The NEAR-GOOS Data Exchange System
for Better Ocean Services

Naoyuki Hasegawa
Chairman, NEAR-GOOS Coordinating Committee
El Nino Monitoring and Prediction Center
Japan Meteorological Agency
1-3-4, Otemachi, Chiyoda-ku, Tokyo
100-8122, Japan
naohase@naps.kishou.go.jp

Abstract
The North East Asia Regional GOOS (NEAR-GOOS) is a regional pilot project of GOOS to demonstrate the usefulness of international oceanographic data exchange. A framework using the Internet has been set up for the exchange of oceanographic data among various types of data providers/users. The system has now attracted more than twenty users. To prove its benefit, as a pilot project, NEAR-GOOS should extend its activities to the product generation. Data assimilation and numerical prediction, though yet to be refined at the moment, should be in operation in future to provide fundamental dataset for various application to produce the final product for end users.

Keywords: NEAR-GOOS, GOOS, data exchange, data assimilation, numerical prediction



1. Introduction

We should deal with the oceans and seas in a safe, effective and sustainable way. In order to do this, the oceanographic services need to monitor the state of oceans continuously, and give appropriate and timely guidance. For this purpose, ocean observations have to be made and observational data need to be collected as soon as possible and maintained for long time.

The Global Ocean Observing System (GOOS) is a comprehensive programme and is expected to coordinate the efforts of oceanographic services in the world to fulfil this task. The North East Asia Regional GOOS (NEAR-GOOS), implemented by China, Republic of Korea, Japan and Russia, is a regional pilot project of GOOS for the region shown in Fig. 1. It tries to demonstrate how international cooperation can help oceanographic services. The exchange of the existing observations among the participating countries is given high priority in the initial implementation of NEAR-GOOS. This paper describes the current data exchange system for NEAR-GOOS, with particular emphasis on the real time exchange. The personal views of the author on the future direction of NEAR-GOOS is also described.


2. NEAR-GOOS Data Exchange System

Considering that it is important for NEAR-GOOS to use the existing systems to the extent possible, the Integrated Global Ocean Service System (IGOSS) is briefly reviewed here. IGOSS is a system supported by the World Meteorological Organization (WMO) and IOC for the real time exchange of physical oceanographic data among national oceanographic services. It started the operation in mid-1970's and has given the world wide physical upper ocean observational data to the oceanographic services.

IGOSS involves not only research vessels and buoys which belong to various oceanographic services, but also many merchant ships and other non-research purpose ships. The data from the ships and buoys are transmitted to oceanographic or meteorological services through the telecommunication satellites, or coastal radio stations. Once the data are delivered to one of the oceanographic or meteorological services connected to the Global Telecommunication System (GTS) , then they are disseminated worldwide through it.

The current NEAR-GOOS data exchange system is summarized in Fig. 2. The data are exchanged in two different modes, one is the real time mode and the other is the delayed mode. Here, the term 'real time' indicates 'within 30 days after the data collection'. The Real Time Data Base (RTDB) has been established at the Japan Meteorological Agency (JMA), and the Delayed Mode Data Base (DMDB) has been established at the Japan Oceanographic Data Center (JODC). The users including data providers and the data bases are connected through the Internet.

The telecommunication system for IGOSS relies on GTS for international dissemination of the observational data as explained in the previous section. Therefore, the data users other than national Meteorological Services have not always been able to use the data, particularly in real time. For those users without GTS access, RTDB retrieves the oceanographic data on GTS for the NEAR-GOOS region and makes them available to the NEAR-GOOS users.

Therefore, one way of contributing to the NEAR-GOOS data exchange is to participate in the IGOSS by sending the data through GTS. For example, the Fisheries Agency of Japan started to contribute their data to NEAR-GOOS through GTS in 1997. Figure 3 shows the numbers of the sub-surface temperature reports from the ships of the Fisheries Agency before and after they started participating in the NEAR-GOOS activity. The general increase in the numbers of the reports is quite visible.

The data exchange over GTS has some limitations. For example, only a limited physical parameters can be exchanged, and the data have to be written in a defined format. The other way to contribute to the real time data exchange using the Internet gives more flexibility. The data in any format are accepted so long as the format is well documented. For the ease of the users, RTDB re-formats all the data including GTS data into agreed formats so that the users do not have to worry about the different formats from different data sources.

The data providers could send the data to RTDB, or they could open their data at their own server and allow RTDB to retrieve them. For example, the Far Eastern Regional Hydrometeorological Research Institute of Russia sends their data regularly to RTDB by writing them on the RTDB server in their own format. Some institutes have indicated the willingness to provide the data on their web servers as their contribution to NEAR-GOOS.

Thirty days after the data collection at RTDB, the data are transferred to DMDB for longer term maintenance. DMDB collects not only the data through RTDB but also those which are not exchanged in real time. These data are also accessible from the users through the Internet.

The NEAR-GOOS also defined Associate Data Bases. These data bases are established in participating countries and also play very important roles in the NEAR-GOOS data exchange system. They retrieve the data from the data producers in the country, and make them available to the NEAR-GOOS. Associate Data Bases also retrieve data from other databases so that the users in the country can access the data more efficiently.

Figure 4 shows the distribution of the sea surface temperature data at RTDB in November 1997. Note that for the ease of the data selection, for the moment, RTDB holds the GTS data not only in the NEAR-GOOS area but also over most of western North Pacific (20N - 90N, 110E - 180E). JMA produces daily SST analysis based on those data, and the analysis is also provided through the NEAR-GOOS data exchange system in a graphical form and in grid point values (Fig. 5). Figure 6 shows the distribution of the sub-surface temperature observations.

