Pub Date : 2021-02-11DOI: 10.1080/1755876X.2021.1884405
D. Byrne, K. Horsburgh, J. Williams
ABSTRACT Storm surges are coastal sea-level variations caused by meteorological conditions. It is vital that they are forecasted accurately to reduce the potential for financial damage and loss of life. In this study, we investigate how effectively the variational assimilation of sparse sea level observations from tide gauges can be used for operational forecasting in the North Sea. Novel data assimilation ideas are considered and evaluated: a new shortest-path method for generating improved distance-based correlations in the presence of coastal boundaries and an adaptive error covariance model. An assimilation setup is validated by removing selections of tide gauges from the assimilation procedure for a North Sea case study. These experiments show widespread improvements in RMSE and correlations, reaching up to 16 cm and 0.7 (respectively) at some locations. Simulated forecast experiments show RMSE improvements of up to 5 cm for the first 24 h of forecasting, which is useful operationally. Beyond 24 h, improvements quickly diminish however. Using the setup based on the shortest path algorithm shows little difference when compared to a simpler Euclidean method at most locations. Analysis of this event shows that improvements due to data assimilation are bounded and relatively short lived.
{"title":"Variational data assimilation of sea surface height into a regional storm surge model: Benefits and limitations","authors":"D. Byrne, K. Horsburgh, J. Williams","doi":"10.1080/1755876X.2021.1884405","DOIUrl":"https://doi.org/10.1080/1755876X.2021.1884405","url":null,"abstract":"ABSTRACT Storm surges are coastal sea-level variations caused by meteorological conditions. It is vital that they are forecasted accurately to reduce the potential for financial damage and loss of life. In this study, we investigate how effectively the variational assimilation of sparse sea level observations from tide gauges can be used for operational forecasting in the North Sea. Novel data assimilation ideas are considered and evaluated: a new shortest-path method for generating improved distance-based correlations in the presence of coastal boundaries and an adaptive error covariance model. An assimilation setup is validated by removing selections of tide gauges from the assimilation procedure for a North Sea case study. These experiments show widespread improvements in RMSE and correlations, reaching up to 16 cm and 0.7 (respectively) at some locations. Simulated forecast experiments show RMSE improvements of up to 5 cm for the first 24 h of forecasting, which is useful operationally. Beyond 24 h, improvements quickly diminish however. Using the setup based on the shortest path algorithm shows little difference when compared to a simpler Euclidean method at most locations. Analysis of this event shows that improvements due to data assimilation are bounded and relatively short lived.","PeriodicalId":50105,"journal":{"name":"Journal of Operational Oceanography","volume":"21 1","pages":"1 - 14"},"PeriodicalIF":3.1,"publicationDate":"2021-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82237726","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-02-08DOI: 10.1080/1755876X.2021.1883293
M. de Vos, Michael A. Barnes, L. Biddle, S. Swart, Carla-Louise Ramjukadh, M. Vichi
ABSTRACT Antarctic sea ice is prevalently seen as a major player in the climate system, but it is also an important factor in polar maritime safety. Remote sensing and forecasting of Southern Ocean sea ice at time scales suitable for navigation and research planning remain challenging. In this study, numerical sea ice drift forecasts are assessed from the perspective of informing shipping operations. A series of tests is performed to ascertain whether an operational global ocean and sea ice model and a simple free-drift model can provide accurate drift estimates over short lead times. Both approaches are evaluated against ice drift measurements from buoys deployed during two research cruises in the Southern Ocean marginal ice zone during winter and spring. The numerical forecast model was able to forecast sea ice trajectories over 24 h with an average position error of 16.6 km during winter and 9.2 km during spring. The simpler free-drift model, using empirically optimised wind scaling, returned an average position error of 15.9 and 9.3 km during winter and spring respectively. Model skill for both the dynamical and free-drift models is lower in winter than in spring. Free-drift model skill appears linked with sea ice consolidation, which may assist in determining when and where this approach is fit for purpose. Lingering uncertainties regarding the rheological representation of sea ice in the dynamical model and the quality of the wind and ocean forcing remain, potentially affecting model skill over tactical navigation time frames.
