Modelling of Site Amplification via Large Scale Nonlinear Simulations with Applications to North America

This paper presents the development of large-scale simulation-based data sets used to inform new site amplification models for Central and Eastern North America (CENA). Linear elastic, equivalent linear, and nonlinear one-dimensional site response simulations of site conditions in CENA are employed. An analysis tree is introduced to capture the range of expected CENA geologic conditions. Independent variables include the following: (1) representative and random shear wave velocity ( VS) profiles using data from the literature; (2) randomized, nonlinear shear modulus reduction and damping vs. shear strain curves with constraint on soil shear strength; and (3) outcrop ground motions representative of the VS = 3,000 m/s CENA reference rock condition. The resulting database of 1,747,278 simulations is conditioned on several parameters relevant to site amplification, which facilitates model development that is the subject of a companion paper. The database is openly available for use by other researchers.

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Interannual Variability of North American Winter Temperature Extremes and Its Associated Circulation Anomalies in Observations and CMIP5 Simulations

Journal of Climate ◽

10.1175/jcli-d-19-0404.1 ◽

2020 ◽

Vol 33 (3) ◽

pp. 847-865 ◽

Cited By ~ 1

Author(s):

B. Yu ◽

H. Lin ◽

V. V. Kharin ◽

X. L. Wang

Keyword(s):

North America ◽

Surface Temperature ◽

Atmospheric Circulation ◽

North American ◽

North Pacific ◽

Large Scale ◽

Temperature Extremes ◽

Temperature Extreme ◽

Central Canada ◽

Leading Mode

AbstractThe interannual variability of wintertime North American surface temperature extremes and its generation and maintenance are analyzed in this study. The leading mode of the temperature extreme anomalies, revealed by empirical orthogonal function (EOF) analyses of December–February mean temperature extreme indices over North America, is characterized by an anomalous center of action over western-central Canada. In association with the leading mode of temperature extreme variability, the large-scale atmospheric circulation features an anomalous Pacific–North American (PNA)-like pattern from the preceding fall to winter, which has important implications for seasonal prediction of North American temperature extremes. A positive PNA pattern leads to more warm and fewer cold extremes over western-central Canada. The anomalous circulation over the PNA sector drives thermal advection that contributes to temperature anomalies over North America, as well as a Pacific decadal oscillation (PDO)-like sea surface temperature (SST) anomaly pattern in the midlatitude North Pacific. The PNA-like circulation anomaly tends to be supported by SST warming in the tropical central-eastern Pacific and a positive synoptic-scale eddy vorticity forcing feedback on the large-scale circulation over the PNA sector. The leading extreme mode–associated atmospheric circulation patterns obtained from the observational and reanalysis data, together with the anomalous SST and synoptic eddy activities, are reasonably well simulated in most CMIP5 models and in the multimodel mean. For most models considered, the simulated patterns of atmospheric circulation, SST, and synoptic eddy activities have lower spatial variances than the corresponding observational and reanalysis patterns over the PNA sector, especially over the North Pacific.

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Atmospheric Conditions Associated with Labrador Sea Deep Convection: New Insights from a Case Study of the 2006/07 and 2007/08 Winters

Journal of Climate ◽

10.1175/jcli-d-15-0527.1 ◽

2016 ◽

Vol 29 (14) ◽

pp. 5281-5297 ◽

Cited By ~ 10

Author(s):

Who M. Kim ◽

Stephen Yeager ◽

Ping Chang ◽

Gokhan Danabasoglu

Keyword(s):

North America ◽

North Atlantic ◽

Large Scale ◽

Initial Conditions ◽

Deep Convection ◽

La Niña ◽

Labrador Sea ◽

Atmospheric Conditions ◽

Circulation Anomaly ◽

La Nina

Abstract Deep convection in the Labrador Sea (LS) resumed in the winter of 2007/08 under a moderately positive North Atlantic Oscillation (NAO) state. This is in sharp contrast with the previous winter with weak convection, despite a similar positive NAO state. This disparity is explored here by analyzing reanalysis data and forced-ocean simulations. It is found that the difference in deep convection is primarily due to differences in large-scale atmospheric conditions that are not accounted for by the conventional NAO definition. Specifically, the 2007/08 winter was characterized by an atmospheric circulation anomaly centered in the western North Atlantic, rather than the eastern North Atlantic that the conventional NAO emphasizes. This anomalous circulation was also accompanied by anomalously cold conditions over northern North America. The controlling influence of these atmospheric conditions on LS deep convection in the 2008 winter is confirmed by sensitivity experiments where surface forcing and/or initial conditions are modified. An extended analysis for the 1949–2009 period shows that about half of the winters with strong heat losses in the LS are associated with such a west-centered circulation anomaly and cold conditions over northern North America. These are found to be accompanied by La Niña–like conditions in the tropical Pacific, suggesting that the atmospheric response to La Niña may have a strong influence on LS deep convection.

