scholarly journals Composite Analysis of Large-Scale Environments Conducive to Western Pacific Polar/Subtropical Jet Superposition

2016 ◽  
Vol 29 (19) ◽  
pp. 7145-7165 ◽  
Author(s):  
Zachary J. Handlos ◽  
Jonathan E. Martin
Keyword(s):  
Large Scale ◽  
Hadley Cell ◽  
Entrance Region ◽  
Western Pacific ◽  
Northwest Pacific ◽  
Jet Streams ◽  
Research Attention ◽  
Subtropical Jet ◽  
Cold Surges ◽  
The Western Pacific

Abstract Although considerable research attention has been devoted to examination of the Northern Hemisphere polar and subtropical jet streams, relatively little has been directed toward understanding the circumstances that conspire to produce the relatively rare vertical superposition of these usually separate features. This study investigates the structure and evolution of large-scale environments associated with jet superposition events in the northwest Pacific. An objective identification scheme, using NCEP–NCAR Reanalysis 1 data, is employed to identify all jet superpositions in the western Pacific (30°–40°N, 135°–175°E) for boreal winters (DJF) between 1979/80 and 2009/10. The analysis reveals that environments conducive to western Pacific jet superposition share several large-scale features usually associated with East Asian winter monsoon (EAWM) northerly cold surges, including the presence of an enhanced Hadley cell–like circulation within the jet entrance region. It is further demonstrated that several EAWM indices are statistically significantly correlated with jet superposition frequency in the western Pacific. The life cycle of EAWM cold surges promotes interaction between tropical convection and internal jet dynamics. Low–potential vorticity (PV), high- air, appearing to be associated with anomalous convection in the western Pacific lower latitudes, is advected poleward toward the equatorward side of the jet in upper-tropospheric isentropic layers, resulting in anomalous anticyclonic wind shear that accelerates the jet. This, along with geostrophic cold air advection in the left jet entrance region that drives the polar tropopause downward through the jet core, promotes the development of the deep, vertical PV wall characteristic of superposed jets. A conceptual model synthesizing the results of this analysis is introduced.

scholarly journals Geochronology and Geochemical Properties of Mid-Pleistocene Sediments on the Caiwei Guyot in the Northwest Pacific Imply a Surface-to-Deep Linkage

2021 ◽  
Vol 9 (3) ◽  
pp. 253
Author(s):  
Liang Yi ◽  
Haifeng Wang ◽  
Xiguang Deng ◽  
Haifan Yuan ◽  
Dong Xu ◽  
...  
Keyword(s):  
Accumulation Rate ◽  
Western Pacific ◽  
Global Ocean ◽  
Northwest Pacific ◽  
Local Circulation ◽  
Research Attention ◽  
Ice Volume ◽  
Global Ice Volume ◽  
Geochemical Properties ◽  
The Western Pacific

Seamounts are ubiquitous topographic units in the global ocean, and their effects on local circulation have attracted great research attention in physical oceanography; however, fewer relevant efforts were made on geological timescales in previous studies. The Caiwei (Pako) Guyot in the Magellan Seamounts of the western Pacific is a typical seamount and oceanographic characteristics have been well documented. In this study, we investigate a sediment core by geochronological and geochemical studies to reveal a topography-induce surface-to-bottom linkage. The principal results are as follows: (1) Two magnetozones are recognized in core MABC–11, which can be correlated to the Brunhes and Matuyama chrons; (2) Elements Ca, Si, Cl, K, Mn, Ti, and Fe are seven elements with high intensities by geochemical scanning; (3) Ca intensity can be tuned to global ice volume to refine the age model on glacial-interglacial timescales; (4) The averaged sediment accumulation rate is ~0.73 mm/kyr, agreeing with the estimate of the excess 230Th data in the upper part. Based on these results, a proxy of element Mn is derived, whose variability can be correlated with changes in global ice volume and deep-water masses on glacial-interglacial timescales. This record is also characterized by an evident 23-kyr cycle, highlighting a direct influence of solar insolation on deep-sea sedimentary processes. Overall, sedimentary archives of the Caiwei Guyot not only record an intensified abyssal ventilation during interglaciations in the western Pacific, but also provide a unique window for investigating the topography-induced linkage between the upper and bottom ocean on orbital timescales.

