A breakdown of ENSO-North Pacific Teleconnection in early January

2020 ◽  
Author(s):  
Chang-Hyun Park ◽  
Seok-Woo Son ◽  
Jung Choi
Keyword(s):  
Indian Ocean ◽  
North Pacific ◽  
Southern Oscillation ◽  
Kuroshio Extension ◽  
Destructive Interference ◽  
Western North America ◽  
Aleutian Low ◽  
Circulation Anomaly ◽  
West Indian Ocean ◽  
Static Energy

<p>During El Niño winters, East Asia and western North America become anomalously warm because of the combined effect of anti-cyclonic circulation anomaly over Kuroshio Extension and Philippine sea, and an enhanced Aleutian Low. However, this El Niño-Southern Oscillation (ENSO)-North Pacific teleconnection disappears in early January. In this study, we suggest that this breakdown in regional teleconnection is partly due to Madden-Julian Oscillation (MJO). In early December of El Niño winters, MJOs frequently form and reach at Western Pacific, causing positive intraseasonal Pacific North American (PNA)-like teleconnection, which is same pattern to the El Niño teleconnection. In mid-December, however, as MJOs are frequently organized over Indian Ocean, it causes a destructive interference, cancelling El Niño teleconnection in early January. Although weak and not statistically significant, this sharp decline of ENSO teleconnection in early January also appears in La Niña winters. A preference of MJO organization and its propagation in ENSO winters are explained by moist static energy anomalies in the west Indian Ocean. This result suggests that MJO is important for predicting ENSO teleconnection on intraseasonal scales.</p>

scholarly journals Temporal variations of net Kuroshio transport based on a repeated hydrographic section along 137°E

2021 ◽  
Author(s):  
Yuma Kawakami ◽  
Atsushi Kojima ◽  
Kiyoshi Murakami ◽  
Toshiya Nakano ◽  
Shusaku Sugimoto
Keyword(s):  
North Pacific ◽  
Kuroshio Extension ◽  
Temporal Variations ◽  
Japan Meteorological Agency ◽  
Aleutian Low ◽  
Wind Stress Curl ◽  
The North ◽  
Decadal Scale ◽  
Intensity Fluctuations ◽  
Kuroshio Transport

AbstractTemporal variations of net Kuroshio transport are examined for 1972–2018 based on a repeated hydrographic section along 137°E, which is maintained by the Japan Meteorological Agency. The net Kuroshio transport obtained by integration of geostrophic current velocity relative to 1000 dbar depth fluctuates on inter-annual and decadal timescales. The predominant timescale of the net Kuroshio transport changes with time; the inter-annual variation is pronounced in 1972–1990 and 2000–2018, and the decadal variation is detected only before 2000. We find that a winter wind stress curl variation in the central North Pacific which reflects meridional movements of the Aleutian Low and intensity fluctuations of the North Pacific subtropical high on an inter-annual timescale and intensity fluctuations of the Aleutian Low on a decadal timescale, causes the net Kuroshio transport variation. In addition to the inter-annual and decadal variations, we further pointed out a bi-decadal-scale variation of the net Kuroshio transport and its possible link to the Aleutian Low intensity fluctuation. Moreover, our results indicate that during large net Kuroshio transport, sea surface temperature around the Kuroshio and Kuroshio Extension region tends to increase, resulting in vigorous upward sensible and latent heat release.

Interdecadal Change in the Relationship between ENSO and the Intraseasonal Oscillation in East Asia

2010 ◽  
Vol 23 (13) ◽  
pp. 3599-3612 ◽  
Author(s):  
Kyung-Sook Yun ◽  
Kyong-Hwan Seo ◽  
Kyung-Ja Ha
Keyword(s):  
Indian Ocean ◽  
North Pacific ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
Intraseasonal Oscillation ◽  
Longwave Radiation ◽  
Strong Relationship ◽  
Early Summer ◽  
Boreal Summer ◽  
Interdecadal Change

