Bycatch and discards by Taiwanese large-scale tuna longline fleets in the Indian Ocean

AbstractThe spatial and temporal distribution of upper-tropospheric humidity (UTH) observed by the Sounder for Atmospheric Profiling of Humidity in the Intertropics by Radiometry (SAPHIR)/Megha-Tropiques radiometer is analyzed over two subregions of the Indian Ocean during October–December over 2011–14. The properties of the distribution of UTH were studied with regard to the phase of the Madden–Julian oscillation (active or suppressed) and large-scale advection versus local production of moisture. To address these topics, first, a Lagrangian back-trajectory transport model was used to assess the role of the large-scale transport of air masses in the intraseasonal variability of UTH. Second, the temporal evolution of the distribution of UTH is analyzed using the computation of the higher moments of its probability distribution function (PDF) defined for each time step over the domain. The results highlight significant differences in the PDF of UTH depending on the phase of the MJO. The modeled trajectories ending in the considered domain originate from an area that strongly varies depending on the phases of the MJO: during the active phases, the air masses are spatially constrained within the tropical Indian Ocean domain, whereas a distinct upper-tropospheric (200–150 hPa) westerly flow guides the intraseasonal variability of UTH during the suppressed phases. Statistical relationships between the cloud fractions and the UTH PDF moments of are found to be very similar regardless of the convective activity. However, the occurrence of thin cirrus clouds is associated with a drying of the upper troposphere (enhanced during suppressed phases), whereas the occurrence of thick cirrus anvil clouds appears to be significantly related to a moistening of the upper troposphere.

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KOMPOSISI UKURAN, PERBANDINGAN JENIS KELAMIN, DAN TINGKAT KEMATANGAN GONAD IKAN TODAK BERPARUH PENDEK (Tetrapturus angustirostris) DI SAMUDERAHINDIA

BAWAL Widya Riset Perikanan Tangkap ◽

10.15578/bawal.3.2.2010.123-128 ◽

2017 ◽

Vol 3 (2) ◽

pp. 123

Author(s):

Dian Novianto ◽

Budi Nugraha ◽

Andi Bahtiar

Keyword(s):

Indian Ocean ◽

Sex Ratio ◽

Size Composition ◽

Maturity Stage ◽

Chi Square ◽

Male And Female ◽

Level Ii ◽

Chi Square Test ◽

The Indian Ocean ◽

Tuna Longline

Ikan todak berparuh pendek atau ikan tumbuk atau shortbill spearfish (Tetrapturus angustirostris) merupakan salah satu hasil tangkapan sampingan rawai tuna. Informasi mengenai ikan todak berparuh pendek seperti komposisi ukuran, perbandingan kelamin, dan tingkat kematangan gonadsangat terbatas. Tulisan ini bertujuan untuk menyajikan data dan informasi mengenai aspek biologi ikan todak berparuh pendek yang merupakan hasil tangkapan sampingan dari rawai tuna yang beroperasi di Samudera Hindia. Penelitian ini dilakukan pada bulan September sampai Desember 2008 di perairan Samudera Hindia. Hasil penelitian menunjukan bahwa ikan todak berparuh pendek memiliki kisaran panjang tubuh 135-175 cmLJFL dan modus pada kisaran 155-165 cmLJFL.Perbandingan jenis kelamin ikan jantan dan betina 1:13,5, berdasarkan atas hasil uji chi-square menunjukan bahwa rasio ikan jantan dan betina pada periode penelitian ini tidak seimbang. Pada bulan September ikan todak berparuh pendek betina didominansi oleh tingkat kematangan gonad IIsebesar 66,7%, bulan Oktober oleh tingkat kematangan gonad V sebesar 46,2%, bulan Nopember oleh tingkat kematangan gonad II sebesar 53,3%, sedangkan pada bulan Desember oleh tingkat kematangan gonad III sebesar 42,9%. Pada bulan Nopember sampai Desember terlihat bahwa tingkat kematangan gonad V mulai berkurang, hal ini menunjukan bahwa pada bulan Nopember sampai Desember diduga banyak ikan todak berparuh pendek betina yang sudah memijah. Shortbill Spearfish (Tetrapturus angustirostris) is one of bycatch of tuna longline. Information about shortbill spearfish on the size composition, sex ratio, and maturity stage is still very limited. The objective this paper is to present the data and information about shortbill spearfish which is a bycatch of tuna longline that operated in the Indian Ocean. Research was conducted during September until December 2008 in Indian Ocean. The results showed that the shortbill spearfish have body length about 135-175 cmLJFL and modes in 155-165 cmLJFL. Sex ratio of the male and female was 1:13.5. Based on chi-square test showed that the ratio of male and female in the period of the study was not balanced. In September, the female stage maturity was dominated by level II of 66.7%, October by level V of 46.2%, November by level II of 53.3%, and December by level III of 42.9%. During November until December showed that the maturity stage of level V was decreased, this shows that in this time the female of shortbill spearfish was spawned.

