scholarly journals Interdecadal changes in synoptic transient eddy activity over the Northeast Pacific and their role in tropospheric Arctic amplification

2021 ◽  
Author(s):  
Dong Xiao ◽  
Hongli Ren
Keyword(s):  
Heat Flux ◽  
North Pacific ◽  
The Arctic ◽  
Transient Eddy ◽  
Arctic Amplification ◽  
Eddy Activity ◽  
The North ◽  
Eddy Heat Flux ◽  
Subtropical Jet ◽  
The North Pacific

AbstractArctic amplification refers to the greater surface warming of the Arctic than of other regions during recent decades. A similar phenomenon occurs in the troposphere and is termed “tropospheric Arctic amplification” (TAA). The poleward eddy heat flux and eddy moisture flux are critical to Arctic warming. In this study, we investigate the synoptic transient eddy activity over the North Pacific associated with TAA and its relationship with the subtropical jet stream, and propose the following mechanism. A poleward shift of the subtropical jet axis results in anomalies of the meridional gradient of zonal wind over the North Pacific, which drive a meridional dipole pattern of synoptic transient wave intensity over the North Pacific, referred to as the North Pacific Synoptic Transient wave intensity Dipole (NPSTD). The NPSTD index underwent an interdecadal shift in the late 1990s accompanying that of the subtropical jet stream. During the positive phase of the NPSTD index, synoptic eddy heat flux transports more heat to the Arctic Circle, and the eddy heat flux diverges, increasing Arctic temperature. This mechanism highlights the need to consider synoptic transient eddy activity over the North Pacific as the link between the mean state of the North Pacific subtropical upper jet and TAA.

scholarly journals On the Efficiency of Baroclinic Eddy Growth and How It Reduces the North Pacific Storm-Track Intensity in Midwinter

2019 ◽  
Vol 32 (23) ◽  
pp. 8373-8398 ◽  
Author(s):  
Sebastian Schemm ◽  
Gwendal Rivière
Keyword(s):  
Heat Flux ◽  
North Pacific ◽  
Storm Track ◽  
The North ◽  
Eddy Heat Flux ◽  
Subtropical Jet ◽  
The Pacific ◽  
The Mean ◽  
The North Pacific ◽  
North Pacific Storm Track

Abstract This study investigates the efficiency of baroclinic eddy growth in an effort to better understand the suppression of the North Pacific storm-track intensity in winter. The efficiency of baroclinic eddy growth depends on the magnitude and orientation of the vertical tilt of the eddy geopotential isolines. The eddy efficiency is maximized if the orientation of the vertical tilt creates an eddy heat flux that aligns with the mean baroclinicity (defined as minus the temperature gradient divided by a stratification parameter) and if the magnitude of the vertical tilt is neither too strong nor too weak. The eddy efficiency is, in contrast to most other eddy measures, independent of the eddy amplitude and thus useful for improving our mechanistic understanding of the effective eddy growth. During the midwinter suppression, the eddy efficiency is reduced north of 40°N over a region upstream of the main storm track, and baroclinic growth is reduced despite a maximum in baroclinicity. Eulerian diagnostics and feature tracking suggest that the reduction in eddy efficiency is due to a stronger poleward tilt with height of eddies entering the Pacific through the northern seeding branch, which results in a more eastward-oriented eddy heat flux and a reduced alignment with the baroclinicity. The stronger poleward tilt with height is constrained by the eddy propagation direction, which is more equatorward when the subtropical jet moves equatorward in winter. In addition, the westward tilt with height is too strong. South of 40°N, the eddy efficiency increases during midwinter but in a region far away from the main storm track.

scholarly journals The mean meridional circulation and midlatitude ozone buildup

2005 ◽  
Vol 5 (3) ◽  
pp. 4223-4256
Author(s):  
G. Nikulin ◽  
A. Karpechko
Keyword(s):  
Heat Flux ◽  
North Pacific ◽  
Meridional Circulation ◽  
Residual Velocity ◽  
The North ◽  
Eddy Heat Flux ◽  
Mean Meridional Circulation ◽  
The Mean ◽  
Temperature Tendency ◽  
The North Pacific

Abstract. The development of wintertime ozone buildup over the Northern Hemisphere (NH) midlatitudes and its connection with the mean meridional circulation in the stratosphere are examined statistically on a monthly basis from October to March (1980–2002). The ozone buildup begins locally in October with positive ozone tendencies over the North Pacific, which spread eastward and westward in November and finally cover all midlatitudes in December. During October–January a longitudinal distribution of the ozone tendencies mirrors a structure of quasi-stationary planetary waves in the lower stratosphere and has less similarity with this structure in February–March when chemistry begins to play a more important role. From November to March, zonal mean ozone tendencies (50°–60° N) show strong correlation (|r|=0.7) with different parameters used as proxies of the mean meridional circulation, namely: eddy heat flux, the vertical residual velocity (diabatically-derived) and temperature tendency. The correlation patterns between ozone tendency and the vertical residual velocity or temperature tendency are more homogeneous from month to month than ones for eddy heat flux. A partial exception is December when correlation is strong only for the vertical residual velocity. In October zonal mean ozone tendencies have no coupling with the proxies. However, positive tendencies averaged over the North Pacific correlate well, with all of them suggesting that intensification of northward ozone transport starts locally over the Pacific already in October. We show that the NH midlatitude ozone buildup has stable statistical relation with the mean meridional circulation in all months from October to March and half of the interannual variability in monthly ozone tendencies can be explained by applying different proxies of the mean meridional circulation.