Abstract The northward-propagating intraseasonal oscillation (NPISO) during the boreal summer is closely linked to the onset/retreat and intensity of the East Asian summer monsoon (EASM). In this study, interdecadal variability in the relationships between the NPISO and El Niño–Southern Oscillation (ENSO) was investigated using long-term outgoing longwave radiation data obtained from the 40-yr ECMWF Re-Analysis (ERA-40) for a 44-yr period (1958 to 2001). It was found that before the late 1970s, the preceding winter ENSO influenced the early summer (i.e., May to June) NPISO activity, whereas after the late 1970s a strong relationship appeared during the later summertime (i.e., July to August). The May–June NPISO before the late 1970s was modulated by springtime Indian Ocean sea surface temperature warming and central North Pacific suppressed convection anomalies and was consequently related to the ENSO-induced west Pacific (WP) pattern, which shows a north–south dipole structure over the North Pacific from winter through spring. After the late 1970s, because of an anomalously strengthened Walker–Hadley circulation, Indian Ocean SST warming was significantly maintained until summer, which promoted a strong suppressed convection anomaly over the Philippine Sea during summer and consequently an enhanced western North Pacific subtropical high and Pacific–Japan (PJ) pattern.

Simulation of the 1976/77 Climate Transition over the North Pacific: Sensitivity to Tropical Forcing

2006 ◽  
Vol 19 (23) ◽  
pp. 6170-6180 ◽  
Author(s):  
Clara Deser ◽  
Adam S. Phillips
Keyword(s):  
Indian Ocean ◽  
North Pacific ◽  
Equatorial Pacific ◽  
Ensemble Average ◽  
Aleutian Low ◽  
The North ◽  
Tropical Ssts ◽  
Climate Transition ◽  
Western Half ◽  
The North Pacific

Abstract This study examines the contribution of tropical sea surface temperature (SST) forcing to the 1976/77 climate transition of the winter atmospheric circulation over the North Pacific using a combined observational and modeling approach. The National Center for Atmospheric Research (NCAR) Community Atmospheric Model version 3 (CAM3) simulates approximately 75% of the observed 4-hPa deepening of the wintertime Aleutian low from 1950–76 to 1977–2000 when forced with the observed evolution of tropical SSTs in a 10-member ensemble average. This response is driven by precipitation increases over the western half of the equatorial Pacific Ocean. In contrast, the NCAR Community Climate Model version 3 (CCM3), the predecessor to CAM3, simulates no significant change in the strength of the Aleutian low when forced with the same tropical SSTs in a 12-member ensemble average. The lack of response in CCM3 is traced to an erroneously large precipitation increase over the tropical Indian Ocean whose dynamical impact is to weaken the Aleutian low; this, when combined with the response to rainfall increases over the western and central equatorial Pacific, results in near-zero net change in the strength of the Aleutian low. The observed distribution of tropical precipitation anomalies associated with the 1976/77 transition, estimated from a combination of direct measurements at land stations and indirect information from surface marine cloudiness and wind divergence fields, supports the models’ simulated rainfall increases over the western half of the Pacific but not the magnitude of CCM3’s rainfall increase over the Indian Ocean.

scholarly journals Modulation of Boreal Summer Intraseasonal Oscillations over the Western North Pacific by ENSO

2016 ◽  
Vol 29 (20) ◽  
pp. 7189-7201 ◽  
Author(s):  
Fei Liu ◽  
Tim Li ◽  
Hui Wang ◽  
Li Deng ◽  
Yuanwen Zhang
Keyword(s):  
Indian Ocean ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Boreal Summer ◽  
Maritime Continent ◽  
La Nina

Abstract The authors investigate the effects of El Niño and La Niña on the intraseasonal oscillation (ISO) in the boreal summer (May–October) over the western North Pacific (WNP). It is found that during El Niño summers, the ISO is dominated by a higher-frequency oscillation with a period of around 20–40 days, whereas during La Niña summers the ISO is dominated by a lower-frequency period of around 40–70 days. The former is characterized by northwestward-propagating convection anomalies in the WNP, and the latter is characterized by northward- and eastward-propagating convective signals over the tropical Indian Ocean/Maritime Continent. The possible mechanisms through which El Niño–Southern Oscillation (ENSO)-induced background mean state changes influence the ISO behavior are examined through idealized numerical experiments. It is found that enhanced (weakened) mean moisture and easterly (westerly) vertical wind shear in the WNP during El Niño (La Niña) are the main causes of the strengthened (weakened) 20–40-day northwestward-propagating ISO mode, whereas the 40–70-day ISO initiated from the Indian Ocean can only affect the WNP during La Niña years because the dry (moist) background moisture near the Maritime Continent during El Niño (La Niña) suppresses (enhances) the ISO over the Maritime Continent, and the ISO propagates less over the Maritime Continent during El Niño years than in La Niña years.

