Models of the Frequency Dependence of Q in the Mantle Underlying Tectonic Areas of North America, Eurasia and Eastern Pacific

1986 ◽  
Author(s):  
Z. A. Der ◽  
W. W. Chan ◽  
A. C. Lees ◽  
M. E. Marshall
Keyword(s):  
North America ◽  
Frequency Dependence ◽  
Eastern Pacific

Regional attenuation models in Central and Eastern North America using the NGA-East database

2021 ◽  
pp. 875529302110187
Author(s):  
Jeff Bayless
Keyword(s):  
North America ◽  
Frequency Dependence ◽  
Gulf Coast ◽  
Site Response ◽  
Epistemic Uncertainty ◽  
Amplitude Spectrum ◽  
Active Regions ◽  
Atlantic Coastal Plain ◽  
Eastern North America ◽  
Anelastic Attenuation

The anelastic attenuation term found in ground motion prediction equations (GMPEs) represents the distance dependence of the effect of intrinsic and scattering attenuation on the wavefield as it propagates through the crust and contains the frequency-dependent quality factor, [Formula: see text], which is an inverse measure of the effective anelastic attenuation. In this work, regional estimates of [Formula: see text] in Central and Eastern North America (CENA) are developed using the NGA-East regionalization. The technique employed uses smoothed Fourier amplitude spectrum (FAS) data from well-recorded events in CENA as collected and processed by NGA-East. Regional [Formula: see text] is estimated using an assumption of average geometrical spreading applicable to the distance ranges considered. Corrections for the radiation pattern effect and for site response based on [Formula: see text] result in a small but statistically significant improvement to the residual analysis. Apparent [Formula: see text] estimates from multiple events are combined within each region to develop the regional models. Models are provided for three NGA-East regions: the Gulf Coast, Central North America, and the Appalachian Province. Consideration of the model uncertainties suggests that the latter two regions could be combined. There were not sufficient data to adequately constrain the model in the Atlantic Coastal Plain region. Tectonically stable regions are usually described by higher [Formula: see text] and weaker frequency dependence ([Formula: see text]), while active regions are typically characterized by lower [Formula: see text] and stronger frequency dependence, and the results are consistent with these expectations. Significantly different regional [Formula: see text] is found for events with data recorded in multiple regions, which supports the NGA-East regionalization. An inspection of two well-recorded events with data both in the Mississippi embayment and in southern Texas indicates that the Gulf Coast regionalization by Cramer in 2017 may be an improvement to that of NGA-East for anelastic attenuation. The [Formula: see text] models developed serve as epistemic uncertainty alternatives in CENA based on a literature review and a comparison with previously published models.

scholarly journals Verification of Extratropical Cyclones within the NCEP Operational Models. Part I: Analysis Errors and Short-Term NAM and GFS Forecasts

2009 ◽  
Vol 24 (5) ◽  
pp. 1173-1190 ◽  
Author(s):  
Michael E. Charles ◽  
Brian A. Colle
Keyword(s):  
United States ◽  
North America ◽  
North American ◽  
Eastern Pacific ◽  
Extratropical Cyclones ◽  
Global Forecast System ◽  
Eastern United States ◽  
Forecast System ◽  
Short Term ◽  
The North

Abstract This paper verifies extratropical cyclones around North America and the adjacent oceans within the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) and North American Mesoscale (NAM) models during the 2002–07 cool seasons (October–March). The analyzed cyclones in the Global Forecast System (GFS) model, North American Mesoscale (NAM) model, and the North American Regional Reanalysis (NARR) were also compared against sea level pressure (SLP) observations around extratropical cyclones. The GFS analysis of SLP was clearly superior to the NAM and NARR analyses. The analyzed cyclone pressures in the NAM improved in 2006–07 when its data assimilation was switched to the Gridpoint Statistical Interpolation (GSI). The NCEP GFS has more skillful cyclone intensity and position forecasts than the NAM over the continental United States and adjacent oceans, especially over the eastern Pacific, where the NAM has a large positive (underdeepening) bias in cyclone central pressure. For the short-term (0–60 h) forecasts, the GFS and NAM cyclone errors over the eastern Pacific are larger than the other regions to the east. There are relatively large biases in cyclone position for both models, which vary spatially around North America. The eastern Pacific has four to eight cyclone events per year on average, with errors >10 mb at hour 48 in the GFS; this number has not decreased in recent years. There has been little improvement in the 0–2-day cyclone forecasts during the past 5 yr over the eastern United States, while there has been a relatively large improvement in the cyclone pressure predictions over the eastern Pacific in the NAM.