{"title":"Evaluating numerical and free-drift forecasts of sea ice drift during a Southern Ocean research expedition: An operational perspective","authors":"M. de Vos, Michael A. Barnes, L. Biddle, S. Swart, Carla-Louise Ramjukadh, M. Vichi","doi":"10.1080/1755876X.2021.1883293","DOIUrl":"https://doi.org/10.1080/1755876X.2021.1883293","url":null,"abstract":"ABSTRACT Antarctic sea ice is prevalently seen as a major player in the climate system, but it is also an important factor in polar maritime safety. Remote sensing and forecasting of Southern Ocean sea ice at time scales suitable for navigation and research planning remain challenging. In this study, numerical sea ice drift forecasts are assessed from the perspective of informing shipping operations. A series of tests is performed to ascertain whether an operational global ocean and sea ice model and a simple free-drift model can provide accurate drift estimates over short lead times. Both approaches are evaluated against ice drift measurements from buoys deployed during two research cruises in the Southern Ocean marginal ice zone during winter and spring. The numerical forecast model was able to forecast sea ice trajectories over 24 h with an average position error of 16.6 km during winter and 9.2 km during spring. The simpler free-drift model, using empirically optimised wind scaling, returned an average position error of 15.9 and 9.3 km during winter and spring respectively. Model skill for both the dynamical and free-drift models is lower in winter than in spring. Free-drift model skill appears linked with sea ice consolidation, which may assist in determining when and where this approach is fit for purpose. Lingering uncertainties regarding the rheological representation of sea ice in the dynamical model and the quality of the wind and ocean forcing remain, potentially affecting model skill over tactical navigation time frames.","PeriodicalId":50105,"journal":{"name":"Journal of Operational Oceanography","volume":"5 1","pages":"187 - 203"},"PeriodicalIF":3.1,"publicationDate":"2021-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85391879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-15DOI: 10.1080/1755876X.2021.1872894
U. Nielsen
ABSTRACT The article presents a study investigating the level of variation in sea state parameters encountered by sailing ships crossing the oceans. The sea state parameters have been obtained from a reanalysis, in this case the ERA5. The study is based on the use of different interpolation schemes to compute parameters in geographical positions off the fixed grid. It is shown that the variation in sea state parameters can be significant. Consequently, in case of sailing ships, covering relatively long distances in a short time (30–60 min), it is recommended to rely on bilinear interpolation rather than nearest neighbour. The variation in the sea state parameters is, in fact, at a level which means that the normal assumption of a stationary seaway in periods up to 3 h likely is violated for ships sailing the typical service speed (15–20+ kt).
{"title":"Spatio-temporal variation in sea state parameters along virtual ship route paths","authors":"U. Nielsen","doi":"10.1080/1755876X.2021.1872894","DOIUrl":"https://doi.org/10.1080/1755876X.2021.1872894","url":null,"abstract":"ABSTRACT The article presents a study investigating the level of variation in sea state parameters encountered by sailing ships crossing the oceans. The sea state parameters have been obtained from a reanalysis, in this case the ERA5. The study is based on the use of different interpolation schemes to compute parameters in geographical positions off the fixed grid. It is shown that the variation in sea state parameters can be significant. Consequently, in case of sailing ships, covering relatively long distances in a short time (30–60 min), it is recommended to rely on bilinear interpolation rather than nearest neighbour. The variation in the sea state parameters is, in fact, at a level which means that the normal assumption of a stationary seaway in periods up to 3 h likely is violated for ships sailing the typical service speed (15–20+ kt).","PeriodicalId":50105,"journal":{"name":"Journal of Operational Oceanography","volume":"90 1","pages":"169 - 186"},"PeriodicalIF":3.1,"publicationDate":"2021-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80451261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-13DOI: 10.1080/1755876X.2020.1846267
N. Aditya, K. Sandhya, R. Harikumar, T. M. Balakrishnan Nair
ABSTRACT Fishing is the most dangerous profession in the world. To reduce the number of accidents caused by capsizing of vessels, Indian National Centre for Ocean Information Services (INCOIS) has designed and developed an advisory and forecast services system for the Indian ocean regime, which warns users against potential zones and times at which vessel overturning can take place, three days in advance. This paper discusses the development and various aspects of such a system, its decision-making mechanism, and the Standard Operating Procedure (SOP). Warning advisories issued by the system are based upon a newly coined index-Boat Safety Index (BSI). The advisory system is verified with a few real-life incidents of the past. The refinement of the advisory system is planned by updating suitable thresholds for the indices based upon regular feedback from the users. The boats operating along the Indian coast are classified into different categories based upon their beam size, and category-specific advisories are issued.
