Interannual Modality of Upper-Ocean Temperature: 4D Structure Revealed by Argo Data

2015 ◽  
Vol 28 (9) ◽  
pp. 3441-3452 ◽  
Author(s):  
Ge Chen ◽  
Hanou Chen
Keyword(s):  
Interannual Variability ◽  
Southern Oscillation ◽  
Hadley Circulation ◽  
Walker Circulation ◽  
Upper Ocean ◽  
Kelvin Wave ◽  
Argo Data ◽  
Sea Temperature ◽  
Equatorial Undercurrent ◽  
The Pacific

Abstract Using the newly available decade-long Argo data for the period 2004–13, a detailed study is carried out on deriving four-dimensional (4D) modality of sea temperature in the upper ocean with emphasis on its interannual variability in terms of amplitude, phase, and periodicity. Three principal modes with central periodicities at 19.2, 33.8, and 50.3 months have been identified, and their relationship with El Niño–Southern Oscillation (ENSO) is investigated, yielding a number of useful results and conclusions: 1) A striking tick-shaped pipe-like feature of interannual variability maxima, which is named the “Niño pipe” in this paper, has been revealed within the 10°S–10°N upper Pacific Ocean. 2) The pipe core extends downward from ~50 m at 130°E to ~250 m near the date line before tilting upward to the sea surface at about 275°E, coinciding nicely with the pathway of the Pacific equatorial undercurrent (EUC). 3) The double-peak zonal modality pattern of the Niño pipe in the upper Pacific is echoed in the subsurface Atlantic and Indian Oceans through Walker circulation, while its single-peak meridional modality pattern is mirrored in the subsurface North and South Pacific through Hadley circulation. 4) A coherent three-peak modal structure implies a strong coupling between sea level variability at the surface and sea temperature variability around the thermocline. Accumulating evidence suggests that Rossby/Kelvin wave dynamics in tandem with EUC-based thermocline dynamics are the main mechanisms of the three-mode Niño pipe in ENSO cycles.

scholarly journals Origin of Sustained Continuous Measurements of Surface Wind and Upper-Ocean Current and Temperature on the Pacific Equator: EQUA Project

2021 ◽  
pp. 1-47
Author(s):  
David Halpern
Keyword(s):  
Time Series ◽  
Surface Wind ◽  
Temperature Measurements ◽  
Ocean Current ◽  
Upper Ocean ◽  
Kelvin Wave ◽  
Equatorial Undercurrent ◽  
Pilot Experiment ◽  
The Pacific

AbstractIn 1976, a pilot experiment, called first Equatorial Mooring (EQUA-1), tested an innovative technique for anchoring a taut-line surface mooring at 0°, 150°W where the water depth is 4.5 km. The 36-day deployment contained a wind recorder and fixed-level current meters at 50 and 100 m in the Equatorial Undercurrent (EUC). The following year, in a second pilot experiment, named EQUA-2, a similar mooring was deployed at 0°, 125°W for 99 days. EQUA-2, with current meters at 10, 50, 100, 150 and 200 m, recorded a surge in EUC transport during April 1977 when 3-day averaged eastward current speeds at 50-m depth reached 2 m s‒1. The associated eastward transport per unit meridional width over the 50- to 200-m layer was 190 m2 s‒1. Based on observations recorded in April 1980, the EQUA-2 pulse would correspond to a total EUC transport surge of about 38 Sverdrups and would represent an equatorially trapped first-mode baroclinic Kelvin wave. This paper describes EQUA Project observations and why and how I created the high risk-of-failure opportunity to record pioneering time series measurements at the equator. The enduring legacy of the EQUA Project is the sustained maintenance of in-situ surface wind and upper-ocean current and temperature measurements at numerous sites in the equatorial oceans, starting in the Pacific to improve forecasts of the El Niño and La Niña phenomenon. For example, the 40-year records of surface wind and upper-ocean current and temperature measurements at 0°, 110°W and 0°, 140°W are some of oceanography’s longest time series recorded far from land.

scholarly journals Intraseasonal and Interannual Variability in North American Storm Tracks and Its Relationship to Equatorial Pacific Variability

