When during Their Life Cycle Are Extratropical Cyclones Attended by Fronts?

2018 ◽  
Vol 99 (1) ◽  
pp. 149-165 ◽  
Author(s):  
Sebastian Schemm ◽  
Michael Sprenger ◽  
Heini Wernli
Keyword(s):  
Life Cycle ◽  
Baroclinic Instability ◽  
Storm Track ◽  
Extratropical Cyclones ◽  
Historical Discourse ◽  
Identification Schemes ◽  
The North ◽  
Surface Front ◽  
The North Pacific

Abstract For nearly a century, the study of atmospheric dynamics in the midlatitudes has presented dichotomic perspectives on one of its focal points: the birth and life cycle of cyclones. In particular, the role of fronts has driven much of the historical discourse on cyclogenesis. In the 1910s–20s, the Bergen School of Meteorology postulated that cyclogenesis occurs on a preexisting front. This concept was later replaced by the baroclinic instability paradigm, which describes the development of a surface front as a consequence of the growing cyclone rather than its cause. However, there is ample observational evidence for cyclogenesis on well-marked fronts (frontal-wave cyclones) as well as for cyclogenesis in the absence of fronts in broader baroclinic zones. Thus, after a century of research on the link between extratropical cyclones and fronts, this study has the objective of climatologically quantifying their relationship. By combining identification schemes for cyclones and fronts, the fraction of cyclones with attendant fronts is quantified at all times during the cyclones’ life cycle. The storm-track regions over the North Atlantic are dominated by cyclones that form on preexisting fronts. Over the North Pacific, the result more strongly depends on the front definition. Cyclones that acquire their fronts during the life cycle dominate over the continents and in the Mediterranean. Further, cyclones that develop attendant fronts during their life cycle typically do so around the time they attain maximum intensity. At the time of cyclolysis, at least 40% of all cyclones are still associated with a front. The number of occluded fronts at lysis has not been considered.

scholarly journals The North Pacific Storm-Track Suppression Explained From a Cyclone Life-Cycle Perspective

2020 ◽  
Author(s):  
Sebastian Schemm ◽  
Heini Wernli ◽  
Hanin Binder
Keyword(s):  
Life Cycle ◽  
East China Sea ◽  
North Pacific ◽  
Storm Track ◽  
East China ◽  
The East China Sea ◽  
China Sea ◽  
The North ◽  
The North Pacific ◽  
North Pacific Storm Track

Abstract. Surface cyclones that feed the part of the North Pacific storm track that experience a midwinter suppression originate from three regions: the East China Sea (~ 30º N), the Kuroshio extension (~ 35º N), and downstream of Kamchatka (~ 53º N). In terms of cyclone numbers, Kuroshio (45 %) and Kamchatka (40 %) cyclones dominate in the region where eddy kinetic energy is suppressed, while the relevance of East China Sea cyclones increases from winter (15 %) to spring (20 %). The equatorward movement during midwinter of the baroclinicity and the associated upper-level jet influences cyclones from the three genesis regions in different ways. In January, Kamchatka cyclones are less numerous, less intense and their lifetime shortens; broadly consistent with the reduced baroclinicity in which they grow. The opposite is found for East China Sea cyclones, which in winter live longer, are more intense, and experience more frequently explosive deepening. The fraction of explosive East China Sea cyclones is particularly high in January when they benefit from the increased baroclinicity in their environment. Again, a different and more complex behavior is found for Kuroshio cyclones. In midwinter, their number increases, but their lifetime decreases; on average they reach higher intensity, in terms of minimum sea-level pressure, but the fraction of explosively deepening cyclones reduces and the latitude where maximum growth occurs shifts equatorward. Therefore, the life cycle of Kuroshio cyclones seems to be accelerated in midwinter with a stronger and earlier but also shorter deepening phase followed by an earlier decay. Once they reach the latitude where eddy kinetic energy is suppressed in midwinter, their baroclinic conversion efficiency is strongly reduced. Together, this detailed cyclone life-cycle analysis reveals that the North Pacific storm-track suppression in midwinter is related to fewer and weaker Kamchatka cyclones and to more equatorward intensifying and then more rapidly decaying Kuroshio cyclones. The less numerous cyclone branch from the East China Sea partially opposes the midwinter suppression.

