scholarly journals Northern Hemisphere Modes of Variability and the Timing of Spring in Western North America

2011 ◽  
Vol 24 (15) ◽  
pp. 4003-4014 ◽  
Author(s):  
Toby R. Ault ◽  
Alison K. Macalady ◽  
Gregory T. Pederson ◽  
Julio L. Betancourt ◽  
Mark D. Schwartz
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
Principal Component ◽  
Reanalysis Data ◽  
Onset Date ◽  
Western North America ◽  
Spatial And Temporal Patterns ◽  
Modes Of Variability ◽  
Index Model ◽  
Maximum Temperatures

Abstract Spatial and temporal patterns of variability in spring onset are identified across western North America using a spring index (SI) model based on weather station minimum and maximum temperatures (Tmin and Tmax, respectively). Principal component analysis shows that two significant and independent patterns explain roughly half of the total variance in the timing of spring onset from 1920 to 2005. However, these patterns of spring onset do not appear to be linear responses to the primary modes of variability in the Northern Hemisphere: the Pacific–North American pattern (PNA) and the northern annular mode (NAM). Instead, over the period when reanalysis data and the spring index model overlap (1950–2005), the patterns of spring onset are local responses to the state of both the PNA and NAM, which together modulate the onset date of spring by 10–20 days on interannual time scales. They do so by controlling the number and intensity of warm days. There is also a regionwide trend in spring advancement of about −1.5 days decade−1 from 1950 to 2005. Trends in the NAM and PNA can only explain about one-third (−0.5 day decade−1) of this trend.

A morphometric study of geographic variation in the snowshoe hare (Lepus americanus)

1985 ◽  
Vol 63 (3) ◽  
pp. 567-579 ◽  
Author(s):  
David W. Nagorsen
Keyword(s):  
North America ◽  
Great Lakes ◽  
Geographic Variation ◽  
Principal Component ◽  
Lepus Americanus ◽  
Morphometric Study ◽  
Western North America ◽  
Environmental Selection ◽  
Local Selection ◽  
Central Canada

Geographic variation in Lepus americanus was studied by multivariate analyses of 15 cranial measurements. A total of 1494 specimens from the entire geographic range were grouped into 37 geographic samples of males and females. Principal component analyses demonstrated that hares are largest in eastern North America, Alaska, and northwestern Canada, and smallest in the Pacific Northwest. Size clines exist in the Appalachian Mountains and western North America but size is relatively uniform throughout central Canada and the Great Lakes. A multiple regression of size with 16 climatic variables factors demonstrated that size and climate are strongly correlated; the size trends may reflect environmental selection. The differentiation of hares from the western Cordillera and Pacific coast, the similarity of populations from central Canada and the Great Lakes, and the clines in the Appalachians and western North America were evident in discriminant analyses. These patterns of variation among populations can be attributed to both gene flow and local selection. There is no evidence from the morphometric analyses for classifying populations into the 15 subspecies currently recognized.

scholarly journals Annular versus Nonannular Variability of the Northern Hemisphere Atmospheric Circulation

2008 ◽  
Vol 21 (13) ◽  
pp. 3180-3190 ◽  
Author(s):  
J. M. Castanheira ◽  
M. L. R. Liberato ◽  
L. de la Torre ◽  
H-F. Graf ◽  
A. Rocha
Keyword(s):  
Northern Hemisphere ◽  
Geopotential Height ◽  
Normal Modes ◽  
Principal Component ◽  
Reanalysis Data ◽  
Residual Variability ◽  
Middle Latitudes ◽  
Symmetric Component ◽  
Tropospheric Circulation ◽  
Highly Correlated