scholarly journals A Multivariate Estimate of the Cold Season Atmospheric Response to North Pacific SST Variability

2018 ◽  
Vol 31 (7) ◽  
pp. 2771-2796 ◽  
Author(s):  
Adèle Révelard ◽  
Claude Frankignoul ◽  
Young-Oh Kwon
Keyword(s):  
North Pacific ◽  
Kuroshio Extension ◽  
Storm Track ◽  
Late Winter ◽  
Aleutian Low ◽  
Central Pacific ◽  
The North ◽  
Sst Variability ◽  
The North Pacific ◽  
Robust Response

The Generalized Equilibrium Feedback Analysis (GEFA) is used to distinguish the influence of the Oyashio Extension (OE) and the Kuroshio Extension (KE) variability on the atmosphere from 1979 to 2014 from that of the main SST variability modes, using seasonal mean anomalies. Remote SST anomalies are associated with each single oceanic regressor, but the multivariate approach efficiently confines their SST footprints. In autumn [October–December (OND)], the OE meridional shifts are followed by a North Pacific Oscillation (NPO)-like signal. The OE influence is not investigated in winter [December–February (DJF)] because of multicollinearity, but a robust response with a strong signal over the Bering Sea is found in late winter/early spring [February–April (FMA)], a northeastward strengthening of the Aleutian low following a northward OE shift. A robust response to the KE variability is found in autumn, but not in winter and late winter when the KE SST footprint becomes increasingly small and noisy as regressors are added in GEFA. In autumn, a positive PDO is followed by a northward strengthening of the Aleutian low and a southward shift of the storm track in the central Pacific, reflecting the surface heat flux footprint in the central Pacific. In winter, the PDO shifts the maximum baroclinicity and storm track southward, the response strongly tilts westward with height in the North Pacific, and there is a negative NAO-like teleconnection. In late winter, the North Pacific NPO-like response to the PDO interferes negatively with the response to the OE and is only detected when the OE is represented in GEFA. A different PDO influence on the atmospheric circulation is found from 1958 to 1977.

scholarly journals Interactions between Kuroshio Extension and Central Tropical Pacific lead to preferred decadal-timescale oscillations in Pacific climate

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Youngji Joh ◽  
Emanuele Di Lorenzo
Keyword(s):  
North Pacific ◽  
Spectral Power ◽  
Southern Oscillation ◽  
Kuroshio Extension ◽  
Low Frequency ◽  
Tropical Pacific ◽  
Wind Stress Curl ◽  
Decadal Timescale ◽  
The North ◽  
Mechanistic Basis

Abstract The Kuroshio Extension (KE) exhibits prominent decadal fluctuations that enhance the low-frequency variability of North Pacific climate. Using available observations, we show evidence that a preferred decadal timescale in the KE emerges from the interaction between KE and the central tropical Pacific via Meridional Modes. Specifically, we show that changes in the KE states apply a persistent downstream atmospheric response (e.g. wind stress curl, 0–12 months timescales) that projects on the atmospheric forcing of the Pacific Meridional Modes (PMM) over 9 months timescales. Subsequently, the PMM energizes the central tropical Pacific El Niño Southern Oscillation (CP-ENSO) and its atmospheric teleconnections back to the Northern Hemisphere (1–3 months timescale), which in turn excites oceanic Rossby waves in the central/eastern North Pacific that propagate westward changing the KE (~3 years timescales). Consistent with this hypothesis, the cross-correlation function between the KE and the PMM/CP-ENSO indices exhibits a significant sinusoidal shape corresponding to a preferred spectral power at decadal timescales (~10 years). This dynamics pathway (KE→PMM/CP-ENSO→KE) may provide a new mechanistic basis to explain the preferred decadal-timescale of the North Pacific and enhance decadal predictability of Pacific climate.

