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Spatiotemporal variation and mechanisms of temperature inversion in the bay of bengal and the eastern equatorial Indian Ocean

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Acta Oceanologica Sinica 2022年第4期41卷 23-39页

作者： K M Azam Chowdhury Wensheng Jiang Guimei Liu Md Kawser Ahmed Shaila Akhter College of Oceanic and Atmospheric Sciences Ocean University of ChinaQingdao 266100China KeyLab of Marine Environment and Ecology of Ministry of Education Ocean University of ChinaQingdao 266100China Department of Oceanography&International Centre for Ocean Governance(ICOG) University of DhakaDhaka 1000Bangladesh National Marine Environmental Forecasting Center Beijing 100081China

In the northern bay of bengal,the existence of intense temperature inversion during winter is a widely accepted ***,occurrences of temperature inversion during other seasons and the spatial distribution within and adjacent to the bay of bengal are not well *** this study,a higher resolution spatiotemporal variation of temperature inversion and its mechanisms are examined with mixed layer heat and salt budget analysis utilizing long-term Argo(2004 to 2020)and RAMA(2007 to 2020)profiles data in the bay of bengal and eastern equatorial Indian Ocean(EEIO).Temperature inversion exists(17.5%of the total 39293 Argo and 51.6%of the 28894 RAMA profiles)throughout the year in the entire study *** shows strong seasonal variation,with the highest occurrences in winter and the lowest in *** winter inversion in the northern bay of bengal,two other regions with frequent temperature inversion are identified in this study for the first time:the northeastern part of the bay of bengal and the eastern part of the EEIO during summer and *** processes of temperature inversion for different subregions are revealed in the current *** of heat(mean~25 W/m;)below the haline-stratified shallow mixed layer leads to a relatively warmer subsurface layer along with the simultaneous cooling tendency in mixed layer,which controls more occurrence of temperature inversion in the northern bay of bengal throughout the *** lower cooling tendency due to net surface heat loss and higher mixed layer salinity leaves the southern part of the bay less supportive to the formation of temperature inversion than the northern *** the EEIO,slightly cooling tendency in the mixed layer along with the subduction of warm-salty Arabian Sea water beneath the cold-fresher bay of bengal water,and downwelling of thermocline creates a favorable environment for forming temperature inversion mainly during summer and *** isothermal layer

关键词： temperature inversion bay of bengal Argo and RAMA data intrusion of the Arabian Sea water eastern equatorial Indian Ocean penetrative heat below mixed layer depth

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Characterization and seasonal distribution of microplastics in the nearshore sediments of the south-east coast of India,bay of bengal

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Frontiers of Environmental Science & Engineering 2022年第1期16卷 129-139页

作者： K.Dhineka M.Sambandam S.K.Sivadas T.Kaviarasan Umakanta Pradhan Mehmuna Begum Pravakar Mishra M.V.Ramana Murthy National Centre for Coastal Research(NCCR) Ministry of Earth Science(MoES)Chennai 600100India*

In view of increasing Microplastics(MPs)contamination in the marine environment and dearth of baseline data,a study was conducted on the abundance,characterization,and seasonal distribution of MPs in the nearshore sediments of the south-east coast of *** samples(n=130)were collected at a distance of 1 km and 10 km from the shore region at varying depths(8–45 m)along the Chennai to Puducherry coast(165 km stretch),representing two seasons,i.e.,south-west(July 2019 and July 2020)and north-east(January 2020)*** average abundance of MPs at the 22 offshore sites along the Chennai to Puducherry coast varied from 9±4.3 to 19±12.9 particles/50 g dry weight,in July 2019 and January 2020,*** 2020 had an average abundance of 10±4.5 particles/50 g dry ***,high levels of MPs were found at 1km stations and transects in proximity to the river inlets,and temporally,the north-east month recorded the maximum *** dominant morphotype was the filament,and the major polymers were polyethylene and *** Electron Microscope(SEM)images revealed the surface irregularity and degradation of MPs due to *** study highlights that high sediment contamination by MPs occurs during heavy rainfall and accumulates closer to river ***,this study suggests that appropriate management of plastic wastes on the landside will reduce MP contamination in the marine environment.

