High Frequency Radar Surface Currents

HF radar systems utilize high frequency radio waves to measure the surface currents in the coastal ocean. Radar antennas (typically in pairs) are positioned on shore and can measure surface currents (the top 1-2 m of the water column) up to 200 km away with resolutions ranging from 500 m to 6 km depending on the radar frequency. The observations of the currents are usually 1-hour averages displayed in near real time. There are over 10 HF Radar systems presently operating throughout the Indian Ocean. For details Indian Coastal Ocean Radar Network (ICORN)

Objective

The main objectives of the ICORN are as follows

·       Installation and maintenance of Coastal HF radar Network along the Indian coast including Islands.

·       Measuring the sea surface currents and wave heights in near-real time along the coast up to 200km radially from each remote site (using varied frequency like 5 and 25 MHz).

·       Transmission of data in near-real time to central servers at NIOT & INCOIS and then dissemination of data through INCOIS.

·       Utilizing the data obtained from the HF radar network for better understanding of the coastal circulation and oceanographic/Engineering

This project was funded by Ministry of Earth Sciences through Ocean Observation Network (OON) Programme.

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HF Radar Radials

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HF Radar Surface Currents

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Introduction

Indian Coastal Ocean Radar Network(ICORN) has been established along Indian coast under NIOT’s Tsunami Early Warning System project (TEWS) of Ministry of Earth Sciences( MoES), Government of India. This Network includes, ten remote HF Radar sites and two central sites viz. in NIOT, Chennai and INCOIS, Hyderabad and are working continuously since the year 2010. During the 12th five year plan, Coastal HF Radar systems were included in “Ocean Observation Network”(OON) program of MoES, Administrative order(MoES/36/OOIS/OON/2012). High Frequency (HF) Radar is a tool for synoptic on-line mapping of surface current fields and the spatial distribution of the wave directional spectrum. These instruments map surface currents in wide swaths of coastal waters up to 200 km offshore, 24 hours a day, and in all weather conditions. Data on coastal currents will be useful to scientists to understand the ocean circulation along the Indian coast, and to validate and improve the circulation models in bays and estuaries. Assimilation of in situ data into model further enhances the confidence of model forecasting. Scientists can use this data to study the movement of juvenile fish and invertebrates, the influx of nutrients from the deep ocean, and the outflow of pollutants from land. The near-real-time data from HF Radar systems can be incorporated with Coast Guard in search-and-rescue operations and oil spill models. This data can also be included in commercial and recreational planning along beaches and ships navigating into ports. The physics behind HF radar is relatively straightforwardBarrick (1972a), Barrick (1972b), and Barrick, Evans, and Weber (1977). A transmitter broadcasts electromagnetic waves usually between 3MHz and 30MHz. These signals scatter off waves on the ocean surface.

If a signal strikes an ocean wave that is exactly half of the broadcast signal’s wavelength the ocean wave reflects the signal back to the transmitter. This phenomenon is known as Bragg scattering. Since there are abundant waves of all wavelengths present in the sea, there are always plenty of waves that fit this criterion. In ideal conditions with ideal ocean waves, we can predict the frequency of the returning signal based on the ocean wave’s size (it’s half the wavelength of the transmitted signal) and its calculated phase speed (how quickly it moves). Of course in the real world, ocean waves are never ideal, but for these purposes, they are close enough. Surface currents, however, cause these waves to move. This movement of the ocean waves shifts the frequency of the returning signal due to the Doppler Effect. The frequency increases if the current pulls the waves towards the transmitter and decreases if it pushes them away. By measuring this Doppler shift, we can determine the speed of the currents towards or away from the transmitter. To calculate the directions of the currents, we need a second HF radar installation measuring the same currents from a different angle.ICORN uses systems manufactured by CODAR Ocean Sensors. NIOT has created a database of surface current information since 2009 along the Indian coast, and some of the development has been done using these data. The installation details of HF radar systems are depicted in Table 1.1 and all the sites are working with 5MHz frequency.

Observation of Phailin and Hudhud cyclone

Bay of Bengal is subjected to an average two tropical cyclone per year and the coastal states are prone to inundation from these storms surges. Indian coastal HFR networks could detect all the storm surges and tropical cyclones events in its coverage.These networks have measured High wave activities during major cyclones like Jal, Phailin and Hudhud Manu et al. (2015) and corresponding observation are also made for ocean surface currents Figure 1.13

Site Description

The selection of HF Radar sites depends on the frequency of operation, accessibility, and the objectives of the project. The Installation site should be free from any interference from the nearby frequency and metallic constructions. The position of receiver and transmitter antenna and the orientation with the shoreline should be as per the manual. The following section gives a description of all the 10 sites operated by NIOT.

