Overview of Regional and Coastal Systems

Jiang Zhu

Abstract During the GODAE period, some coastal and regional systems for short-range ocean forecasts in the Asia-Oceania have been developed. This paper first provides an overview of these operational forecast systems and some preoperational systems developed by Australia, China, Denmark, India, Japan and Korea in the terms of model domain, resolutions, models, data inputs and data assimilation schemes. These systems cover some key ocean areas in Asia-Oceania. Then services, products, users and feedbacks provided by these systems are shown briefly. Some operational ocean analyses and forecasts support both data products and online graphical public services. Some systems such as the Bluelink ocean forecasting system of Australia have proved skilful in forecasting, coastally trapped waves, coastal upwelling, offshore ocean state and boundary currents of Australian coast. As evidence of the utility of these regional systems, some highlighted examples are also given. For example, some Japanese systems successfully predicted the Korushio large meander in 2004; an operational system provided service for the 2008 Olympic sailing events; a Japan Sea/East Sea forecasting system has been used for successful reproduction and prediction of large numbers of giant jelly-fishes in Japan/Sea Sea. All these systems are strongly connected with the GODAE products. The Argo and GHRSST datasets are essential inputs for initialization of these forecast systems. The Indian Ocean is relatively less covered by these regional systems. However, GOOS-CLIVAR's effort in establishing Indian Ocean Observing system will improve the situation and some of its progresses are highlighted.

From the practices of testing and applying these regional and coastal systems, some scientific problems can be explored and important lessons can be learnt. In this lecture notes, as an example, we discuss the SST predictability and forecast error growth in China marginal seas. Based on a series of 7-day hindcast experiments over one year period (2006) with the initial conditions provided by assimilating SST and altimetry data, the root mean square errors (RMSEs) of the

Institute of Atmospheric Physics, Chinese Academy of Sciences, Qi jia huo zi, De sheng men wai Street, Beijing 100029, People's Republic of China e-mail: [email protected]

A. Schiller, G. B. Brassington (eds.), Operational Oceanography in the 21st Century, 413

DOI 10.1007/978-94-007-0332-2_17, © Springer Science+Business Media B.V. 2011

hindcasted SST are less than 0.7°C in the shallow Bohai and Yellow Sea (BYS) with the forecast lead time up to seven days. In the East China Sea (ECS) where the energetic Kuroshio passes, the RMSEs of SST reach to 0.9°C as the lead time increases to 7 days. In the South China Sea (SCS), the 7-day hindcasts have a mean RMSE less than 0.6°C. The hindcast skills also show some seasonal dependence. It is found that in the SCS the skills are higher in the summer season and lower in the winter. Analysis of results shows that the hindcast RMSEs are strongly associated with the strong SST fronts and surface current jets which can introduce hindcast errors due to the horizontal advections. Some problems for further improvement are identified.

17.1 Introduction

Coastal ocean nowcast/forecast systems are an increased interest in a wide range of society. For instance, improved forecasts of future states in target areas are required for marine management and rescues, pollution control, and mitigation of the damage of coastal flooding and harmful algal blooms, in addition to the traditional requirement of shipping navigation and fishery managements. The 2002 GODAE Development and Implementation Plan states: "Climate and seasonal forecasting, navy applications, marine safety, fisheries, the offshore industry and management of shelf/coastal areas are among the expected beneficiaries of GODAE." The usefulness of GODAE systems to coastal and shelf seas forecasting will therefore be one of the measures of the success of the project. During the GODAE period, various coastal and regional systems for short-range ocean forecasts in the Asia-Oceania have been developed. Operational forecast systems and some pre-opera-tional systems developed by Australia, China, Denmark, India, Japan and Korea are some examples as Table 17.1. These systems cover some key ocean areas in Asia-Oceania.

Bluelink is an Australian partnership between the Commonwealth Scientific and Industrial Research Organisation, the Australian Bureau of Meteorology (ABoM) and the Royal Australian Navy. The primary objective of Bluelink is the development of a forecast system for the mesoscale ocean circulation in the Australian region and adjacent basins of importance. The Bluelink forecast system (Brassington et al. 2007) became operational at the ABoM in August 2007 providing seven day forecasts twice per week.

In Japan, several systems have been developed. Japan Meteorological Agency (JMA) started operational use of new ocean analysis/forecasting system for western North Pacific in 2008 March. This system provides the information of the ocean state in the Sea around Japan. Monitoring and forecasting of major currents around Japan such as the Kuroshio, the Oyashio, and the Tsushima currents are being paid particular attention because variations of these currents strongly affect the ocean state around Japan. Outputs of this system are being used for various purposes. The current field in this system is used for prediction of the position of drifting

Table 17.1 A summary of ocean forecasting systems in the Asia-Oceania regions

System name Ocean model Nesting strategy Atmospheric forcing

Ocean data input

Data assimilation scheme

Agency/ Institution

Bluelink OFAM

MOVE/MRI. MRI.COM COM-WNP

JCOPEL2 Modified

POMgcs

Kyoto U Kyoto U

' OGCM NMEFC POM

HYCOM

YEOS BSHcmod

ESROM MOM3

Global model BoM"s operational global weather prediction model One-way nesting JMA"s operational atmospheric analysis; results of climate forecasting model One-way nesting 6-hourly NCEP Global

Forecast System or NCEP/ NCAR reanalysis

One-way nesting

One-way nesting NMEFC "s mesoscale weather forecast

One-way nesting ECMWF reanalysis mesoscale weather forecast Two-way nesting DMI weather forecast ECMWF reanalysis