scholarly journals Contributions of ENSO and East Indian Ocean SSTA to the Interannual Variability of Northwest Pacific Tropical Cyclone Frequency*

2011 ◽  
Vol 24 (2) ◽  
pp. 509-521 ◽  
Author(s):  
Ruifen Zhan ◽  
Yuqing Wang ◽  
Xiaotu Lei
Keyword(s):  
Tropical Cyclone ◽  
Indian Ocean ◽  
Interannual Variability ◽  
Large Scale ◽  
Western Pacific ◽  
Boreal Summer ◽  
Northwest Pacific ◽  
East Indian ◽  
East Indian Ocean ◽  
The Western Pacific

Abstract This study attempts to understand contributions of ENSO and the boreal summer sea surface temperature anomaly (SSTA) in the East Indian Ocean (EIO) to the interannual variability of tropical cyclone (TC) frequency over the western North Pacific (WNP) and the involved physical mechanisms. The results show that both ENSO and EIO SSTA have a large control on the WNP TC genesis frequency, but their effects are significantly different. ENSO remarkably affects the east–west shift of the mean genesis location and accordingly contributes to the intense TC activity. The EIO SSTA affects the TC genesis in the entire genesis region over the WNP and largely determines the numbers of both the total and weak TCs. ENSO modulates the large-scale atmospheric circulation and barotropic energy conversion over the WNP, contributing to changes in both the TC genesis location and the frequency of intense TCs. The EIO SSTA significantly affects both the western Pacific summer monsoon and the equatorial Kelvin wave activity over the western Pacific, two major large-scale dynamical controls of TC genesis over the WNP. In general the warm (cold) EIO SSTA suppresses (promotes) the TC genesis over the WNP. Therefore, a better understanding of the combined contributions of ENSO and EIO SSTA could help improve the seasonal prediction of the WNP TC activity.

scholarly journals Exploring the sensitivity of Northern Hemisphere atmospheric circulation to different surface temperature forcing using a statistical–dynamical atmospheric model

2019 ◽  
Vol 26 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Sonja Totz ◽  
Stefan Petri ◽  
Jascha Lehmann ◽  
Erik Peukert ◽  
Dim Coumou
Keyword(s):  
Temperature Gradient ◽  
Large Scale ◽  
Planetary Waves ◽  
Hadley Cell ◽  
Storm Tracks ◽  
Meridional Temperature Gradient ◽  
Jet Streams ◽  
Global Mean Temperature ◽  
Mean Temperature ◽  
Global Mean

Abstract. Climate and weather conditions in the mid-latitudes are strongly driven by the large-scale atmosphere circulation. Observational data indicate that important components of the large-scale circulation have changed in recent decades, including the strength and the width of the Hadley cell, jets, storm tracks and planetary waves. Here, we use a new statistical–dynamical atmosphere model (SDAM) to test the individual sensitivities of the large-scale atmospheric circulation to changes in the zonal temperature gradient, meridional temperature gradient and global-mean temperature. We analyze the Northern Hemisphere Hadley circulation, jet streams, storm tracks and planetary waves by systematically altering the zonal temperature asymmetry, the meridional temperature gradient and the global-mean temperature. Our results show that the strength of the Hadley cell, storm tracks and jet streams depend, in terms of relative changes, almost linearly on both the global-mean temperature and the meridional temperature gradient, whereas the zonal temperature asymmetry has little or no influence. The magnitude of planetary waves is affected by all three temperature components, as expected from theoretical dynamical considerations. The width of the Hadley cell behaves nonlinearly with respect to all three temperature components in the SDAM. Moreover, some of these observed large-scale atmospheric changes are expected from dynamical equations and are therefore an important part of model validation.

scholarly journals Observed Evolution of Northward-Propagating Intraseasonal Variation over the Western Pacific: A Case Study in Boreal Early Summer