Cuddalore

Cuddalore (CUDA) site is situated at Sothikuppam village Figure 1.2. which is 15 km away from the Cuddalore city of Tamilnadu. NIOT built a permanent concrete building to house the HF Radar systems. These site has been established back in March 2008 and in operational since then. Figure 1.2:

Kalpakkam

Kalpakkam (KALP) is situated 60km south of Chennai Figure 1.3 and these HF Radar systems are kept in Department of Atomic Energy township. This site also have a concrete building to keep the HF Radar systems.

Machilipatanam

Machilipatanam (MACH) site is located at the Manginapudi Beach Figure 1.4 which is located at 11 km from Machilipatnam City in Krishna District and 85 km away from Vijayawada, Andhra Pradesh.

Yanam

Yanam(YANM) Site is located at coast of S Yanam Figure 1.5 village which is 15km away from the Amlapuram city of Andhra Pradesh.

 

 

Gopalpur

Gopalpur located at Gopalpur port Figure 1.6 in Ganjam district in Odisha. This site does not have permanent housing to keep HF Radar equipment, and a container is used for safe keeping.

Puri

Puri(PURI) site is situated at the campus of well-known Shri Jagannath Sanskrit University Puri, Odisha Figure 1.7. Here also a container is used for keeping HF radar Equipments.

Wasi Borsi

Wasi borsi(WASI) Site is situated at Light house of village Borsi Machhiwad, in Gulf of khambhat Figure 1.8. The Lighthouse is about 20 Km west of Maroli Railway Station on Mumbai- Surat rail section, Gujarat.

 

Jegri

Jegri (JGRI) site is located at Jegri Light house in Gulf of Khambhat Figure 1.9 which is 10 km away from the Mahuva city of Gujarat.

Port Blair

Port blair (PTBL) site is located along the coast of Rangachang village Figure 1.10 which is 20km away from Port Blair in Andaman & Nicobar Islands, India.

Hutbay

Hutbay (HTBY) site is located at Jetty, In Hutbay Island Figure 1.11 which is also called as little Andaman in Andaman & Nicobar Islands, India.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Coastal and Environmental Engineering

Coastal and Environmental engineering (CEE) group focuses primarily on carrying out research on the coastal processes, issues pertaining to engineering along the coastline and coastal environmental quality. CEE has undertaken two major plan projects viz., Shoreline management and Technical criteria atlas and a component of Ocean observation, the HF Radar network under the XII plan. Major projects of national importance undertaken by the group include seabed investigation engineering and model studies for development of Gulf of Khambat (Project Kalpasar) and Engineering feasibility and Environmental Impact Assessment studies for marine coal handling facility off Cheyyur, Tamilnadu. The group has the credit of working on World Bank projects viz., Waste load allocation and assimilation capacity, State wide environmental action plan for various states, development of guidelines for EIA’s of infrastructure development; European Union funded project on assessment of impacts of Tributlytin (TBT) on multiple coastal uses, stabilisation of Haldia channel etc.

CEE group is at the forefront of coastal related research and development compared to traditional coastal engineering institutions due to the ability to integrate field investigations, mathematical modeling studies, engineering solutions and field execution tailored to site-specific requirements; all under one roof. The group has primarily concentrated in evolving areas where research input is higher. This can be clearly seen from the different types of projects handled over the years which have resulted in accumulation of a spectrum of data bank covering almost the entire coastline of the mainland and the islands of Andaman and Nicobar and Lakshadweep. A large number of case studies have been undertaken along the entire coastline for validation of model studies and corroborated using field data. Significant contribution to society and industry by the CEE group is by providing technical support for ports and harbours, erosion mitigation studies; fisheries harbour development, navigation and allied activities. Areas of expertise include detailed engineering designs for intakes and outfalls, breakwaters, dredgeability and disposal studies, configuration of dam alignment based on engineering, geophysical studies and geological site setting, comprehensive and rapid environmental impact assessment for coastal infrastructure and Risk Assessment (RA) studies for hazardous cargo handling.

Field observations form the crux of the data collection program to create baseline data with site specific information. Collection of data using internationally acceptable standard procedures/methods and transformation of raw data to usable information are the strengths of the group which has enabled providing engineering solutions. The number of parameters measured at each site varies from 13 to 100 at places. CEE group has state of the art infrastructure for measurement of geotechnical, oceanographic, ecological and allied environmental laboratories. To cater the computational requirements numerical modelling and statistical analysis a high performance cluster has been setup by the group. Laboratory analysis is carried out generally as per Indian Standards (BIS) and according to international standards in absence of national code. Also code of practice was developed in-house for surveys, measurement and geosynthetics design in the coastal zone. The group has reviewed BIS, PIANC standards for latest updates in the field of coastal engineering. CEE is entrusted by Ministry of Environment, Forest and Climate Change (MoEF&CC) to undertake HTL/LTL mapping to complex CRZ demarcation on the cartographic front.

