scholarly journals Pauzhetka Caldera (South Kamchatka), the biggest in Kamchatka for the past 1 Ma: exploring temporal evolution and origin of voluminous silicic magmatism

2021 ◽  
Author(s):  
Vesta Davydova ◽  
Ilya Bindeman ◽  
Maria Shchekleina ◽  
Sergey Rychagov
Keyword(s):  
Temporal Evolution ◽  
The Past ◽  
Silicic Magmatism

scholarly journals Stratosphere-troposphere exchange from the Lagrangian perspective: a case study and method sensitivities

2004 ◽  
Vol 4 (3) ◽  
pp. 3249-3284 ◽  
Author(s):  
M. S. Bourqui
Keyword(s):  
Residence Time ◽  
Wave Breaking ◽  
Temporal Evolution ◽  
Baroclinic Wave ◽  
End Effects ◽  
The Past ◽  
Effective Removal ◽  
Residence Time Distributions ◽  
Temporal And Spatial

Abstract. An important part of extra-tropical stratosphere-to-troposphere transport occurs in association with baroclinic wave breaking and cut-off decay at the tropopause. In the last decade many studies have attempted to estimate stratosphere-troposphere exchange (STE) in such synoptic events with various methods, and more recently efforts have been put on inter-comparing these methods. However, large uncertainties remain on the sensitivities to methods intrinsic parameters, and on the best measure for STE with regard to end effects on chemistry. The goal of the present study is to address these two fundamental issues in the context of the application of a trajectory-based Lagrangian method, which has been applied in the past to climatological studies and has also been involved in inter-comparison studies, to a typical baroclinic wave breaking event. The analysis sheds light on (i) the fine mesoscale temporal and spatial structures that are associated with episodic, rapid inflows of stratospheric air into the troposphere; (ii) the spatial resolution of 1°×1° required to reasonably capture STE fluxes in such a wave breaking event; (iii) the effective removal of spurious exchange events using a threshold residence time; (iv) the relevance of residence time distributions for capturing the effective chemical forcing of STE; (v) the large differences in the temporal evolution and geographical distribution of STE fluxes across the 2 and the 4 potential vorticity unit iso-surface definitions of the tropopause.

scholarly journals Constraining N<sub>2</sub>O emissions since 1940 using firn air isotope measurements in both hemispheres

2017 ◽  
Vol 17 (7) ◽  
pp. 4539-4564 ◽  
Author(s):  
Markella Prokopiou ◽  
Patricia Martinerie ◽  
Célia J. Sapart ◽  
Emmanuel Witrant ◽  
Guillaume Monteil ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Mole Fraction ◽  
Radiative Forcing ◽  
Temporal Evolution ◽  
Atmospheric Model ◽  
Site Preference ◽  
Ocean Water ◽  
The Third ◽  
The Past ◽  
Global Mean

Abstract. N2O is currently the third most important anthropogenic greenhouse gas in terms of radiative forcing and its atmospheric mole fraction is rising steadily. To quantify the growth rate and its causes over the past decades, we performed a multi-site reconstruction of the atmospheric N2O mole fraction and isotopic composition using new and previously published firn air data collected from Greenland and Antarctica in combination with a firn diffusion and densification model. The multi-site reconstruction showed that while the global mean N2O mole fraction increased from (290 ± 1) nmol mol−1 in 1940 to (322 ± 1) nmol mol−1 in 2008, the isotopic composition of atmospheric N2O decreased by (−2.2 ± 0.2) ‰ for δ15Nav, (−1.0 ± 0.3) ‰ for δ18O, (−1.3 ± 0.6) ‰ for δ15Nα, and (−2.8 ± 0.6) ‰ for δ15Nβ over the same period. The detailed temporal evolution of the mole fraction and isotopic composition derived from the firn air model was then used in a two-box atmospheric model (comprising a stratospheric box and a tropospheric box) to infer changes in the isotopic source signature over time. The precise value of the source strength depends on the choice of the N2O lifetime, which we choose to fix at 123 years. The average isotopic composition over the investigated period is δ15Nav =  (−7.6 ± 0.8) ‰ (vs. air-N2), δ18O  =  (32.2 ± 0.2) ‰ (vs. Vienna Standard Mean Ocean Water – VSMOW) for δ18O, δ15Nα =  (−3.0 ± 1.9) ‰ and δ15Nβ =  (−11.7 ± 2.3) ‰. δ15Nav, and δ15Nβ show some temporal variability, while for the other signatures the error bars of the reconstruction are too large to retrieve reliable temporal changes. Possible processes that may explain trends in 15N are discussed. The 15N site preference ( = δ15Nα − δ15Nβ) provides evidence of a shift in emissions from denitrification to nitrification, although the uncertainty envelopes are large.