Latest Cretaceous and early Tertiary Tudiclidae and Melongenidae (Gastropoda) from the Pacific Slope of North America

1988 ◽  
Vol 62 (6) ◽  
pp. 880-889 ◽  
Author(s):  
Louella R. Saul
Keyword(s):  
North America ◽  
New Genus ◽  
Eastern Pacific ◽  
Early Tertiary ◽  
Late Paleocene ◽  
The Pacific ◽  
Pacific Slope

Four species belonging in Tudiclidae and one in Melongenidae have been confused with perissityids. The new genus Rapopsis is proposed for a tudiclid species, R. joseana n. sp. of early Maastrichtian age. Three other tudiclid species may belong in the Tethyan genus Pyropsis, P. fantozzii n. sp. of early to middle Paleocene age, P. striata (Stanton, 1896) of later Paleocene age, and ?P. gabbi (Stanton, 1896) probably of early to middle Paleocene age. The melongenid genus Protobusycon, represented by P. judithae n. sp. of late Paleocene age, has not previously been recognized in eastern Pacific faunas.

scholarly journals On the Role of the Eastern Pacific Teleconnection in ENSO Impacts on Wintertime Weather over East Asia and North America

2019 ◽  
Vol 32 (4) ◽  
pp. 1217-1234 ◽  
Author(s):  
Ying Dai ◽  
Benkui Tan
Keyword(s):  
North America ◽  
Surface Temperature ◽  
East Asia ◽  
El Niño ◽  
El Nino ◽  
Eastern Pacific ◽  
Frequency Of Occurrence ◽  
Temperature Anomalies ◽  
La Nina ◽  
Weather Events

Previous studies have mainly focused on the influence of El Niño–Southern Oscillation (ENSO) on seasonal-mean conditions over East Asia and North America. This study, instead, proposes an ENSO pathway that influences the weather events over East Asia and North America, in which the eastern Pacific teleconnection pattern (EP) plays an important role. On the one hand, the EP pattern can induce significant surface temperature anomalies over East Asia during its development and mature stages, with the positive (negative) EPs causing colder (warmer) than normal weather events. Besides, the frequency of occurrence of EPs is significantly modulated by ENSO, with 50% of the positive EPs occurring in La Niña winters, and 47% of the negative EPs occurring in El Niño winters. As a result, in El Niño winters, more negative and fewer positive EPs tend to occur, and thus more warm and fewer cold weather events are expected in East Asia. For La Niña winters, the reverse is true. On the other hand, for the EP pattern without its canonical convection pattern (referred to as the nonconvective EP), extremely cold anomalies over the northern United States and western Canada are induced in its negative phase. Moreover, when there are positive sea surface temperature anomalies in the central equatorial Pacific, the frequency of occurrence of negative nonconvective EPs is 2.0 times greater than the climatological value, and thus an enhanced likelihood of extremely cold spells over North America may be expected.

scholarly journals A Quantitative Tomotectonic Plate Reconstruction of Western North America and the Eastern Pacific Basin

2020 ◽  
Vol 21 (8) ◽  
Author(s):  
Edward J. Clennett ◽  
Karin Sigloch ◽  
Mitchell G. Mihalynuk ◽  
Maria Seton ◽  
Martha A. Henderson ◽  
...  
Keyword(s):  
North America ◽  
Eastern Pacific ◽  
Pacific Basin ◽  
Western North America ◽  
Plate Reconstruction

Stratospheric cirrus clouds related to deep convection over North America observed by satellite measurements

2021 ◽  
Author(s):  
Ling Zou ◽  
Lars Hoffmann ◽  
Sabine Griessbach ◽  
Lunche Wang
Keyword(s):  
North America ◽  
Formation Mechanism ◽  
Great Plains ◽  
Gravity Waves ◽  
North Atlantic ◽  
Deep Convection ◽  
Eastern Pacific ◽  
Western Canada ◽  
The North ◽  
North Eastern

<p>Cirrus clouds in the stratosphere (SCCs) regulate the water vapor budget in the stratosphere, impact the stratosphere and tropopshere exchange, and affect the surface energy balance. But the knowledge of its occurrence and formation mechanism is limited, especially in middle and high latitudes. In this study, we aim to assess the occurrence frequencies of SCC over North America based on The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) instrument during the years 2006 to 2018. Possible driving forces such as deep convection are assessed based on Atmospheric Infrared Sounder (AIRS) observations during the same time. </p><p>Results show that at nighttime, SCCs are most frequently observed during the thunderstorm season over the Great Plains from May to August (MJJA) with maximum occurrence frequency of 6.2%. During the months from November to February (NDJF), the highest SCCs occurrence frequencies are 5.5% over the North-Eastern Pacific, western Canada and 4.4% over the western North Atlantic. Occurrence frequencies of deep convection and strong storm systems from AIRS show similar hotspots like the SCCs, with highest occurrence frequencies being observed over the Great Plains in MJJA (4.4%) and over the North-Eastern Pacific, western Canada and the western North Atlantic in NDJF (~2.5%). Both, seasonal patterns and daily time series of SCCs and deep convection show a high degree of spatial and temporal correlation. As further analysis indicates that the maximum fraction of SCCs generated by deep convection is 74% over the Great Plains in MJJA and about 50% over the western North Atlantic, the North-Eastern Pacific and western Canada in NDJF, we conclude that, locally and regionally, deep convection is a leading factor for the formation of SCCs over North America. Other studies stressed the relevance of isentropic transport, double tropopause events, or gravity waves for the formation of SCCs. </p><p>In this study, we also analyzed the impact of gravity waves as a secondary formation mechanism for SCCs, as the Great Plains is a well-known hotspot for stratospheric gravity waves. In case of SCCs that are not directly linked to deep convection, we found that stratospheric gravity wave observations correlate in as much as 30% of the cases over the Great Plains in MJJA, about 50% over the North-Eastern Pacific, western Canada and maximally 90% over eastern Canada and the north-west Atlantic in NDJF. </p><p>Our results provide better understanding of the physical processes and climate variability related to SCCs and will be of interest for modelers as SCC sources such as deep convection and gravity waves are small-scale processes that are difficult to represent in global general circulation models. </p>