关键词： Microplastics Coastal sediment Characterization bay of bengal India

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Distribution and generic composition of culturable marine actinomycetes from the sediments of Indian continental slope of bay of bengal

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Chinese Journal of Oceanology and Limnology 2008年第2期26卷 166-177页

作者： Surajit DAS P. S. LYLA S. AJMAL KHAN Centre of Advanced Study in Marine Biology Annamalai University Parangipettai-608 502 Tamil Nadu India

Actinomycetes population from continental slope sediment of the bay of bengal was studied. Samples were collected during two voyages of FORV Sagar Sampada in 2004 （May-June） and 2005 （July） respectively from 11 transects （each transect had ca. 200 m, 500 m, and 1 000 m depth stations）. The physicochemical parameters of overlying water, and sediment samples were also recorded. The actinomycete population ranged from 5.17 to 51.94 CFU/g dry sediment weight and 9.38 to 45.22 CFU/g dry sediment weight during the two cruises respectively. No actinomycete colony was isolated from stations in 1 000 m depth. Two-way analysis of variance showed significant variation among stations （ANOVA two-way, P〈0.05）, but no significance was found between the two cruises （ANOVA two-way, P〈0.05）. Populations in stations in 500 m depth in both cruises were higher than that of 200 m depth stations with statistically insignificant difference （ANOVA two-way, P〉0.05）. Three actinomycetes genera were identified. Streptomyces was found to be the dominating one in both the cruises, followed by Micromonospora, and Actinomyces. The spore of Streptomyces isolates showed the abundance in spiral spore chain. Spore surface was smooth. Multiple regression analysis revealed that the influencing physico-chemical factors were sediment pH, sediment temperature, TOC, porosity, salinity, and pressure. The media used in the present study was prepared with seawater. Thus, they may represent an autochthonous marine flora and deny the theory of land runoff carriage into the sea for adaptation to the salinity of the seawater and sediments.

关键词： marine actinomycetes generic composition physico-chemical parameters continental slope bay of bengal

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Abundance and Ecology of Endemic Asterorotalia trispinosa from the Western bay of bengal: Implications for its Application as a Paleomonsoon Proxy

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Acta Geologica Sinica(English Edition) 2017年第6期91卷 2268-2282页

作者： Rajeev SARASWAT Manumalenki MANASA Thejasino SUOKHRIE Mohammad Syed SAALIM Rajiv NIGAM Micropaleontology Laboratory CSIR-National Institute of Oceanography

A total of 97 surface sediment samples were collected from the continental shelf and slope of the western bay of bengal to assess the potential application of Asterorotalia trispinosa as a paleomonsoon proxy. The relative abundance of living as well as total （living and dead） A. trispinosa ranges from being absent to a maximum of-31%. The highest abundance ofA. trispinosa is close to the outfall region of the Ganga-Brahmaputra Rivers and decreases away from the river mouths. Contrary to that, A. trispinosa is rare in front of both the Cauvery and Pennar river outfall regions, in the central part of the western bay of bengal. The living A. trispinosa abundance is the lowest in between two major river systems, viz. Ganga-Brahmaputra-Mahanadi and Krishna-Godavari. The relative abundance of both the total and living A. trispinosa is strongly positively correlated with ambient seawater temperature, and negatively correlated with %Corg and salinity. Based on the spatial distribution, we conclude that A. trispinosa is stenohaline in nature, rather than euryhaline, and further that the increased relative abundance of A. trispinosa indicates warmer and only marginally hyposaline environment. Even though the ecological preference of A. trispinosa suggests it as a potential paleomonsoon proxy, the restricted distribution implies limited application.