Abstract The annular variability of the northern winter extratropical circulation is reassessed based on reanalysis data that are dynamically filtered by normal modes. One-half of the variability of the monthly averaged barotropic zonally symmetric circulation of the Northern Hemisphere is statistically distinct from the remaining variability and is represented by its leading empirical orthogonal function (EOF) alone. The daily time series of the circulation anomalies projected onto the leading EOF is highly correlated (r ≥ 0.7) with the lower-stratospheric northern annular mode (NAM) indices showing that annular variability extends from the stratosphere deep into the troposphere. However, the geopotential and wind anomalies associated with the leading principal component (PC1) of the barotropic zonally symmetric circulation are displaced northward relative to the zonal mean anomalies associated with the PC1 of the geopotential height variability at single-isobaric tropospheric levels. The regression pattern of the 500-hPa geopotential height (Z500) onto the lower-stratospheric NAM also shows zonally symmetric components displaced northward with respect to those of the leading EOF of the Z500 field. A principal component analysis (PCA) of the residual variability of the Z500 field remaining after the substraction of the Z500 regressed onto the lower-stratospheric NAM index also reveals a pattern with a zonally symmetric component at midlatitudes. However, this zonally symmetric component appears as the second EOF of the residual variability and is the imprint of two independent dipoles over the Pacific and Atlantic Oceans. Results show that a zonally symmetric component of the middle- and lower-tropospheric circulation variability exists at high latitudes. At the middle latitudes, the zonally symmetric component, if any exists, is artificially overemphasized by the PCA on single-isobaric tropospheric levels.

Using High-Resolution Reanalysis Data to Explore Localized Western North America Hydroclimate Relationships with ENSO

2017 ◽  
Vol 30 (14) ◽  
pp. 5395-5417 ◽  
Author(s):  
Joshua P. Heyer ◽  
Simon C. Brewer ◽  
Jacqueline J. Shinker
Keyword(s):  
High Resolution ◽  
North America ◽  
El Niño ◽  
El Nino ◽  
Reanalysis Data ◽  
Tropical Pacific ◽  
Series Data ◽  
Western North America ◽  
Surface Precipitation ◽  
Sst Variability

Many studies have used observational data to explore associations between El Niño–Southern Oscillation (ENSO) and western North America (NA) hydroclimate at regional spatial scales. However, relationships between tropical Pacific sea surface temperature (SST) variability and western NA hydroclimate at local scales using reanalysis data are less understood. Here, the current understanding of relationships between large-scale tropical Pacific SST variability and western NA hydroclimate is extended to localized headwaters. To accomplish this, high-resolution reanalysis data (i.e., monthly mean surface precipitation rate, 2-m temperature, 850-mb specific humidity, and 500-mb omega) were used for gridpoint correlation analyses with Niño-3.4 SST and El Niño Modoki indices. Reanalysis time series data were provided by the National Centers for Environmental Prediction North American Regional Reanalysis (NARR) product. To validate the accuracy of NARR surface data, observational Livneh precipitation and temperature data were used. Resulting correlations between tropical Pacific indices and NARR surface precipitation and 2-m temperature are consistent with previous research both spatially and temporally, indicating that the strongest correlations occur primarily over southwestern NA during the winter (DJF). The results herein demonstrate the potential of high-resolution reanalysis data to reveal distinct correlations over topographically complex watersheds in the U.S. Intermountain West (IMW) over the recent record, 1979–2015. The use of the high-resolution NARR product as a viable option to explore western NA hydroclimate is demonstrated here.

scholarly journals Changes toward Earlier Streamflow Timing across Western North America

2005 ◽  
Vol 18 (8) ◽  
pp. 1136-1155 ◽  
Author(s):  
Iris T. Stewart ◽  
Daniel R. Cayan ◽  
Michael D. Dettinger
Keyword(s):  
North America ◽  
Large Scale ◽  
Center Of Mass ◽  
Principal Component ◽  
Warming Trend ◽  
Western North America ◽  
Climate Fluctuations ◽  
Climate Indicators ◽  
Decadal Scale ◽  
Streamflow Timing

