Research Publications

Permanent URI for this communityhttps://dspacenew8-imu.refread.com/handle/123456789/127

Browse

Filters

Settings

Author: search.filters.author.Patnaik, K. V. K. R. K.End date: 2029

Search Results

Now showing 1 - 10 of 27
  • No Thumbnail Available
    Item
    Intensification of pre-monsoon cyclone: Insights from spring snowmelt discharge /
    (Research Square, 2024-11-11) Patnaik, K. V. K. R. K. ; Ganapathi, P.
    The intensification of pre-monsoon cyclones in the northern Bay of Bengal, particularly Cyclones Yaas (2021), is increasingly attributed to the rising influx of snowmelt water from the Ganges and Brahmaputra rivers. Cyclone Yaas intensified over high sea surface temperatures (31.5 to 32°C) and significant freshwater discharge, leading to notable stratification and increased ocean heat content in the upper layers. As Yaas moved through a warm core eddy, the sinking of water caused the isotherms to deepen by 25–50 meters, a process that was further intensified by freshwater discharge due to spring snowmelt. Key ocean heat content in the top 30-meter layer was critical during Yaas's formation, with total incoming shortwave radiation of 420 W/m² and net radiation of 390 W/m² closely aligning with the heat content of 400 W/m² in the central and western Bay, providing the necessary energy for intensification. This study employs integrated datasets, including in situ observations, ERA5-based freshwater flux analysis, and high-resolution numerical simulations, to reveal cyclone-ocean interactions. Findings indicate that similar snowmelt dynamics contributed to the intensification of recent cyclones. With the rising temperatures due to global warming, even minor changes in increasing snowmelt and surface runoff can significantly affect upper ocean dynamics. This highlights the critical role of pre-monsoon freshwater discharge in strengthening cyclones and emphasises the need for better prediction models to understand future cyclone behavior, which can help reduce risks in this vulnerable region. Additionally, in terms of biological processes, the increased fresh water discharge during spring in the northern Bay of Bengal caused high stratification and intense downwelling, which suppressed nutrient-rich subsurface waters and resulted in limited chlorophyll concentrations (1 mg/m³) along Yaas's track, despite phytoplankton blooms in regions of high wind stress.
  • No Thumbnail Available
    Item
    The intrusion of spicy water favours the intensification of arabian sea cyclones /
    (Taylor & Francis, 2022-09-08) Patnaik, K. V. K. R. K.
    The intensity of the cyclones in the Arabian Sea has been increasing in recent years. Approximately ten storms were intensified into severe cyclones over spicy waters of the northern Arabian Sea during 1998-2019. Reduction in upwelling was observed due to decreasing wind speed, which raised the sea surface temperature (SST) and the intrusion of spicy waters from the Red Sea and the Persian Gulf acted as a barrier to mixing in the top layers, especially in May. Consequently, there was a noticeable increase in the heat content of the 50 m surface layer. This research presents two main rationales that explain the intensification of these cyclones. The first rationale explores the increasing trends in SST and ocean internal energy, while the second investigates the influence of the intrusion of spicy Persian Gulf waters into the Oman coast. The results showed that spicy water from the north suppressed the upwelling in the cold core eddy off the Oman coast and that higher SSTs and high latent heat flux almost double the climatological values off the Oman coast in May.
  • No Thumbnail Available
    Item
    Assessment of coringa mangrove shoreline migration using geospatial techniques /
    (Taylor & Francis, 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.
  • No Thumbnail Available
    Item
    On the relation of vegetation and southwest monsoon rainfall over Western Ghats, India /
    (Springer Nature, 2016-07-05) Patnaik, K. V. K. R. K.
    This article presents the tendency of the normalized difference vegetation index (NDVI) and the dependence of vegetation on the rainfall and number of rainy and non-rainy days over Western Ghats. The study makes use of MODIS Terra NDVI data with 8-day intervals and 250-m resolution from 2000 to 2010 during the southwest monsoon (June to September) season. The results show an increasing tendency of the NDVI over different test sites in Western Ghats. The relation of the NDVI with the Antecedent Precipitation Index obtained from rainfall showed good agreement, and the relation of rainfall and the NDVI was mainly dependent on the available soil moisture levels and elevations of the test sites. Correlations were significant and positive with the number of rainy days and negative with the number of non-rainy days with a nearly 2-month lag.
  • No Thumbnail Available
    Item
    Variability in MODIS NDVI in Relation to Southwest Monsoon over Western Ghats, India /
    (ISEIS, 2016-01-01) Patnaik, K. V. K. R. K.