The NEAR-GOOS data are open to anybody. The users can use the data freely. However, for the sake of the security of the data servers, those who wish to use the data are requested to go through minimal formalities and to acquire an account at the data servers. At the end of March 1998, 28 users are registered and exchanging the oceanographical data.

3. Future direction of NEAR-GOOS

NEAR-GOOS should eventually benefit the end-users, who require useful products. They are generated through various applications using the basic dataset which may come from 'core' data processing. The author believes the most promising 'core' data processing includes data assimilation and numerical prediction. The data assimilation is a proven tool essential for atmospheric numerical prediction which is widely used in weather forecasting. It is now applied to the ocean in the operation and in the experiment.

An area of successful operation of ocean data assimilation is the monitoring of El Nino events (e.g., Kimoto et al.). An El Nino event is often defined in terms of warm sea surface temperature anomaly in the eastern equatorial Pacific. However, the sign of its onset and the stage of its life cycle can often be identified in the three dimensional temperature structure. Data assimilation technology using a general circulation model provides us with a consistent three dimensional ocean conditions from the limited number of sub-surface observations, and therefore, it is now an important tool for El Nino monitoring. The data assimilation is also used as the initial condition for the dynamical forecasting. A number of operational and research centers are running coupled ocean and atmosphere models which predict El Nino events reasonably well.

Three dimensional distribution of ocean parameters as it is may be already valuable for fisheries, for example. Moreover, the fundamental physical parameters in a gridded format can be used in various applications. One area of such application is transport models. Such application is now common in the atmospheric fields. For example, one can predict the position and extent of the volcanic ash for flight safety when a volcano erupts, or the movement of hazardous materials emitted into the atmosphere by an accident of a nuclear plant. Once the ocean data assimilation and numerical prediction are in operation, similar technology can be applied to various marine problems such as the ocean pollution.

The data assimilation can be done when sufficient data are available in real time, and modeling technology is established. The required data include the in situ and remote sensing observational data, forcing from the atmosphere, and volume flux from the outside in case of semi-closed seas as the NEAR-GOOS region. NEAR-GOOS provides the framework for the data collection, and part of the required data are already available through it. In addition, momentum and heat flux can be estimated from the atmospheric data assimilation used in the operational meteorological services, which are available through various mechanisms depending on the data and the institutions. Research is being undertaken in many institutes on several different ways to estimate the flow through small openings of the NEAR-GOOS area as reported in various papers in this volume. Methods include the direct measurement of the ocean current, the use of satellite altimeter data, the use of sea level gauges. Other researchers are using the submarine telephone cables to measure the voltage difference between the both sides of the flow and trying to estimate the volume transport from this measurement.

Because of the difference in the dominant processes, the status of modeling capability differs from region to region. The attempts to simulate the ocean circulation in the NEAR-GOOS region have been made by several researchers with some encouraging results (e.g., Mooer and Kang 1997, Awaji et al. 1998). Typically the models are driven by climatological mean winds and with fixed values for transport through the openings. The simulated current structure shows many features consistent with the observations, such as the two branches of the Tsushima Current, the Liman Current, etc. The research of modeling of this area is at the level of successful simulation of climatological structure. Attempts to assimilate the satellite altimeter data have also been made (Hirose et al. 1997).

Many of these techniques are yet to be refined for operational use. However, the current state of advancement in the research on both the observation and modeling suggest that data assimilation and numerical prediction may be feasible in future in the NEAR-GOOS area.

4. Concluding remarks

The NEAR-GOOS data exchange system is now under review by the NEAR-GOOS Coordinating Committee. The structure of the data exchange system may have to be modified slightly so that the system becomes more efficient particularly in collecting the data from many different data providers. A mechanism for quality control will also be proposed in near future, taking into account the benefit from the maximum use of existing activities such as the Global Temperature and Salinity Pilot Project (GTSPP) within the framework of IGOSS. Some more information on NEAR-GOOS is available at the web sites below:

http://www.unesco.org/ioc/goos/neargoos.htm
(for general information on NEAR-GOOS)

http://goos.kishou.go.jp
(for the Real Time Data Base)

http://www.jodc.jhd.go.jp/NEAR-GOOS.html
(for the Delayed Mode Data Base)

Acknowledgment

Some part of this paper was written based on the discussion in the informal meeting on the use of NEAR-GOOS data bases which was held at the time of the Symposium. The author expresses his sincere appreciation to the scientists who participated in this informal meeting. All the comments received at this meeting will be reflected in the discussion in the future NEAR-GOOS Coordinating Committee, and will contribute to the further development of NEAR-GOOS.

Reference

Awaji, T., K. Akitomo, J.-H. Yoon and Y. Sekine 1998. Research activities of numerical modeling for marginal sea and high-latitude processes associated with the Japanese GOOS. This volume.

Hirose, N., I. Fukumori and J.-H. Yoon 1997. Assimilation of sea surface topography with a reduced gravity model of the Japan Sea. CREAMS '97 International Symposium, 28-30 January 1997, Fukuoka, Japan, 97-100.

Kimoto, M., I. Yoshikawa, and M. Ishii 1997. An ocean data assimilation system for climate monitoring. J. Meteor. Soc. Japan, 75, 1-16.

Mooers, C. N. K., and H. S. Kang 1997. On the 26-sigma level POM model for Japan (East) (Note regarding the term 'East Sea') Sea circulation. CREAMS '97 International Symposium, 28-30 January 1997, Fukuoka, Japan, 15-23.

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