Extra-tropical cyclonic/anticyclonic activity in North-Eastern Pacific and air temperature extremes in Western North America

Abstract. The wintertime influence of tropical Pacific sea surface temperature (SST) variability on subseasonal variability is revisited by identifying the dominant mode of covariability between 10–60 d band-pass-filtered surface air temperature (SAT) variability over the North American continent and winter-mean SST over the tropical Pacific. We find that the El Niño–Southern Oscillation (ENSO) explains a dominant fraction of the year-to-year changes in subseasonal SAT variability that are covarying with SST and thus likely more predictable. In agreement with previous studies, we find a tendency for La Niña conditions to enhance the subseasonal SAT variability over western North America. This modulation of subseasonal variability is achieved through interactions between subseasonal eddies and La Niña-related changes in the winter-mean circulation. Specifically, eastward-propagating quasi-stationary eddies over the North Pacific are more efficient in extracting energy from the mean flow through the baroclinic conversion during La Niña. Structural changes of these eddies are crucial to enhance the efficiency of the energy conversion via amplified downgradient heat fluxes that energize subseasonal eddy thermal anomalies. The enhanced likelihood of cold extremes over western North America is associated with both an increased subseasonal SAT variability and the cold winter-mean response to La Niña.

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The Galium trifidum group (Galium sect. Aparinoides, Rubiaceae)

Canadian Journal of Botany ◽

10.1139/b76-206 ◽

1976 ◽

Vol 54 (16) ◽

pp. 1911-1925 ◽

Cited By ~ 3

Author(s):

C. Puff

Keyword(s):

North America ◽

Eastern North America ◽

Great Lakes Region ◽

Western North America ◽

Eastern Asia ◽

Chromosome Counts ◽

New Classification ◽

North Eastern ◽

North Western

By using morphology, karyology, pollen size, leaf flavonoids, ecological observations, and modification experiments, a new classification of the Galium trifidum group is proposed. Nine taxa in five species are recognized: (1) G. tinctorium, with ssp. tinctorium and sap. floridanum (new comb.) in eastern North America; (2) G. brevipes, a rare species centered in the Great Lakes region; (3) G. trifidum, with ssp. trifidum in northern North America. Asia, and Europe, ssp. columbianum (new comb.) in (north)western North America and (north)eastern Asia, and ssp. subbiflorum (new comb.) and ssp. halophilum (new comb.) in northern North America; (4) G. innocuum in southeastern Asia; (5) G. karakulense in central Asia.New chromosome counts of n = 12 and 2n = 24 are reported for G. tinctorium ssp. tinctorium and ssp. floridanum; and G. trifidum ssp. trifidum, ssp. columbianum, and ssp. subbiflorum.

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

Geochemistry Geophysics Geosystems ◽

10.1029/2020gc009117 ◽

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

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

10.5194/egusphere-egu21-242 ◽

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

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.&#160;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.&#160;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.&#160;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.&#160;

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Empirical evidence for deep convection related stratospheric cirrus clouds over North America

10.5194/acp-2021-90 ◽

2021 ◽

Author(s):

Ling Zou ◽

Lars Hoffmann ◽

Sabine Griessbach ◽

Reinhold Spang ◽

Lunche Wang

Keyword(s):

North America ◽

Great Plains ◽

Gravity Waves ◽

North Atlantic ◽

Deep Convection ◽

Cirrus Clouds ◽

Eastern Pacific ◽

Western Canada ◽

The North ◽

North Eastern

Abstract. Cirrus clouds in the lowermost stratosphere affect stratospheric water vapor and the Earth's radiation budget. The knowledge of its occurrence and driving forces is limited. To assess the distribution and possible formation mechanisms of stratospheric cirrus clouds (SCCs) over North America, we analyzed SCC occurrence frequencies observed by 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. Results show that at nighttime, SCCs are most frequently observed during the thunderstorm season over the Great Plains from May to August (MJJA) with a 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 from AIRS, which includes storm systems, fronts, mesoscale convective systems and mesoscale convective complexes at mid- and high latitude, 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 relation. Further analysis indicates that the maximum fraction of SCCs related to 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 the leading factor related to occurrence of SCCs over North America. In this study, we also analyzed the impact of gravity waves as another important factor related to the occurrence SCCs, as the Great Plains is a well-known hotspot for stratospheric gravity waves. In the cases where SCCs are not directly linked to deep convection, we found that stratospheric gravity wave observations correlate with SCCs in as much as 30 % of the cases over the Great Plains in MJJA, about 50 % over the North-Eastern Pacific, western Canada and up to 90 % over eastern Canada and the north-west Atlantic in NDJF. 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.

