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Annex III Invited Contributions

TOPC Requirements for a Global Hydrological Network for Climate

J. Landwehr and J. Cihlar

Background

The Terrestrial Observation Panel for Climate (TOPC) is a scientific advisory panel jointly sponsored by GTOS and GCOS, which in turn are both sponsored by WMO, UNEP, and ICSU, and GTOS by FAO and UNESCO, and GTOS by IOC. TOPC has several assignments, but a primary task is "to plan, formulate and design a long-term systematic observing system for those terrestrial properties and attributes which control the physical, biological and chemical processes affecting climate, are affected by climate change or serve as indicators of climate change, and which are essential to provide information concerning the impact of climate and climate change. 1 TOPC has completed a GCOS/GTOS plan for climate-related terrestrial observations, which identifies variables of concern to the biosphere, hydrosphere and cryosphere, accompanied by a rational for including each variable in an observation network.2 TOPC has also proposed an observing strategy comprised of five hierarchical levels of observation by which to integrate this information; this system is called the Global Hierarchical Observation Strategy for Terrestrial System (GHOST) 3.

Neither GCOS 4 nor GTOS 5 directly make observations nor generate data products; rather they each provide an operational framework for integrating, and enhancing observational systems of participating countries and organisations. Similarly, TOPC is not a data producer, but rather identifies data needs and works to facilitate a solution. Three Global Terrestrial Networks (GTN) have been established to date -- one for glaciers (GTN-G), permafrost (GTN-P), and terrestrial carbon flux measurements (GTN-E). 6., 7 These networks have been incorporated into the United Nations Framework Convention on Climate Change (UNFCCC) Reporting Guidelines for Global Climate Observing Systems. 8 The next GTN that must be developed is a GTN-H, that is a global terrestrial network for hydrology with which to assess climate variability, change and impacts. The genesis for this meeting arose from this need.

Hydrospheric Variables

TOPC has already identified hydrospheric variables to be critical for climate assessment 9 but collections of appropriate and freely exchanged data are limited 10 The set of 10 variables that TOPC has identified as necessary for analysis of climate change detection as well as impact assessment, from both a societal and scientific focus, includes

1. Surface water flow - discharge.

2. Surface water storage fluxes

3. Ground water storage fluxes]

4. Precipitation - accumulated (solid and liquid).

5. Evapotranspiration

6. Relative humidity (atmospheric water content near the surface)

7. Biogeochemical transport from land to oceans]

8 Soil moisture

9. Snow water equivalent (SWE) from snow melt

10. Water Use

The first nine variables were identified in the TOPC 1997 report 2, which also provides a rational for selection, as well as the frequency, spatial resolution, accuracy and precision needed. The latter attributes are generally dependent upon the tier or relevant observational level. The tenth variable, water use, was added to the TOPC list during the most recent TOPC meeting. 11 (It is suggested that a good model for reporting this variable can be found in the 5-year reports by the USGS of water use in the United states. 12) Soil moisture (#8) has also been considered to be a biosphere variable in the TOPC report, and snow water equivalent (#9) to be a cryopsheric variable. Note that the set of variable includes all 3 phases of terrestrial hydrology: above, on and below the surface.

Single variable versus multi-variable data collection

Networks can be constructed as collections of single or multiple variables; both are needed. That is, information about one of the hydrospheric variables identified above can be useful as single variable time series of comparable quality globally available for many locations. This type of information is necessary to distinguish regional versus global trends.

For example, using the GTN-P web-available map product as an organising idea, the GTN-H could provide a comparable global map and accompanying data records for rivers discharging into the ocean, when any one of several possible conditions are met. These include: i) the river is among the top 300 major inputs of freshwater into the ocean which should account for about 60 percent of the estimated continental runoff (= precipitation minus evaporation) which flows into the oceans; ii) the river is a major freshwater source for a climatically sensitive region of the oceans, e.g. the North Atlantic or the Arctic Ocean; or iii) the river basin contributing the outflow has a population of above 1,000,000 inhabitants.

Multivariate time series of comparable quality and measurement frequency over a region are critical to modelling and process analysis, water balance studies, GIS support, etc. This has been one of the underlying tenets of WHYCOS 14 as well as other efforts.

Conclusion

The ideal is availability of data with minimal constraints, well-documented metadata, and easy (web) accessibility which would make it most valuable both for scientific and management use. To date, this has proved a challenge to the hydrologic community.

References

1.http://www.wmo.ch/web/gcos/topc.htm

2. GCOS/GTOS Plan for Terrestrial Climate-related Observations, version 2.0, June 1997, GCOS-32 (WMO/TD-No. 796, UNEP/DEIA/TR.97-7)

http://www.wmo.ch/web/gcos/pub/topv2_1.html

3. GHOST - Global Hierarchical Observing Strategy, June 1997, GCOS-33 WMO-No. 862)

http://www.wmo.ch/web/gcos/pub/ghost.html

4. http://www.wmo.ch/web/gcos/whatisgcos.htm

5. http://www.fao.org/GTOS/PAGES/D&IPlan.htm

6. http://sts.gsc.nrcan.gc.ca/permafrost/gtn-p.htm

7. Thematic GT-Net Networks discussed on:

http://www.fao.org/GTOS/PAGES/Gtnet.htm

8. http://cop5.unfccc.de/resource/docs/1999/sbsta/13a02.htm

9. Report of the GCOS/GTOS Terrestrial Observation Panel for Climate, third session, Cape Town, South Africa, March 19-22, 1996,GCOS-23, GTOS-1.

http://www.wmo.ch/web/gcos/Publications/gcos-23.pdf

10. Report of the GCOS/GTOS Terrestrial Observation Panel for Climate, fourth session, Corvallis, USA, May 26-29, 1998, GCOS-46, GTOS-15.

http://www.fao.org/gtos/PAGES/topc/TOPC400.htm

11. Report of the GCOS/GTOS Terrestrial Observation Panel for Climate, fifth session, Birmingham, England, July 27-30, 1999, in review.