scholarly journals Potential Impact of Preceding Aleutian Low Variation on El Niño–Southern Oscillation during the Following Winter

2020 ◽  
Vol 33 (8) ◽  
pp. 3061-3077 ◽  
Author(s):  
Shangfeng Chen ◽  
Wen Chen ◽  
Renguang Wu ◽  
Bin Yu ◽  
Hans-F. Graf
Keyword(s):  
El Niño ◽  
North Pacific ◽  
El Nino ◽  
Southern Oscillation ◽  
Eastern Pacific ◽  
Synoptic Scale ◽  
Aleutian Low ◽  
Central Pacific ◽  
Sst Warming ◽  
Anomalous Cyclone

AbstractThe present study reveals a close relation between the interannual variation of Aleutian low intensity (ALI) in March and the subsequent winter El Niño–Southern Oscillation (ENSO). When March ALI is weaker (stronger) than normal, an El Niño (a La Niña)–like sea surface temperature (SST) warming (cooling) tends to appear in the equatorial central-eastern Pacific during the subsequent winter. The physical process linking March ALI to the following winter ENSO is as follows. When March ALI is below normal, a notable atmospheric dipole pattern develops over the North Pacific, with an anticyclonic anomaly over the Aleutian region and a cyclonic anomaly over the subtropical west-central Pacific. The formation of the anomalous cyclone is attributed to feedback of the synoptic-scale eddy-to-mean-flow energy flux and associated vorticity transportation. Specifically, easterly wind anomalies over the midlatitudes related to the weakened ALI are accompanied by a decrease in synoptic-scale eddy activity, which forces an anomalous cyclone to its southern flank. The accompanying westerly wind anomalies over the tropical west-central Pacific induce SST warming in the equatorial central-eastern Pacific during the following summer–autumn via triggering eastward-propagating warm Kelvin waves, which may sustain and develop into an El Niño event during the following winter via positive air–sea feedback. The relation of March ALI with the following winter ENSO is independent of the preceding tropical Pacific SST, the preceding-winter North Pacific Oscillation, and the spring Arctic Oscillation. The results of this analysis may provide an additional source for the prediction of ENSO.

A review of Aleutian Low variability for the last 7,500 years using pan-Pacific delta 18O records

2020 ◽  
Author(s):  
Kana Nagashima ◽  
Jason Addison ◽  
Naomi Harada
Keyword(s):  
North Pacific ◽  
Late Holocene ◽  
Southern Oscillation ◽  
North Pacific Ocean ◽  
Principal Component ◽  
Aleutian Low ◽  
Pressure System ◽  
The Holocene ◽  
The North ◽  
The North Pacific

<p>   The North Pacific Ocean is the largest geographic feature in the Northern Hemisphere and its interactions with the overlying atmosphere drives critical components of the global climate system. The Aleutian Low (AL), the semi-permanent atmospheric low-pressure system centered near the Aleutian Islands, is dynamically linked to environmental change in the North Pacific and surrounding continental areas. However, the multi-centennial and longer time-scale history of the AL during the Holocene is poorly understood.</p><p>   In this study, AL variability since 7.5 ka was examined by applying principal component analysis (PCA) to published δ<sup>18</sup>O data of sedimentary calcite, peat, and speleothem deposits (n = 7) from western North America. Extracted Principal Component 1 (PC1) is characterized by multi-centennial to millennial-scale oscillations, with a spatial loading pattern that suggests PC1 reflects intensification and westward shifts of the AL during ca. 7.3–7.1, 6.3–5.2, 3.6–3.3, 2.9–2.7, 2.6–2.1, 1.8–1.2 and 0.5–0.3 ka. The timing of these shifts are coeval to periods characterized by large meanderings of the Westerly Jet (WJ) Stream over East Asia and solar activity minima, which together suggest that AL variability is related to declines in solar irradiance through its interactions with the WJ. In contrast, PC2 represents a dramatic change between the middle and late Holocene, and appears to reflect long-term intensified AL conditions related to orbitally-driven El Niño–Southern Oscillation intensification between the middle to late Holocene at ~4.5 ka. These findings are critically important for understanding background natural climate variability during the Holocene.</p>