scholarly journals The storm-track suppression over the western North Pacific from a cyclone life-cycle perspective

2021 ◽  
Vol 2 (1) ◽  
pp. 55-69
Author(s):  
Sebastian Schemm ◽  
Heini Wernli ◽  
Hanin Binder
Keyword(s):  
Life Cycle ◽  
East China Sea ◽  
North Pacific ◽  
Western North Pacific ◽  
Storm Track ◽  
East China ◽  
The East China Sea ◽  
China Sea ◽  
The North ◽  
The North Pacific

Abstract. Surface cyclones that feed the western part of the North Pacific storm track and experience a midwinter suppression originate from three regions: the East China Sea (∼30∘ N), the Kuroshio extension (∼35∘ N), and downstream of Kamchatka (∼53∘ N). In midwinter, in terms of cyclone numbers, Kuroshio (45 %) and Kamchatka (40 %) cyclones dominate in the region where eddy kinetic energy is suppressed, while the relevance of East China Sea cyclones increases from winter (15 %) to spring (20 %). The equatorward movement of the baroclinicity and the associated upper-level jet toward midwinter influence cyclones from the three genesis regions in different ways. In January, Kamchatka cyclones are less numerous and less intense, and their lifetime shortens, broadly consistent with the reduced baroclinicity in which they grow. The opposite is found for East China Sea cyclones, which in winter live longer, are more intense, and experience more frequently explosive deepening. The fraction of explosive East China Sea cyclones is particularly high in January when they benefit from the increased baroclinicity in their environment. Again, a different and more complex behavior is found for Kuroshio cyclones. In midwinter, their number increases, but their lifetime decreases; on average they reach higher intensity in terms of minimum sea level pressure, but the fraction of explosively deepening cyclones decreases and the latitude where maximum growth occurs shifts equatorward. Therefore, the life cycle of Kuroshio cyclones seems to be accelerated in midwinter with a stronger and earlier but also shorter deepening phase followed by an earlier decay. Once they reach the latitude where eddy kinetic energy is suppressed in midwinter, their baroclinic conversion efficiency is strongly reduced. Together, this detailed cyclone life-cycle analysis reveals that the North Pacific storm-track suppression in midwinter is related to fewer and weaker Kamchatka cyclones and to more equatorward intensifying and then more rapidly decaying Kuroshio cyclones. The less numerous cyclone branch from the East China Sea partially opposes the midwinter suppression. The cyclones passing through the suppressed region over the western North Pacific do not propagate far downstream and decay in the central North Pacific. The behavior of cyclones in the eastern North Pacific requires further analysis.

scholarly journals Role of the Cold Okhotsk Sea on the Climate of the North Pacific Subtropical High and Baiu Precipitation

2021 ◽  
Vol 34 (2) ◽  
pp. 495-507
Author(s):  
Kenta Kawasaki ◽  
Yoshihiro Tachibana ◽  
Tetsu Nakamura ◽  
Koji Yamazaki
Keyword(s):  
North Pacific ◽  
Storm Track ◽  
Moisture Flux ◽  
Early Summer ◽  
Subtropical High ◽  
Okhotsk Sea ◽  
Marginal Seas ◽  
The North ◽  
The North Pacific

AbstractSummertime temperatures in marginal seas are, in general, colder than on the surrounding continent because of the large contrast in heat capacity between the land and the ocean. The Okhotsk Sea, which is covered by sea ice until early summer, is much colder than the surrounding continent in summer. The Okhotsk Sea is thus located in an area with one of the largest temperature contrasts of all the marginal seas in summertime midlatitudes. Cooled air over the Okhotsk Sea may have an impact on remote summer climates, such as by serving as the source of cold-air advection that results in a poor crop harvest in Japan. Here, we examine the role of the Okhotsk Sea on the early summer climate of the western part of the North Pacific through an ideal numerical experiment by artificially changing the model’s default oceanic condition in the Okhotsk Sea to a condition of land cover. Simulation results reveal that the presence of the Okhotsk Sea increases precipitation of the baiu/mei-yu front through strengthening of the northward moisture flux at the western edge of an intensified North Pacific subtropical high. The Okhotsk influence farther extends toward western North America to which the strengthened jet stream with a storm track extends. This remote influence is achievable through feedback from a transient eddy anomaly that is activated by the surface temperature gradient between the cold Okhotsk Sea and the warm Pacific Ocean. The findings imply that the existence of the Okhotsk Sea strengthens the East Asian summer monsoons.