2013 ◽  
Vol 141 (2) ◽  
pp. 690-706 ◽  
Author(s):  
Masaki Katsumata ◽  
Hiroyuki Yamada ◽  
Hisayuki Kubota ◽  
Qoosaku Moteki ◽  
Ryuichi Shirooka
Keyword(s):  
Boundary Layer ◽  
Large Scale ◽  
Lower Troposphere ◽  
Western Pacific ◽  
Boreal Summer ◽  
Intraseasonal Variation ◽  
Middle Troposphere ◽  
Inactive Period ◽  
The Western Pacific

Abstract This report describes the in situ observed evolution of the atmospheric profile during an event of the boreal summer intraseasonal variation (BSISV) in the tropical western Pacific Ocean. The convectively active region of the BSISV proceeded northward over the sounding and radar network. Over the array, the situation changed from a convectively inactive period to an active period. Inspection of the sounding data revealed the gradual moistening of the lower troposphere during the convectively inactive period. The sounding-derived heat and moisture budget analyses indicated that both the convective- and large-scale processes caused moistening of the lower and middle troposphere where the radar echo tops were observed most frequently. This study is the first to identify such a “preconditioning” process for the BSISV in the western Pacific using detailed in situ observational data. During the preconditioning, an increase in CAPE was observed, as in previous studies of the MJO. An increase of moisture in the boundary layer was responsible for the increase of CAPE. The large-scale horizontal convergence in the boundary layer may be a key factor to moisten the boundary layer through the convective-scale processes, as well as through the large-scale processes to moisten the lower and middle troposphere.

scholarly journals The Storm-Track Response to Idealized SST Perturbations in an Aquaplanet GCM

2008 ◽  
Vol 65 (9) ◽  
pp. 2842-2860 ◽  
Author(s):  
David James Brayshaw ◽  
Brian Hoskins ◽  
Michael Blackburn
Keyword(s):  
Large Scale ◽  
Storm Track ◽  
Hadley Cell ◽  
Atmospheric Response ◽  
Subtropical Jet ◽  
Poleward Shift ◽  
Sst Anomaly ◽  
Hadley Centre ◽  
Sst Gradient ◽  
Sst Anomalies

Abstract The tropospheric response to midlatitude SST anomalies has been investigated through a series of aquaplanet simulations using a high-resolution version of the Hadley Centre atmosphere model (HadAM3) under perpetual equinox conditions. Model integrations show that increases in the midlatitude SST gradient generally lead to stronger storm tracks that are shifted slightly poleward, consistent with changes in the lower-tropospheric baroclinicity. The large-scale atmospheric response is, however, highly sensitive to the position of the SST gradient anomaly relative to that of the subtropical jet in the unperturbed atmosphere. In particular, when SST gradients are increased very close to the subtropical jet, then the Hadley cell and subtropical jet is strengthened while the storm track and eddy-driven jet are shifted equatorward. Conversely, if the subtropical SST gradients are reduced and the midlatitude gradients increased, then the storm track shows a strong poleward shift and a well-separated eddy-driven jet is produced. The sign of the SST anomaly is shown to play a secondary role in determining the overall tropospheric response. These findings are used to provide a new and consistent interpretation of some previous GCM studies concerning the atmospheric response to midlatitude SST anomalies.

Subseasonal Dynamical Prediction of East Asian Cold Surges

2017 ◽  
Vol 32 (4) ◽  
pp. 1675-1694 ◽  
Author(s):  
Qiaoping Li ◽  
Song Yang ◽  
Tongwen Wu ◽  
Xiangwen Liu
Keyword(s):  
Geopotential Height ◽  
Lead Time ◽  
Large Scale ◽  
Wave Train ◽  
East Asian ◽  
Eastern China ◽  
Northwest Pacific ◽  
Cold Surge ◽  
Circulation Patterns ◽  
Cold Surges