2013 ◽  
Vol 141 (10) ◽  
pp. 3610-3625 ◽  
Author(s):  
Kevin M. Grise ◽  
Seok-Woo Son ◽  
John R. Gyakum
Keyword(s):  
North America ◽  
Interannual Variability ◽  
North American ◽  
Southern Oscillation ◽  
Extratropical Cyclones ◽  
The North ◽  
The Pacific ◽  
Cyclone Tracks ◽  
Lagrangian Tracking ◽  
The North Atlantic Oscillation

Abstract Extratropical cyclones play a principal role in wintertime precipitation and severe weather over North America. On average, the greatest number of cyclones track 1) from the lee of the Rocky Mountains eastward across the Great Lakes and 2) over the Gulf Stream along the eastern coastline of North America. However, the cyclone tracks are highly variable within individual winters and between winter seasons. In this study, the authors apply a Lagrangian tracking algorithm to examine variability in extratropical cyclone tracks over North America during winter. A series of methodological criteria is used to isolate cyclone development and decay regions and to account for the elevated topography over western North America. The results confirm the signatures of four climate phenomena in the intraseasonal and interannual variability in North American cyclone tracks: the North Atlantic Oscillation (NAO), the El Niño–Southern Oscillation (ENSO), the Pacific–North American pattern (PNA), and the Madden–Julian oscillation (MJO). Similar signatures are found using Eulerian bandpass-filtered eddy variances. Variability in the number of extratropical cyclones at most locations in North America is linked to fluctuations in Rossby wave trains extending from the central tropical Pacific Ocean. Only over the far northeastern United States and northeastern Canada is cyclone variability strongly linked to the NAO. The results suggest that Pacific sector variability (ENSO, PNA, and MJO) is a key contributor to intraseasonal and interannual variability in the frequency of extratropical cyclones at most locations across North America.

scholarly journals Variations in the Flow of the Global Atmosphere Associated with a Composite Convectively Coupled Oceanic Kelvin Wave

2010 ◽  
Vol 23 (15) ◽  
pp. 4192-4201 ◽  
Author(s):  
Paul E. Roundy ◽  
Lynn M. Gribble-Verhagen
Keyword(s):  
Southern Oscillation ◽  
Deep Convection ◽  
Composite Analysis ◽  
High Latitudes ◽  
Madden Julian Oscillation ◽  
Global Flow ◽  
Kelvin Wave ◽  
Coupled Mode ◽  
The Pacific ◽  
The Pacific Ocean

Abstract Kelvin waves in the Pacific Ocean occasionally develop and propagate eastward together with anomalies of deep convection and low-level westerly wind. This pattern suggests coupling between the oceanic waves and atmospheric convection. A simple composite analysis based on observed coupled events from October through April demonstrates that this apparent coupled mode is associated with significant large anomalies in the global flow that extend to high latitudes. These high-latitude anomalies are significantly larger than those that are linearly associated with the El Niño–Southern Oscillation (ENSO), and they evolve on time scales between those of the Madden–Julian oscillation and ENSO, potentially providing an opportunity for enhanced subseasonal predictability in the flow of the global atmosphere.

scholarly journals Weakened Interannual Variability in the Tropical Pacific Ocean since 2000

2013 ◽  
Vol 26 (8) ◽  
pp. 2601-2613 ◽  
Author(s):  
Zeng-Zhen Hu ◽  
Arun Kumar ◽  
Hong-Li Ren ◽  
Hui Wang ◽  
Michelle L’Heureux ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Interannual Variability ◽  
Southern Oscillation ◽  
Walker Circulation ◽  
Tropical Pacific ◽  
Warm Water ◽  
Water Volume ◽  
Tropical Pacific Ocean ◽  
Trade Winds ◽  
The Tropical Pacific

Abstract An interdecadal shift in the variability and mean state of the tropical Pacific Ocean is investigated within the context of changes in El Niño–Southern Oscillation (ENSO). Compared with 1979–99, the interannual variability in the tropical Pacific was significantly weaker in 2000–11, and this shift can be seen by coherent changes in both the tropical atmosphere and ocean. For example, the equatorial thermocline tilt became steeper during 2000–11, which was consistent with positive (negative) sea surface temperature anomalies, increased (decreased) precipitation, and enhanced (suppressed) convection in the western (central and eastern) tropical Pacific, which reflected an intensification of the Walker circulation. The combination of a steeper thermocline slope with stronger surface trade winds is proposed to have hampered the eastward migration of the warm water along the equatorial Pacific. As a consequence, the variability of the warm water volume was reduced and thus ENSO amplitude also decreased. Sensitivity experiments with the Zebiak–Cane model confirm the link between thermocline slope, wind stress, and the amplitude of ENSO.

