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 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.Item Hydrodynamic variability along the outlet channel of Kolleru lake, India(Proquest, 2011-04) Prasad, K. V. S. R.; Apparao, A. P. V.; Arun Kumar, S. V. V.; Patnaik, K. V. K. R. K.; Venkata Ramu, Ch.Hydrodynamic parameters like Salinity intrusion, circulation and mixing properties, flushing characteristics, Total salt etc., along outlet channel of Kolleru Lake have been studied during May 2010-April 2011. The observations reveal that the channel had lost 94.2% of Total Salt during May-November 2010 and regained upto 94.0% by April 2011. Flushing time has been varied from 1.81 to 5.61 tidal cycles. The Diffusion Coefficient (Kx) varied randomly between 0.0032 x 105 and 5.6 x 105 m2/s during July-August 2010. The yearly mean Kx ranges between 0.0095 x 105 and 2.1 x 105 m2/s. The seasonal variation of depth mean salinity along the axis of the channel shows a wide range. During periods of very high discharge, salt wedge has been formed near the confluence and extended few kilometers upstream. For moderate discharge, the channel has become partially mixed with a high degree of stratification.Item Observational analysis on the run-up height and inundation along the Andhra coast during December 26, 2004 Indian Ocean tsunami(Elsevier, 2012-02-02) Patnaik, K. V. K. R. K.; Arun Kumar, S. V. V.; Venkata Ramu, Ch.; Prasad, K. V. S. R.The 26 December 2004 earthquake with magnitude of 9.3 triggered one of the most destructive tsunamis in the Indian Ocean and caused widespread inundation and extensive damage in terms of life and property along the coasts of several Asian countries. In India, the Andaman and Nicobar group of Islands, the coastal states of Tamil Nadu, Andhra Pradesh and Kerala were severely affected. Post tsunami field surveys were conducted along the Andhra coast (central part of east coast of India) to assess the tsunami run-up heights and inundation. Estimation of tsunami run-up heights and inundation relative to the mean sea level were made based on the water marks on permanent structures and marks of debris on trees. Observations revealed that the Andhra coast was largely affected by the tsunami and in general the intensity of the tsunami along the Andhra coast decreased from south to north. Maximum run-up heights of 4.5 m were observed in the southern parts and minimum run-up heights of 2 m were observed in the northern parts of the Andhra coast. While, the distance of inundation varied from 60 to 900 m along the coast. The interdependency between the tsunami run-up height and inundation with the physical setup of the shoreline has been identified. Also local features such as dunes, vegetation and steepness of beaches played vital role in reducing the impact of tsunami. Dependency of tsunami parameters on Coastal Characteristic Index (CCI) was attempted for the first time for the Indian coast. Good correlation has been observed between run-up heights, inundation and CCI. The width of the continental shelf also played a crucial role in causing damage to the coast.Item East India coastal current induced eddies and their interaction with tropical storms over Bay of Bengal(Taylor & Francis, 2014-02-01) Patnaik, K. V. K. R. K.; Maneesha, K.; Sadhuram, Y.; Prasad, K. V. S. R.; Ramana Murty, T. V.; Brahmananda Rao, V.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.Item Variability in MODIS NDVI in relation to Southwest Monsoon over Western Ghats, India(International Society for Environmental Information Sciences, 2016-03-01) Lakshmi Kumar, T.V.; Koteswara Rao, K.; Barbosa, H.; Prabha Jothi, E.; Patnaik, K. V. K. R. K.; Uma, R.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.