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Miocene salmon (Oncorhynchus) from Western North America: Gill Raker evolution correlated with plankton productivity in the Eastern Pacific

Palaeogeography Palaeoclimatology Palaeoecology ◽

10.1016/j.palaeo.2007.02.011 ◽

2007 ◽

Vol 249 (3-4) ◽

pp. 412-424 ◽

Cited By ~ 15

Author(s):

Thomas P. Eiting ◽

Gerald R. Smith

Keyword(s):

North America ◽

Eastern Pacific ◽

Western North America ◽

Gill Raker

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Empirical evidence for deep convection being a major source of stratospheric ice clouds over North America

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-10457-2021 ◽

2021 ◽

Vol 21 (13) ◽

pp. 10457-10475

Author(s):

Ling Zou ◽

Lars Hoffmann ◽

Sabine Griessbach ◽

Reinhold Spang ◽

Lunche Wang

Keyword(s):

North America ◽

Great Plains ◽

Gravity Waves ◽

North Atlantic ◽

Deep Convection ◽

Eastern Pacific ◽

Western Canada ◽

Ice Clouds ◽

The North ◽

North Eastern

Abstract. Ice clouds in the lowermost stratosphere affect stratospheric water vapour and the Earth's radiation budget. The knowledge of its occurrence and driving forces is limited. To assess the distribution and possible formation mechanisms of stratospheric ice clouds (SICs) over North America, we analysed SIC occurrence frequencies observed by 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. Results show that at nighttime, SICs are most frequently observed during the thunderstorm season over the Great Plains from May to August (MJJA) with a maximum occurrence frequency of 6.2 %. During the months from November to February (NDJF), the highest SICs occurrence frequencies are 5.5 % over the north-eastern Pacific and western Canada and 4.4 % over the western North Atlantic. Occurrence frequencies of deep convection from AIRS, which includes storm systems, fronts, mesoscale convective systems, and mesoscale convective complexes at midlatitude and high latitude, show similar hotspots like the SICs, 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 SICs and deep convection show a high degree of spatial and temporal relation. Further analysis indicates that the maximum fraction of SICs related to 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 the leading factor related to the occurrence of SICs over North America. In this study, we also analysed the impact of gravity waves as another important factor related to the occurrence of SICs, as the Great Plains is a well-known hotspot for stratospheric gravity waves. In the cases where SICs are not directly linked to deep convection, we found that stratospheric gravity wave observations correlate with SICs with as much as 30 % of the cases over the Great Plains in MJJA, about 50 % over the north-eastern Pacific and western Canada, and up to 90 % over eastern Canada and the north-west Atlantic in NDJF. Our results provide a better understanding of the physical processes and climate variability related to SICs and will be of interest for modellers as SIC sources such as deep convection and gravity waves are small-scale processes that are difficult to represent in global general circulation models.

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Influence of ENSO on North American subseasonal surface air temperature variability

10.5194/wcd-2020-22 ◽

2020 ◽

Author(s):

Patrick Martineau ◽

Hisashi Nakamura ◽

Yu Kosaka

Keyword(s):

North America ◽

Air Temperature ◽

North Pacific ◽

Surface Air Temperature ◽

La Niña ◽

Western North America ◽

The North ◽

Subseasonal Variability ◽

La Nina ◽

The North Pacific

Abstract. The wintertime influence of El Niño-Southern Oscillation (ENSO) on subseasonal variability is revisited by identifying the dominant mode of covariability between 10–60 day band-pass-filtered surface air temperature (SAT) variability over the North American continent and winter-mean sea surface temperature (SST) over the North Pacific sector. We find, in agreement with previous studies, that La Niña conditions tend to enhance the subseasonal SAT variability over western North America. This modulation of subseasonal variability is achieved through interactions between subseasonal eddies and La Niña-related changes in the winter-mean circulation. Specifically, eastward-propagating quasi-stationary eddies over the North Pacific are more efficient in extracting energy from the mean flow through the baroclinic conversion of energy over the North Pacific sector during La Niña. Changes in the vertical structure of these wave anomalies are crucial to enhance the efficiency of energy conversion via amplified downgradient heat fluxes that energize subseasonal eddy thermal anomalies. The combination of increased subseasonal SAT variability and the cold winter-mean response to La Niña both contribute to enhancing the likelihood of cold extremes over western North America.

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