关键词： Asterorotalia trispinosa ecology paleomonsoon riverine influx bay of bengal

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Interannual variability in the barrier layer and forcing mechanism in the eastern equatorial Indian Ocean and bay of bengal

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Acta Oceanologica Sinica 2020年第7期39卷 19-31页

作者： Tian Ma Xuhua Cheng Yiquan Qi Jiajia Chen Key Laboratory of Marine Hazards Forecasting Ministry of Natural ResourcesHohai UniversityNanjing 210098China College of Oceanography Hohai UniversityNanjing 210098China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519000China

Interannual variability(IAV)in the barrier layer thickness(BLT)and forcing mechanisms in the eastern equatorial Indian Ocean(EEIO)and bay of bengal(BoB)are examined using monthly Argo data sets during 2002–*** BLT during November–January(NDJ)in the EEIO shows strong IAV,which is associated with the Indian Ocean dipole mode(IOD),with the IOD leading the BLT by two *** the negative IOD phase,the westerly wind anomalies driving the downwelling Kelvin waves increase the isothermal layer depth(ILD).Moreover,the variability in the mixed layer depth(MLD)is *** by the Wyrtki jet,the MLD presents negative anomalies west of 85°E and strong positive anomalies between 85°E and 93°***,the BLT shows positive anomalies except between 86°E and 92°E in the ***,the IAV in the BLT during December–February(DJF)in the BoB is also *** the eastern and northeastern BoB,the IAV in the BLT is remotely forced by equatorial zonal wind stress anomalies associated with the El Ni?o-Southern Oscillation(ENSO).In the western BoB,the regional surface wind forcing-related ENSO modulates the BLT variations.

关键词： barrier layer thickness interannual variability eastern equatorial Indian Ocean bay of bengal

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Annual and interannual variations of sea-level anomaly in the bay of bengal and the Andaman Sea

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Acta Oceanologica Sinica 2007年第6期26卷 13-29页

作者： QIU Yun LI Li YU Weidong HU Jianyu State key laboratory of Marine Environmental Science College of Oceanography and Environmental Science Xiamen University Xiamen 361005 China Third Institute of Oceanography State Oceanic Administration Xiamen 361005 China First Institute of Oceanography State Oceanic Administration Qinddao 266061 China

Annual and interannual variations of sea-level anomaly （SLA） in the bay of bengal and the Andaman Sea are investigated using altimeter - derived SLA data from 1993 to 2003. It is found that the SLA annual variation in the study area can be divided into three phases with distinctive patterns. During the southwest monsoon （May -September）, positive SLA presents in the equatorial region and extends northward along the eastern boundary of the bay, and the SLA distribution in the interior bay appears to be high in the east and low in the west with two cyclonic ceils developing in the north and south of the western bay respectively, between which an anticyclonic cell exists. During the early northeast monsoon （ October - December） , the whole bay is dominated by a large cyclonic cell with the pattern of high SLA in the east and low in the west still retained, and the SLA distribution outside the bay is changed in response to the reversal of the Indian Monsoon Current （IMC） in November. During the late northeast monsoon （January -April） , a large anticyclonic cell of SLA develops in the bay with negative SLA prevailing in the equatorial region and extending northward along the eastern boundary of bay. Therefore, the SLA distribution in the interior bay reverses to be high in the west and low in the east. It is suggested that the SLA annual variation in the bay is primarily driven by the local wind stress curl, involving Sverdrup balance while the abrupt SLA variation during the peak of northeast monsoon may be partly caused by the semiannual fluctuation of wind in the equatorial region. This fast adjustment in the interior bay is induced by the upwelling coastal Kelvin wave excited by the decay of Wyrtki jet during December through January. Besides the annual variation, in the bay, there are obvious SLA fluctuations with the periods of 2 and 3 - 7 a, which are driven by the interannual variability of large - scale wind field in the equatorial region. The coastal Kelvin wav

关键词： bay of bengal sea-level anomaly low-frequency variation satellite altimeter

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Effects of monsoon onset vortex on heat budget in the mixed layer of the bay of bengal

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Journal of Oceanology and Limnology 2020年第6期38卷 1616-1631页

作者： Effects of monsoon onset vortex on heat budget in the mixed layer of the bay of bengalXU Kang LIU Boqi LIU Yu WANG Weiqiang HE Zhuoqi State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou) Guangzhou 511458China Innovation Academy of South China Sea Ecology and Environmental Engineering Chinese Academy of SciencesGuangzhou 510301China State Key Laboratory of Severe Weather and Institute of Climate System Chinese Academy of Meteorological SciencesBeijing 100081China Institute of Deep-sea Science and Engineering Chinese Academy of SciencesSanya 572000China University of Chinese Academy of Sciences Beijing 100049China Laboratory for Regional Oceanography and Numerical Modeling Qingdao National Laboratory for Marine Science and TechnologyQingdao 266071China State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China