{"title":"Development of small vessel advisory and forecast services system for safe navigation and operations at sea","authors":"N. Aditya, K. Sandhya, R. Harikumar, T. M. Balakrishnan Nair","doi":"10.1080/1755876X.2020.1846267","DOIUrl":"https://doi.org/10.1080/1755876X.2020.1846267","url":null,"abstract":"ABSTRACT Fishing is the most dangerous profession in the world. To reduce the number of accidents caused by capsizing of vessels, Indian National Centre for Ocean Information Services (INCOIS) has designed and developed an advisory and forecast services system for the Indian ocean regime, which warns users against potential zones and times at which vessel overturning can take place, three days in advance. This paper discusses the development and various aspects of such a system, its decision-making mechanism, and the Standard Operating Procedure (SOP). Warning advisories issued by the system are based upon a newly coined index-Boat Safety Index (BSI). The advisory system is verified with a few real-life incidents of the past. The refinement of the advisory system is planned by updating suitable thresholds for the indices based upon regular feedback from the users. The boats operating along the Indian coast are classified into different categories based upon their beam size, and category-specific advisories are issued.","PeriodicalId":50105,"journal":{"name":"Journal of Operational Oceanography","volume":"13 1","pages":"52 - 67"},"PeriodicalIF":3.1,"publicationDate":"2020-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81469555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-10DOI: 10.1080/1755876X.2020.1846266
Radharani Sen, Suchita Pandey, Sumit Dandapat, P. A. Francis, A. Chakraborty
ABSTRACT This study investigates the seasonal transport variability of the North Indian Ocean (NIO) boundary currents, in particular, the East India Coastal Current (EICC) in the Bay of Bengal (BoB), West India Coastal Current (WICC) in the Arabian Sea (AS) and Somali Current (SC) in the Equatorial Indian Ocean (EIO) using a high-resolution Regional Ocean Modeling System (ROMS) with climatological river input. The simulation result indicates that northward EICC peaks in March and its mean transport is 2.65 Sv during February to April. The southward EICC extends down to 200 m depth and transports 0.67 Sv during October–December. Northward WICC which extends down to 100 m depth transports 0.31 Sv along the west coast of India during the winter monsoon. Southwestward SC flows between 6.5°N to 3°N, and northeastward cross-equatorial SC goes up to 11°N along the Somali coast. Northeastward SC which is the strongest coastal current in the NIO transports 13.05 Sv during the summer monsoon. The average transport of southwestward SC is 2.57 Sv only. The study suggests that wind stress and wind stress curl (WSC) plays a vital role in the semiannual reversal of transport and remote forcing modulated by equatorial wind anomalies dominates the southward EICC transport.
{"title":"A numerical study on seasonal transport variability of the North Indian Ocean boundary currents using Regional Ocean Modeling System (ROMS)","authors":"Radharani Sen, Suchita Pandey, Sumit Dandapat, P. A. Francis, A. Chakraborty","doi":"10.1080/1755876X.2020.1846266","DOIUrl":"https://doi.org/10.1080/1755876X.2020.1846266","url":null,"abstract":"ABSTRACT This study investigates the seasonal transport variability of the North Indian Ocean (NIO) boundary currents, in particular, the East India Coastal Current (EICC) in the Bay of Bengal (BoB), West India Coastal Current (WICC) in the Arabian Sea (AS) and Somali Current (SC) in the Equatorial Indian Ocean (EIO) using a high-resolution Regional Ocean Modeling System (ROMS) with climatological river input. The simulation result indicates that northward EICC peaks in March and its mean transport is 2.65 Sv during February to April. The southward EICC extends down to 200 m depth and transports 0.67 Sv during October–December. Northward WICC which extends down to 100 m depth transports 0.31 Sv along the west coast of India during the winter monsoon. Southwestward SC flows between 6.5°N to 3°N, and northeastward cross-equatorial SC goes up to 11°N along the Somali coast. Northeastward SC which is the strongest coastal current in the NIO transports 13.05 Sv during the summer monsoon. The average transport of southwestward SC is 2.57 Sv only. The study suggests that wind stress and wind stress curl (WSC) plays a vital role in the semiannual reversal of transport and remote forcing modulated by equatorial wind anomalies dominates the southward EICC transport.","PeriodicalId":50105,"journal":{"name":"Journal of Operational Oceanography","volume":"92 1","pages":"32 - 51"},"PeriodicalIF":3.1,"publicationDate":"2020-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90659489","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-09DOI: 10.1080/1755876X.2020.1843298
K. Chakraborty, A. Lotliker, G. Gupta, V. Narayanan Nampoothiri S., A. Paul, Jayashree Ghosh, Trishneeta Bhattacharya, S. K. Baliarsingh, A. Samanta
