Journal Articles
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Item Upper ocean thermal features during tropical cyclones over Bay of Bengal(International Journal of Innovation Research & Development, 2012-12) Venkata Ramu, Ch.; Patnaik, K. V. K. R. K.; Prasad, K. V. S. R.; Arun Kumar, S. V. V.; Acharyulu, P. S. N.The upper ocean is dramatically affected during tropical cyclones (TCs). Cyclones interact not only with the surface but also with the deeper oceans, the depth depending upon the strength of the wind mixing. Hence, it is necessary to consider the thermal structure of the upper ocean for cyclone studies. Rapid intensification of cyclone Nargis in the Bay of Bengal from category-1 to category-4 within 24 hours was attributed to the presence of a pre-existing warm SSHA evidenced by the insitu (Argo data) and altimeter observations. The warmer layers of 260C extended up to 100 m beneath the surface such as Isothermal layer depth (ILD) and barrier layer thickness (BLT) and Upper Ocean Heat Content (UOHC) during the cyclone progression were computed. The rate of intensification and final intensity of cyclones are sensitive to the initial spatial distribution of the mixed layer. The most apparent effect of TC passage is noted by the marked SST cooling, and the response of the ocean mixed layer temperature typically 1 to 60C towards the right of the storm track. In the present work, the response of Upper Ocean to the tropical cyclones over Bay of Bengal based on the satellite Altimetry, ARGO, RAMA buoys and QUICKSCAT forced (MOM-GODAS) data. The present studies suggest the use of sea surface height anomalies (SSHA) data derivable from satellite altimeters are more useful instead of sea surface temperatures in the atmospheric models, particularly, in the cyclone and coupled models.Item Assessment of coringa mangrove shoreline migration using geospatial techniques(Journal of Operational Oceanography, 2020-11-06) Sharma, Garima.; Patnaik, K. V. K. R. K.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.Item Study on the wave diffraction patterns in the Kakinada bay(Journal of offshore structure and technology, 2020) Sharma, Garima.; Patnaik, K. V. K. R. K.Kakinada is one of the major upcoming ports of India and holds great importance for shipping activities. This region is said to be low-lying area and highly susceptible to erosion. To protect the port from action of waves, tides and strong currents, breakwater was constructed at the entrance of the channel. Current study makes an attempt to understand how wave energy gets reduced and wave diffraction occurs due to presence of the breakwater. Numerical solution of the mild slope equation and diffraction pattern are studied using MIKE 21 PMS model. Intense wave activity is higher during south west monsoon season than north east monsoon season. Significant wave heights have reduced considerably to 0–0.15 m because of the breakwater during both the seasons and no waves are entering inside the bay. Waves have bent at the breakwater due to diffraction along with the formation of concentric ripples with the decreased wave heights.Item Long term morphodynamic evolution of Kakinada bay using upscaling methods(Marine Engineers Review (India), 2020) Sharma, Garima.; Sivakholundu, K. M.; Patnaik, K. V. K. R. K.Kakinada Bay has evolved over the last century dynamically by the action of wind, waves, tides and currents. Formation of Hope Island and development of Coringa Mangroves are attributed to the hydrodynamic 'forcings' and sediment dynamics. This study aims to predict the future morphological development of Kakinada Bay for next 100 years. The morphological model was built up in the DELFT 3D package. Model setting parameters were fixed after analysing their effect on the simulation results. For reducing the computational time and effort for simulating long term morphological development, upscaling methods such as morphological acceleration factor (MORFAC) and morphological tide were incorporated in the morphological model. Morphological tide was formed using tidal constituents - M2, O1 and K1. The MORFAC value for this study was chosen as 30 after undergoing the sensitivity test analysis using Brier Score Skill (BSS) Score. The model was run for 19 years for hindcasting and 100 years for forecasting. In order to establish confidence in the model, it was calibrated and validated using hindcast modelling. The hindcast simulation results were used to match the simulated shoreline with satellite observed shoreline from year 1988 to 2000, and 2006 to 2013 and the results were in good agreement. It was observed that the south-western part of the bay has accreted more rapidly while south-eastern part of the bay has undergone slight erosion. Thereafter long term morphological model was run for 100 years to predict the future evolution of bay. Results of these simulations show the capability of the long term morphological model to predict the spatial and temporal geo-morphological changes.null.listelement.badge A study on the seasonal variability of nearshore waves off Visakhapatnam, east coast of India(International Journal of Innovative Research and Development, 2012-12) Suresh, R. R. V.; Patnaik, K. V. K. R. K.; Ramesh, U. S.; Misra, S. C.Wave rider buoy data during the period June 2009 to May 2010 was analyzed to examine the seasonal trends in the nearshore waves off Visakhapatnam, east coast of India. During fair weather conditions, wave heights were observed to be higher in the southwest monsoon season with maximum significant wave height (Hs) of about 2.76m in the month of July and average Hs of about 1.6m. The higher values of spectral band width emphasize that the wave heights covered a wide range for major period of the year. A large standard deviation of swell period represents the occurrence of distant swell in a wide range to the study region. The seasonal cycle of wave heights off Visakhapatnam, East Coast of India is dominated by SW monsoon winds. The waves at study area are resultant of sea and large swells from south of Bay of Bengal