BREAKING GRAVITY WAVES ON A JET STREAM OVER THE NORTH PACIFIC

Abstract The north–south semiannual oscillation (SAO) of the North Pacific jet stream, part of the atmospheric SAO in the Northern Hemisphere, can be well depicted by the semiannual component of the monthly-mean eddy streamfunction. Expressed by the semiannual eddy streamfunction budget, the dynamic processes develop and maintain the SAO, including the adjustment between vorticity advection and convergence of vorticity flux of the monthly-mean mode and the convergence of transient vorticity flux. An empirical orthogonal function analysis of these dynamic processes shows an east–west elongated cyclonic (anticyclonic) cell of the semiannual eddy streamfunction anomaly, which appears in January and July (October and April) south of the Siberia–Alaska landmass. The maximum (minimum) adjustment processes by the monthly-mean mode and the maximum (minimum) feedback impact of transient activity on the SAO occur in December and June (September and March), a month ahead of the maximum (minimum) north–south SAO of the North Pacific jet stream. Because vorticity is supplied by the convergence of vorticity flux associated with divergent flow, the SAO for the rotational flow is established by diabatic heat and heat transport through the divergent circulation over the North Pacific Ocean, and by precipitation maintained by convergence of water vapor flux along the oceanic storm track. Additionally, the feedback impact of the modulated transient activity affects the SAO development of the atmospheric rotational and divergent circulations, and the hydrological cycle.

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Subseasonal prediction of the state and evolution of the North Pacific jet stream

Journal of Geophysical Research Atmospheres ◽

10.1029/2021jd035094 ◽

2021 ◽

Author(s):

ANDREW C. WINTERS

Keyword(s):

North Pacific ◽

The State ◽

Jet Stream ◽

The North ◽

The North Pacific

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Hawaiian Regional Climate Variability during Two Types of El Niño

Journal of Climate ◽

10.1175/jcli-d-19-0985.1 ◽

2020 ◽

Vol 33 (22) ◽

pp. 9929-9943

Author(s):

Bo-Yi Lu ◽

Pao-Shin Chu ◽

Sung-Hun Kim ◽

Christina Karamperidou

Keyword(s):

El Niño ◽

North Pacific ◽

El Nino ◽

Moisture Flux ◽

Jet Stream ◽

Flux Divergence ◽

The North ◽

The Impact ◽

The North Pacific ◽

Moisture Flux Divergence

AbstractThe large-scale atmospheric circulation of the North Pacific associated with two types of El Niño—the eastern Pacific (EP) and central Pacific (CP)—is studied in relation to Hawaiian winter (December–February) rainfall and temperature. The eastern and central equatorial Pacific undergo active convective heating during EP El Niño winters. The local Hadley circulation is enhanced and an upper-level westerly jet stream of the North Pacific is elongated eastward. Due to the impact of both phenomena, stronger anomalous descending motion, moisture flux divergence anomalies near Hawaii, and reduction of easterly trade winds, which are characteristic of EP winters, are unfavorable for winter rainfall in Hawaii. As a result of this robust signal, dry conditions prevail in Hawaii and the standard deviation of rainfall during EP winters is smaller than the climatology. For CP winters, the maximum equatorial ocean warming is weaker and shifted westward to near the date line. The subtropical jet stream retreats westward relative to EP winters and the anomalously sinking motion near Hawaii is variable and generally weaker. Although the anomalous moisture flux divergence still exists over the subtropical North Pacific, its magnitude is weaker relative to EP winters. Without strong external forcing, rainfall in the Hawaiian Islands during CP winters is close to the long-term mean. The spread of rainfall from one CP event to another is also larger. The near-surface minimum temperature from three stations in Hawaii reveals cooling during EP winters and slight warming during CP winters.

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Responses of the East Asian jet stream to the North Pacific subtropical front in spring

Advances in Atmospheric Sciences ◽

10.1007/s00376-016-6026-x ◽

2017 ◽

Vol 34 (2) ◽

pp. 144-156 ◽

Cited By ~ 9

Author(s):

Leying Zhang ◽

Haiming Xu ◽

Ning Shi ◽

Jiechun Deng

Keyword(s):

North Pacific ◽

East Asian ◽

Jet Stream ◽

Subtropical Front ◽

The North ◽

East Asian Jet Stream ◽

The North Pacific

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

Journal of Climate ◽

10.1175/jcli-d-15-0833.1 ◽

2017 ◽

Vol 30 (1) ◽

pp. 39-54 ◽

Cited By ~ 11

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.

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