ABSTRACT This study describes an assessment of an ocean-ecosystem model in simulating marine ecosystem dynamics in the Indian coastal waters. Long-term sustained in-situ observations of temperature, salinity, chlorophyll-a and dissolved oxygen (DO) collected in the coastal waters of India, and ship-based observations are used for this assessment. The model captures observed trend of temperature, salinity and chlorophyll-a with high correlation in both eastern and western shelf waters except for salinity and DO along west and DO along east coast. The model performs very well in simulating the Indian coastal shelf ecosystem dynamics. The seasonal occurrence of prominent phytoplankton bloom in the central-east coast during pre-monsoon, south-west coast during monsoon and north-west coast during post-monsoon is realistically reproduced by the model. The model also reproduces the seasonal presence of significantly low DO content in the upwelled water at a shallow depth leading to coastal hypoxia in the south-west and central-east coast of India during summer monsoon. A fine-tuned model is useful in understanding better Indian coastal shelf ecosystem and predicting future changes in time and space, like the occurrence of coastal hypoxia or anticipating phytoplankton blooms. Such information is useful for predicting potential fishing grounds in coastal waters and fisheries management.
{"title":"Assessment of an ocean-ecosystem model in simulating the Indian coastal marine ecosystem dynamics","authors":"K. Chakraborty, A. Lotliker, G. Gupta, V. Narayanan Nampoothiri S., A. Paul, Jayashree Ghosh, Trishneeta Bhattacharya, S. K. Baliarsingh, A. Samanta","doi":"10.1080/1755876X.2020.1843298","DOIUrl":"https://doi.org/10.1080/1755876X.2020.1843298","url":null,"abstract":"ABSTRACT This study describes an assessment of an ocean-ecosystem model in simulating marine ecosystem dynamics in the Indian coastal waters. Long-term sustained in-situ observations of temperature, salinity, chlorophyll-a and dissolved oxygen (DO) collected in the coastal waters of India, and ship-based observations are used for this assessment. The model captures observed trend of temperature, salinity and chlorophyll-a with high correlation in both eastern and western shelf waters except for salinity and DO along west and DO along east coast. The model performs very well in simulating the Indian coastal shelf ecosystem dynamics. The seasonal occurrence of prominent phytoplankton bloom in the central-east coast during pre-monsoon, south-west coast during monsoon and north-west coast during post-monsoon is realistically reproduced by the model. The model also reproduces the seasonal presence of significantly low DO content in the upwelled water at a shallow depth leading to coastal hypoxia in the south-west and central-east coast of India during summer monsoon. A fine-tuned model is useful in understanding better Indian coastal shelf ecosystem and predicting future changes in time and space, like the occurrence of coastal hypoxia or anticipating phytoplankton blooms. Such information is useful for predicting potential fishing grounds in coastal waters and fisheries management.","PeriodicalId":50105,"journal":{"name":"Journal of Operational Oceanography","volume":"3 1","pages":"137 - 155"},"PeriodicalIF":3.1,"publicationDate":"2020-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82408372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-06DOI: 10.1080/1755876X.2020.1840245
G. Sharma, K. Patnaik
ABSTRACT Coringa Mangroves in the Kakinada Bay have evolved as the second-largest mangroves in the East Coast of India over the last century. The Coringa Mangrove shoreline has accreted considerably in the past decades as observed from the satellite imageries, adding value to the natural biodiversity of flora and fauna. This study is focused on quantifying the long term changes of Coringa mangrove shoreline using the Landsat imageries for years 1977, 1988, 2000, and 2013 using the Digital Shoreline Analysis System. For a mangrove shoreline length of 20.5 km, 41 transects were cast at an interval of 500 m for calculating the change and their migration distance using three statistical methods, namely End Point Rate (EPR), Net Shoreline Movement (NSM) and Linear Regression Rate (LRR). Results showed that there was considerable growth of mangroves in the bay leading to the seaward migration of the mangrove shoreline from the year 1977–2013. The study observed the difference in the mangrove shoreline migration dynamics in the South-eastern (near the bottom of the spit) and the western part of the Kakinada Bay. The calculated average degradation rate due to erosion is −5.19 m.yr−1 and the average accretion rate leading to their growth is 14.83 m.yr−1 for all transects of the 20.5 km mangrove shoreline stretch during this period. The results hold importance as they help in identifying the regions prone to mangrove degradation and enable management planning for the protection of the eroding stretch of the mangrove shoreline.