Abstract Predictability of East Asian cold surges is studied using daily data from the hindcasts of 45-day integrations by the NCEP Climate Forecast System version 2 (CFSv2). Prediction skills of the CFSv2 in forecasting cold surges, their annual variation, and their physical links to large-scale atmospheric circulation patterns are examined. Results show that the climatological characteristics of the East Asian winter monsoon can be reasonably reproduced by the CFSv2. The model can well capture the frequency, intensity, and location of cold surges at a lead time of about two weeks. Obviously, fewer-than-observed cold surge days are found in the predictions when the lead time is above 14 days. The spatiotemporal evolutions of high-, mid-, and low-level circulation patterns during cold surge occurrences are all accurately indicated in the CFSv2 prediction. Except for precipitation, the other variables associated with cold surges, such as geopotential height, wind, sea level pressure, and surface air temperature, exhibit higher skills. The lead time of skillful prediction of precipitation is limited to around 1 week, with systematic wet biases over the South China Sea, the Philippine Islands, and the northwest Pacific, but dry biases over India, the Indo-China Peninsula, and most high-latitude regions. Wave train–like patterns of geopotential height and wind differ distinguishably when cold surges occur in northern and southern regions (using 35°N as the dividing line), and the CFSv2 gives a consistent prediction to these anomalous patterns. A weaker-than-observed Siberian high and weaker northerly winds over eastern China are found in the predictions especially at longer lead times.

scholarly journals The influence of radiation flux in Northwest Pacific on the Western Pacific warm pools and typhoons over the past 170 years

2021 ◽  
Author(s):  
Chai Boyu ◽  
Feng Xu ◽  
Jianjun Xu ◽  
Han Li-guo ◽  
CHEN Si-qi ◽  
...  
Keyword(s):  
Radiation Flux ◽  
Longwave Radiation ◽  
Warm Pool ◽  
Western Pacific ◽  
Shortwave Radiation ◽  
Northwest Pacific ◽  
Western Pacific Warm Pool ◽  
The Past ◽  
Pacific Warm Pool ◽  
The Western Pacific

Abstract Based on various statistical methods and empirical orthogonal function (EOF) analysis, this study analyzes the correlation of radiation flux of Northwest Pacific in the 100 years scale with the western Pacific warm pool and typhoon development. The key results are as follows. First, the surface downwelling longwave radiation (SDLR) received by key areas in Northwest Pacific significantly increased over the past 170 years. The surface downwelling shortwave radiation (SDSR) decreased, and TOA (Top of Atmosphere) incident shortwave radiation (TISR) slightly fluctuated and increased in the 11a (11 years) period. Second, there was the strongest correlation between the Western Pacific warm pool and SDLR, and both increased continuously. Third, since 1945, there has been a tendency of increasing after decreasing in the annual frequency and the share of severe typhoons, and the formation area distribution of typhoons has turned more even. Taking 1998 as a cut-off point, before 1998, there was no obvious correlation between the strong typhoon frequency and SDLR. However, such correction became stronger after 1998. They were affected by the changes of SDLR, SDSR, TISR, vapor, vorticity, vertical velocity, SST and h100 . Forth, the SDLR and TISR are major factors influencing the Western Pacific warm pool, typhoon motion and other varieties. While SDLR mainly increases in the tropical areas, TISR tends to fluctuate and increase slightly. Their changes are consistent with the change general characteristics of strengthening of typhoon.

scholarly journals GLOBAL EVOLUTION AND PALEOGEOGRAPHIC DISTRIBUTION OF MID - CRETACEOUS ORBITOLINIDS

2019 ◽  
Author(s):  
Marcelle Boudagher-Fadel ◽  
G. David Price
Keyword(s):  
Sea Level ◽  
Morphological Changes ◽  
Western Pacific ◽  
Northwest Pacific ◽  
Thin Sections ◽  
The North ◽  
Southern Tibetan Plateau ◽  
Stratigraphic Ranges ◽  
Tectonic Forces ◽  
The Western Pacific

