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Bhaskar T.V.S.U.,INCOIS | Swain D.,Space physic Laboratories | Ravichandran M.,INCOIS
International Journal of Oceans and Oceanography | Year: 2010

Spatial and temporal distribution of sonic layer depth (SLD) in the Arabian Sea (AS) was studied using temperature and salinity (T/S) profiles from Argo floats during the years 2003 - 2004 and World Ocean Atlas 2001 (WOA01) climatology. SLD was obtained from sound velocity profiles computed from T/S data. SLD variability as obtained from Argo matched well with those obtained from the WOA01 in certain locations and showed remarkable difference in some other. SLD variability in the AS is mainly related to seasonal variations in T/S owing to influence of seasonal phenomena as well as the geography of the region. Deeper SLDs were observed during summer monsoon (> 90 m) and winter monsoon (> 80 m) respectively. Up-welling and down-welling (Ekman dynamics) associated with the Findlater Jet controlled SLD during the summer monsoon. While in winter monsoon, cooling and convective mixing regulated SLD in the study region. Weak winds, high insolation and positive net heat flux lead to the formation of thin, warm and stratified sonic layer during pre and post summer monsoon periods, respectively. Examination of SLD in selected areas further revealed clear seasonal changes reflecting strong monsoon signals in the AS. © Research India Publications.

Vivek G.,SRM University | Srinivasa Kumar T.,INCOIS
ACRS 2015 - 36th Asian Conference on Remote Sensing: Fostering Resilient Growth in Asia, Proceedings | Year: 2015

Tropical cyclone is a rapidly rotating storm system characterized by a low pressure center, strong winds, and a spiral arrangements of thunderstorms that produce heavy rain. Tropical cyclones typically form over large bodies of relatively warm water. On 6th October 2014 Hud Hud originates from a low pressure system that formed under the influence of an upper air cyclonic circulation in the Andaman Sea. On 9th October 2014 the IMD department classified the Hud Hud as a very severe cyclonic storm on IMD scale and category 4 on Staffir-Simpson scale. The cyclone hit the coast of Visakhapatnam on 12th October 2014 at wind speed of 175 km/h which caused extensive damage to the city and the neighbouring districts. The remote sensing technique used here is NDVI. NDVI will separate vegetation and nonvegetation part. The main objective is change detection. The NDVI will be classified in ERDAS and calculated the area using ARCGIS. The satellite data of 4th October, 14th October 2014 and 7th December 2014 has been taken to show the before the cyclone, after the cyclone passes and after a month of cyclone.

Rao A.D.,Indian Institute of Technology Delhi | Joshi M.,Indian Institute of Technology Delhi | Jain I.,Indian Institute of Technology Delhi | Ravichandran M.,INCOIS
Estuarine, Coastal and Shelf Science | Year: 2010

Thermister chain data at different depths for June 1998 cyclone in the Arabian Sea at a location (69.2 E,15.5 N) which is about 60 km to the left of the cyclone track indicates subsurface warming below 60 m and inertial oscillations of temperature with a periodicity of about 2 days. The oscillations continued for ∼15 days even after the cyclone crossed the coast. The analysis of the buoy, DS1 located at the same position also suggests a stabilized southward flow after about two weeks of the cyclone crossed the coast. Analysis of the buoy data for May 1999 cyclone in the same region also indicates similar pattern. In order to investigate the effect of cyclone-ocean interaction and primarily to understand the process for the subsurface warming, 3-dimensional Princeton Ocean Model is configured for the eastern part of the Arabian Sea. The model uses high horizontal resolution of about 6 km near the coast and a terrain following sigma coordinate in the vertical with 26 levels. The study focuses on surface cooling and temperature rise in the underlying waters and explains its mechanism through upwelling and downwelling respectively. The simulations in concurrence with the observations suggest that the occurrence of subsurface warming precedes the surface cooling with a lag of ~a day as the cyclone advances DS1. The simulations also demonstrate local temperature stratification plays an important role for cooling of the upper ocean and warming of the subsurface waters and extent of warming is directly related to the depth of the thermocline. © 2010 Elsevier Ltd.

Suresh R.R.V.,Andhra University | Annapurnaiah K.,INCOIS | Reddy K.G.,Andhra University | Lakshmi T.N.,Andhra University | Balakrishnan Nair T.M.,INCOIS
International Journal of Oceans and Oceanography | Year: 2010

The waves along the east coast of India during south-west monsoon have great importance due to the prevailing rough conditions. Significant Wave height (Hs) and other wave conditions are measured at a location of 20m water depth off east coast of India during south-west monsoon 2009. Wind-sea (Hsw) and swell (Hss) components are separated from the measured data, to look into the characteristics of the waves at the measured location. It is observed that the sea-state is dominated by swells arriving from south-east (SE) to south (S). The maximum measured Hs is 2.62 m. Good positive correlation of 0.84 is observed between Hss and Hs. The contribution of Hss to Hs is 63.2 % and remaining is due to Hsw. Wave age shows the presence of young sea with significant occurrence of swell. The spectral band width parameter (e), calculated from the measured data indicates that the wave components cover wide range of frequencies. The high values of spectral narrowness parameter (v) and peakedness parameter (Qp) are observed during the study period. © Research India Publications.

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