scholarly journals ANALISIS KEJADIAN EL NINO TAHUN 2015 DAN PENGARUHNYA TERHADAP PENINGKATAN TITIK API DI WILAYAH SUMATERA DAN KALIMANTAN

2016 ◽  
Vol 17 (1) ◽  
pp. 11 ◽  
Author(s):  
Ardila Yananto ◽  
Saraswati Dewi
Keyword(s):  
Pacific Ocean ◽  
El Niño ◽  
Southern Oscillation Index ◽  
Rainfall Intensity ◽  
El Nino ◽  
Southern Oscillation ◽  
Walker Circulation ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Temporal And Spatial

IntisariKejadian El Nino yang berdampak pada sebagian besar wilayah Indonesia akan selalu berasosiasi dengan kekeringan akibat dari berkurangnya intensitas curah hujan. Lebih jauh akibat dari kekeringan tersebut telah menimbulkan meningkatnya titik api secara signifikan dibandingkan dengan tahun-tahun sebelumnya khususnya di wilayah Sumatera dan Kalimantan, dimana hal tersebut telah mengakibatkan terjadinya bencana asap pada tahun 2015. Tujuan utama penulisan karya tulis ini adalah untuk menganalisis kejadian El Nino pada tahun 2015 dan pengaruhnya terhadap peningkatan titik api di wilayah Sumatera dan Kalimantan baik dalam skala temporal maupun spasial. Dari hasil penelitian ini dapat diketahui bahwa berdasarkan parameter NINO 3.4 SST Indeks dan Southern Oscillation Index (SOI) pada tahun 2015 telah terjadi fenomana El Nino pada level kuat yang ditandai dengan adanya pelemahan sirkulasi walker sehingga pusat tekanan rendah perpindah dari Samudera Pasifik bagian Barat ke Samudera Pasifik bagian Timur, dimana hal ini telah menyebabkan adanya penurunan intensitas curah hujan (anomali negatif) disebagian besar wilayah Indonesia terutama pada bulan Juli hingga Oktober 2015 dan oleh karena itulah pada bulan Juli hingga Oktober 2015 tersebut terjadi peningkatan jumlah titik api yang sangat tajam di wilayah Indonesia dimana persebaran titik api tersebut sebagian besar terkonsentrasi di Provinsi Sumatera Selatan dan Kalimantan Tengah. AbstractEl Nino that impact most areas of Indonesia will always be associated in drought due to reduced rainfall intensity. Drought, in further, has resulted in increasing titik apis significantly compared to previous years, especially in the Sumatra and Kalimantan, that was creating smog disaster in 2015. The main objective of this research was to analyze the occurrence of El Nino in 2015 and its influence on increase of titik api in Sumatera and Kalimantan both in temporal and spatial scale. From this research it is known that based on the NINO 3.4 SST index and the Southern Oscillation Index (SOI) it is known there was a strong El Niño event occurred in 2015 showed there was a weakening Walker circulation so that the low pressure center moved from Western part of the Pacific Ocean to the Eastern Pacific Ocean, where this has led to a decrease rainfall intensity (negative anomaly) in most parts of Indonesia, especially from July to October 2015 and because of that from July to October 2015 there was very hight increasing number of titik apis in Indonesia where the spread of titik api the mostly concentrated in the province of South Sumatera and Central Kalimantan. 

scholarly journals Decadal sea-level variability in the Australasian Mediterranean Sea

Ocean Science ◽  
2021 ◽  
Vol 17 (5) ◽  
pp. 1473-1487
Author(s):  
Patrick Wagner ◽  
Claus W. Böning
Keyword(s):  
Mediterranean Sea ◽  
Interannual Variability ◽  
Sea Level ◽  
Wind Stress ◽  
Southern Oscillation ◽  
Horizontal Resolution ◽  
Intrinsic Variability ◽  
Sea Level Variability ◽  
The Pacific ◽  
Regional Sea Level