Skillful Subseasonal Prediction of United States Extreme Warm Days and Standardized Precipitation Index in Boreal Summer

2021 ◽  
pp. 1-34
Author(s):  
Douglas E. Miller ◽  
Zhuo Wang ◽  
Bo Li ◽  
Daniel S. Harnos ◽  
Trent Ford
Keyword(s):  
United States ◽  
Heat Flux ◽  
Soil Moisture ◽  
Statistical Model ◽  
North Pacific ◽  
Standardized Precipitation Index ◽  
Boreal Summer ◽  
The North ◽  
Moisture Conditions ◽  
The North Pacific

AbstractSkillful subseasonal prediction of extreme heat and precipitation greatly benefits multiple sectors, including water management, public health, and agriculture, in mitigating the impact of extreme events. A statistical model is developed to predict the weekly frequency of extreme warm days and 14-day standardized precipitation index (SPI) during boreal summer in the United States (US). We use a leading principal component of US soil moisture and an index based on the North Pacific sea surface temperature (SST) as predictors. The model outperforms the NCEP’s Climate Forecast System version 2 (CFSv2) at weeks 3-4 in the eastern US. It is found that the North Pacific SST anomalies persist several weeks and are associated with a persistent wave train pattern (WTZ500), which leads to increased occurrences of blocking and extreme temperature over the eastern US. Extreme dry soil moisture conditions persist into week 4 and are associated with an increase in sensible heat flux and decrease in latent heat flux, which may help maintain the overlying anticyclone. The clear sky conditions associated with blocking anticyclones further decrease soil moisture conditions and increase the frequency of extreme warm days. This skillful statistical model has the potential to aid in irrigation scheduling, crop planning, reservoir operation, and provide mitigation of impacts from extreme heat events.

scholarly journals Heat transport pathways into the Arctic and their connections to surface air temperatures

2019 ◽  
Vol 19 (6) ◽  
pp. 3927-3937 ◽  
Author(s):  
Daniel Mewes ◽  
Christoph Jacobi
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Large Scale ◽  
The Arctic ◽  
Positive Temperature ◽  
Transport Pathways ◽  
Temperature Anomalies ◽  
The North ◽  
The North Atlantic ◽  
The North Pacific

Abstract. Arctic amplification causes the meridional temperature gradient between middle and high latitudes to decrease. Through this decrease the large-scale circulation in the midlatitudes may change and therefore the meridional transport of heat and moisture increases. This in turn may increase Arctic warming even further. To investigate patterns of Arctic temperature, horizontal transports and their changes in time, we analysed ERA-Interim daily winter data of vertically integrated horizontal moist static energy transport using self-organizing maps (SOMs). Three general transport pathways have been identified: the North Atlantic pathway with transport mainly over the northern Atlantic, the North Pacific pathway with transport from the Pacific region, and the Siberian pathway with transport towards the Arctic over the eastern Siberian region. Transports that originate from the North Pacific are connected to negative temperature anomalies over the central Arctic. These North Pacific pathways have been becoming less frequent during the last decades. Patterns with origin of transport in Siberia are found to have no trend and show cold temperature anomalies north of Svalbard. It was found that transport patterns that favour transport through the North Atlantic into the central Arctic are connected to positive temperature anomalies over large regions of the Arctic. These temperature anomalies resemble the warm Arctic–cold continents pattern. Further, it could be shown that transport through the North Atlantic has been becoming more frequent during the last decades.

Bathyal benthic polychaetes from the N.E. Atlantic Ocean, S.W. of the British Isles

1983 ◽  
Vol 63 (3) ◽  
pp. 593-608 ◽  
Author(s):  
Jørgen B. Kirkegaard
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
New Genus ◽  
New Combination ◽  
The Arctic ◽  
British Isles ◽  
The North ◽  
Two New Species ◽  
The North Atlantic ◽  
The North Pacific

From bathyal depths in the Bay of Biscay, southwest of the British Isles, 89 species of polychaetes are described, among which are two new species, one new genus, and one new Combination, i.e. Pholoe fauveli sp. nov., Paracapitella southwardi n.gen., n. sp., and Galathowenia oculata, new combination. Of the species taken, 52 % are also known from abyssal depths. The bathyal polychaete fauna of the North Atlantic seems to be common with that of the Arctic and the North Pacific.

scholarly journals Genetic diversity and biogeography in Chaetomorpha melagonium (Ulvophyceae, Cladophorales) based on internal transcribed spacer (ITS rDNA) sequences

2017 ◽  
Vol 60 (3) ◽  
Author(s):  
Christian Boedeker ◽  
Frederik Leliaert ◽  
Giuseppe C. Zuccarello
Keyword(s):  
Genetic Diversity ◽  
North Atlantic ◽  
North Pacific ◽  
Internal Transcribed Spacer ◽  
Distinct Species ◽  
The Arctic ◽  
The North ◽  
Rdna Sequences ◽  
The North Atlantic ◽  
The North Pacific

Abstractis a morphologically distinct species of green algae that occurs throughout the North Atlantic, the North Pacific and the Arctic Ocean. In this study, we analyzed the intraspecific genetic diversity among 14 samples of

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