Abstract The highly variable timing of streamflow in snowmelt-dominated basins across western North America is an important consequence, and indicator, of climate fluctuations. Changes in the timing of snowmelt-derived streamflow from 1948 to 2002 were investigated in a network of 302 western North America gauges by examining the center of mass for flow, spring pulse onset dates, and seasonal fractional flows through trend and principal component analyses. Statistical analysis of the streamflow timing measures with Pacific climate indicators identified local and key large-scale processes that govern the regionally coherent parts of the changes and their relative importance. Widespread and regionally coherent trends toward earlier onsets of springtime snowmelt and streamflow have taken place across most of western North America, affecting an area that is much larger than previously recognized. These timing changes have resulted in increasing fractions of annual flow occurring earlier in the water year by 1–4 weeks. The immediate (or proximal) forcings for the spatially coherent parts of the year-to-year fluctuations and longer-term trends of streamflow timing have been higher winter and spring temperatures. Although these temperature changes are partly controlled by the decadal-scale Pacific climate mode [Pacific decadal oscillation (PDO)], a separate and significant part of the variance is associated with a springtime warming trend that spans the PDO phases.

scholarly journals Phylogenomic analyses in the apple genus Malus s.l. reveal widespread hybridization and allopolyploidy driving the diversifications, with insights into the complex biogeographic history in the Northern Hemisphere

2021 ◽  
Author(s):  
Bin-Bin Liu ◽  
Chen Ren ◽  
Myounghai Kwak ◽  
Richard Hodel ◽  
Chao Xu ◽  
...  
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
Crop Improvement ◽  
Gene Tree ◽  
Nuclear Gene ◽  
Western North America ◽  
Fossil Species ◽  
Biogeographic History ◽  
Hybridization Event ◽  
Analytical Approaches

Phylogenomic evidence from an increasing number of studies has demonstrated that different data sets and analytical approaches often reconstruct strongly supported but conflicting relationships. In this study, hundreds of single-copy nuclear (SCN) genes (785) and complete plastomes (75) were used to infer the phylogenetic relationships and estimate the historical biogeography of the apple genus Malus sensu lato, an economically important lineage disjunctly distributed in the Northern Hemisphere involved in known and suspected hybridization and allopolyploidy events. The nuclear phylogeny recovered the monophyly of Malus s.l. (including Docynia); however, it was supported to be biphyletic in the plastid phylogeny. An ancient chloroplast capture event best explains the cytonuclear discordance that occurred in the Eocene in western North America. Our conflict analysis demonstrated that ILS, hybridization, and allopolyploidy could explain the widespread nuclear gene tree discordance. We detected one deep hybridization event (Malus doumeri) involving the ancestor of pome-bearing species and Docynia delavayi, and one recent hybridization event (Malus coronaria) between M. sieversii and a combined clade of M. ioensis and M. angustifolia. Furthermore, our historical biogeographic analysis combining living and fossil species supported a widespread East Asian-western North American origin of Malus s.l., followed by a series of extinction events in the Eocene in northern East Aisa and western North America. This study provides a valuable evolutionary framework for the breeding and crop improvement of apples and their close relatives.

Morphometrics and Redescription of Aphyllon fasciculatum and Aphyllon franciscanum, Two Widespread but Previously Conflated Species in Western North America

2021 ◽  
Vol 46 (2) ◽  
pp. 446-455
Author(s):  
Adam C. Schneider ◽  
Ben E. Benton
Keyword(s):  
North America ◽  
Principal Component ◽  
Calyx Lobe ◽  
Corolla Tube ◽  
Herbarium Specimens ◽  
Western North America ◽  
Widespread Species ◽  
Floral Color ◽  
Discriminant Analyses ◽  
Floral Characters

Abstract— We continue the taxonomic reevaluation of Aphyllon sect. Aphyllon by describing a widespread species throughout western North America previously recognized within a polyphyletic A. fasciculatum. To support our description and revised key, we analyzed fifteen continuous and discrete characters sampled from 186 herbarium specimens and iNaturalist observations representing the geographic and host ranges. Principal component and multiple correspondence analyses reveal clear variation in floral characters. Discriminant analyses show that three aspects of floral color, corolla lobe tip shape, the calyx cup to calyx lobe ratio, calyx lobe length, and degree of bend in the corolla tube are useful distinguishing features, but not diagnostic in every case.

