Atmospheric pressure variability over Western North America and the North Pacific reconstructed using tree-ring records

2015 ◽  
Vol 387 ◽  
pp. 149
Author(s):  
Erika K. Wise ◽  
Matthew P. Dannenberg
Keyword(s):  
North America ◽  
Tree Ring ◽  
North Pacific ◽  
Atmospheric Pressure ◽  
Western North America ◽  
The North ◽  
The North Pacific

Reconstructing Past Climatic Anomalies in the North Pacific and Western North America from Tree-Ring Data

1976 ◽  
Vol 6 (4) ◽  
pp. 563-579 ◽  
Author(s):  
T.J. Blasing ◽  
H.C. Fritts
Keyword(s):  
North America ◽  
19Th Century ◽  
Tree Ring ◽  
North Pacific ◽  
Climatic Conditions ◽  
Climatic Data ◽  
Western North America ◽  
The North ◽  
Tree Ring Data ◽  
The North Pacific

Winter climatic anomalies in the North Pacific sector and western North America are statistically calibrated with tree-ring data in western North America and reconstructed back to AD 1700. The results are verified using climatic data from the last half of the 19th century, which is prior to the calibration period. Climatic conditions reconstructed for 18th and 19th century winters are then summarized and compared with the 20th century record.

scholarly journals Asian dust storm influence on North American ambient PM levels: observational evidence and controlling factors

2008 ◽  
Vol 8 (10) ◽  
pp. 2717-2728 ◽  
Author(s):  
T. L. Zhao ◽  
S. L. Gong ◽  
X. Y. Zhang ◽  
D. A. Jaffe
Keyword(s):  
North America ◽  
North Pacific ◽  
Asian Dust ◽  
Observational Evidence ◽  
Dust Storms ◽  
Western North America ◽  
Transport Pathway ◽  
The North ◽  
Asian Dust Storms ◽  
The North Pacific

Abstract. New observational evidence of the trans-Pacific transport of Asian dust and its contribution to the ambient particulate matter (PM) levels in North America was revealed, based on the interannual variations between Asian dust storms and the ambient PM levels in western North America from year 2000 to 2006. A high correlation was found between them with an R2 value of 0.83. From analysis of the differences in the correlation between 2005 and 2006, three factors explain the variation of trans-Pacific transport and influences of Asian dust storms on PM levels in western North America. These were identified by modeling results and the re-analysis data. They were 1) Strength of frontal cyclones from Mongolia to north eastern China: The frontal cyclones in East Asia not only bring strong cold air outbreaks, generating dust storms in East Asia, but also lift Asian dust into westerly winds of the free troposphere for trans-Pacific transport; 2) Pattern of transport pathway over the North Pacific: The circulation patterns of westerlies over the North Pacific govern the trans-Pacific transport pattern. Strong zonal airflow of the westerly jet in the free troposphere over the North Pacific favor significant trans-Pacific transport of Asian dust; 3) Variation of precipitation in the North Pacific: The scavenging of Asian dust particles by precipitation is a major process of dust removal on the trans-Pacific transport pathway. Therefore, variation of precipitation in the North Pacific could affect trans-Pacific transport of Asian dust.

scholarly journals Asian dust storm influence on North American ambient PM levels: observational evidence and controlling factors

2007 ◽  
Vol 7 (4) ◽  
pp. 9663-9686 ◽  
Author(s):  
T. L. Zhao ◽  
S. L. Gong ◽  
X. Y. Zhang ◽  
D. A. Jaffe
Keyword(s):  
North America ◽  
North Pacific ◽  
Asian Dust ◽  
Observational Evidence ◽  
Dust Storms ◽  
Western North America ◽  
Transport Pathway ◽  
The North ◽  
Asian Dust Storms ◽  
The North Pacific

Abstract. New observational evidence of the trans-Pacific transport of Asian dust and its contribution to the ambient particulate matter (PM) levels in North America was revealed, based on the interannual variations between Asian dust storms and the ambient PM levels in western North America from year 2000 to 2006. A high correlation was found between them with an R2 value of 0.83. From analysis of the differences in the correlation between 2005 and 2006, three factors explain the variation of trans-Pacific transport and influences of Asian dust storms on PM levels in western North America. These were identified by modeling results and the re-analysis data. They were 1) Strength of frontal cyclones from Mongolia to north eastern China: The frontal cyclones in East Asia not only bring strong cold air outbreaks, generating dust storms in East Asia, but also lift Asian dust into westerly winds of the free troposphere for trans-Pacific transport; 2) Pattern of transport pathway over the North Pacific: The circulation patterns of westerlies over the North Pacific govern the trans-Pacific transport pattern. Strong zonal airflow of the westerly jet in the free troposphere over the North Pacific favor significant trans-Pacific transport of Asian dust; 3) Variation of precipitation in the North Pacific: The scavenging of Asian dust particles by precipitation is a major process of dust removal on the trans-Pacific transport pathway; therefore, variation of precipitation in the North Pacific could affect trans-Pacific transport of Asian dust.

scholarly journals Can ENSO-Like Convection Force an ENSO-Like Extratropical Response on Subseasonal Time Scales?

