Toward the Practical Application of Oceanic Forecasts

The reality of global warming is the modulation of climate modes that excite climate variations. In order to improve accuracy in prediction of the phenomenon, the advancement of not only atmospheric general circulation models, but also of oceanic general circulation models, is necessary. To advance oceanic general circulation models, a practical application of oceanic forecasts, like that of atmospheric forecasts, is essential. Making prediction of oceanic variations on a daily basis will create a new future for the industrial, governmental, and academic sectors.

Global warming and climate variations

A climate regime shift that occurred around 1976 is well known among climate researchers. The increase rate of the average surface temperature doubled compared with that of before 1976, and it exceeded 0.1 degree per 10 years in a recent decade. This is largely due to the recent perennial El Nino-like condition across the entire tropical Pacific Ocean (called decadal El Nino) as well as to the fact that El Nino phenomena themselves occurred more frequently. Therefore major El Nino phenomena were more easily generated recently. This is understandable because the El Nino phenomenon is a mechanism to release accumulated heat in the tropical ocean into the atmosphere and subtropical oceans. The increased sea level around islands in the central tropical Pacific Ocean was caused actually by the decadal El Nino phenomenon rather than directly by the global warming. The Indian Ocean Dipole Mode phenomenon (an El Nino-like phenomenon that occurs in the tropical Indian Ocean and causes heat waves in East Asia) also has recently begun to be easily generated due to the increased sea surface temperature of the Indian Ocean. In this way, global warming can be identified as concrete oceanic and atmospheric climate variations. Attention should be drawn to the fact that great concern began to be expressed from around 1976 over global warming in relation to greenhouse effects, accompanying the increase in concentration of greenhouse gas due to deforestation and enormous consumption of fossil fuels.

Prediction of climate variations

Against this background, the importance of oceanographic and meteorological interdisciplinary research for predicting oceanic and atmospheric climate variations has long been recognized. This trend accelerated on the wake of the major El Nino that began in 1982/1983. As a result, the Tropical Ocean and Global Atmosphere (TOGA) program was implemented for 10 years from 1985 to 1994 under the World Climate Research Program (WCRP) sponsored by World Meteorological Organization (WMO), Intergovernmental Oceanographic Commission (IOC) of UNESCO and International Council for Science (ICSU).
To predict oceanic and atmospheric climate variations, it is necessary to operate with an atmospheric general circulation model coupled with an oceanic general circulation model. Observational data from wide areas are introduced to this coupled model as initial values, so that they can be assimilated readily. Both atmospheric and oceanic models have biases, and as they are complicated and nonlinear they display more chaotic behaviors if they exceed prediction limits. Therefore, with real-time observational data being assimilated into the model appropriately, a numerical integration must be done continuously to obtain the results of predictions without a break. Observational data from wide areas include sea winds, altimetry data of sea surfaces, water temperature, precipitation, and the distribution of cloudiness through satellite observation; atmospheric data through sonde observation 1) in the air, such as wind velocity, atmospheric pressure, temperature, and humidity; and water temperature data through vessels.
Data on sea water temperature, ocean currents, and wind velocity obtained through 70 mooring buoys(TRITON/TAO) deployed in the equatorial area of the Pacific Ocean have also been used recently through the Tropical Ocean and Global Atmosphere (TOGA) program. In the future, it is hoped an improved observation system can be put in place not only for predictions of El Nino phenomena in the Pacific Ocean but also for predictions of Indian Ocean Dipole Mode phenomena in the Indian Ocean and similar phenomena in the Atlantic Ocean.

Necessity of oceanic forecasts

Atmospheric general circulation models used for the predictions of climate changes are basically the same as those used for daily weather forecasts, but in order to aim at increasing their accuracy, improvements are being constantly made by the Japan Meteorological Agency and related research institutes. With regard to oceanic general circulation models, it is also necessary to predict ocean currents, water temperature, salinity concentration and the like on a daily basis, especially as they might have an impact on human activities, and to continue the search for ways of improvement.
In order to promote this, the Frontier Research Center for Global Change started the Japan Coastal Ocean Predictability Experiment (JCOPE) in 1997 when the center was established. Based on its results, predictive data for two month periods on currents and water temperature variations from the sea surface to the sea bottom in the western Pacific Ocean, including seas close to Japan, have been made available since December 2001 through its website (http://www.jamstec.go.jp/frsgc/jcope/index.html).
"Oceanic forecasts" began to be developed much later, compared with the long history of atmospheric forecasts, but it can be said that the practical application of oceanic forecasts has finally come on to the horizon. Current spatial resolution is approximately 10 kilometers, but imminent flows in bays can also be predicted by improving a nesting method 2) and other methods. In addition, it is possible to develop a system predicting chemical variables and biological variables, with the current system predicting physical variables as a platform.
If oceanic forecasts like this are made on a daily basis, it is thought that ocean management will become easier. Considering that the unrestrained coastal management of a certain country that disposes of radioactive and other waste is costly to neighboring countries, countries far away, and even future generations, and that the overdevelopment of marine resources is likely to endanger even the existence of human beings themselves in the end, and considering the importance of countermeasures against illegal dumping in the ocean and of ensuring the safety of marine traffic, it is also possible that oceanic forecasts will help create a system for each country to truly manage the world's oceans in cooperation with each other. Oceanic forecasts will also further prompt the advancement of the ocean part of the combined atmospheric and oceanic general circulation model used for the prediction of climate variations, and eventually contribute to the clarification and prediction of the climate variations of not only tropical regions, but also of subtropical and subarctic regions. This is also thought to have useful effects on the prediction of the decadal climate variations, which appears in the world oceans as a signal of global warming, and on the design of social infrastructure based on the predictions.

Future direction

Measures to promote the prediction of El Nino phenomena, and other oceanic climate variations, and the prediction of oceanic variations, namely oceanic forecasts, were also included in the initial design of the Global Ocean Observing System (GOOS), which was initiated by UNESCO's Intergovernmental Oceanographic Commission (IOC) and based on Chapter 17 of the Action Plan, Agenda 21, adopted by the UN Conference on Environment and Development (UNCED) in Rio de Janeiro in 1992. The development of a precise oceanic forecast system that is verified by daily in situ data is essential for the prediction of climate variations, i.e., the reality of so-called global warming phenomenon. It is also capable of activating all the industrial, governmental, and academic sectors through the improvement of a global observation system, the verification of results of predictions with the use of general circulation models, and the improvement of general circulation models. These sectors can also be involved in the utilization of results of predictions for ocean management, the establishment of a mechanism for conveying the results of predictions through mobile terminals, in a search for beneficiaries' additional needs, and the possibility of the introduction of systems for professions specializing in the management of marine resources and environments, and oceanic (weather) forecasters. It is hoped that Japan will take the initiative in the establishment of such a system, and promote the formation of an international network for its system technology, and the international standardization of the system technology.
1) Sonde observation: Sonde observations are made by releasing balloons with meteorological instruments attached, and observing the vertical distributions of temperature, atmospheric pressure, humidity, etc. Sonde observations are made in various parts of the world at fixed times under the World Weather Watch (WWW) system of the World Meteorological Organization.
2) Nesting: Nesting is a method of running simulations by calculating with the use of fine grids for phenomena or regions of interest, and coarse grids for areas around them, and by exchanging information.
・In order to promote the advancement of system technology and the establishment of an international network for oceanic forecasts, the Study Group for Prediction and Information on Oceanic Conditions has been working actively (head office: cowfs.jimu@jamstec.go.jp).