12. USGS, Estimated Use of Water in the United States in 1995

http://water.usgs.gov/watuse/pdf1995/html/

  1. http://www.geography.uc.edu/~kenhinke/CALM/map.html

14. http://www.wmo.ch/web/homs/whycos.html

15. http://www.gos.udel.edu/ios/specific.asp

Hydrological Data and Information Requirements

P. Döll

1. General interest for a global hydrological network for climate and water resources

At the Center for Environmental Systems Research, one of our main research topics is the large-scale (global and continental) modelling of water related problems. We are developing a global model of water availability and water use (WaterGAP, a raster model with a resolution of 0.5°), which is used to develop scenarios of the future water (quantity) situation, e.g. for the World Commission on Water for the 21st Century. Besides, WaterGAP is applied in environmental security research. In the future, we intend to extend WaterGAP to water quality aspects. WaterGAP requires a large number of input data sets and some data sets for model validation, related to hydrological modelling and the modelling of water use by the domestic, industrial and agricultural sectors. For questions of environmental security and water management, additional data sets are needed. As all the desirable data are related to water and climate, and are global data sets, it appears to be appropriate to collect and archive them in a global hydrological network for climate and water resources.

2. Problem dimension from my perspective

My perspective is the perspective of a data user who wants easy access to a large variety of data for the whole globe which are well documented. Besides, to a very small extent, we have also derived 0.5 degree gridded data sets (irrigated areas, lakes and wetlands, drainage direction map); for these data sets, I want to find a location / an archive where our data sets can be easily found and retrieved (with due acknowledgment of the authorship).

3. Perceived objective and deliverables of a hydrological network

The hydrological network should produce, archive and distribute data sets incl. meta data sets. It should serve as a contact point with the authors of the data sets in case of questions. Maybe the network could also foster common research projects.

4. Data and information requirements

Spatial scale: global, temporal scale: long time series, temporal resolution: variable

Gridded data (spatial resolution 0.5° or higher):

Point data:

Polygon data (for administrative units):

Data should include information on how data set was derived, and on uncertainty of data.

5. Principal scientific and technological issues and problems

Water use data: In the main water use sector, the irrigation sector, water use is mostly not measured. In all sectors, the measurements are done by local users and results are not collected and archived centrally such that it is impossible to obtain measurement data when working at a larger scale. Following the USGS approach for the USA, the other countries should collect highly differentiated information on water use for spatial subunits by sending out, in a regular fashion (e.g. every five years) questionnaires to the administration in charge of the spatial subunit. Such a data collection requires a well-organized administration and the existence of measurement data at the local scale.

6. Possible users of the network

Researchers, water management planner (at the country-scale)

7. Product generation for users

Standard data sets should be made available, selection of spatial and temporal domain should be possible. To provide tailor-made products might be too ambitious, costly.

8. Approach and steps to implement a hydrological network

Water use data: 1. Identify, for each country, an institution that could collect water use data centrally (like USGS in USA). 2. Discuss USGS approach and modify approach 3. Find money

Additional Information:

For the generation of scenarios of future water availability and water use, information on the driving forces is required. These include meteorological information from GCMs; it would be desirable not only to be able to obtain selected results like from the IPCC Data Distribution Centre web site, but also meta data that include information on the uncertainty of the distributed GCM results. For water use scenarios, an existing gridded population distributing data set could be included; it would be desirable to develop population scenarios (also gridded). Other data relevant to water management issues include water prices.

Hydrological Observation Requirements

P. Jones

GCOS has set up two 'baseline' networks for long-term climate monitoring and related issues such as climate change detection. GUAN (GCOS Upper Air Network) consists of about 150 sites around the world where countries with stations will take radiosonde soundings with know equipment and to the highest levels possible. The network is only part of a more complete array of about 800 sites. The 150 sites, therefore, form a standard for assessing changes in instrumentation for the rest of the network.

GSN (GCOS Surface Network) is a near-1000 station network of roughly one station per 5 degree by 5 degree grid box. Countries with stations in this network will attempt to maintain the site, instruments and the environment in the immediate vicinity. Standard WMO statements regarding instrument changes etc apply to both GSN and GUAN (overlapping measurements etc when sites/instruments/times change). GSN is capable of monitoring hemispheric and global scale temperature variations (when combined with marine data) but needs to be augmented by more data to consider spatial variations in detail. For precipitation the network is inadequate for most applications, but it forms a baseline for more highly resolved data sets at the regional scale.

The Global Precipitation Climatology Centre (GPCC) produces gridded data at fine resolution from the basic GSN network augmented by SYNOP data and much more finely resolved national data sets. Drawback is that these data only extend back to 1986.