Abstract. Strong regional sea-level trends, mainly related to basin-wide wind stress anomalies, have been observed in the western tropical Pacific over the last 3 decades. Analyses of regional sea level in the densely populated regions of the neighbouring Australasian Mediterranean Sea (AMS; also called tropical Asian seas) are hindered by its complex topography and respective studies are sparse. We used a series of global eddy-permitting ocean models, including a high-resolution configuration that resolves the AMS with 120∘ horizontal resolution, forced by a comprehensive atmospheric forcing product over 1958–2016 to characterize the patterns and magnitude of decadal sea-level variability in the AMS. The nature of this variability is elucidated further by sensitivity experiments with interannual variability restricted to either the momentum or buoyancy fluxes, building on an experiment employing a repeated-year forcing without interannual variability in all forcing components. Our results suggest that decadal fluctuations of the El Niño–Southern Oscillation (ENSO) account for over 80 % of the variability in all deep basins of the region, except for the central South China Sea (SCS). Changes related to the Pacific Decadal Oscillation (PDO) are most pronounced in the shallow Arafura and Timor seas and in the central SCS. On average, buoyancy fluxes account for less than 10 % of decadal SSH variability, but this ratio is highly variable over time and can reach values of up to 50 %. In particular, our results suggest that buoyancy flux forcing amplifies the dominant wind-stress-driven anomalies related to ENSO cycles. Intrinsic variability is mostly negligible except in the SCS, where it accounts for 25 % of the total decadal SSH variability.

scholarly journals Imprint of the Pacific Walker Circulation in global precipitation δ18O

2021 ◽  
pp. 1-55
Author(s):  
Georgina Falster ◽  
Bronwen Konecky ◽  
Midhun Madhavan ◽  
Samantha Stevenson ◽  
Sloan Coats
Keyword(s):  
Data Processing ◽  
Water Cycle ◽  
Southern Oscillation ◽  
Walker Circulation ◽  
Future Climate Change ◽  
Moisture Source ◽  
Global Water Cycle ◽  
The Pacific ◽  
Global Water

AbstractCharacterising variability in the global water cycle is fundamental to predicting impacts of future climate change; understanding the role of the Pacific Walker circulation (PWC) in the regional expression of global water cycle changes is critical to understanding this variability. Water isotopes are ideal tracers of the role of the PWC in global water cycling, because they retain information about circulation-dependent processes including moisture source, transport, and delivery. We collated publicly-available measurements of precipitation δ18O (δ18OP), and used novel data processing techniques to synthesise long (34-year), globally-distributed composite records from temporally discontinuous δ18OP measurements. We investigated relationships between global-scale δ18OP variability and PWC strength, as well as other possible drivers of global δ18OP variability—including the El Niño Southern Oscillation (ENSO) and global mean temperature—and used isotope-enabled climate model simulations to assess potential biases arising from uneven geographical distribution of the observations or our data processing methodology. Co-variability underlying the δ18OP composites is more strongly correlated with the PWC (r = 0.74) than any other index of climate variability tested. We propose that the PWC imprint in global δ18OP arises from multiple complementary processes, including PWC-related changes in moisture source and transport length, and a PWC- or ENSO-driven ‘amount effect’ in tropical regions. The clear PWC imprint in global δ18OP implies a strong PWC influence on the regional expression of global water cycle variability on interannual to decadal timescales, and hence that uncertainty in the future state of the PWC translates to uncertainties in future changes in the global water cycle.

scholarly journals Explaining and forecasting interannual variability in the flow of the Nile River

2014 ◽  
Vol 11 (5) ◽  
pp. 4851-4878
Author(s):  
M. S. Siam ◽  
E. A. B. Eltahir
Keyword(s):  
Interannual Variability ◽  
Southern Oscillation ◽  
Eastern Pacific ◽  
Nile River ◽  
Data Sets ◽  
Bayesian Theorem ◽  
The Bible ◽  
The Pacific ◽  
Hybrid Forecasting ◽  
First Time

Abstract. The natural interannual variability in the flow of Nile River had a significant impact on the ancient civilizations and cultures that flourished on the banks of the river. This is evident from stories in the Bible and Koran, and from the numerous Nilometers discovered near ancient temples. Here, we analyze extensive data sets collected during the 20th century and define four modes of natural variability in the flow of Nile River, identifying a new significant potential for improving predictability of floods and droughts. Previous studies have identified a significant teleconnection between the Nile flow and the Eastern Pacific Ocean. El Niño–Southern Oscillation (ENSO) explains about 25% of the interannual variability in the Nile flow. Here, we identify, for the first time, a region in the southern Indian Ocean with similarly strong teleconnection to the Nile flow. Sea Surface Temperature (SST) in the region (50–80° E and 25–35° S) explains 28% of the interannual variability in the Nile flow. During those years with anomalous SST conditions in both Oceans, we estimate that indices of the SSTs in the Pacific and Indian Oceans can collectively explain up to 84% of the interannual variability in the flow of Nile. Building on these findings, we use classical Bayesian theorem to develop a new hybrid forecasting algorithm that predicts the Nile flow based on global models predictions of indices of the SST in the Eastern Pacific and Southern Indian Oceans.