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Interannual Rainfall Extremes over Southwest Western Australia Linked to Indian Ocean Climate Variability

Journal of Climate ◽

10.1175/jcli3700.1 ◽

2006 ◽

Vol 19 (10) ◽

pp. 1948-1969 ◽

Cited By ~ 84

Author(s):

Matthew H. England ◽

Caroline C. Ummenhofer ◽

Agus Santoso

Keyword(s):

Indian Ocean ◽

Western Australia ◽

Wind Field ◽

Large Scale ◽

Extreme Rainfall ◽

Ekman Transport ◽

Eastern Indian Ocean ◽

Basin Scale ◽

Rainfall Extremes ◽

The Indian Ocean

Abstract Interannual rainfall extremes over southwest Western Australia (SWWA) are examined using observations, reanalysis data, and a long-term natural integration of the global coupled climate system. The authors reveal a characteristic dipole pattern of Indian Ocean sea surface temperature (SST) anomalies during extreme rainfall years, remarkably consistent between the reanalysis fields and the coupled climate model but different from most previous definitions of SST dipoles in the region. In particular, the dipole exhibits peak amplitudes in the eastern Indian Ocean adjacent to the west coast of Australia. During dry years, anomalously cool waters appear in the tropical/subtropical eastern Indian Ocean, adjacent to a region of unusually warm water in the subtropics off SWWA. This dipole of anomalous SST seesaws in sign between dry and wet years and appears to occur in phase with a large-scale reorganization of winds over the tropical/subtropical Indian Ocean. The wind field alters SST via anomalous Ekman transport in the tropical Indian Ocean and via anomalous air–sea heat fluxes in the subtropics. The winds also change the large-scale advection of moisture onto the SWWA coast. At the basin scale, the anomalous wind field can be interpreted as an acceleration (deceleration) of the Indian Ocean climatological mean anticyclone during dry (wet) years. In addition, dry (wet) years see a strengthening (weakening) and coinciding southward (northward) shift of the subpolar westerlies, which results in a similar southward (northward) shift of the rain-bearing fronts associated with the subpolar front. A link is also noted between extreme rainfall years and the Indian Ocean Dipole (IOD). Namely, in some years the IOD acts to reinforce the eastern tropical pole of SST described above, and to strengthen wind anomalies along the northern flank of the Indian Ocean anticyclone. In this manner, both tropical and extratropical processes in the Indian Ocean generate SST and wind anomalies off SWWA, which lead to moisture transport and rainfall extremes in the region. An analysis of the seasonal evolution of the climate extremes reveals a progressive amplification of anomalies in SST and atmospheric circulation toward a wintertime maximum, coinciding with the season of highest SWWA rainfall. The anomalies in SST can appear as early as the summertime months, however, which may have important implications for predictability of SWWA rainfall extremes.

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Distinctive Roles of Air–Sea Coupling on Different MJO Events: A New Perspective Revealed from the DYNAMO/CINDY Field Campaign*

Monthly Weather Review ◽

10.1175/mwr-d-14-00221.1 ◽

2015 ◽

Vol 143 (3) ◽

pp. 794-812 ◽

Cited By ~ 31

Author(s):

Xiouhua Fu ◽

Wanqiu Wang ◽

June-Yi Lee ◽

Bin Wang ◽

Kazuyoshi Kikuchi ◽

...