We investigated the effects of monsoon onset vortex(MOV)on the mixed layer heat budget in the bay of bengal(BOB)in spring 2003 using the reanalysis *** results suggest that the solar radiation flux penetrating the mixed layer and the existence of barrier layer are both able to modulate the effects of MOV on the evolution of sea surface temperature(SST)in the *** to the formation of BOB MOV,the local SST raised quickly due to mass of solar radiation reaching the sea surface under the clear-sky ***,since the mixed layer was shallow before the onset of the Asian summer monsoon(ASM),some solar radiation flux could penetrate to directly heat the deeper water,which partly offset the warming effect of shortwave *** the other hand,the in-situ SST started to cool due to the upwelling of cold water when the MOV generated over the BOB,along with the rapidly increased surface wind speed and its resultant deeper mixed *** the MOV developed and moved northward,the SST tended to decrease remarkably because of the strong upward surface latent heat flux over the BOB ascribed to the wind-evaporation ***,the MOV-related precipitation brought more fresh water into the upper ocean to produce a thicker barrier layer,whose thermal barrier effect damped the cooling effect of entrainment upwelling on the decrease tendency of the BOB *** other words,the thermal barrier effect could slow down the decreasing trend of the BOB SST even after the onset of ASM,which facilitated the further enhancement of the MOV.

关键词： monsoon onset vortex(MOV) bay of bengal air-sea interaction mixed layer depth barrier layer thickness heat budget analysis

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Seasonal influence of freshwater discharge on spatio-temporal variations in primary productivity, sea surface temperature, and euphotic zone depth in the northern bay of bengal

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Acta Oceanologica Sinica 2024年第6期43卷 1-14页

作者： Hafez Ahmad Felix Jose Md.Simul Bhuyan Md.Nazrul Islam Padmanava Dash Geosystems Research Institute/Department of Geosciences Mississippi State UniversityStarkville 39759USA Department of Oceanography University of ChittagongChittagong 4331Bangladesh Department of Marine&Earth Sciences Florida Gulf Coast UniversityFort Myers 33965USA Bangladesh Oceanographic Research Institute Cox’s Bazar 4730Bangladesh Faculty of Marine Sciences&Fisheries Institute of Marine SciencesUniversity of ChittagongChittagong 4331Bangladesh Department of Geography and Environment Jahangirnagar UniversityDhaka 1342Bangladesh Department of Geosciences Mississippi State UniversityStarkville 39759USA

Ocean productivity is the foundation of marine food web,which continuously removes atmospheric carbon dioxide and supports life at sea and on ***-temporal variability of net primary productivity(NPP),sea surface temperature(SST),sea surface salinity(SSS),mixed layer depth(MLD),and euphotic zone depth(EZD) in the northern B ay of bengal(BoB) during three monsoon seasons were examined in this study based on remote sensing data for the period 2005 to *** compare the NPP distribution between the coastal zones and open BoB,the study area was divided into five zones(Z1-Z5).Results suggest that most productive zones Z2 and Zl are located at the head bay area and are directly influenced by freshwater discharge together with riverine sediment and nutrient *** Z1-Z5,the NPP ranges from 5 315.38 mg/(m^(2)·d) to 346.7 mg/(m^(2)·d)(carbon,since then the same).The highest monthly average NPP of 5 315.38 mg/(m^(2)·d) in February and 5 039.36 mg/(m^(2)·d) in June were observed from Z2,while the lowest monthly average of 346.72 mg/(m^(2)·d) was observed in March from Z4,which is an oceanic *** values vary from 6-154 m for the study area,and it has an inverse correlation with NPP *** is deeper during the summer season and shallower during the wintertime,with a corresponding increase in *** the year,monthly SST shows slight fluctuation for the entire study area,and statistical analysis shows a significant correlation among NPP,and EZD,overall positive between NPP and MLD,whereas no significant correlation among SSS,and SST for the northern ***-term trends in SST and productivity were significantly po sitive in head bay zones but negatively productive in the open *** findings in this study on the distribution of NPP,SST,SSS,MLD,and EZD and their seasonal variability in five different zones of BoB can be used to further improve the management of marine resources and overall environmental condition in response to clim

