Introduction

The knowledge of the ocean is essential for many stakeholders dealing with climatology, fisheries, ports and harbours, coastal zone management, navy and coast Guard organizations, public health institutions, environmental agencies, tourism industry, weather forecasters, offshore mining and oil industries and climate research. Ocean observing systems has a central role to deliver ocean services to the society. However, data produced by these systems need to be translated into ocean information services by analysis systems and also assimilated in ocean general circulation models to deliver past, present and future state of the ocean and also different products required by user agencies. A distributed or centralized data management system is critical to timely delivery of Ocean services. Ocean observation systems consist of (a) in-situ measurements, using sensors mounted on ships, buoys, moorings, coastal stations to capture changes in time and depth at specific points or tracks and (b) remote sensing systems such as satellites, aircraft, radar,

M. Ravichandran (H)

Indian National Centre for Ocean Information Services (INCOIS), Ministry of Earth Sciences, Post Box No. 21, IDA Jeedimetla, Hyderabad 500055, India e-mail: [email protected]

A. Schiller, G. B. Brassington (eds.), Operational Oceanography in the 21st Century, 55

DOI 10.1007/978-94-007-0332-2_3, © Springer Science+Business Media B.V. 2011

etc to capture the spatial and temporal variations synoptically, as manifested at the surface. Remote sensing in general and satellite measurements in particular (Le Traon PY, this volume) provide horizontal distribution of surface variables, such as temperature, sea surface height, ocean color, as well as several meteorological parameters for the calculation of air-sea momentum, heat and fresh water fluxes (Masumoto et al. 2009). These satellite data enable studies of phenomena across a very wide range of time scales, from intraseasonal to decadal and complement the in-situ observing systems.

Ocean observations also help answering some fundamental research questions, such as identified by National Science Foundation (NSF) reports (NSF 2001; Ko-blinsky and Smith 2001). They are (a) determining the role of ocean on climate and climate change, (b) quantifying the exchange of heat, water, momentum and gases between the ocean and atmosphere, (c) determining the cycling of carbon in the oceans and the role of the oceans in moderating the increase in atmospheric carbon dioxide, (d) improving models of ocean mixing and large-scale ocean circulation, (e) understanding the patterns and controls on biological diversity in the oceans, (f) determining the origin, development and impact of episodic coastal events such as harmful algal blooms, (g) assessing the health of the coastal ocean, (h) determining the nature and extent of microbial life in the deep crustal biosphere, (i) studying subduction zone thrust faults that may result in large, tsunamigenerating earthquakes and (j) improving models of global earth structure and core-mantle dynamics.

Climate research became a major focus of scientific debate/discusstion by the latter half of the twentieth century, especially after the identification of the impact of green house gases and global warming on Earth's climate system. Many countries, both the developed and developing ones, are spending considerable amount of their resources for climate research so that governments and society can take appropriate steps in planning and development. A sustained observation program to detect, track, and predict changes in physical, chemical, geological and biological systems and their effects is needed to measure the impacts of humans on the ocean as well as the impact of the human activity. The ocean, comprising over 70% of the surface of the planet, is currently monitored far less effectively and completely than terrestrial systems, yet humans depend strongly on the sea as a source of food and for transportation and trade, among many other uses. Further, the ocean strongly affects large-scale weather patterns, such as El-Nino and Sothern Oscillation (ENSO), Indian Ocean Dipole (IOD), etc. In order to understand and ultimately predict how the ocean-atmosphere interaction affects weather and climate, and how human activities affect both the physical system and living marine resources, an integrated ocean observing system is needed to monitor the 'state' of the ocean. Just as continuous measurements of weather and climatic conditions are maintained on land, similarly sustained measurements of the ocean are required to monitor change and to assist in understanding and predicting its impacts.

There are two different classes of in-situ observing systems—those based on fixed points (Eulerian) and those whose location varies with time (Lagrangian). Fixed point observations are made either from moorings or from repeated occu pation of stations. Observations whose location varies with time are made from platforms that move as a result of the motion of the ocean or of a moving vessel. Some moving platforms are thought to follow the motion of water parcels fairly well. Successful operation of a global in-situ observing system requires that there be coordination of activities on a number of levels. Sensors and best practices learned from other experiences need to be agreed. Deployment opportunities need to be identified and instruments delivered to take advantage of them; where no opportunistic deployment is feasible, timely provision of special deployment efforts needs to be made. The data coverage of the system needs to be monitored along with sensor lifetimes and provision made to anticipate where gaps will appear so that deployment can be arranged. Successful implementation depends fundamentally upon near-real time transmission of both observations and relevant metadata. Given that a number of nations participate in each of the observing networks and both 'operational' and 'research' programs are involved, this monitoring/system management function is non-trivial and critical (Clark and Wilson 2009).

Though some of the ocean processes can be addressed and described using local observations, many processes need to be addressed using observations from other locations since remote forcing may play an important role. Accounting for remote forcing effects would require observing all basins. But no country can afford to have observations in all basins. Hence, many national and regional programs are networked through the United Nations. The Global Ocean Observing System (GOOS) is an oceanographic component of Global Earth Observing System of Systems (GEOSS). It is a system of programmes, each of which is working on different and complementary aspects, for establishing an ocean observation capability for all of the world's nations. UN sponsorship and UNESCO assemblies assure that international cooperation is always the first priority of the Global Ocean Observing System. GOOS is designed to (1) monitor, understand and predict weather and climate, (2) describe and forecast the state of the ocean, including living resources, (3) improve management of marine and coastal ecosystems and resources, (4) mitigate damage from natural hazards and pollution, (5) protect life and property on coasts and at sea and (6) enable scientific research. GOOS is sponsored by the Intergovernmental Oceanographic Commission (IOC), the United Nations Environment Program (UNEP), the World Meteorological Organisation (WMO) and the International Council for Science (ICSU), and implemented by member states via their government agencies, navies and oceanographic research institutions working together in a wide range of thematic panels and regional alliances. More detail about GOOS can be found at http://www.ioc-goos.org/. The Joint Technical Commission for Oceanography and Marine Meteorology (JCOMM) of the WMO and IOC provides coordination at the international level for oceanographic and marine observations from all in-situ observing systems. The present status of location of different elements of in-situ observing system is available at http://wo.jcommops. org/cgi-bin/WebObjects/JCOMMOPS.

An in-situ observing system consists many elements such as tide gauges, ship based marine meteorology from Voluntary Observing Ships(VOS), Ships of Opportunity (SOOP) based XBT/XCTD sections, repeat hydrography, drifting and moored buoys, acoustic tomography, argo profiling floats, gliders, etc. Each element has some advantages and disadvantages in terms of temporal and spatial resolutions. Integrating all the elements, sustaining and improving the different components of observing system to meet the evolving needs for societal benefits is an imperative need for ocean observing system. Though the sensors used in these platforms/elements records primarily physical variables, the time has come to have multi-disciplinary approach to understand the total system. In the following sections, the elements of different observing systems pertaining to physical variables are explained in terms of its capability to observe the ocean, technology and some of its applications. The implementation plan for one of the poorly observed Indian Ocean is briefed in Sect. 3.3. The strengths and weaknesses of each platform and the final concluding remarks emphasizing the requirement of optimal mix of different in-situ platforms to deliver meaningful information are presented in Sect. 3.4.

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