2.2     THE WMO GTS

In a sense the WMO GDPS GTS all along has been a closed private communication system, much like America On Line (AOL), CompuServe, etc. That is, the GTS can be visualised as an "INTRANET" albeit with old technology and whose subscriber have, so far, been the world’s national meteorological services.

Specifically, the GTS consists of an integrated network circuits which interconnect meteorological telecommunication centres. The circuits of the GTS are composed of a combination of terrestrial and satellite communication links. They comprise of point-to-point circuits, point-to-multi-point circuits for data distribution, multi-point to point circuits for data collection, as well as two-way multi-point circuits. And just like the Internet the GTS has a hierarchical structure:

The MTN is the backbone of the GTS. It links together three World Meteorological Centres and 15 RTHs. In this hierarchical structure RA I has four RTHs, namely Algiers, Cairo, Dakar, and Nairobi. These RTHs connect to the MTN via other RMTN or directly. The MTN has the main function of providing an efficient and reliable communication service between its centres, in order to ensure rapid and reliable global and inter regional exchange of observational data, processed information and other data required by Members

The RMTN is RA I highest circuit network level. It consists of an integrated network of circuits interconnecting meteorological centres, which are complimented by radio broadcasts where necessary. The RMTNs are there to ensure the collection of observational data and the regional selective distribution of meteorological and other related information to Members in RA I. The Data/Products Collection and Transmission platforms can be either satellite-based or ground-based.

2.2.1    Satellite-based platform

Satellite-based data/products collection and/or data distribution platforms are integrated into the GTS as an essential element of the global, regional and national levels of the GTS. The satellites are used for data collection of the observation data from the Data Collection Platforms (DCPs) and for distribution of data and/or products through the MDD and PDUS systems of METEOSAT or FAX-E of EUTELSAT. All these supplement the point-to-point GTS circuits, and several countries have implemented satellite-based telecommunication systems for their national meteorological telecommunication networks.

2.2.2 Ground-based Platform

The national meteorological Services collect observational data from their own network of ground-based observing stations (automatic and manual), quality control the data, use it, and at the same time put it on the national meteorological telecommunication network. Using the present store-and-forward procedures the data is then put on the GTS to be forwarded to the RMTN at the RTH and on to the MTN. Depending on the responsibility of the NMC, locally prepared products could also be forwarded.

The point-to-point links within the GTS are well defined and are in hierarchical structure which NMC links to which RTH and in which RTH links to which of the three WMO world centres in the backbone. However, for practical and efficiency considerations bilateral links may also be established on the GTS. Significant improvements continue to be recorded on the implementation status of the GTS at various levels in RA I. From the total of 87 Regional Meteorological Telecommunication Network circuits, 78% were implemented by 1998, 5 of which were digital at a high speed of 64 kbps, 21 were medium speed telephone type circuits and 42 were low speed telegraphic type circuits. The implemented circuits composed of 6 circuits on MTN, 13 on inter regional circuits and 49 regional ones. However, despite these improvements made in links implementation the total process of handling meteorological data/products remain a problem in RA I that needs further attention

In RA I, the RMC and RSMC which are generally co-located with RTHs may have lots of data/products, some are locally prepared others are imported. For these products to reach, the NMCs there must have good links between the NMCs and the RMC or RSMC. In many cases the links are still at low speed telegraphic ones. Some of the centres (RMC/ RSMC/NMC) may not be appropriately equipped - in terms of computer hardware, software or expertise - to generate or receive the required data and products. While some centres may have to start from a scratch, a few may merely need to upgrade.

Because of the variability of the extent of the problem, the suggested modular solution is thought to be more appropriate as this will facilitate for a centre to determine according to the needs and availability of resources and how to prioritise the modules for implementation.