Both GSN and GUAN have online monitoring centres that have been set up to check both the receipt and the quality of data received. Reports go back to countries, generally through focal points. Archive centres have also been set up and historical data (daily records for the main climate variables for the whole record of the station) has been requested from all the countries that operate stations. Once received, the archive centre will make the data available via CD's and the WWW.

Neither network is ideal from a climate point of view, nor will they alone answer any of the questions in the climate change detection debate. Both networks were set up by WMO/GCOS through expert groups defining a network, which was then modified/agreed with each member country.

For a Global Hydrological Network a similar strategy would seem appropriate:

Issues in the Establishment of a Global Hydrological Network for Climate

B. M. Fekete and C. J. Vörösmarty[2]

Water Systems Analysis Group's interest in a global hydrological network

Water Systems Analysis Group of University of New Hampshire has over a decade experience in continental and global water balance and water transport models [21], [20], [16],[17]. Our group has developed various tools (water balance and water transport models and specialized GIS tools for gridded river network analysis) and global databases (RivDIS V1.0 [19] discharge station data, STN-30p gridded networks [18], [5] and gridded runoff fields [5], [6]). Our group is working on numerous projects that integrate hydrological models in atmospheric models, assess water resources and study the fresh water fluxes to the coastal regions, etc.

We see river discharge as a key information in studying the hydrological cycle. However, discharge is the most accurately measured element of the water cycle [11], [10], [14], its availability for large scale studies is limited [8]. Water is recognised as one of the most important limiting natural resources [13], [3], [4] and scientists recognize the value of river discharge information in global circulation models [12], [9], [15], [1], [2].

Our group is convinced that the availability of discharge data is essential in geo-sciences. We think, that access to discharge data would benefit both the data donor countries and the research community.

The problems of collecting hydrological data

The problems of collecting hydrological data is not any different than collecting other kind of data.

Still the availability and quality of hydrological data are still far better than other elements of the water resource questions (such as information irrigational, industrial or municipal water use, reservoir operation, etc.).

In order to improve the accessibility of hydrological information, we need to convince the hydrologic community about the benefits of collecting and sharing hydrological data. We think, that the best way to demonstrate the potentials by developing data products derived from the already available data. USGS already uploads discharge and stage height data for over 4000 gauging stations across the US. We are working on a prototype systems, which accesses this data via USGS's WEB interface and combines it with our river routing and modelling tools to derive gridded runoff and discharge fields.

Many countries need help or assistance to establish and maintain hydrological monitoring network. This requires search for potential funding.

WSAG Potential Contribution to a global hydrological monitoring network

Our group developed data processing capabilities in the last 10 years, which enables us to deliver value added product from hydrological monitoring data. Our tools allow:

WSAG group is currently working on a prototype system to present river discharge data and value added gridded products such as gridded runoff and discharge fields for the Gulf of Maine basins (at 2-minute resolution). We are about to implement this system for the North American continent at 0.1 degree resolution (by the fall of this year) and the Danube basin at 5 or 3-minute resolution (by the end of this year). Our system already downloads real-time stage height and discharge data from over 4000 USGS gauging stations . In similar fashion, we are about to download real-time data from Hydroinfo (http://www.datanet.hu/hydroinfo/index.htm) website maintained by Water Resource Research Center, (Budapest, Hungary), which contains daily stage height and discharge information for gauging stations along the Danube and its major tributaries.

Our group is interested in extending the afore mentioned regional systems to global coverage.

Data requirements

A global hydrological network probably should concentrate on river flow information such as discharge and stage height. Since discharge is typically estimated by using stage height/discharge rating curves. We would prefer to have stage height data available with the corresponding rating curves.

Another question could be the network density. It is tempting to request as many station data as many is possible, but even if the data were available, processing large amount of data (particularly to perform thorough quality control) could be overwhelming. Fortunately, river discharges are integrated signals, therefore focusing on key gauging stations can give a good representation on the large scale hydrological processes. Our group did a little analysis on how many station would be necessary to monitor the actively flowing portion of the global land mass. Assuming 25,000 : km2 station network density, 2300 discharge gauging stations would be sufficient to cover the actively flowing portion of the continental land mass. However, the 25,000 : km2 area is an arbitrary threshold and someone could argue there are regions where denser network is necessary, the opposite is also true, that there are relatively large regions with quite uniform hydrology, where coarser station density might be satisfactory.

Comments on scientific or technological problems

The collection of hydrological data is well established in many countries. Automated real-time monitoring is in operation large part of the globe. The scientific challenge is to use the available hydrological data and develop data products which would convince the water management community about the benefits of monitoring and sharing hydrological data.

The timing of the establishment of such a network is probably the best from technological point. The recent advances in telecommunication technologies (the rapid growth of the Internet in particular) offer cost efficient solutions for the data exchange. Internet communication can be established over a wide range of hardware from amateur radio to fiber optic cables. A global hydrological monitoring system can rely on a well-established technology and computer network, which is already in place for large part of the globe. We would recommend WMO to join UNDP's Sustainable Development Networking Programme (http://www3.undp.org) and support the need for building the Internet in developing countries.