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Wildfires in the southern Canadian Rocky Mountains and their relationship to mid-tropospheric anomalies

Canadian Journal of Forest Research ◽

10.1139/x93-153 ◽

1993 ◽

Vol 23 (6) ◽

pp. 1213-1222 ◽

Cited By ~ 128

Author(s):

E.A. Johnson ◽

D.R. Wowchuk

Keyword(s):

North America ◽

Rocky Mountains ◽

Large Scale ◽

Fire Frequency ◽

Fuel Moisture ◽

Large Fire ◽

Canadian Rocky Mountains ◽

Area Burned ◽

Upper Level ◽

Moisture Conditions

In this paper we present evidence for a large-scale (synoptic-scale) meteorological mechanism controlling the fire frequency in the southern Canadian Rocky Mountains. This large-scale control may explain the similarity in average fire frequencies and timing of change in average fire frequencies for the southern Canadian Rocky Mountains. Over the last 86 years the size distribution of fires (annual area burned) in the southern Canadian Rockies was distinctly bimodal, with a separation between small- and large-fire years at approximately 10–25 ha annual area burned. During the last 35 years, large-fire years had significantly lower fuel moisture conditions and many mid-tropospheric surface-blocking events (high-pressure upper level ridges) during July and August (the period of greatest fire activity). Small-fire years in this period exhibited significantly higher fuel moisture conditions and fewer persistent mid-tropospheric surface-blocking events during July and August. Mid-tropospheric surface-blocking events during large-fire years were teleconnected (spatially and temporally correlated in 50 kPa heights) to upper level troughs in the North Pacific and eastern North America. This relationship takes the form of the positive mode of the Pacific North America pattern.

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Observed decrease in atmospheric mercury explained by global decline in anthropogenic emissions

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1516312113 ◽

2016 ◽

Vol 113 (3) ◽

pp. 526-531 ◽

Cited By ~ 175

Author(s):

Yanxu Zhang ◽

Daniel J. Jacob ◽

Hannah M. Horowitz ◽

Long Chen ◽

Helen M. Amos ◽

...

Keyword(s):

North America ◽

Large Scale ◽

Elemental Mercury ◽

Atmospheric Mercury ◽

Small Scale ◽

Commercial Products ◽

Earth Observing System ◽

Global Emission ◽

Emission Controls ◽

Phase Out

Observations of elemental mercury (Hg0) at sites in North America and Europe show large decreases (∼1–2% y−1) from 1990 to present. Observations in background northern hemisphere air, including Mauna Loa Observatory (Hawaii) and CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container) aircraft flights, show weaker decreases (<1% y−1). These decreases are inconsistent with current global emission inventories indicating flat or increasing emissions over that period. However, the inventories have three major flaws: (i) they do not account for the decline in atmospheric release of Hg from commercial products; (ii) they are biased in their estimate of artisanal and small-scale gold mining emissions; and (iii) they do not properly account for the change in Hg0/HgII speciation of emissions from coal-fired utilities after implementation of emission controls targeted at SO2 and NOx. We construct an improved global emission inventory for the period 1990 to 2010 accounting for the above factors and find a 20% decrease in total Hg emissions and a 30% decrease in anthropogenic Hg0 emissions, with much larger decreases in North America and Europe offsetting the effect of increasing emissions in Asia. Implementation of our inventory in a global 3D atmospheric Hg simulation [GEOS-Chem (Goddard Earth Observing System-Chemistry)] coupled to land and ocean reservoirs reproduces the observed large-scale trends in atmospheric Hg0 concentrations and in HgII wet deposition. The large trends observed in North America and Europe reflect the phase-out of Hg from commercial products as well as the cobenefit from SO2 and NOx emission controls on coal-fired utilities.

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Aquaculture in North America: An Assessment of Future Prospects

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f82-016 ◽

1982 ◽

Vol 39 (1) ◽

pp. 151-154 ◽

Cited By ~ 1

Author(s):

P. A. Larkin

Keyword(s):

North America ◽

Large Scale ◽

Geographical Location ◽

Aquatic Environments ◽

Future Prospects ◽

Growing Period ◽

Close Proximity ◽

Cheap Alternative ◽

Alternative Sources ◽

Simple Technology

The farming of aquatic environments is already a large-scale world enterprise involving relatively simple technology, but aquacultural production in North America is only a small part of the world total. Aquaculture is only economically rewarding where high rates of production over a long growing period can be coupled with close proximity to large markets in which there are few cheap alternative sources of protein. Much of North American aquaculture is aimed at meeting demands of recreational fishermen rather than as a way of producing food. There are many opportunities for development of aquaculture in North America and it seems reasonable to project substantial increases in production in the next two decades.Key words: aquaculture, geographical location, North America, future prospects, economics

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Charcoal in soils of the Allerød-Younger Dryas transition were the result of natural fires and not necessarily the effect of an extra-terrestrial impact

Netherlands Journal of Geosciences – Geologie en Mijnbouw ◽

10.1017/s0016774600023416 ◽

2008 ◽

Vol 87 (4) ◽

pp. 359-361 ◽

Cited By ~ 43

Author(s):

T. van der Hammen ◽

B. van Geel

Keyword(s):