Keyword(s):

Indian Ocean ◽

Large Scale ◽

Essential Role ◽

Intraseasonal Variability ◽

Physical Processes ◽

Field Campaign ◽

Strongly Coupled ◽

The Indian Ocean ◽

New Perspective ◽

Sst Anomalies

Abstract Previous observational analysis and modeling studies indicate that air–sea coupling plays an essential role in improving MJO simulations and extending MJO forecasting skills. However, whether the SST feedback plays an indispensable role for the existence of the MJO remains controversial, and the precise physical processes through which the SST feedback may lead to better MJO simulations and forecasts remain elusive. The DYNAMO/Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY) field campaign recently completed over the Indian Ocean reveals a new perspective and provides better data to improve understanding of the MJO. It is found that among the five MJO events that occurred during the DYNAMO/CINDY field campaign, only two MJO events (the November and March ones) have robust SST anomalies associated with them. For the other three MJO events (the October, December, and January ones), no coherent SST anomalies are observed. This observational scenario suggests that the roles of air–sea coupling on the MJO vary greatly from event to event. To elucidate the varying roles of air–sea coupling on different MJO events, a suite of hindcast experiments was conducted with a particular focus on the October and November MJO events. The numerical results confirm that the October MJO is largely controlled by atmospheric internal dynamics, while the November MJO is strongly coupled with underlying ocean. For the November MJO event, the positive SST anomalies significantly improve MJO forecasting by enhancing the response of a Kelvin–Rossby wave couplet, which prolongs the feedback between convection and large-scale circulations, and thus favors the development of stratiform rainfall, in turn, facilitating the production of eddy available potential energy and significantly amplifying the intensity of the model November MJO.

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Distribution of Bigeye Tuna in the Indian Ocean as Seen from Tuna Longline Catches.

NIPPON SUISAN GAKKAISHI ◽

10.2331/suisan.57.1683 ◽

1991 ◽

Vol 57 (9) ◽

pp. 1683-1687

Author(s):

Masahiko Mohri ◽

Eiji Hanamoto ◽

Shoichi Takeuchi

Keyword(s):

Indian Ocean ◽

Bigeye Tuna ◽

The Indian Ocean ◽

Tuna Longline

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Remote influences on the Indian monsoon Low-Level Jet intraseasonal variations

10.5194/egusphere-egu2020-19411 ◽

2020 ◽

Author(s):

Takeshi Izumo ◽

Maratt Satheesan Swathi ◽

Matthieu Lengaigne ◽

Jérôme Vialard ◽

Dr Ramesh Kumar

Keyword(s):

Indian Ocean ◽

Indian Summer Monsoon ◽

Arabian Sea ◽

Large Scale ◽

Indian Monsoon ◽

Westerly Wind ◽

Low Level ◽

Intraseasonal Variations ◽

The Indian Ocean ◽

Low Level Jet

A strong Low-Level Jet (LLJ), also known as the Findlater jet, develops over the Arabian Sea during the Indian summer monsoon. This jet is an essential source of moisture for monsoonal rainfall over the densely-populated Indian subcontinent and is a key contributor to the Indian Ocean oceanic productivity by sustaining the western Arabian Sea upwelling systems. The LLJ intensity fluctuates intraseasonally within the ~20- to 90-day band, in relation with the northward-propagating active and break phases of the Indian summer monsoon. Our observational analyses reveal that these large-scale regional convective perturbations&#160; only explain about half of the intraseasonal LLJ variance, the other half being unrelated to large-scale convective perturbations over the Indian Ocean. We show that convective fluctuations in two regions outside the Indian Ocean can remotely force a LLJ intensification, four days later. Enhanced atmosphericdeep convection over the northwestern tropical Pacific yields westerly wind anomalies that propagate westward to the Arabian Sea as baroclinic atmospheric Rossby Waves. Suppressed convection over the eastern Pacific / North American monsoon region yields westerly wind anomalies that propagate eastward to the Indian Ocean as dry baroclinic equatorial Kelvin waves. Those largely independent remote influences jointly explain ~40% of the intraseasonal LLJ variance that is not related to convective perturbations over the Indian Ocean (i.e. ~20% of the total), with the northwestern Pacific contributing twice as much as the eastern Pacific. Taking into account these two remote influences should thus enhance the ability to predict the LLJ.&#160;Related reference:&#160;Swathi M.S, Takeshi Izumo, Matthieu Lengaigne, J&#233;r&#244;me Vialard and M.R. Ramesh Kumar:Remote influences on the Indian monsoon Low-Level Jet intraseasonal variations, accepted in Climate Dynamics.