Outline of users of information from a network

Product generation

WSAG can envision short term and long term products. On the short term, real-time processing of hydrological data and generation of global gridded runoff and discharge fields is very feasible. Such information can be made available to the public via WEB interface as we discussed in section 3. On the long term, discharge forecast using climate data inputs from atmospheric models is also feasible.

Basic approach to implement a hydrological network

As we discussed in section 3, there are regions, where real-time hydrological monitoring networks are already in operation. Observations from some of the existing networks are already available on-line via the Internet. These existing data sources can be the starting point of a hydrological monitoring network. Our group already started to develop a system, which accesses these data sources and processes the observation in a simulated river network context. Once, our system is completed, we can demonstrate the benefits of sharing hydrological data to other nations.

The important next step is to convince those countries which do not share their data to change their policy. Some countries might need financial or technical assistance to equip and maintain their real-time monitoring network. WSAG group already started to include budget for data collection in its reseach projects. This could provide short term solution, but it is certainly can not be considered as a long term solution. Research grants are typically awarded for 3-4 year periods after which the continuation of the monitoring can not be guaranteed.

References

[1] M. T. Coe. A linked global model of terrestrial hydrologic processes: simulation of modern rivers, lakes, and wetlands. Journal of Geophysical Research, 103:8885-8899, 1998.

[2] M. H. Costa and J. A. Foley. Water balance of the amazon basin: Dependence on vegetation cover and canopy conductance. Journal of Geophysical Research, 102:,973-989, 1997.

[3] M. Falkenmark. Environment and development: Urgent need for a water perspective. Water International, 16:229-240, 1991.

[4] M. Falkenmark and A. K. Biswas. Further momentum to water issues: Comprehensive water problem assessment in the being. Ambio, 24:380-382, 1995.

[5] B. M. Fekete, C. J. Vörösmarty, and W. Grabs. Global, Composite Runoff Fields Based on Observed River Discharge and Simulated Water Balances. Technical Report 22, Global Runoff Data Centre, Koblenz, Germany, 1999.

[6] B. M. Fekete, C. J. Vörösmarty, and W. Grabs. High Resolution Fields of Global Runoff Combining Observed River Discharge and Simulated Water Balances. Global Biochemical Cycles, submitted, 2000.

[7] B. M. Fekete, C. J. Vörösmarty, and W. Grabs. UNH/GRDC Composite Runoff Fields V1.0. http://www.grdc.sr.unh.edu/, 2000.

[8] W. Grabs, T. De Couet, and J. Pauler. Freshwater fluxes from the continents into the world oceans based on data of the global runoff data base. Technical Report 10, Global Runoff Data Centre, Koblenz, Germany, 1996.

[9] W. J. Gutowski, Y. Chen, and Z. Ötles. Atmospheric water-vapor transport in NCEP reanalyses: Comparison with river discharge in the Central United States. Bulletin of the American Meteorological Society, 1996.

[10] S. Hagemann and L. Dümenil. A parameterization of the lateral waterflow for the global scale. Climate Dynamics, 14:17-31, 1998.

[11] P. Krahe and W. Grabs. Development of a GIS-supported water balance model as a tool for the validation of climate models and hydrometeorological data sets. In Workshop on Continental Scale Hydrological Models: Charting Future. WMO/IAHS, 1996.

[12] J. R. Miller, G. L. Russel, and G. Caliri. Continental-scale river flow in climate models. Journal of Climate, 7:914-928, 1994.

[13] S. L. Postel, G. C. Daily, and P. R. Ehrlich. Human appropriation of renewable fresh water. Science, 271:785-788, 1996.

[14] S. E. Rantz. Measurement and Computation of Streamflow: Volume 2. Computation of Discharge. USGS Water-Supply Paper, 1982.

[15] B. Rudolf. The Global Precipitation Climatology Project (GPCP) and links to the GEWEX Hydrometeorological Panel (GHP). Technical report, Global Precipitation Climatology Centre, 1998.

[16] C. J. Vörösmarty. Modelling the transport and transformation of terrestrial materials to freshwater and coastal ecosystems. Technical Report 39, International Geosphere-Biosphere Programme (IGBP), 1997.

[17] C. J. Vörösmarty, C. A. Federer, and A. L. Schloss. Potential evaporation functions compared on US watersheds: Possible implications for global-scale water balance and terrestrial ecosystem modelling. Journal of Hydrology, 207:147-169, 1998.

[18] C. J. Vörösmarty, B. M. Fekete, M. Meybeck, and R. B. Lammers. Global System of Rivers: Its role in organizing continental land mass and defining land-to-ocean linkages. Global Biochemical Cycles, in press, 2000.

[19] C. J. Vörösmarty, B. M. Fekete, and B. A. Tucker. River Discharge Database, Version 1.0 (RivDIS v1.0), Volumes 0 through 6. A contribution to IHP-V Theme 1. Technical Documents Series. Technical report, UNESCO, Paris, 1996.

[20] C. J. Vörösmarty and B. Moore. Osztott parameteru vízmérleg és folyami transportmodellek a globális éghajlatváltozások vizsgálatához. Vízugyi Közlemények, 74:297-318, 1992.

[21] C. J. Vörösmarty, B. Moore III, A. L. Grace, M. Gildea, J. M. Melillo, B. J. Peterson, E. B. Rastetter, and P. A. Steudler. Continental scale models of water balance and fluvial transport: An application to South America. Global Biochemical Cycles, 3:241-265, 1989.