scholarly journals Temporal evolution of main ambient PM<sub>2.5</sub> sources in Santiago, Chile, from 1998 to 2012

2017 ◽  
Author(s):  
Francisco Barraza ◽  
Fabrice Lambert ◽  
Héctor Jorquera ◽  
Ana María Villalobos ◽  
Laura Gallardo
Keyword(s):  
Public Transport ◽  
Temporal Evolution ◽  
World Health ◽  
Mitigation Measures ◽  
Motor Vehicles ◽  
Urban Dust ◽  
Atmospheric Conditions ◽  
The Past ◽  
Wood Burning ◽  
Industrial Sources

Abstract. The inhabitants of Santiago in Chile have been exposed to harmful levels of air pollutants for decades. The city's poor air quality is a result of sustained emissions and stable atmospheric conditions, averse to mixing and ventilation and favorable for the formation of oxidants and secondary aerosols. Identifying and quantifying the sources that contribute to the ambient levels of pollutants is key for designing adequate mitigation measures. Knowledge about the temporal evolution of the contribution of each source to ambient pollution levels is also paramount to evaluate the effectiveness of pollution reduction measures that have been implemented in the past decades. Here, we quantify the main sources that have contributed to fine particulate matter (PM2.5) between 1998 and 2012 in Santiago's center by using two different source-receptor models (PMF 5.0 and Unmix 6.0), that re applied to elemental measurements on 1243 24-hour filter samples of ambient PM2.5 collected between April-1998 to August-2012. Both models resolve six sources that contribute to ambient PM2.5: motor vehicles (37 %), industrial sources (19 %), copper smelters (14 %), wood burning (12 %), coastal sources (10 %), and urban dust (3 %). Our results show that over the 15 years analyzed here, the emissions from motor vehicles, industrial sources, copper smelters, and coastal sources declined by about 21, 39, 81, 59, and 59 % respectively, while wood burning didn’t change and urban dust increase by 72 %. These changes are consistent with emission reduction measures, such as improved vehicle and smelting technology, introduction of low sulfur fuel for vehicles and natural gas for industrial processes, emission controls for vehicles, public transport improvements etc. However, it is also apparent that the mitigation expected from improved public transport, vehicle technology, and fuel has been largely nullified by the ever-rising number of private vehicle journeys in the past decade. As a consequence, Santiago still experiences PM2.5 levels above the annual and 24-hours Chilean and World Health Organization standards.

scholarly journals Hurricane Sandy’s flood frequency increasing from year 1800 to 2100

2016 ◽  
Vol 113 (43) ◽  
pp. 12071-12075 ◽  
Author(s):  
Ning Lin ◽  
Robert E. Kopp ◽  
Benjamin P. Horton ◽  
Jeffrey P. Donnelly
Keyword(s):  
New York ◽  
Sea Level ◽  
Storm Surge ◽  
21St Century ◽  
Return Period ◽  
Temporal Evolution ◽  
Flood Hazard ◽  
Flood Frequency ◽  
The Past ◽  
Probabilistic Projections

Coastal flood hazard varies in response to changes in storm surge climatology and the sea level. Here we combine probabilistic projections of the sea level and storm surge climatology to estimate the temporal evolution of flood hazard. We find that New York City’s flood hazard has increased significantly over the past two centuries and is very likely to increase more sharply over the 21st century. Due to the effect of sea level rise, the return period of Hurricane Sandy’s flood height decreased by a factor of ∼3× from year 1800 to 2000 and is estimated to decrease by a further ∼4.4× from 2000 to 2100 under a moderate-emissions pathway. When potential storm climatology change over the 21st century is also accounted for, Sandy’s return period is estimated to decrease by ∼3× to 17× from 2000 to 2100.