In situ temperature and salinity; along track SSHA; gridded SST

Along track SSHA; in-situ T, S; along track SST

Gridded SST Argo profiles

Gridded SSHA; gridded SST; in situ T, S

In situ temperature; gridded SSHA; SST

EnOI

ABoM

3DVAR with vertical coupled TS-EOF modes; IAU 3DVAR with vertical JAMSTEC coupled TS-EOF FRA modes; IAU 4D-VAR Kyoto U

Nudging for SST and NMEFC

OI for profiles EnOI IAP

Kaiman filtering 3DVAR

DMI KORDI

targets (e.g., oil spill). Also, the ocean state in this system is used for identifying causes associated with unusual sea level. Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has started an operational ocean forecast experiment for Northwestern Pacific (Japan Coastal Ocean Predictability Experiment; JCOPE) in December 2001. Fisheries Research Agency (FRA) has been operated the first version of JCOPE ocean forecast system (JCOPE1) since April 2007 for management of fishery resources of Japan by coupling the JCOPE1 with ecosystem model (FRA-JCOPE). JAMSTEC has further developed the second version of the system (JCOPE2) with enhanced model and data assimilation schemes. Output of JCOPE2 is used for ship routing of oil tankers, fishery and drilling ships. Most recently Kyoto University has constructed a high-resolution 4-dimensional variational (4D-VAR) ocean data assimilation system with the aim of developing an integrated monitoring of synoptic to meso-scale features observed in the mixed water region for the northwestern North Pacific which is one of the most energetic regions in the world oceans. They have demonstrated that the downscaling is a powerful approach towards the better nowcast and forecast of coastal circulations in the regions such as offshore of Shimokita Peninsula where vigorous interactions with the marginal seas occur.

The National Marine Environment Forecast Centre (NMEFC) of China started its operational numerical ocean forecasting in 1990s. There are several operational forecast systems covering different domains: from large scale of western North Pacific to relatively small coastal regions such as the Bohai Sea. Their products are delivered to users across public, government and commerce. In 2006, Chinese Academy of Sciences (CAS) started developing a preoperational ocean nowcast/forecast system around the Chinese coast lead by the Institute of Atmospheric Physics (IAP). Since 2008, this system development has been enhanced further by multi-institution collaboration and establishing a long term in situ observation network of four offshore buoys that will be operated and maintained by Institute of Oceanography and Institute of South China Sea Oceanography. The aims of the system are to provide a test bed to explore the coast and shelf sea predictability and transit to operational agencies.

Besides the above mentioned national efforts, international collaboration also plays an important role. The Yellow Sea is a semi-enclosed sea surrounded by China and Korea. Extensive research and cooperation have been carried out in this region both in national and international level by China and Korea. However, the existing works need yet to be integrated into a forecasting system. Major bottle-necks in developing the Yellow Sea monitoring-forecasting system are the lack of high quality, near real time weather forecasts, as well as coupled 3D ocean-ice models and operational infrastructure. With support from EU FP6 project YEOS (Yellow Sea Observation, forecasting and information System, 2007-2009, http://ocean.dmi.dk/yeos) and Danish Sailors' Union, European weather and ocean-ice forecasting system has been applied to the Yellow Sea and a pre-operational weather-ocean-ice forecasting system has been demonstrated in a period covering Beijing Olympic Game 2008. A wide range of users have enjoyed the high resolution ocean and weather services provided by the YEOS information system. YEOS also improved data exchange between China, Korean and EU partners.

17.2 Overview of Systems

The geographic coverage of each system is shown in Fig. 17.1. Most of these systems use nesting schemes with different domain/resolution. The single domain for each system in Fig. 17.1 mainly represents one of its main focuses of each system. Most systems concentrated in the western North Pacific with centres in the Japan Islands, Korea Peninsula and Chinese coast. The Bluelink system, surrounding Australia, covers part of the Southern Ocean and the western Indian Ocean.

17.2.1 Bluelink

The key elements of the Bluelink system are the Bluelink Ocean Data Assimilation System (BODAS; Oke et al. 2005) and the Ocean Forecasting Australia Model

Fig. 17.1 The geographic coverage of each system in Asia and Oceania

(OFAM), a global ocean general circulation model. OFAM is based on version 4.0d of the Modular Ocean Model (Griffies et al. 2004), using the hybrid mixed layer model described by Chen et al. (1994). OFAM is intended to be used for reanalyses and short-range prediction. The horizontal grid has 1191 and 968 points in the zonal and meridional directions respectively; with 1/10° horizontal resolution around Australia (90-180E, south of 17N). Outside of this domain, the horizontal resolution decreases to 0.9° across the Pacific and Indian basins (to 10E, 60Wand 40N) and to 2° in the Atlantic Ocean. OFAM has 47 vertical levels, with 10 m resolution down to 200 m depth. The topography for OFAM is a composite of topography from a wide range of sources including dbdb2 (www7320.nrlssc.navy.mil/DBDB2 WWW/) and GEBCO (www.ngdc.noaa.gov/mgg/gebco/). Horizontal diffusion is zero. An ensemble optimal interpolation (EnOI) scheme is used for assimilating sea level anomaly from satellite altimetry, Argo profiles and satellite SST. For detailed description of the assimilation scheme see Oke et al. (2008). The operational system, OceanMAPSv1.0b (Brassington et al. 2007) produces a 9 day hind-analysis and 7 day forecast twice per week using the surface fluxes from the Bureau of Meteorology global weather forecasts. Near real-time altimetry is obtained from Jason-1 and Envisat and real-time SST is obtained from AMSR-E. In situ observations are sourced from the GTS and the GDAC's for Argo and sorted for duplicates and automatically quality controlled. An operational graphical web service (http:// www.bom.gov.au/oceanography/forecasts) and a data product service is supported at the ABoM.

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