Global Runoff Data Centre

W. Fröhlich

1. GRDC - main present activities

2. An European Flood Forecasting System (EFFS)

2.1 Main Objectives:

2.2 Scientific objectives:

2.3 Participants

2.4 Part of GRDC

3. GEWEX - CEOP-I (2001-2002)

GRDC contributions will include:

4. GRDC input to the Expert meeting:

· Make clear and transparent for all data-provider the benefit of a high dense hydrological near-real-time data network by developing useful products (e.g. gridded run-off fields..)

· Finally, do not reduce the efforts to request the free access to all hydrological data acc. Resolution 25

· Think about possibilities of remote sensing of water-level and discharge

WHYCOS: Status of Implementation and Development as of July 2000

J. Bassier

This document provides a brief description of the status of the various WHYCOS components (HYCOSs).

A. Regional HYCOSs under implementation

MED-HYCOS (the Mediterranean Rim)

The implementation of the MED-HYCOS project has continued and the agreement between WMO and the French Institute of Research for Development (IRD) for the hosting of the Pilot Regional Centre (PRC) at the IRD premises in Montpellier (France) has been extended until 31 December 2000. The network of DCP stations is being expanded; 35 stations have been sent to the eligible participating countries, 22 are already operational and the others are expected to be commissioned soon. The real time data transmitted by the DCPs are readily accessible on the project web site. The year 1999 was devoted principally to the enhancement of the MED-HYCOS Information System. New on-line tools for the analysis of the data available at the Regional Data Bank have been developed including in particular, cartographic interface for accessing hydrological data and information. Five experts from NHSs of the participating countries have been seconded to the PRC for varying periods up to one year to assist with the development of the MED-HYCOS Information System.

Data and information are available on the following Internet server: http://medhycos.mpl.ird.fr/

A proposal for MED-HYCOS phase II for the next four years (2001-2004) has been submitted by to the screening process. The project has been classified as a priority by the regional Mediterranean Technical Advisory Committee (MEDTAC) and by the Financial Advisory Committee of GWP. PRC and WMO Secretariat are finalizing the proposal for the extension of the project.

SADC-HYCOS (Southern Africa)

This project involving the countries of the South African Development Community - SADC (Angola, Botswana, Lesotho, Malawi, Mozambique, Namibia, South Africa, Swaziland, Tanzania, Zambia and Zimbabwe) is in its full implementation phase. The progress of the project has been significant over the past year. Twenty-seven out of the planned 50 data collection platforms were installed and were fully operational at the end of November 1999. Most of the remaining stations are expected to be installed in 2000. A data base administrator has been assigned to the project by the PRC at the end of 1999.

The current phase of SADC HYCOS was initially planned to terminate in June 2000. However due to initial delays at the start of the project, security problems in some of the participating countries and devastating floods in the Eastern part of the project area in the beginning of year 2000, the SADC Water Sector Coordination Unit, in coordination with the PRC and WMO proposed to the European Commission that the project be extended until August 2001. This proposal was accepted by the European Commission.

Data and information on SADC-HYCOS are available at the following Internet site: http://www-dwaf.pwv.gov.za/sadchycos/ (use of Internet Explorer 5.0 software is required)

A Phase II Concept Note endorsed by SADC Water Sector has been submitted to GWP screening process in early 2000 and has been considered among the priorities for the sector. The proposal is made for a one-year consolidation and project preparation phase followed by a four-year period of implementation.

AOC-HYCOS Pilot Phase (Western and Central Africa)

This project was launched thanks to a grant of 2 million French Francs (US$ 300 000) from the Ministry of Foreign Affairs of France. Representatives of the NHSs of eleven countries from the sub-region (Burkina Faso, Cape Verde, Chad, Gambia, Ghana, Guinea, Mali, Mauritania, Niger, Nigeria and Senegal) that had expressed their interest in the project participated in a meeting (Ouagadougou, Burkina Faso, December 1999) to discuss the implementation of this pilot phase. One of the key objectives of the pilot phase is the transfer to a regional body and the consolidation of the activities of the Regional Hydrological Observatory for Western and Central Africa (OHRAOC). The OHRAOC was developed and operated by the French Institute of Research for Development (IRD, formerly ORSTOM). The Ouagadougou meeting supported a proposal that the Niger Basin Authority (NBA) and the CILSS Regional Centre AGRHYMET would have joint responsibility for the coordination of the pilot phase of AOC-HYCOS and for the operation of the regional database and associated Internet server. During the transition period, data and information are available at the Internet site http://ohraoc.ird.bf. The pilot phase is being considered by donors as a test run for a comprehensive regional HYCOS project, which could involve up to 23 countries of the sub-region. A technical review of the pilot phase and a donor meeting to discuss the funding of the comprehensive AOC HYCOS project are planned for 2001.

B. Regional HYCOSs under development

IGAD-HYCOS (Eastern Africa)

A project encompassing the Member countries of the Intergovernmental Authority for Development - IGAD (Djibouti, Eritrea, Ethiopia, Kenya, Sudan and Uganda) has been developed in 1999. The project document has been prepared by the WMO Secretariat with inputs from local experts and from the IGAD Secretariat. Funding for this preparatory phase was provided by the European Commission. The document was presented to the seventh meeting of the Heads of Meteorological and Hydrological Services of IGAD sub-region, which was held in Nairobi, Kenya in January 2000. The meeting recognised the importance of the project implementation for water resources development and management in the region and mandated the WMO and IGAD Secretariats to finalize the project document with a view to obtaining funds for project implementation. The project document has been endorsed by IGAD Member countries and been submitted to the European Commission.