    Eleven years (2000 to 2010) of Normalized Difference Vegetation Index (NDVI) data, derived from Moderate Imaging Spectroradiometer (MODIS) Terra with 250 m resolution is used in the present study to discuss the changes in the vegetal cover over Western Ghats, India. The NDVI over Western Ghats (number of test sites are 16) showed increasing tendency and the pronounced changes in NDVI have been studied in the context of southwest monsoon's distribution and activity. The NDVI progression is observed from June with a minimum value of 0.179 and yielded to a maximum at 0.565 during September/October, on an average. The study then relates NDVI with different rainy events to understand the connection between the ground vegetation and the south west monsoon. The results of the study inferred are as follows: i) NDVI, Antecedent Precipitation Index (API) are in good agreement throughout the monsoon which is evidenced by correlation; ii) NDVI maintained good correlation with a number of Light and Moderate Rainy days alternatively but not with the number of Heavy Rainy days; iii) Relation of NDVI with Isolated, Scattered distributions and active monsoons is substantial; and iv) Rate of Green Up is captured by the satellite during the crop growing season over the Western Ghats.
  • No Thumbnail Available
    Item
    Biophysical responses to tropical cyclone Hudhud over the Bay of Bengal /
    (Taylor & Francis, 2019-11-04) Patnaik, K. V. K. R. K.
    Cyclone Hudhud originated in the Andaman Sea on 6 October 2014. Later, it intensified into a cyclonic storm on 8 October and eventually made landfall at Visakhapatnam on 12 October as a very severe cyclonic storm. It was intensified off of Visakhapatnam by high stratified waters with a thick barrier layer that held significant heat content. In this study, we analysed the data along the cyclone track using a combination of satellite, in-situ Argo and Bio-Argo data to assess the upper oceanic changes along the Hudhud track. Notable changes were detected in the upper ocean due to its extreme intensification and prior passage through cold-core eddies. A high translation speed and persistent stratification dominated the effects caused by the cold-core eddies on the intensification of the cyclone and the same was attributed to the upwelled subsurface chlorophyll maxima. The biophysical changes in the top 150 m layer derived from Argo floats were in good agreement with the satellite and model data. Further, it was observed that the increase in lightning flash rates also influenced surface productivity during the cyclone. Subsequent to the passage of the cyclone, the ocean took two weeks to achieve its original state.
  • No Thumbnail Available
    Item
    East India Coastal Current induced eddies and their interaction with tropical storms over Bay of Bengal
    (Taylor & Francis, 2024-02-01) Patnaik, K. V. K. R. K.
    Eddies of about 10 to 500km in diameter, persisting for periods of days to months are commonly referred to as mesoscale eddies in oceanography. Energetic eddies are frequently found in the vicinity of faster flowing currents like the Gulf Stream and the Kuroshio. The present study deals with the role of eddies, occurring in the vicinity of the East India Coastal Current (EICC), particularly in the months of April to May and October to November, during the intensification of tropical cyclones in the Bay of Bengal. Although the Bay of Bengal is well known for mesoscale eddies, the role of these in the intensification/weakening of the storms is quantitatively unknown. In this study, an attempt has been made to conduct a quantitative analysis of the role of these eddies (warm/cold) in the intensification of the storms over the Bay of Bengal. It is found that in the case of a severe cyclone occurring over the period of 16 to 19 October, 1999 the intensity of the storm was enhanced by 260% due to its interaction with a warm eddy. This is much higher than that reported in case of, for example, Hurricane Opal (119%) and Typhoon Maemi (138%). The enthalpy fluxes (latent plus sensible) are much higher (lower) over warm (cold) eddies. The warm eddy opposes the cooling induced by the storm and helps the intensification through the supply of large amount of enthalpy flux. This emphasizes the importance of eddies in the intensification of storms over the Bay of Bengal, which is omitted by meteorologists in forecasting the intensification of storms.
  • No Thumbnail Available
    Item
    Planning and feasibility study of LNG terminal for visakhapatnam port trust
    (Twenty Seventh National Convention of Marine Engineers, 2013-08) Chandrasekhar, B.; Patnaik, K. V. K. R. K.
    To meet India’s growing energy demands, it is proposed to establish a LNG terminal at east coast for Visakhapatnam port trust. Its location is found to be feasible near the newly proposed Satellite Port and at proposed fishing harbour at Mullakuddu, Bheemunipatnam. This work comprises of the preliminary study and feasibility report along with plant process and basic requirements for setting up of LNG terminal for handling, storage and evacuation at Bheemunipatnam for Visakhapatnam Port Trust. The proposed LNG terminal facility at Bheemunipatnam is planned with the following infrastructural facilities for the smooth handling of LNG, which consists of a Jetty, LNG Tanks, Vaporisation plant, Fire control mechanism, Maintenance workshops, Administration Building, Guard houses, Utility area & Control rooms. As the first phase, the planned LNG terminal capacity is 2mmtpa with two LNG storage tanks of 85,000 m3 capacity, with a provision to increase it to 5mmtpa in future.
  • No Thumbnail Available
    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.
  • Thumbnail Image
    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.