Journal Articles
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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.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.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.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.Item Intra-annual studies of mixed layer depth in the Arabian Sea using a 3 ½ layer Indian ocean model(Bentham Open, 2009-09-04) Patnaik, K. V. K. R. K.; Sreenivas, P.; Venkata Ramu, Ch.; Arun Kumar, S. V. V.; Prasad, K. V. S. R.Mixed layer is the upper layer of the ocean, where significant physical, chemical and biological activities take place. Knowledge of mixed layer depth variability is important in the studies of air-sea interaction, acoustic propagation, heat transport and fisheries. The Arabian Sea experiences extremes in atmospheric forcing that lead to intra-annual and inter-annual variability. Since the climatic conditions over the Arabian Sea are highly variable, the mixed layer depth also changes seasonally. Hence the intra-annual variability of mixed layer depth in the Arabian Sea has been examined using 3 ½ layer Indian Ocean model. The model is integrated for 8 years (1993–2000) with annually varying monthly averaged winds derived from ERS-2 scatterometer. In addition to this data, inter annually varying monthly averaged satellite estimates of precipitation from Global Precipitation Climatology were also incorporated in the model. Model results show a steady deepening of mixed layer depth in the central Arabian Sea during southwest monsoon period. The model shows its capability to predict the shallow mixed layer depths caused by coastal upwelling off Somalia during southwest monsoon period and is able to capture the Lakshadweep high/low as it predicted successfully the deeper/shallow mixed layer observed during these periods.Item Role of nearshore waves in identifying vulnerable zones during storm and normal events(Enviroscan, 2010) Arun Kumar, S. V. V.; Prasad, K. V. S. R.; Patnaik, K. V. K. R. K.; Venkata Ramu, Ch.; Sreenivas, P.During the SW Monsoon season, the average nearshore wave energy 3 along the coast is higher for the stations 3 and 20 with values 4.3 x10 2 J/m (Fig. 2). From the southern end of the coast, the wave energy is 3 2 decreasing having a least value of 2.2 x10 J/m in the Lawson's Bay (station 13). Hence, during this season, RK Beach, Jodugullapalem Beach and Sagar nagar Beach are the high energetic zones and so there is a possibility of erosion at these places.Item Contribution of tides to sea level variations along Visakhapatnam, India(Taylor & Francis, 2010-08-07) Prasad, K. V. S. R.; Sreenivas, P.; Patnaik, K. V. K. R. K.The sea level variations along Visakhapatnam coast are governed by astronomical tides and nontidal oscillations including atmospheric pressure, winds, coastal currents, Ekman Pumping, and river influx. Tidal and nontidal sea level oscillations are usually studied separately because of the vastly different ways in which they are forced. In this study the tidal oscillations along Visakhapatnam are analyzed using GOTIC2 tidal model. The correlation between monthly mean sea level and monthly mean tides is 47% (r = 0.68) and increases to 54% (r = 0.74) when applied for inverse-barometric effect. The major six partial tides are computed and presented. The tidal variations from Neap tide to Spring tide are studied.