Landscape Spatial-Temporal Evolution and Ecological Effects in Kunming City over the Past Twenty Years

2014 ◽  
Vol 675-677 ◽  
pp. 1171-1178
Author(s):  
Huan Yu ◽  
Jin Ma ◽  
Shi Jun Ni ◽  
Ai Nong Li ◽  
Guang Bin Lei ◽  
...  
Keyword(s):  
Temporal Evolution ◽  
Water Area ◽  
Capital City ◽  
Coordinated Development ◽  
Ecological Processes ◽  
Functional Changes ◽  
The Past ◽  
Class Level ◽  
Regional Landscape ◽  
Land Water

Landscape pattern change will cause flow and change of energy, material and nutrient between different units of land, and can cause regional ecological processes and systems functional changes. As the capital city of Yunnan Province and the southwest gateway to China, Kunming city landscape structure takes place significant changes under the high-intensity human disturbance, then the environmental effects are certainly very obvious. Based on the past two decades land cover changes of Kunming, study applies 10 types of landscape indices on class level and landscape level, analyzes the landscape changes of forest, grass land, water area, farm land, residential surface, industrial land and bare land from year 1990 to 2010, then explores the various types of spatial and temporal evolution of the landscape, the regional landscape effects on the ecosystem, and provides a scientific reference for understanding the trend of ecological environment and promoting the coordinated development of regional economy and environment.

Segregation, transport, and interaction of climate proxies in polycrystalline ice

2003 ◽  
Vol 81 (1-2) ◽  
pp. 89-97 ◽  
Author(s):  
A W Rempel ◽  
J S Wettlaufer
Keyword(s):  
High Spatial Resolution ◽  
Temporal Evolution ◽  
Volume Fraction ◽  
Ice Cores ◽  
The Past ◽  
Impurity Segregation ◽  
Polycrystalline Ice ◽  
Earth’S Climate ◽  
Trace Constituents ◽  
Climate Proxies

The most detailed records of the Earth's climate during the past few hundred millennia are derived from ice cores retrieved from Greenland and Antarctica. The analyses of these records assume that the distributions of the trace constituents that are used as proxies for past climate have not significantly altered since deposition at the surface, and yet careful studies, at high spatial resolution, have identified core segments where appreciable post-depositional changes have occurred. To improve the reliability and resolution of paleoclimate interpretations, we have examined the mechanisms underlying the transport and interaction of climate proxies in polycrystalline ice, many of which are soluble impurities that are found principally in premelted liquid that lines the boundaries between ice grains. We find that the rate of post-depositional alteration depends critically on where the trace constituents reside; whether in the premelted liquid, in which case they exert a controlling influence on the total volume fraction of liquid that is present, or in the grains themselves. In the former case, the premelted liquid reservoir contains the principle conduits through which many of the impurities are transported and interact, and in the latter case, the temporal evolution of impurity concentration is both slower and more complex. We provide quantitative models that describe these processes and highlight the importance of impurity segregation for our understanding of past climates. PACS Nos.: 66.30Jt, 91.60Ed, 92.40Sn, 92.40Vq, 92.70-j

scholarly journals Modelling multimodal expression of emotion in a virtual agent

2009 ◽  
Vol 364 (1535) ◽  
pp. 3539-3548 ◽  
Author(s):  
Catherine Pelachaud
Keyword(s):  
Facial Expressions ◽  
Temporal Evolution ◽  
Conversational Agent ◽  
Virtual Agent ◽  
Embodied Conversational Agent ◽  
The Past ◽  
Multimodal Signals ◽  
Expression Of Emotion ◽  
Representation Scheme ◽  
Temporal Dynamism

Over the past few years we have been developing an expressive embodied conversational agent system. In particular, we have developed a model of multimodal behaviours that includes dynamism and complex facial expressions. The first feature refers to the qualitative execution of behaviours. Our model is based on perceptual studies and encompasses several parameters that modulate multimodal behaviours. The second feature, the model of complex expressions, follows a componential approach where a new expression is obtained by combining facial areas of other expressions. Lately we have been working on adding temporal dynamism to expressions. So far they have been designed statically, typically at their apex. Only full-blown expressions could be modelled. To overcome this limitation, we have defined a representation scheme that describes the temporal evolution of the expression of an emotion. It is no longer represented by a static definition but by a temporally ordered sequence of multimodal signals.

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