scholarly journals Petrobactin, a siderophore produced by Alteromonas, mediates community iron acquisition in the global ocean

2021 ◽  
Author(s):  
Lauren E. Manck ◽  
Jiwoon Park ◽  
Benjamin J. Tully ◽  
Alfonso M. Poire ◽  
Randelle M. Bundy ◽  
...  
Keyword(s):  
Biosynthetic Pathway ◽  
Iron Acquisition ◽  
Biogeochemical Cycling ◽  
Iron Bioavailability ◽  
Siderophore Production ◽  
Global Ocean ◽  
The North ◽  
The North Pacific ◽  
Alteromonas Macleodii

AbstractIt is now widely accepted that siderophores play a role in marine iron biogeochemical cycling. However, the mechanisms by which siderophores affect the availability of iron from specific sources and the resulting significance of these processes on iron biogeochemical cycling as a whole have remained largely untested. In this study, we develop a model system for testing the effects of siderophore production on iron bioavailability using the marine copiotroph Alteromonas macleodii ATCC 27126. Through the generation of the knockout cell line ΔasbB::kmr, which lacks siderophore biosynthetic capabilities, we demonstrate that the production of the siderophore petrobactin enables the acquisition of iron from mineral sources and weaker iron-ligand complexes. Notably, the utilization of lithogenic iron, such as that from atmospheric dust, indicates a significant role for siderophores in the incorporation of new iron into marine systems. We have also detected petrobactin, a photoreactive siderophore, directly from seawater in the mid-latitudes of the North Pacific and have identified the biosynthetic pathway for petrobactin in bacterial metagenome-assembled genomes widely distributed across the global ocean. Together, these results improve our mechanistic understanding of the role of siderophore production in iron biogeochemical cycling in the marine environment wherein iron speciation, bioavailability, and residence time can be directly influenced by microbial activities.

scholarly journals On the Relationship between Synoptic Wintertime Atmospheric Variability and Path Shifts in the Gulf Stream and the Kuroshio Extension

2009 ◽  
Vol 22 (12) ◽  
pp. 3177-3192 ◽  
Author(s):  
Terrence M. Joyce ◽  
Young-Oh Kwon ◽  
Lisan Yu
Keyword(s):  
North Atlantic ◽  
North Pacific ◽  
Gulf Stream ◽  
Kuroshio Extension ◽  
Storm Track ◽  
Western Boundary ◽  
Atmospheric Variability ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific

Abstract Coherent, large-scale shifts in the paths of the Gulf Stream (GS) and the Kuroshio Extension (KE) occur on interannual to decadal time scales. Attention has usually been drawn to causes for these shifts in the overlying atmosphere, with some built-in delay of up to a few years resulting from propagation of wind-forced variability within the ocean. However, these shifts in the latitudes of separated western boundary currents can cause substantial changes in SST, which may influence the synoptic atmospheric variability with little or no time delay. Various measures of wintertime atmospheric variability in the synoptic band (2–8 days) are examined using a relatively new dataset for air–sea exchange [Objectively Analyzed Air–Sea Fluxes (OAFlux)] and subsurface temperature indices of the Gulf Stream and Kuroshio path that are insulated from direct air–sea exchange, and therefore are preferable to SST. Significant changes are found in the atmospheric variability following changes in the paths of these currents, sometimes in a local fashion such as meridional shifts in measures of local storm tracks, and sometimes in nonlocal, broad regions coincident with and downstream of the oceanic forcing. Differences between the North Pacific (KE) and North Atlantic (GS) may be partly related to the more zonal orientation of the KE and the stronger SST signals of the GS, but could also be due to differences in mean storm-track characteristics over the North Pacific and North Atlantic.

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