be one of the possible climate variability modes related to SEP days. This study reveals that the daily circulation pattern may be the linkage between SEP days and climate variability modes in NC.

scholarly journals Impact of COVID-19 Lockdown and Atmospheric Circulation on the Air Quality in Wuhan During Early 2020

2021 ◽  
Vol 299 ◽  
pp. 02011
Author(s):  
Youyong Xie ◽  
Xiefei Zhi
Keyword(s):  
Air Quality ◽  
Atmospheric Circulation ◽  
Air Pollutants ◽  
General Circulation ◽  
Circulation Pattern ◽  
Atmospheric Circulation Patterns ◽  
Atmospheric General Circulation ◽  
Circulation Patterns ◽  
The Impact

Previous studies indicated that the air quality was improved in Wuhan during COVID-19 lockdown. However, the impact of atmospheric general circulation on the changes of air quality has not been taken into account. The present study aims to discuss the improvement of air quality in Wuhan and its possible reasons during COVID-19 lockdown. The results showed that all air pollutants except O3 decreased in Wuhan during early 2020. The occurrence days of A, C, W and NW types’ circulation pattern during early 2020 are more than those during the same period of 1979-2020. The occurrence days of SW type’s circulation pattern is slightly less than those during early 1979-2020. With more occurrence days of these dominant atmospheric circulation patterns, the number of polluted days could rise in Wuhan during early 2020. Nevertheless, this scenario didn’t occur. The COVID-19 lockdown did improve the air quality in Wuhan during early 2020.

Effect of Boiler Feedwater Inlet Locations on the Water Circulation Characteristics in a Firetube Boiler With the Non-Symmetrically Arranged Tube Passes 3 and 4

2002 ◽  
Author(s):  
Hyunjae Park ◽  
Anthony Bowman ◽  
Tod Stansfield ◽  
Brian Huibregtse ◽  
Steve Wilkinson ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Vessel ◽  
Water Circulation ◽  
Feed Water ◽  
Boiler Furnace ◽  
Boiler Water ◽  
Furnace Section ◽  
Circulation Patterns ◽  
Boiler Feedwater ◽  
Circulation Characteristics

Since the furnace section of a boiler is the primary heat transfer surface for the production of vapor, the overall water circulation patterns in the boiler will be significantly influenced by the circulation patterns near the furnace area. Boiler water circulation characteristics for a newly designed 4-pass firetube boiler with the non-symmetric arrangement of tube passes 3 and 4 were investigated in the previous work [1], in which the attraction forces between 28 different temperature nodes on the furnace wall were evaluated to predict the characteristics of water circulation near the boiler furnace. It was found that various non-symmetric water circulation patterns would occur for different firing conditions. As a consequence, in this paper, the analysis methods developed in the authors’ previous work are explicitly employed to predict and improve the water circulation in a firetube boiler when 6 different boiler feedwater inlet locations (3 on the right-hand side and 3 on the left-hand side of the boiler vessel shell) are used. Each side has 3 different feedwater inlet locations below the centerline of the boiler pressure vessel along its length. Investigation of the analysis results reveals that non-symmetric water circulation patterns are not unavoidable, but improvements in the water circulation and potentially the heat transfer rate can be achieved when the boiler feed water inlet is located near the front head of the boiler pressure vessel.

scholarly journals Evaluasi Standar Operasional Prosedur Dan Pola Sirkulasi Pengunjung Museum Tjong A Fie: Kajian Historic House Museum

HUMANIS ◽  
2018 ◽  
pp. 271
Author(s):  
Devy Charisma Sembiring ◽  
I Ketut Setiawan ◽  
Rochtri Agung Bawono
Keyword(s):  
Circulation Pattern ◽  
Literature Study ◽  
Historical Figures ◽  
Circulation Patterns ◽  
House Museum ◽  
Historic House ◽  
Heritage Building ◽  
The City ◽  
Collection Methods ◽  
Data Processing Methods

Museum Tjong A Fie is one of the museum located in Medan City, North Sumatera. This museum was originally a residence of historical figures in the development of the city of Medan is Tjong A Fie originating from China. Museum Tjong A Fie has been designated as a cultural heritage building and used as a museum. This research will discuss Standard Operating Procedures and Visitor Circulation Pattern of Tjong A Fie Museum as a part that must be considered in the organization of the museum. The author uses data collection methods such as observation, interview and literature study and data processing methods through qualitative and comparative analysis. The theory used to refine the interpretation of the results of analysis is Management Theory. Based on the results of research found that the Museum Tjong A Fie has no SOP according to the standard and mandate of PP No. 66 Year 2015. Circulation pattern shows two circulation patterns are unstructured and structured. The recommendations offered include the need to develop SOPs in accordance with the mandate of museum legislation and governance.