2018 ◽  
Vol 31 (20) ◽  
pp. 8339-8349 ◽  
Author(s):  
Michael Goss ◽  
Sukyoung Lee ◽  
Steven B. Feldstein ◽  
Noah S. Diffenbaugh
Keyword(s):  
North America ◽  
El Niño ◽  
North Pacific ◽  
El Nino ◽  
La Niña ◽  
Convective Heating ◽  
Western North America ◽  
The North ◽  
La Nina ◽  
The North Pacific

A daily El Niño–Southern Oscillation (ENSO) index is developed based on precipitation rate and is used to investigate subseasonal time-scale extratropical circulation anomalies associated with ENSO-like convective heating. The index, referred to as the El Niño precipitation index (ENPI), is anomalously positive when there is El Niño–like convection. Conversely, the ENPI is anomalously negative when there is La Niña–like convection. It is found that when precipitation becomes El Niño–like (La Niña–like) on subseasonal time scales, the 300-hPa geopotential height field over the North Pacific and western North America becomes El Niño–like (La Niña–like) within 5–10 days. The composites show a small association with the MJO. These results are supported by previous modeling studies, which show that the response over the North Pacific and western North America to an equatorial Pacific heating anomaly occurs within about one week. This suggests that the mean seasonal extratropical response to El Niño (La Niña) may in effect simply be the average of the subseasonal response to subseasonally varying El Niño–like (La Niña–like) convective heating. Implications for subseasonal to seasonal forecasting are discussed.

scholarly journals The spring transition of the North Pacific jet and its relation to deep stratosphere-to-troposphere mass transport over western North America

2021 ◽  
Vol 21 (4) ◽  
pp. 2781-2794
Author(s):  
Melissa L. Breeden ◽  
Amy H. Butler ◽  
John R. Albers ◽  
Michael Sprenger ◽  
Andrew O'Neil Langford
Keyword(s):  
North America ◽  
El Niño ◽  
North Pacific ◽  
El Nino ◽  
Late Winter ◽  
Western North America ◽  
The North ◽  
Jet Structure ◽  
Stratospheric Intrusions ◽  
The North Pacific

Abstract. Stratosphere-to-troposphere mass transport to the planetary boundary layer (STT-PBL) peaks over the western United States during boreal spring, when deep stratospheric intrusions are most frequent. The tropopause-level jet structure modulates the frequency and character of intrusions, although the precise relationship between STT-PBL and jet variability has not been extensively investigated. In this study, we demonstrate how the North Pacific jet transition from winter to summer leads to the observed peak in STT-PBL. We show that the transition enhances STT-PBL through an increase in storm track activity which produces highly amplified Rossby waves and more frequent deep stratospheric intrusions over western North America. This dynamic transition coincides with the gradually deepening PBL, further facilitating STT-PBL in spring. We find that La Niña conditions in late winter are associated with an earlier jet transition and enhanced STT-PBL due to deeper and more frequent tropopause folds. An opposite response is found during El Niño conditions. El Niño–Southern Oscillation (ENSO) conditions also influence STT-PBL in late spring or early summer, during which time La Niña conditions are associated with larger and more frequent tropopause folds than both El Niño and ENSO-neutral conditions. These results suggest that knowledge of ENSO state and the North Pacific jet structure in late winter could be leveraged for predicting the strength of STT-PBL in the following months.

scholarly journals The Spring Transition of the North Pacific Jet and its Relation to Deep Stratosphere-to-Troposphere Mass Transport over Western North America

2020 ◽  
Author(s):  
Melissa Leah Breeden ◽  
Amy Hawes Butler ◽  
John Robert Albers ◽  
Michael Sprenger ◽  
Andrew O’Neil Langford
Keyword(s):  
Boundary Layer ◽  
North America ◽  
Mass Transport ◽  
North Pacific ◽  
Late Winter ◽  
Western North America ◽  
The North ◽  
Jet Structure ◽  
Stratospheric Intrusions ◽  
The North Pacific