North America ◽

Large Scale ◽

Sand Dunes ◽

Younger Dryas ◽

Natural Fires ◽

Water Tables ◽

Pine Trees ◽

Climate Cooling ◽

Fossil Records ◽

Terrestrial Material

AbstractDuring the warm Bølling-Allerød interstadial, tree species migrated from their refugia in southern Europe northwards into the area within the present temperate climatic zone. It is evident from high levels of charcoal in fossil records in this region that, especially during the later part of the Bølling-Allerød interstadial, many fires occurred. The start of the Younger Dryas was characterised by rapid and intense cooling and rising water tables, with catastrophic effects on the vegetation. Thermophilous pine trees could not survive the cold Younger Dryas climate. Dead wood provided an abundant source of fuel for intense, large-scale fires seen in many records as a concentration of charcoal particles in so-called ’Usselo-soils’ dated to ca 10,95014C BP. A similar trend in increased charcoal indicating increased burning is seen at many sites across North America at this time and it has been suggested by Firestone et al. (2007) that this was caused by an explosion of extra-terrestrial material over northern North America, causing the Younger Dryas climate cooling and Megafaunal extinction. We argue that there is no need to invoke an extraterrestrial cause to explain the charcoal in the fossilized soils. The volume of forest trees that died as a result of the cold Younger Dryas climate would easily have supplied sufficient fuel for intense, large-scale fires and can be used to account for the concentration of charcoal particles. As soils were no longer covered by dense vegetation, much erosion occurred during the Younger Dryas and therefore, at many places, Usselo soils, rich in charcoal, were preserved under aeolian sand dunes.

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Correspondence between Site Amplification and Topographical, Geological Parameters: Collation of Data from Swiss and Japanese Stations, and Neural Networks-Based Prediction of Local Response

Bulletin of the Seismological Society of America ◽

10.1785/0120210225 ◽

2021 ◽

Author(s):

Paolo Bergamo ◽

Conny Hammer ◽

Donat Fäh

Keyword(s):

Frequency Response ◽

Large Scale ◽

Site Response ◽

Low Frequency ◽

Field Measurements ◽

Site Amplification ◽

Local Response ◽

Regional Variability ◽

Individual Site ◽

Digital Elevation

ABSTRACT We address the relation between seismic local amplification and topographical and geological indicators describing the site morphology. We focus on parameters that can be derived from layers of diffuse information (e.g., digital elevation models, geological maps) and do not require in situ surveys; we term these parameters as “indirect” proxies, as opposed to “direct” indicators (e.g., f0, VS30) derived from field measurements. We first compiled an extensive database of indirect parameters covering 142 and 637 instrumented sites in Switzerland and Japan, respectively; we collected topographical indicators at various spatial extents and focused on shared features in the geological descriptions of the two countries. We paired this proxy database with a companion dataset of site amplification factors at 10 frequencies within 0.5–20 Hz, empirically measured at the same Swiss and Japanese stations. We then assessed the robustness of the correlation between individual site-condition indicators and local response by means of statistical analyses; we also compared the proxy-site amplification relations at Swiss versus Japanese sites. Finally, we tested the prediction of site amplification by feeding ensembles of indirect parameters to a neural network (NN) structure. The main results are: (1) indirect indicators show higher correlation with site amplification in the low-frequency range (0.5–3.33 Hz); (2) topographical parameters primarily relate to local response not because of topographical amplification effects but because topographical features correspond to the properties of the subsurface, hence to stratigraphic amplification; (3) large-scale topographical indicators relate to low-frequency response, smaller-scale to higher-frequency response; (4) site amplification versus indirect proxy relations show a more marked regional variability when compared with direct indicators; and (5) the NN-based prediction of site response is the best achieved in the 1.67–5 Hz band, with both geological and topographical proxies provided as input; topographical indicators alone perform better than geological parameters.

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Invasive Cereal Aphids of North America: Ecology and Pest Management

Annual Review of Entomology ◽

10.1146/annurev-ento-011118-111838 ◽

2019 ◽

Vol 64 (1) ◽

pp. 73-93 ◽

Cited By ~ 10

Author(s):

Michael J. Brewer ◽

Frank B. Peairs ◽

Norman C. Elliott

Keyword(s):

North America ◽

Pest Management ◽

Great Plains ◽

Large Scale ◽

Production Systems ◽

Cereal Crops ◽

Cereal Aphids ◽

Sugarcane Aphid ◽

Cereal Production ◽

Abundance And Diversity

Aphid invasions of North American cereal crops generally have started with colonization of a new region or crop, followed by range expansion and outbreaks that vary in frequency and scale owing to geographically variable influences. To improve understanding of this process and management, we compare the invasion ecology of and management response to three cereal aphids: sugarcane aphid, Russian wheat aphid, and greenbug. The region exploited is determined primarily by climate and host plant availability. Once an area is permanently or annually colonized, outbreak intensity is also affected by natural enemies and managed inputs, such as aphid-resistant cultivars and insecticides. Over time, increases in natural enemy abundance and diversity, improved compatibility among management tactics, and limited threshold-based insecticide use have likely increased resilience of aphid regulation. Application of pest management foundational practices followed by a focus on compatible strategies are relevant worldwide. Area-wide pest management is most appropriate to large-scale cereal production systems, as exemplified in the Great Plains of North America.

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