{"title":"Assessment of Coringa Mangrove shoreline migration using geospatial techniques","authors":"G. Sharma, K. Patnaik","doi":"10.1080/1755876X.2020.1840245","DOIUrl":"https://doi.org/10.1080/1755876X.2020.1840245","url":null,"abstract":"ABSTRACT Coringa Mangroves in the Kakinada Bay have evolved as the second-largest mangroves in the East Coast of India over the last century. The Coringa Mangrove shoreline has accreted considerably in the past decades as observed from the satellite imageries, adding value to the natural biodiversity of flora and fauna. This study is focused on quantifying the long term changes of Coringa mangrove shoreline using the Landsat imageries for years 1977, 1988, 2000, and 2013 using the Digital Shoreline Analysis System. For a mangrove shoreline length of 20.5 km, 41 transects were cast at an interval of 500 m for calculating the change and their migration distance using three statistical methods, namely End Point Rate (EPR), Net Shoreline Movement (NSM) and Linear Regression Rate (LRR). Results showed that there was considerable growth of mangroves in the bay leading to the seaward migration of the mangrove shoreline from the year 1977–2013. The study observed the difference in the mangrove shoreline migration dynamics in the South-eastern (near the bottom of the spit) and the western part of the Kakinada Bay. The calculated average degradation rate due to erosion is −5.19 m.yr−1 and the average accretion rate leading to their growth is 14.83 m.yr−1 for all transects of the 20.5 km mangrove shoreline stretch during this period. The results hold importance as they help in identifying the regions prone to mangrove degradation and enable management planning for the protection of the eroding stretch of the mangrove shoreline.","PeriodicalId":50105,"journal":{"name":"Journal of Operational Oceanography","volume":"39 1","pages":"126 - 135"},"PeriodicalIF":3.1,"publicationDate":"2020-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82604028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-09-10DOI: 10.1080/1755876X.2020.1817659
R. Roy Chowdhury, S. Prasanna Kumar, A. Chakraborty
ABSTRACT Madi was a category-2 cyclonic storm formed over the south-western Bay of Bengal (BoB) in December 2013. It formed on 6th December as a depression, and by 8th December it became a very severe cyclonic storm. Some unique features of Madi were: (a) an unexpected reduction in the intensity during its north-westward movement, (b) sudden change in track by almost 180o in a south-westerly direction, and (c) swift dissipation in the open ocean while moving over cold-core eddies during its south-westward movement. The rapid weakening in intensity before track reversal occurred mainly due to its passage over cold-core eddies, where the upper-ocean heat content was reduced due to eddy-pumping of cold water from the subsurface. An analysis of the eddy-feedback factor reiterated that the slower movement of the cyclone was due to the cold-core eddy. When the cyclone entered into the cold-core eddy region, it slowed-down and changed its track towards a south-westerly direction under the influence of prevailing north-easterly winds. The biogeochemical response of Madi estimated using the satellite remote sensing and Bio Argo data showed an increase in Chlorophyll-a (Chl-a) concentration from 0.2-0.4–2.7 mg/m3, while the net primary productivity (NPP) increased from 320 to 2500 mg C/m2 /day, both of which were about 7 and 8 times respectively higher than the before-cyclone values. The CO2 flux showed a 4 times increase from its pre-cyclone value of 3.5 mmol/m2 /day, indicating that BoB becomes a strong source to the atmosphere during the cyclone Madi period.