Abstract. Stratosphere-to-troposphere mass transport to the planetary boundary layer (STT-PBL) peaks over the western United States during boreal spring, when deep stratospheric intrusions are most frequent. The tropopause-level jet structure modulates the frequency and character of intrusions, although the precise relationship between STT-PBL and jet variability has not been extensively investigated. In this study, we demonstrate how the north Pacific jet transition from winter to summer leads to the observed peak in STT-PBL. We show that the transition enhances STT-PBL through an increase in storm track activity which produces highly-amplified Rossby waves and more frequent deep stratospheric intrusions over western North America. This dynamic transition coincides with the gradually deepening planetary boundary layer, further facilitating STT-PBL in spring. We find that La Niña conditions in late winter are associated with an earlier jet transition and enhanced STT-PBL due to deeper and more frequent tropopause folds. An opposite response is found during El Niño conditions. ENSO conditions also influence STT-PBL in late spring/early summer, during which time La Niña conditions are associated with larger and more frequent tropopause folds than both El Niño and ENSO neutral conditions. These results suggest that knowledge of ENSO state and the north Pacific jet structure in late winter could be leveraged for predicting the strength of STT-PBL in the following months.

Carex lyngbyei excluded from the flora of eastern North America, and taxonomic notes on related species and hybrids

1987 ◽  
Vol 65 (6) ◽  
pp. 1187-1198 ◽  
Author(s):  
Jacques Cayouette
Keyword(s):  
North America ◽  
North Pacific ◽  
Related Species ◽  
Hybrid Origin ◽  
Eastern North America ◽  
Herbarium Specimens ◽  
Western North America ◽  
Pollen Stainability ◽  
The North ◽  
The North Pacific

Carex lyngbyei has been reported from a few stations in eastern North America over the last century. Herbarium specimens so identified from that area are morphologically very diverse and are quite different from the typical C. lyngbyei along the North Pacific coastline and Iceland. This eastern material was found to belong to four species (C. aquatilis, C. crinita var. gynandra, C. paleacea, and C. recta) and six different hybrids (C. ×saxenii, C. ×gardneri, C. ×exsalina, C. ×subnigra, C. ×super-goodenoughii, and C. ×grantii). Pollen stainability of typical C. lyngbyei and of putative C. lyngbyei from eastern North America supported these revisions: it was high in species and low in hybrids or in species of hybrid origin such as C. recta. In western North America, C. lyngbyei has either 2n = 68, 70, or 72 chromosomes and meiosis appears to be regular. In contrast, some putative C. lyngbyei from eastern Quebec showed a highly disturbed meiosis. Consequently C. lyngbyei is excluded from eastern North America.

Synoptic Features Associated with Temporally Coherent Modes of Variability of the North Pacific Jet Stream

2017 ◽  
Vol 30 (1) ◽  
pp. 39-54 ◽  
Author(s):  
Kyle S. Griffin ◽  
Jonathan E. Martin
Keyword(s):  
North America ◽  
North Pacific ◽  
Jet Stream ◽  
Eof Analysis ◽  
Western North America ◽  
Synoptic Scale ◽  
Exit Region ◽  
Low Level ◽  
The North ◽  
The North Pacific

Time-extended EOF (TE-EOF) analysis is employed to examine the synoptic-scale evolution of the two leading modes of the North Pacific jet stream variability, namely, its zonal extension–retraction (TE-EOF 1) and the north–south shift of its exit region (TE-EOF 2). Use of the TE-EOF analysis enables a temporally coherent examination of the synoptic-scale evolution preceding and following peaks in each of the two leading modes that provides insight into the preferred evolutions of the North Pacific jet. Composite analyses are constructed based upon selecting peaks in the principal component time series of both phases of each TE-EOF whose magnitude exceeded 1.5 standard deviations. Jet extension events are associated with an anomalous cyclonic circulation over the Gulf of Alaska that induces a low-level warm anomaly over western North America. Jet retractions are associated with a nearly opposite configuration characterized by an anomalous anticyclonic circulation over the Aleutians and anomalous low-level cold anomaly over western North America. Similar but lower-amplitude upper-level patterns are noted in the composites of the corresponding poleward-/equatorward-shifted jet phases, with the poleward shift of the jet exit region tied to anomalously low geopotential heights over Alaska and anomalous low-level warmth over north-central North America. An equatorward shift of the exit region is tied to positive height anomalies over Alaska with downstream cold anomalies occurring in western North America. The more extreme downstream impacts that characterize TE-EOF 2 are also longer lasting (>5 days), suggesting potential utility in medium-range forecasts.

Sign in / Sign up

Export Citation Format

Share Document