scholarly journals Barrier to Gene Flow Between Eastern and Western Populations of Cronartium ribicola in North America

2000 ◽  
Vol 90 (10) ◽  
pp. 1073-1078 ◽  
Author(s):  
R. C. Hamelin ◽  
R. S. Hunt ◽  
B. W. Geils ◽  
G. D. Jensen ◽  
V. Jacobi ◽  
...  
Keyword(s):  
Gene Flow ◽  
New Mexico ◽  
North America ◽  
Random Amplified Polymorphic Dna ◽  
Principal Component ◽  
Genetic Distances ◽  
Group Method ◽  
Cronartium Ribicola ◽  
Western North America ◽  
Pair Group

The population structure of Cronartium ribicola from eastern and western North America was studied to test the null hypothesis that populations are panmictic across the continent. Random amplified polymorphic DNA markers previously characterized in eastern populations were mostly fixed in western populations, yielding high levels of genetic differentiation between eastern and western populations (φst = 0.55; θ = 0.36; P < 0.001). An unweighted pair-group method, arithmetic mean dendro-gram based on genetic distances separated the four eastern and four western populations into two distinct clusters along geographic lines. Similarly, a principal component analysis using marker frequency yielded one cluster of eastern populations and a second cluster of western populations. The population from New Mexico was clearly within the western cluster in both analyses, confirming the western origin of this recent introduction. This population was completely fixed (Hj = 0.000; n = 45) at all loci suggesting a severe recent population bottleneck. Genetic distances were low among populations of western North America (0.00 to 0.02) and among eastern populations (0.00 to 0.02), indicating a very similar genetic composition. In contrast, genetic distances between eastern and western populations were large, and all were significantly different from 0 (0.07 to 0.19; P < 0.001). Indirect estimates of migration were high among western populations, including the number of migrants among pairs of populations (Nm > 1) between New Mexico and British Columbia populations, but were smaller than one migrant per generation between eastern and western populations. These results suggest the presence of a barrier to gene flow between C. ribicola populations from eastern and western North America.

Allium yamadagensis (Amaryllidaceae) a new species from Turkey

Phytotaxa ◽  
2019 ◽  
Vol 400 (1) ◽  
pp. 31 ◽  
Author(s):  
GÜLNUR EKŞI ◽  
HASAN YILDIRIM
Keyword(s):  
New Species ◽  
North America ◽  
Central Asia ◽  
Northern Hemisphere ◽  
Mediterranean Region ◽  
Molecular Data ◽  
Western North America ◽  
Number Of Species ◽  
Phylogenetic Studies ◽  
A New Species

Allium Linneaus (1753: 294) is one of the largest monocot genera with about 900 species (Govaerts et al. 2019) naturally distributed throughout the northern hemisphere (Stearn 1978, 1992, Fritsch & Keusgen 2006, Friesen et al. 2006, Fritsch & Abbasi 2008). The main centre of biodiversity occurs in Southwestern and Central Asia and the Mediterranean region, a smaller center is found in western North America (Friesen et al. 2006, Nguyen et al. 2008). The genus is characterized by bulbs enclosed in membranous, fibrous or reticulate tunics, free or basally connate tepals and often a subgynobasic style (Friesen et al. 2006). The genus Allium is a member of Amaryllidaceae subfam. Allioideae, tribe Allieae (APGIII 2009, Chase & Reveal 2009). Recent phylogenetic studies based on molecular data were combined with morphology, anatomy, and cytology resulting in new proposals for sectional and subsectional relationships (Linne von Berg et al. 1996, Dubouzet & Shinoda 1999, Friesen et al. 2000, 2006, Gurushidze et al. 2008, Nguyen et al. 2008, Li et al. 2010, Choi et al. 2012). The most recent Allium classification includes 15 subgenera and 80 sections (Friesen et al. 2006). Allium is a taxonomically quite complex and has unresolved nomenclatural problems. In the last decades, many Allium taxa were newly described for Turkey and the number of species known to occur in the country is approximately 200, classified into 15 sections, ca. one-third which being endemic (Kollmann 1984, Koyuncu 2012, Özhatay & Kandemir 2014, Ekşi et al. 2015, 2016, Duman et al. 2017, Fırat et al. 2018).