Observed Subseasonal Variability of Oceanic Barrier and Compensated Layers

2009 ◽  
Vol 22 (22) ◽  
pp. 6104-6119 ◽  
Author(s):  
Hailong Liu ◽  
Semyon A. Grodsky ◽  
James A. Carton
Keyword(s):  
Barrier Layer ◽  
North Pacific ◽  
Southern Oscillation ◽  
Kuroshio Extension ◽  
Tropical Pacific ◽  
Pressure System ◽  
Layer Width ◽  
Barrier Layers ◽  
Subseasonal Variability ◽  
The Tropical Pacific

Abstract A monthly gridded analysis of barrier-layer and compensated-layer width based on observed vertical profiles of temperature and salinity and covering the period 1960–2007 is explored for evidence of subseasonal variability and its causes. In the subtropics and midlatitudes this variability is mostly evident during the local cold season when barrier layers and compensated layers are present. There is significant variability of anomalous (nonseasonal) barrier-layer and compensated-layer width on interannual periods, while in the North Pacific longer-term changes are also detectable. In the winter North Pacific a salinity-stratified barrier layer exists at subpolar latitudes. Farther south along the Kuroshio Extension a compensated layer exists. The width of the barrier layer varies from year to year by up to 60 m while compensated-layer width varies by half as much. During the observation period the barrier-layer width decreased in response to a strengthening of the Aleutian low pressure system, the resulting strengthening of dry northerly winds, and a decrease of precipitation. In contrast, the compensated-layer width increased in response to this pressure system strengthening and related amplification of the midlatitude westerly winds, the resulting increase of net surface heat loss, and its effect on the temperature and salinity of the upper-ocean water masses. The tropical Pacific, Atlantic, and Indian Oceans all have permanent barrier layers. Their interannual variability is less than 20 m but is comparable in magnitude to the time mean barrier-layer width in these areas. In the tropical Pacific west of 160°E and in the eastern tropical Indian Ocean, the barrier-layer width changes by approximately 5 m in response to a 10-unit change in the Southern Oscillation index. It thickens during La Niñas as a result of the presence of abundant rainfall and thins during dry El Niños. Interannual variations of barrier-layer width in the equatorial Pacific are weak east of 160°E with an exception of the area surrounding the eastern edge of the warm pool. Here subduction of salty water contributes to locally stronger variations of barrier-layer width.

scholarly journals Spatio-temporal associations of albacore CPUEs in the Northeastern Pacific with regional SST and climate environmental variables

2014 ◽  
Vol 71 (7) ◽  
pp. 1717-1727 ◽  
Author(s):  
A. Jason Phillips ◽  
Lorenzo Ciannelli ◽  
Richard D. Brodeur ◽  
William G. Pearcy ◽  
John Childers
Keyword(s):  
North Pacific ◽  
Large Scale ◽  
Environmental Variability ◽  
Southern Oscillation ◽  
Spatial Dynamics ◽  
Catch Per Unit Effort ◽  
Variable Effect ◽  
Positive Effects ◽  
The North ◽  
Additive Mixed Models

Abstract This study investigated the spatial distribution of juvenile North Pacific albacore (Thunnus alalunga) in relation to local environmental variability [i.e. sea surface temperature (SST)], and two large-scale indices of climate variability, [the Pacific Decadal Oscillation (PDO) and the Multivariate El Niño/Southern Oscillation Index (MEI)]. Changes in local and climate variables were correlated with 48 years of albacore troll catch per unit effort (CPUE) in 1° latitude/longitude cells, using threshold Generalized Additive Mixed Models (tGAMMs). Model terms were included to account for non-stationary and spatially variable effects of the intervening covariates on albacore CPUE. Results indicate that SST had a positive and spatially variable effect on albacore CPUE, with increasingly positive effects to the North, while PDO had an overall negative effect. Although albacore CPUE increased with SST both before and after a threshold year of 1986, such effect geographically shifted north after 1986. This is the first study to demonstrate the non-stationary spatial dynamics of albacore tuna, linked with a major shift of the North Pacific. Results imply that if ocean temperatures continue to increase, US west coast fisher communities reliant on commercial albacore fisheries are likely to be negatively affected in the southern areas but positively affected in the northern areas, where current albacore landings are highest.

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