关键词： chlorophyll a sea surface temperature euphotic zone depth primary productivity Ganges-Brahmaputra ocean color bay of bengal monsoon

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Modulation of Low-Latitude West Wind on Abnormal Track and Intensity of Tropical Cyclone Nargis (2008) in the bay of bengal

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Advances in Atmospheric Sciences 2012年第2期29卷 407-421页

作者： LI Wei-Wei WANG Chunzai WANG Dongxiao YANG Lei DENG Yi State Key Laboratory of Tropical Oceanography South China Sea Institute of OceanologyChinese Academy of ScienceGuangzhou 510301 NOAA/Atlantic Oceanographic and Meteorological Laboratory MiamiFloridaUSA

Tropical cyclone （TC） Nargis （2008） made landfall in Myanmar on 02 May 2008, bringing a storm surge, major flooding, and resulting in a significant death toll. TC Nargis （2008） displayed abnormal features, including rare eastward motion in its late stage, rapid intensification before landing. Using reanalysis data and a numerical model, we investigated how a low-latitude westerly wind modulated TC Nargis’ （2008） track and provided favorable atmospheric conditions for its rapid intensification. More importantly, we found a possible counterbalance effect of flows from the two hemispheres on the TC track in the bay of bengal. Our analysis indicates that a strong westerly wind burst across the bay of bengal, resulting in TC Nargis’ （2008） eastward movement after its recurvature. This sudden enhancement of westerly wind was mainly due to the rapidly intensified mid-level cross-equatorial flow. Our results show that a high-pressure system in the Southern Hemisphere induced this strong, mid-level, cross-equatorial flow. During the rapid intensification period of TC Nargis （2008）, this strong and broad westerly wind also transported a large amount of water vapor to TC Nargis （2008）. Sufficient water vapor gave rise to continuously high and increased mid-level relative humidity, which was favorable to TC Nargis’ （2008） intensification. Condensation of water vapor increased the energy supply, which eventuated the intensification of TC Nargis （2008） to a category 4 on the Saffir-Simpson scale.

关键词： TC Nargis (2008) tropical cyclone westerly wind cross-equatorial flow bay of bengal

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Southwesterly Water Vapor Transport Induced by Tropical Cyclones over the bay of bengal during the South Asian Monsoon Transition Period

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Journal of Meteorological Research 2022年第1期36卷 140-153页

作者： Beiyao LIU Ying LI State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesChina Meteorological AdministrationBeijing 100081 University of Chinese Academy of Sciences Beijing 100049

Based on best-track,outgoing longwave radiation,sea surface temperature,and reanalysis data during 1979-2018,statistical and composite analyses were performed to investigate characteristics of the southwesterly water vapor transport(WVT)induced by bay of bengal(BoB)tropical cyclones(TCs)during the South Asian summer monsoon(SASM)transition *** results show that the BoB TCs mainly occur several days before/after the date of SASM onset(retreat)in May(October-November),thereby imposing an important impact on southwesterly WVT to China in those two *** WVT is significant in the middle and lower troposphere during the bimodal peak periods of BoB TCs,with large values over the east-central BoB,southeastern Tibetan Plateau,and Southwest and South *** WVT is located more northward at 500 hPa than at 700 hPa,reaching close to 35°N and covering the southeastern Tibetan Plateau owing to weakening of the plateau’s blocking effect at upper *** BoB TCs mainly increase the northward and eastward WVT anomalies compared to the climatological ***,the large southerly WVT anomalies are located in the lower troposphere in low-latitude areas,while the large westerly WVT anomalies appear mainly in the middle troposphere in high-latitude *** indicates an enhanced WVT channel where the southwesterly moisture jet first climbs northwards to the southeastern Tibetan Plateau and then turns eastwards to East China under the influence of the BoB ***,the southwesterly WVT during the TC period in May is stronger and more widespread than that in October-November,being about twice the latter in ***,their maximum contributions to the climatological average do not differ much,with maximums of 12%and19%occurring in Southwest China during the bimodal periods,respectively,implying an important role played by the BoB TCs in the WVT.

关键词： tropical cyclones bay of bengal South Asian summer monsoon southwesterly water vapor transport anomalous characteristics

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