{"title":"A study on the physical and biogeochemical responses of the Bay of Bengal due to cyclone Madi","authors":"R. Roy Chowdhury, S. Prasanna Kumar, A. Chakraborty","doi":"10.1080/1755876X.2020.1817659","DOIUrl":"https://doi.org/10.1080/1755876X.2020.1817659","url":null,"abstract":"ABSTRACT Madi was a category-2 cyclonic storm formed over the south-western Bay of Bengal (BoB) in December 2013. It formed on 6th December as a depression, and by 8th December it became a very severe cyclonic storm. Some unique features of Madi were: (a) an unexpected reduction in the intensity during its north-westward movement, (b) sudden change in track by almost 180o in a south-westerly direction, and (c) swift dissipation in the open ocean while moving over cold-core eddies during its south-westward movement. The rapid weakening in intensity before track reversal occurred mainly due to its passage over cold-core eddies, where the upper-ocean heat content was reduced due to eddy-pumping of cold water from the subsurface. An analysis of the eddy-feedback factor reiterated that the slower movement of the cyclone was due to the cold-core eddy. When the cyclone entered into the cold-core eddy region, it slowed-down and changed its track towards a south-westerly direction under the influence of prevailing north-easterly winds. The biogeochemical response of Madi estimated using the satellite remote sensing and Bio Argo data showed an increase in Chlorophyll-a (Chl-a) concentration from 0.2-0.4–2.7 mg/m3, while the net primary productivity (NPP) increased from 320 to 2500 mg C/m2 /day, both of which were about 7 and 8 times respectively higher than the before-cyclone values. The CO2 flux showed a 4 times increase from its pre-cyclone value of 3.5 mmol/m2 /day, indicating that BoB becomes a strong source to the atmosphere during the cyclone Madi period.","PeriodicalId":50105,"journal":{"name":"Journal of Operational Oceanography","volume":"12 1","pages":"104 - 125"},"PeriodicalIF":3.1,"publicationDate":"2020-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90339516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-09-07DOI: 10.1080/1755876X.2020.1813412
Anju Issac Elizabeth, J. B. Effy, P. A. Francis
ABSTRACT The upper ocean response of Bay of Bengal to two extremely severe post-monsoon tropical cyclones, Phailin and Hudhud, which occurred in the same time of the season (4–12 October 2013 and 6–12 October 2014 respectively) with very similar tracks and life cycles are presented in this study. It is observed that, even though the tropical cyclone Phailin was much stronger than tropical cyclone Hudhud, the cooling of the underlying ocean was more rapid and intense during the passage of tropical cyclone Hudhud. Heat budget analysis of the upper ocean based on realistic simulations using Regional Ocean Modeling System suggests that, while the vertical processes, horizontal advection and the reduction in the net heat flux have contributed to the cooling of the upper ocean in both the cases, the intensity of vertical processes were relatively weaker in the case of tropical cyclone Phailin. Further analysis shows that the surface layers of Bay of Bengal were relatively more stable in October 2013 due to excess rainfall in the preceding summer monsoon compared to October 2014, which was succeeded by a poor monsoon.