Data collection in the coastal zone, unlike a ship borne cruise involves risks of operating in the surf and wave breaker zones, patience, extensive walking and keen observation. Beach profiles generally would need 3 persons to cover 2.5kms a day, at a resolution for CRZ mapping. Establishing local bench marks with a GPS observation is a rigorous exercise that the group undertakes. Bathymetry surveys are usually fast with coverage up to 20 line km a day, provided tide and met-ocean weather cooperates. Water quality and sediment observations require extensive laboratory work. Although remote sensing is progressing towards utility, yet it needs ground truth and often a greater detail is essential for development projects. Overall, for carrying out studies for a 20 km stretch, at least 15 - 20 technical person are required. Moreover deployment of near-shore observations has its own share of issues, - Vandalism, water seepage, buried instruments etc. Against all the odds, CEE group has managed to recover 85-90% data in all the projects well in par with international standards. This essentially translates to 40% of time in a year at site, for two seasons. CEE at NIOT is progressing towards an integrated approach for handling datasets. CEE has been progressing towards near shore and surf zone technologies which are still in development stages internationally.

Since the inception the group is involved in modeling of various coastal processes such as shoreline changes, dredge dump disposal, tranquility, advection dispersion, siltation, storm surge, wave transformation etc. Numerical model studies carried out for project Kalpasar is a landmark achievement of the group. The group has published the NIOT Wave Atlas for the coast of India after two decades since the first wave atlas for Indian coast was published. CEE has the expertise of using numerical models such as Delft-3D, MIKE, ADCIRC, SWAN, SWASH for coastal processes and specific packages like PHAST (for hazardous cargo quantitative risk assessment) and CORMIX (for dispersion studies and outfall design)

CEE group has provided expertise for engineering and design to Port Trusts, Fisheries Department, Public Works Departments, Tourism Department's, local bodies of state and central government. For the first time in India, indigenously designed and developed suction pile was installed by the members of the group. The group is also demonstrating an indigenously designed unique shore protection scheme using geosynthetic tubes at Kadalur Periya Kuppam as part of Ministry of Earth Sciences Shoreline Management project. The project aims at protecting the fish landing centers and fishing hamlets in a natural and sustainable manner without affecting the livelihood and adjacent shorelines.

As part of the EIA sustainable environmental friendly designs have been incorporated in the project inception stage itself. Model studies have been carried out for consequences of handling hazardous cargo and analysis, prediction and design of brine/heated aqueous discharges into water bodies.

The group is a mix of technical personnel with experience, mettle and energy. Present day seniors have seen the transformation of coastal engineering in the past 20 years and have the hands-on experience and competence of carrying out challenging projects under the guidance of veterans in the coastal engineering field. Juniors have undergone meticulous training and requisite energy and are capable of enduring longer data collection programmes. An archive of 250 project reports provides proof of multi-disciplinary works undertaken. The proposals submitted to various state governments and industrial sector are competitive with market and personnel undertaking work scoping are adept with the future technologies. Project reports are vetted by third party contemporaries in the field. Observations have been documented and published in reputed journals for public access. Training to government departments and industry has been provided and student internships / projects are undertaken to disseminate the knowledge. Following is the summary of communications made:

CEE group research focuses in creeks, estuaries, nearshore and coastal areas which are zones extensively utilized by the coastal communities, fisheries and marine industry. The group’s ability to develop application-oriented technology and conduct scientific research in the marine sector thus contributes to sustainable coastal infrastructure development of the nation.

Under the plan projects shoreline response studies have been carried out all along the Tamilnadu coast and priority sites in other states like Uppada in Andhra Pradesh, Querim beach in Goa. For developing Technical Criteria Atlas field data has been collected all along the Indian coastline.  Comprehensive water quality monitoring and biological studies  have been carried out in the open coasts with focus on polluted areas like Ennore & Thane Creeks, Hugli estuary etc. Field data collection has been carried out primarily for calibration of the mathematical model studies and detailed engineering design. These studies have enabled thorough understanding of the coastal processes, shoreline behaviour and response to coastal protection structures, water quality issues in the nearshore, estuarine and creek waters, biological phenomena etc. thus developing the competence, capability and confidence of the group with respect to coastal engineering.