Congo-HYCOS (the CONGO River Basin)

The project document for the Regional Hydrological, Meteorological and Climatological Information System (RHMCIS), including a hydrological component, which would be implemented as CONGO-HYCOS, was submitted to the European Commission in early 1999 and is being considered for possible funding. The concerned countries are Cameroon, Central African Republic, Congo, Democratic Republic of the Congo, Equatorial Guinea and Gabon. Contacts have been established with the World Bank funded Regional Environmental Information Management project and with the Association for Environmental Information Dissemination with the aim of promoting the projects among donors. The project is not actively promoted at present in view of the present security situation in the region.

Baltic-HYCOS (the Baltic Sea riparian countries)

A project document, which concerns the countries of the Baltic Sea drainage basin (Belarus, Czech Republic, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Slovakia, Sweden and Ukraine) has been prepared during 1999 by national experts from the region in co-operation with the WMO Secretariat. It was reviewed and adopted at a meeting of country representatives in Poland in December 1999. Support from external donors, in particular the European Commission is being sought for the project implementation. The meeting also agreed that some initial work on the Regional Data Bank could be undertaken without external resources and this is currently being investigated. Several of the participating countries offered to consider providing hydrological data so as to get this activity initiated.

CARIB-HYCOS (Central America and the Caribbean Islands)

A project document has been prepared which takes into account the needs of some of the island countries of the Caribbean Sea as well as the main land countries of Central America. However, the impact of Hurricane Mitch, which resulted in extensive damage to the hydrological infrastructure in Honduras, Nicaragua, El Salvador and Guatemala, as well as some new proposals from the region, called for a complete revision of this document. The new draft has been finalised by WMO Secretariat in June 2000. CARIB-HYCOS aims at providing a support to natural disaster prevention and water resources management. It has been subdivided into a Continental Component (COC/CARIB-HYCOS) covering Belize, Colombia, Costa Rica, El Salvador, Guatemala, Guyana, Honduras, Mexico, Nicaragua, Panama and Venezuela, and a Caribbean Islands Component (CIC/CARIB-HYCOS) comprising some of the islands of the Greater and of the Lesser Antilles.

Black Sea-HYCOS (the Black Sea riparian countries)

A Black Sea-HYCOS project profile was prepared in June 1999 by experts from three countries of the Black Sea basin assisted by WMO. The project is a cooperative process between the NHSs of the riparian countries of the Black Sea (Bulgaria, Georgia, Moldova, Romania, Russia, Turkey and Ukraine), the Permanent Secretariat of the Black Sea Economic Co-operation (BSEC-PERMIS) and WMO. The project profile was discussed and adopted during the Black-Sea HYCOS start-up meeting, held in November 1999 in BSEC-PERMIS, Istanbul, Turkey. The year 2000 should see the preparation of national reports and the completion of a Regional Synthesis Report. This latter report would present substantial information required for a comprehensive project document to be finalized and submitted to donors by the beginning of 2001.

Aral-HYCOS

A draft project document has been prepared in co-operation with the five Central Asian States of the Aral Sea basin. This document will be discussed at a meeting with the country representatives in Tashkent in September 2000. The project will consolidate a number of on-going activities

C. Other HYCOS initiatives

The development of a project for the Southwest Pacific region was considered during the meeting of experts on "Hydrological Needs of Small Islands" held in Nadi, Fiji (October 1999). Beyond the data collection exercise, the major interest for a Pacific-HYCOS project was identified as enhancing regional co-operation and technical capacities of the NHSs. The meeting requested the WMO Secretariat, in collaboration with the countries and in consultation with the South Pacific Forum Secretariat, to develop a full project proposal. A draft project proposal was available in June 2000.

Work has been initiated for the development of others projects, namely: Danube-HYCOS (start-up meeting held in Budapest, Hungary in November 1999), Caspian-HYCOS (preliminary meeting held in Almaty, Kazakhstan in December 1999).

Proposals have also been made to initiate the development of HYCOS projects in the Amazon and in La Plata river basins in South America, as well as in the Himalayan region and the Arctic region.

GEMS/Water Programme

A.S. Fraser

1. The UNEP GEMS/Water Programme is the primary organization within the United Nations system charged with gathering information and data on water quality resources directly from collaborating national monitoring programmes throughout the world. GEMS/Water provides data, information and assessments through collaborative work with United Nations programmes on global and regional water quality resources issues. The GEMS/Water Collaborating Centre operates and maintains the global database that holds water quality data provided to the programme by participating national governments. The Collaborating Centre works with participating countries and agencies to bring together water quality data for major rivers and lakes throughout the world and contributes to international programmes such as: WWDR, GIWA, GPA, GEF, GESAMP, GWP. In the development of a global hydrological network for climate it is a natural step to consider the interactive dependencies between hydrology and water quality. The GEMS/Water Programme is supportive of the development of this initiative and will collaborate in areas where possible for the betterment of our understanding of world water resources.