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An MJO Simulated by the NICAM at 14- and 7-km Resolutions

Monthly Weather Review ◽

10.1175/2009mwr2965.1 ◽

2009 ◽

Vol 137 (10) ◽

pp. 3254-3268 ◽

Cited By ~ 47

Author(s):

Ping Liu ◽

Masaki Satoh ◽

Bin Wang ◽

Hironori Fudeyasu ◽

Tomoe Nasuno ◽

...

Keyword(s):

Indian Ocean ◽

Large Scale ◽

Atmospheric Model ◽

Easterly Wind ◽

Low Level ◽

Central Indian Ocean ◽

Simulated Event ◽

The Indian Ocean ◽

Substantial Bias ◽

The Tropics

Abstract This study discloses detailed Madden–Julian oscillation (MJO) characteristics in the two 30-day integrations of the global cloud-system-resolving Nonhydrostatic Icosahedral Atmospheric Model (NICAM) using the all-season real-time multivariate MJO index of Wheeler and Hendon. The model anomaly is derived by excluding the observed climatology because the simulation is sufficiently realistic. Results show that the MJO has a realistic evolution in amplitude pattern, geographical locations, eastward propagation, and baroclinic- and westward-tilted structures. In the central Indian Ocean, convection develops with the low-level easterly wind anomaly then matures where the low-level easterly and westerly anomalies meet. Anomalous moisture tilts slightly with height. In contrast, over the western Pacific, the convection grows with a low-level westerly anomaly. Moisture fluctuations, leading convection in eastward propagation, tilt clearly westward with height. The frictional moisture convergence mechanism operates to maintain the MJO. Such success can be attributed to the explicit representation of the interactions between convection and large-scale circulations. The simulated event, however, grows faster in phases 2 and 3, and peaks with 30% higher amplitude than that observed, although the 7-km version shows slight improvement. The fast-growth phases are induced by the fast-growing low-level convergence in the Indian Ocean and the strongly biased ITCZ in the west Pacific when the model undergoes a spinup. The simulated OLR has a substantial bias in the tropics. Possible solutions to the deficiencies are discussed.

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Progress in understanding of Indian Ocean circulation, variability, air-sea exchange and impacts on biogeochemistry

10.5194/os-2021-1 ◽

2021 ◽

Author(s):

Helen E. Phillips ◽

Amit Tandon ◽

Ryo Furue ◽

Raleigh Hood ◽

Caroline Ummenhofer ◽

...

Keyword(s):

Indian Ocean ◽

Climate Variability ◽

Ocean Circulation ◽

Large Scale ◽

New Technologies ◽

Heat Content ◽

Deep Ocean ◽

Small Scale ◽

Circulation Patterns ◽

The Indian Ocean

Abstract. Over the past decade, our understanding of the Indian Ocean has advanced through concerted efforts toward measuring the ocean circulation and its water properties, detecting changes in water masses, and linking physical processes to ecologically important variables. New circulation pathways and mechanisms have been discovered, which control atmospheric and oceanic mean state and variability. This review brings together new understanding of the ocean-atmosphere system in the Indian Ocean since the last comprehensive review, describing the Indian Ocean circulation patterns, air-sea interactions and climate variability. The second International Indian Ocean Expedition (IIOE-2) and related efforts have motivated the application of new technologies to deliver higher-resolution observations and models of Indian Ocean processes. As a result we are discovering the importance of small scale processes in setting the large-scale gradients and circulation, interactions between physical and biogeochemical processes, interactions between boundary currents and the interior, and between the surface and the deep ocean. In the last decade we have seen rapid warming of the Indian Ocean overlaid with extremes in the form of marine heatwaves. These events have motivated studies that have delivered new insight into the variability in ocean heat content and exchanges in the Indian Ocean, and climate variability on interannual to decadal timescales.This synthesis paper reviews the advances in these areas in the last decade.

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