scholarly journals Spatial Distribution and Evolution of Extratropical Cyclone Errors over North America and its Adjacent Oceans in the NCEP Global Forecast System Model

2011 ◽  
Vol 26 (2) ◽  
pp. 129-149 ◽  
Author(s):  
Brian A. Colle ◽  
Michael E. Charles
Keyword(s):  
United States ◽  
North America ◽  
East Coast ◽  
Eastern Pacific ◽  
Central Pressure ◽  
Global Forecast System ◽  
Eastern United States ◽  
Forecast System ◽  
Western Atlantic ◽  
The U.S

Abstract Short- to medium-range (1–5 day) forecasts of extratropical cyclones around North America and its adjacent oceans are verified within the Global Forecast System (GFS) model at the National Centers for Environmental Prediction (NCEP) during the 2002–07 cool seasons (October–March). Cyclones in the immediate lee of the Rockies and U.S. Great Plains have 25%–50% smaller pressure errors than other regions after hour 36. The central pressure and displacement errors are largest over the central and eastern Pacific for the 42–72-h forecast, while the western and central Atlantic pressure errors for 96–120 h are similar to the central and eastern Pacific. For relatively strong cyclones, the western Atlantic and central/eastern Canada pressure errors are larger than those for the Pacific by 108–120 h. There are large spatial variations in the central pressure biases at 72–120 h, with overdeepened GFS cyclones (negative errors) extending from the northern Pacific and Bering Strait eastward to western Canada, while underdeepened GFS cyclones (positive errors) occur across northeast Canada and just east of the U.S. east coast. GFS cyclone tracks and spatial composites using the daily NCEP reanalysis are used to illustrate flow patterns and source regions for some of the large GFS cyclone errors and biases. Relatively large central pressure errors over the central Pacific early in the forecast (30 h) spread eastward over Canada by 66 h and the eastern United States by 84 h. The underdeepened GFS cyclone errors (>1.5 standard deviations) at day 4 over the western Atlantic are associated with an anomalous ridge over the western United States and trough over the eastern United States, and most of the underdeepening occurs with cyclones tracking east-northeastward across the Gulf Stream. Many of the overdeepened cyclones have tracks more parallel to the U.S. east coast. The underdeepened cyclones over the central and eastern Pacific tend to occur farther south (35°–45°N) than the overdeepened events.

Three new species of the Hettangian (Early Jurassic) ammoniteSunrisitesfrom British Columbia, Canada

2008 ◽  
Vol 82 (1) ◽  
pp. 128-139 ◽  
Author(s):  
L. M. Longridge ◽  
P. L. Smith ◽  
J. Pálfy ◽  
H. W. Tipper
Keyword(s):  
British Columbia ◽  
New Species ◽  
Sexual Dimorphism ◽  
North America ◽  
Eastern Pacific ◽  
Northeastern Pacific ◽  
Large Shell ◽  
Three New Species ◽  
First Time ◽  
Stratigraphic Range

Most species of the middle and late Hettangian psiloceratid genusSunrisitesare endemic to the eastern Pacific, where they are common members of ammonoid assemblages. the Taseko Lakes map area in British Columbia yields diverse and well-preservedSunrisitesfaunas which are formally described here for the first time. Three new species are recognized,S. brimblecombei, S. chilcotinensis, andS. senililevis.the new species require an extension of the morphological range of the genus to include forms that become moderately involute at large shell diameters. Signs of sexual dimorphism are apparent within all three new species ofSunrisites.This work extends the stratigraphic range ofSunrisitesto include the latest Hettangian Rursicostatum Zone in North America. The distribution ofSunrisitessuggests that the Hispanic Corridor, which linked the western Tethyan Ocean and the eastern Pacific, may have been open during the Hettangian. Furthermore, occurrences of the genus constrain the Hettangian position of several allochthonous terranes to the northeastern Pacific.

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