2. Difficulties in establishing a global network are manifold but not insurmountable. The network must operate internationally under the good graces of agreements with national governments and agencies. When the political arrangements are made and the strategic orientation of the programme is set, the tactical arrangements to establish a working network need addressing. A companion database needs to be developed that contains meta data on the sampling database. A brief view follows.

- Station Distribution

- Parameters

- Frequency of Sampling

- Transportation Requirements

- Sample Analysis (if required)

- QA/QC

- Data Transmission / Reception

- Database Structure

- Data Storage and Retrieval

- Database Management

3. Environmental issues are usually cross-discipline and interaction and collaboration are necessary to produce comprehensive global assessments. The primary objective of the network is to obtain meaningful data to enable understanding of the components that are identified with all aspects of the hydrologic cycle. Work should contribute to international assessments of the availability and distribution of water resources throughout the world. Climate change is high on the international agenda. The network must be able to contribute to the identification, assessment and recommendation development requirements of regional and global studies.

4. The network should provide data, information and ancillary meta data necessary for determining resolutions to issues of regional and global hydrologic cycles. The data must be representative of a region and compatible with other data obtained from the network. The network must be designed to be able to develop and produce information on trends and changes determined by scientific and statistical procedures. Flexibility in design and operation is necessary to enable new issues to be addressed. Interactions with other databases including water quality are a high priority.

5. A major problem to be addressed will be the desire to handle real-time or near real-time data. To achieve this, telemetry systems operating from remote sites some of which will be in developing countries will be necessary. The mechanisms to be successful are very complex. Quality of data is of primary concern. Suitable mechanisms for screening and editing data must be developed as an integral part of the network. International funding that provides stability of staff and operations of the network must be identified and assured.

6. Users of the data and information provided through the network can be identified.

- United Nations agencies

- United Nations Programmes

- International research organisations

- National governments and agencies

- University research personnel

- Public and private educational institutions

- Private industry

- Public

7. There are several levels of product generating activity that should be built into the network system.

- Database synopsis, time period, stations, parameters, parameter classifications...

- Basic statistical analysis and graphical depiction.

- Regional data availability

- Data summaries

- Interpretive reports

- User requested specific reports

- Regional and global programme contributions

8. Planning and implementation strategy must be considered carefully and by consultation between all stakeholders. The basics:

- Development of mission statement

- Identification of lead agency and key personnel

- Identification of partner agencies and key personnel

- Structure and composition of executive steering committee

- Development of strategic direction

- Identification of primary financing organization

- Preliminary budget development

- Implementation schedule

- Identification and evaluation of existing networks and network components

- Compose network through agreements and establishment of new sites

- Design and establish database systems

- Design and implement data transfer protocol

- Design and implement QA/QC programme

Soil Moisture Observations

J. Leese

Several workshops have been held during the past decade which focused on soil moisture. A 1994 workshop in Tiburion, California identifies scientific requirements of the atmospheric, hydrologic and ecological disciplines for soil moisture observations. It concluded that with recent advances in both knowledge and practice, an opportunity is clearly at hand to establish a comprehensive scientific framework for the global monitoring of soil moisture. One of the major conclusions was that a complicating factor in soil moisture, in addition to heterogeneity of soil properties and land surface attributes, is the complex control of the land surface energy and water balance by the atmosphere and the soil. This control is further modulated by plant activities in the root zone. Observing and understanding the switch between the control by the atmosphere and the control by the soil is central to the design and implementation of any monitoring system of soil moisture.

The GEWEX/BAHC International Workshop on Soil Moisture Monitoring, Analysis and Prediction for Hydrometeorological and Hydroclimatological Applications was held from 16 to 18 May 2000 at the University of Oklahoma, Norman, Oklahoma, USA. In considering the progress in land surfaces processes and modelling which entails the complex aspects of soil moisture it was decided to focus on the dvelopment of a strategic plan for the next five years in soil moisture monitoring, analysis and prediction for hydrometeorological and hydroclimatological applications. The plan should:

-- identify and recommend priorities for research;

-- demonstrate the scientific and technical feasibility of implementing a global system through one or more pilot projects or an evolutionary series of pilot projects; and.

-- contribute to the design of a global system which could be operational by the end of this decade

The Workshop participants concluded that the demonstration of the value of soil moisture in weather and climate prediction during the past decade has created a need to develop a system to provide this type of information on a global basis for operational use and further research. The progress in soil moisture monitoring makes it technically feasible to seriously work toward implementing such a global monitoring system during the coming decade. Among the Workshop recommendations are the following:

* The design for a global monitoring system should be based primarily on model derived estimates with in situ measurements and remotely sensed estimates serving as input data for assimilation and for evaluation of model output.

* Locations which can provide high quality and representative in situ measurements which are distributed over the global land masses should be identified as Reference Measurement Sites for the global monitoring system. The GEWEX and BAHC Programs dealing with land-surface processes and modelling can provide expert guidance on the selection of such Reference Measurement Sites.

* The development and implementation of a global model to produce model-derived estimates of soil moisture should be started immediately to demonstrate the capabilities of such a global monitoring system and to identify areas where further research and/or improvements to the input data are needed to achieve operational capability on a global scale.

* Develop a long-term strategy for remote sensing of properties required for soil moisture retrievals that considers improvements of spatial resolution, L-band and other sensors (precipitation, radiation, snow water equivalent, skin temperature), and recognizes physical hydrologic properties.