{"title":"On the upper ocean response of Bay of Bengal to very severe cyclones Phailin and Hudhud","authors":"Anju Issac Elizabeth, J. B. Effy, P. A. Francis","doi":"10.1080/1755876X.2020.1813412","DOIUrl":"https://doi.org/10.1080/1755876X.2020.1813412","url":null,"abstract":"ABSTRACT\u0000 The upper ocean response of Bay of Bengal to two extremely severe post-monsoon tropical cyclones, Phailin and Hudhud, which occurred in the same time of the season (4–12 October 2013 and 6–12 October 2014 respectively) with very similar tracks and life cycles are presented in this study. It is observed that, even though the tropical cyclone Phailin was much stronger than tropical cyclone Hudhud, the cooling of the underlying ocean was more rapid and intense during the passage of tropical cyclone Hudhud. Heat budget analysis of the upper ocean based on realistic simulations using Regional Ocean Modeling System suggests that, while the vertical processes, horizontal advection and the reduction in the net heat flux have contributed to the cooling of the upper ocean in both the cases, the intensity of vertical processes were relatively weaker in the case of tropical cyclone Phailin. Further analysis shows that the surface layers of Bay of Bengal were relatively more stable in October 2013 due to excess rainfall in the preceding summer monsoon compared to October 2014, which was succeeded by a poor monsoon.","PeriodicalId":50105,"journal":{"name":"Journal of Operational Oceanography","volume":"74 1","pages":"17 - 31"},"PeriodicalIF":3.1,"publicationDate":"2020-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91192847","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-08-21DOI: 10.1080/1755876X.2020.1785097
K. von Schuckmann, P. Le Traon, N. Smith, A. Pascual, S. Djavidnia, J. Gattuso, M. Grégoire, G. Nolan, S. Aaboe, E. Fanjul, L. Aouf, Roland Aznar, T. Badewien, A. Behrens, M. Berta, Laurent Bertino, J. Blackford, G. Bolzon, Federica Borile, M. Bretagnon, R. Brewin, D. Canu, P. Cessi, S. Ciavatta, B. Chapron, Thi Tuyet Trang Chau, F. Chevallier, B. Chtirkova, S. Ciliberti, J. Clark, E. Clementi, Clément Combot, E. Comerma, A. Conchon, G. Coppini, L. Corgnati, G. Cossarini, S. Cravatte, M. de Alfonso, C. de Boyer Montégut, Christian De Lera Fernández, F. J. de los Santos, Anna Denvil-Sommer, Álvaro de Pascual Collar, Paulo Alonso Lourenco Dias Nunes, Valeria Di Biagio, M. Drudi, Owen Embury, P. Falco, O. F. d'Andon, L. Ferrer, D. Ford, H. Freund, M. G. León, M. Sotillo, J. García-Valdecasas, P. Garnesson, G. Garric, F. Gasparin, M. Gehlen, Ana Genua‐Olmedo, G. Geyer, A. Ghermandi, S. Good, J. Gourrion, E. Greiner, A. Griffa, Manuel González, A. Griffa, I. Hernández‐Carrasco, S. Isoard, J. Kennedy, S. Kay, A
Journal of Operational Oceanography Volume 13 Supplement 1 September 2020 CONTENTS Chapter 1: Introduction and the European Environment policy framework s1 1.1 Introduction and main outcomes Karina...
{"title":"Copernicus Marine Service Ocean State Report, Issue 4","authors":"K. von Schuckmann, P. Le Traon, N. Smith, A. Pascual, S. Djavidnia, J. Gattuso, M. Grégoire, G. Nolan, S. Aaboe, E. Fanjul, L. Aouf, Roland Aznar, T. Badewien, A. Behrens, M. Berta, Laurent Bertino, J. Blackford, G. Bolzon, Federica Borile, M. Bretagnon, R. Brewin, D. Canu, P. Cessi, S. Ciavatta, B. Chapron, Thi Tuyet Trang Chau, F. Chevallier, B. Chtirkova, S. Ciliberti, J. Clark, E. Clementi, Clément Combot, E. Comerma, A. Conchon, G. Coppini, L. Corgnati, G. Cossarini, S. Cravatte, M. de Alfonso, C. de Boyer Montégut, Christian De Lera Fernández, F. J. de los Santos, Anna Denvil-Sommer, Álvaro de Pascual Collar, Paulo Alonso Lourenco Dias Nunes, Valeria Di Biagio, M. Drudi, Owen Embury, P. Falco, O. F. d'Andon, L. Ferrer, D. Ford, H. Freund, M. G. León, M. Sotillo, J. García-Valdecasas, P. Garnesson, G. Garric, F. Gasparin, M. Gehlen, Ana Genua‐Olmedo, G. Geyer, A. Ghermandi, S. Good, J. Gourrion, E. Greiner, A. Griffa, Manuel González, A. Griffa, I. Hernández‐Carrasco, S. Isoard, J. Kennedy, S. Kay, A","doi":"10.1080/1755876X.2020.1785097","DOIUrl":"https://doi.org/10.1080/1755876X.2020.1785097","url":null,"abstract":"Journal of Operational Oceanography Volume 13 Supplement 1 September 2020 CONTENTS Chapter 1: Introduction and the European Environment policy framework s1 1.1 Introduction and main outcomes Karina...","PeriodicalId":50105,"journal":{"name":"Journal of Operational Oceanography","volume":"41 1","pages":"S1 - S172"},"PeriodicalIF":3.1,"publicationDate":"2020-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73738257","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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