scholarly journals The Relationship between Northern Hemisphere Winter Blocking and Tropical Modes of Variability

2017 ◽  
Vol 30 (22) ◽  
pp. 9321-9337 ◽  
Author(s):  
Gereon Gollan ◽  
Richard J. Greatbatch
Keyword(s):  
Northern Hemisphere ◽  
North Atlantic ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Western Indian Ocean ◽  
Reanalysis Data ◽  
Boreal Winter ◽  
Modes Of Variability ◽  
Early Late

In the present study, the influence of some major tropical modes of variability on Northern Hemisphere regional blocking frequency variability during boreal winter is investigated. Reanalysis data and an ensemble experiment with the ECMWF model using relaxation toward the ERA-Interim data inside the tropics are used. The tropical modes under investigation are El Niño–Southern Oscillation (ENSO), the Madden–Julian oscillation (MJO), and the upper-tropospheric equatorial zonal-mean zonal wind [[Formula: see text]] E. An early (late) MJO phase refers to the part of the MJO cycle when enhanced (suppressed) precipitation occurs over the western Indian Ocean and suppressed (enhanced) precipitation occurs over the Maritime Continent and the western tropical Pacific. Over the North Pacific sector, it is found that enhanced (suppressed) high-latitude blocking occurs in association with El Niño (La Niña) events, late (early) MJO phases, and westerly (easterly) [[Formula: see text]] E. Over central to southern Europe and the east Atlantic, it is found that late MJO phases, as well as a suppressed MJO, are leading to enhanced blocking frequency. Furthermore, early (late) MJO phases are followed by blocking anomalies over the western North Atlantic region, similar to those associated with a positive (negative) North Atlantic Oscillation. Over northern Europe, the easterly (westerly) phase of [[Formula: see text]] E is associated with enhanced (suppressed) blocking. These results are largely confirmed by both the reanalysis and the model experiment.

Footprints of Atlantic Multidecadal Oscillation in the Low-Frequency Variation of Extreme High Temperature in the Northern Hemisphere

2019 ◽  
Vol 32 (3) ◽  
pp. 791-802 ◽  
Author(s):  
Miaoni Gao ◽  
Jing Yang ◽  
Daoyi Gong ◽  
Peijun Shi ◽  
Zhangang Han ◽  
...  
Keyword(s):  
High Temperature ◽  
North America ◽  
Northern Hemisphere ◽  
Low Frequency ◽  
Atlantic Multidecadal Oscillation ◽  
Frequency Variation ◽  
Eastern Siberia ◽  
Western North America ◽  
Mongolian Plateau ◽  
Extreme High Temperature

The frequency and intensity of extreme high temperature (EHT) in the Northern Hemisphere exhibit remarkable low-frequency (LF) variations (longer than 10 years) in summer during 1951–2017. Five hotspots featuring large LF variations in EHT were identified, including western North America–Mexico, eastern Siberia, Europe, central Asia, and the Mongolian Plateau. The probability density functions show that the higher EHT occurrences over these hotspots in recent decades is consistent with the shifted average and increased variances in daily mean temperature. The common features of the LF variation in EHT frequency over all domains are the remarkable increasing trends and evident decadal to multidecadal variations. The component of decadal to multidecadal variations is the main contribution to the LF variations of temperature in the last century. Further analysis shows that the coherent variability of decadal to multidecadal temperature variations over western North America–Mexico, eastern Siberia, Europe, and the Mongolian Plateau are the footprints of a dominant natural internal signal: the Atlantic multidecadal oscillation. It contributes to the variations in temperature over these hotspots via barotropic circumglobal teleconnection, which imposes striking anomalous pressure over these regions. This study implies that natural internal variability plays an important role in making hotspots more vulnerable to EHT.

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