Members of the Larger Benthic Foraminiferal (LBF) family Orbitolinidae occured from the Cretaceous to the Paleogene, however, they were most diverse during the mid-Cretaceous, and dominated the agglutinated LBF assemblages described from limestones of that period. Various orbitolinid species have been used to zone and date lithologies formed in the shallow, warm waters of the Aptian to the Early Cenomanian, and many, sometimes inaccurate, generic and sub-generic nomenclatures have been proposed to differentiate the often subtle morphological changes that orbitolinids exhibit over time. Until now, it has not been possible to develop an effective global overview of their evolution and environmental development because descriptions of specimens from Asia have been relatively rare. Following our recent study of over 1800 orbitolinid-rich thin sections of material from 13 outcrops of the Langshan Limestone, from the Southern Tibetan Plateau, and from the Barito Basin, South Kalimantan, Indonesia, it has been possible to compare the stratigraphic ranges of these orbitolinids with previously described Tethyan and American forms, based on the use of a planktonic zonal (PZ) scheme, itself tied to the most recent chronostratigraphic scale. This has allowed the reconstruction of the phylogenetic and paleogeographic evolution of the orbitolinids from their Valanginian origin in the Tethys. Although Tethys remained the paleogeographic focus for the orbitolinids, it is inferred here for the first time that a bi-directional paleogeographic migration of some orbitolinid genera occurred from Tethys to the Americas and also to the Western Pacific region. Our observations and dating confirm that global marine regressions in the Aptian were coincident with, and may well have facilitated, these orbitolinid transoceanic migrations. However, migration stopped after rising sea-level in the Early Albian appears to have again isolated these provinces from each other. Tectonic forces associated with the subduction of the Farallon Plate and further sea-level raises led to the opening of the Western Interior Seaway in the North America, which correlates with, and may have been the cause of, the Middle Albian (top of PZ Albian 2) extinction of the American orbitolinids. The extinction of the orbitolinids revealed that the Western Pacific province was split into two sub-provinces, with extinction occurring at the end of the Early Albian (top of PZ Albian 1) in the Northwest Pacific sub-province, and at the end of the Albian (top of PZ Albian 4) in the sub-province that is today South East Asia (on the margins and west of the Wallace Line). The final virtual extinction of the orbitolinids occurred at the end of the Cenomanian in the Tethyan province, which coincides with, and may have been caused by, global anoxic oceanic events that correlate with a near-peak Mesozoic eustatic sea-level high-stand that led to the overall global collapse of the paleotropical reef ecosystem at that time.

scholarly journals Zonal SST Difference as a Potential Environmental Factor Supporting the Longevity of the Madden–Julian Oscillation

2018 ◽  
Vol 31 (18) ◽  
pp. 7549-7564 ◽  
Author(s):  
Tamaki Suematsu ◽  
Hiroaki Miura
Keyword(s):  
Indian Ocean ◽  
Large Scale ◽  
Low Frequency ◽  
Western Pacific ◽  
Madden Julian Oscillation ◽  
Central Pacific ◽  
The Indian Ocean ◽  
The Difference ◽  
The Western Pacific ◽  
Sst Gradient

An environment favorable for the development of the Madden–Julian oscillation (MJO) was investigated by classifying MJO-like atmospheric patterns as MJO and regionally confined convective (RCC) events. Comparison of MJO and RCC events showed that even when preceded by a major convective suppression event, convective events did not develop into an MJO when large-scale buildup of moist static energy (MSE) was inhibited. The difference in the MSE accumulation between MJO and RCC is related to the contrasting low-frequency basic-state sea surface temperature (SST) pattern; the MJO and RCC events were associated with anomalously warm and cold low-frequency SSTs prevailing over the western to central Pacific, respectively. Differences in the SST anomaly field were absent from the intraseasonal frequency range of 20–60 days. The basic-state SST pattern associated with the MJO was characterized by a positive zonal SST gradient from the Indian Ocean to the western Pacific, which provided a long-standing condition that allowed for sufficient buildup of MSE across the Indian Ocean to the western Pacific via large-scale low-level convergence over intraseasonal and longer time scales. The results of this study suggest the importance of such a basic-state SST, with a long-lasting positive zonal SST gradient, for enhancing convection over a longer than intraseasonal time scale in realizing a complete MJO life cycle.

scholarly journals The Large-Scale Deployment of Fish Aggregation Devices Alters Environmentally-Based Migratory Behavior of Skipjack Tuna in the Western Pacific Ocean

PLoS ONE ◽  
2014 ◽  
Vol 9 (5) ◽  
pp. e98226 ◽  
Author(s):  
Xuefang Wang ◽  
Yong Chen ◽  
Samuel Truesdell ◽  
Liuxiong Xu ◽  
Jie Cao ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Large Scale ◽  
Western Pacific ◽  
Migratory Behavior ◽  
Western Pacific Ocean ◽  
Skipjack Tuna ◽  
Fish Aggregation ◽  
The Western Pacific
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