Deep water circulation patterns in the Atlantic during MISs 12-11

2020 ◽  
Author(s):  
Jasmin M. Link ◽  
Norbert Frank
Keyword(s):  
North Atlantic ◽  
Deep Water ◽  
Glacial Maximum ◽  
Water Circulation ◽  
Water Masses ◽  
Overturning Circulation ◽  
The Past ◽  
The North ◽  
Circulation Patterns ◽  
The North Atlantic

<p>Glacial Termination V is one of the most extreme glacial-interglacial transitions of the past 800 ka [1]. However, the changes in orbital forcing from Marine Isotope Stage (MIS) 12 to 11 are comparatively weak. In addition, MIS 11c is exceptionally distinct compared to other interglacials with for example a longer duration [2] and a higher-than-present sea level [3] despite a relative low incoming insolation. Therefore, the term “MIS 11 paradox” was coined [4]. However, only little is known about the Atlantic overturning circulation during this time interval [e.g. 5,6].</p><p>Here, we present Atlantic-wide deep water circulation patterns spanning the glacial maximum of MIS 12, Termination V, and MIS 11. Therefore, sediment cores throughout the Atlantic were analyzed regarding their Nd isotopic composition of authigenic coatings to reconstruct the provenance of the prevailing bottom water masses.</p><p>During the glacial maximum of MIS 12, the deep Atlantic Ocean was bathed with a higher amount of southern sourced water compared to the following interglacial. Termination V is represented by a sharp transition in the high-accumulating sites from the North Atlantic with a switch to northern sourced water masses. MIS 11 is characterized through an active deep water formation in the North Atlantic with active overflows from the Nordic Seas, only disrupted by a short deterioration. A strong export of northern sourced water masses to the South Atlantic points to an overall strong overturning circulation.</p><p> </p><p>[1] Lang and Wolff 2011, Climate of the Past 7: 361-380.</p><p>[2] Candy et al. 2014, Earth-Science Reviews 128: 18-51.</p><p>[3] Dutton et al. 2015, Science 349: aaa4019.</p><p>[4] Berger and Wefer 2003, Geophysical Monograph 137: 41-60.</p><p>[5] Dickson et al. 2009, Nature Geoscience 2: 428-433.</p><p>[6] Vázquez Riveiros et al. 2013, EPSL 371-372: 258-268.</p>

A middle Cenomanian euselachian assemblage from the Dunvegan Formation of northwestern Alberta

2008 ◽  
Vol 45 (10) ◽  
pp. 1185-1197 ◽  
Author(s):  
Todd D. Cook ◽  
Mark V.H. Wilson ◽  
Alison M. Murray
Keyword(s):  
Sea Water ◽  
Water Circulation ◽  
Geographical Range ◽  
Western Interior Seaway ◽  
Salinity Variation ◽  
The Core ◽  
Core Composition ◽  
Circulation Patterns ◽  
Faunal Diversity ◽  
Insight Into

A euselachian assemblage was recovered from the middle Cenomanian Dunvegan Formation situated in northwestern Alberta. This assemblage is the most northern described within the Western Interior Seaway and provides an important insight into the euselachian faunal diversity of this little-known region of the seaway. Despite its high paleolatitude, the assemblage contains a number of elasmobranch taxa, including Hybodus , Squalicorax , Archaeolamna , Cretodus , Dallasiella , and Cretoxyrhina . The Dunvegan assemblage also contains the first known reports from Canada of the odontaspid shark Johnlongia parvidens , the cretoxyrhinid shark Protolamna carteri , and the ray Pseudohypolophus mcnultyi . This assemblage extends the northern geographical range of all taxa. Preliminary comparisons with other middle Cenomanian Western Interior Seaway assemblages show that the core composition of the Dunvegan assemblage is remarkably similar to that of other time-equivalent assemblages; however, conspicuously absent are species that are exceedingly common in other localities situated farther south. We suggest that absence of these taxa from the Dunvegan localities may be caused by a temperature intolerance associated with latitude and sea-water circulation patterns, or by an inability to inhabit environments that exhibit salinity variation.

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