scholarly journals A Transbasin Mode of Interannual Variability of the Central American Gap Winds: Seasonality and Large-Scale Forcing

2017 ◽  
Vol 30 (20) ◽  
pp. 8223-8235
Author(s):  
Jun-Chao Yang ◽  
Xiaopei Lin ◽  
Shang-Ping Xie
Keyword(s):  
Central America ◽  
Large Scale ◽  
Southern Oscillation ◽  
Function Analysis ◽  
Walker Circulation ◽  
Central American ◽  
Boreal Summer ◽  
Wind Variability ◽  
The Pacific ◽  
Gap Winds

Abstract A transbasin mode (TBM) is identified as the leading mode of interannual surface wind variability over the Intra-Americas Seas across Central America based on empirical orthogonal function analysis. The TBM is associated with variability in Central American gap winds, most closely with the Papagayo jet but with considerable signals over the Gulfs of Tehuantepec and Panama. Although El Niño–Southern Oscillation (ENSO) is the main large-scale forcing, the TBM features a distinct seasonality due to sea level pressure (SLP) adjustments across the Pacific and Atlantic. During July–September, ENSO causes meridional SLP gradient anomalies across Central America, intensifying anomalous geostrophic winds funneling through Papagayo to form the TBM. During wintertime, ENSO peaks but imparts little anomalous SLP gradient across Central America with a weak projection on the TBM because of the competing effects of the Pacific–North American teleconnection and tropospheric Kelvin waves. Besides ENSO, tropical Atlantic sea surface temperature anomalies make a weak contribution to the TBM in boreal summer by strengthening the cross-basin gradient. ENSO and the Atlantic forcing constitute a cross-basin seesaw pattern in SLP, manifested as an anomalous Walker circulation across the tropical Americas. The TBM appears to be part of the low-level branch of the anomalous Walker circulation, which modulates Central American wind jets by orographic effect. This study highlights the seasonality of gap wind variability, and calls for further research into its influence on regional climate.

scholarly journals Interannual Variability of the Global Meridional Overturning Circulation Dominated by Pacific Variability

2020 ◽  
Vol 50 (3) ◽  
pp. 559-574
Author(s):  
Neil F. Tandon ◽  
Oleg A. Saenko ◽  
Mark A. Cane ◽  
Paul J. Kushner
Keyword(s):  
Interannual Variability ◽  
Large Scale ◽  
Southern Oscillation ◽  
Meridional Overturning Circulation ◽  
Ekman Transport ◽  
Prominent Feature ◽  
Overturning Circulation ◽  
Near Surface ◽  
The Pacific ◽  
Meridional Overturning

AbstractThe most prominent feature of the time-mean global meridional overturning circulation (MOC) is the Atlantic MOC (AMOC). However, interannual variability of the global MOC is shown here to be dominated by Pacific MOC (PMOC) variability over the full depth of the ocean at most latitudes. This dominance of interannual PMOC variability is robust across modern climate models and an observational state estimate. PMOC interannual variability has large-scale organization, its most prominent feature being a cross-equatorial cell spanning the tropics. Idealized experiments show that this variability is almost entirely wind driven. Interannual anomalies of zonal mean zonal wind stress produce zonally integrated Ekman transport anomalies that are larger in the Pacific Ocean than in the Atlantic Ocean, simply because the Pacific is wider than the Atlantic at most latitudes. This contrast in Ekman transport variability implies greater variability in the near-surface branch of the PMOC when compared with the near-surface branch of the AMOC. These near-surface variations in turn drive compensating flow anomalies below the Ekman layer. Because the baroclinic adjustment time is longer than a year at most latitudes, these compensating flow anomalies have baroclinic structure spanning the full depth of the ocean. Additional analysis reveals that interannual PMOC variations are the dominant contribution to interannual variations of the global meridional heat transport. There is also evidence of interaction between interannual PMOC variability and El Niño–Southern Oscillation.

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