* Make satellite and in situ data available in real time.

* Add soil moisture measurements at synoptic stations as part of the Global Observing System of the World Weather Watch.

Hydrology for the Environment, Life and Policy (HELP):

Real People, Real Catchments, Real Answers

M. Bonell

HELP is a joint UNESCO/WMO programme which is designed to establish a global network of catchments to improve the links between hydrology and the needs of society. It is a cross-cutting programme of the UNESCO International Hydrological Programme and will contribute to the World Freshwater Assessment Programme, and the Hydrology and Water Resources Programme of WMO.

The vital importance of water in sustaining human and environmental health is the key driving force behind HELP. However, no international hydrological programme has addressed key water resource issues in the field and integrated them with policy and management needs. HELP will change this by creating a new approach to integrated catchment management. The new approach is to use real catchments, with real water related problems as the environment within which hydrological scientists, water resources managers and water law and policy experts can be brought together.

HELP is therefore a problem-driven and demand-responsive initiative that will focus on the following eight key issues:

The outputs of HELP will be new data and models which are more suitable for the revision of current water policy and water resources management practices in all of the above eight areas.

Global Network for Isotopes in Precipitation (GNIP)

M. Gröning

1. The Global Network for Isotopes in Precipitation is operated by the Isotope Hydrology Section of the International Atomic Energy Agency, Vienna, Austria. This world-wide survey of the isotopic composition of monthly precipitation started as early as 1961 in co-operation with the WMO in order to study the raising Tritium levels in the atmosphere caused by nuclear weapon tests. The programme also aimed to provide systematic data on the global stable isotope content of precipitation as a basis for the use of environmental isotopes for hydrological investigations. Soon it was recognised that the collected GNIP data were also useful in other water-related fields like climatology, oceanography and hydra-meteorology. The data provided the backbone for the discipline now known as Isotope Hydrology.

The network reached its maximum in the early 1960s with 220 operative stations. Currently, 180 stations are in operation from a total of more than 500 stations in the GNIP database. Altogether more than 100000 isotope measurements were performed within the GNIP. More than 30 percent of all isotope analyses are performed at the IAEA Isotope Hydrology Laboratory, the others are measured in more than 30 collaborating laboratories. All GNIP operation is done on a voluntary basis both by the sample collecting meteorological stations and by the analysing laboratories. Each dataset in the database consists out of monthly means for meteorological data (precipitation amount, mean temperature, relative air humidity) and the isotopic composition (oxygen and hydrogen stable isotope ratios as ä-values and Tritium concentration). In the past the data were published regularly in IAEA data books. Since several years the whole database is available online (http://www.iaea.org/programs/ri/gnip/gnipmain.htm) at the IAEA GNIP homepage. During the last years those data are more and more used for research in climate studies (e.g. El Nino, GCM model verification). Recently the IAEA and WMO have signed a Memorandum of Understanding to put this network on an official basis and to improve the co-operation and to increase the network A Scientific Steering Committee consists out of representatives from IAEA, WMO, PAGES, National Networks and invited experts and meets yearly to review the current status and to recommend improvements. Recent topics are filling the most important gaps in the geographical coverage (Africa, Russia and USA) and to ensure coverage of climatically sensitive regions (El Nino).

2. The climate change has received large attention by the scientific community as well as by the public. The relevance of GNIP and its data collection is not questioned. However, there is a big gap between understanding and active support. A major problem for GNIP is the absolutely voluntary basis of co-operation which is driven by a great enthusiasm of individual researchers and scientists for keeping the sampling and providing cost free isotope analyses in more than 30 network laboratories. No funding mechanism is established to foster the creation of stations (funding for this purpose is not possible within IAEA mandate).

3. The GNIP database is available on a cost free basis for researchers world-wide to foster and to facilitate isotopic investigations in the hydrological cycle (stable isotopes of hydrogen and oxygen as well as Tritium). More and more the available extended data set is used for modelling of atmospheric processes (GCMs) and for coupling of in-situ measurements with long term physical / meteorological processes traceable by isotope fractionation effects.

4. Formerly the data were published in books, since a few years the database is available for download on the IAEA GNIP homepage http://www.iaea.org/programs/ri/gnip/gnipmain.htm.

The strengthening of this network depends on the accessibility and availability of the data (a new online search engine is in preparation). The next envisaged step is the coupling of the information on isotopic composition of precipitation (GNIP) with a hydrological database on isotope data in groundwater and surface water studies (ISOHIS - Isotope Hydrology Information System).

5. Major issues are budgetary constraints (all sampling and analyses outside the IAEA are done on a voluntary basis); time delays between sampling, measurement and publication (related to the problem of ownership and proper acknowledgement when using the data); uneven distribution of stations and lack of spatial coverage in some regions. Some positive developments were encountered recently (National GNIP Network for USA in preparation).

6. The users of GNIP data are scientists working in hydrology, modelling, atmospheric sciences and other disciplines using data of environmental stable isotopes or Tritium for water-related research (including biogeochemical studies and ecosystem studies).

7. The GNIP data are compiled and quality checked by the IAEA prior to release. In few cases the data submission to the IAEA is delayed for several years. However, near real-time production of data is not a major issue for a program operating since nearly 40 years and using statistical trends to derive small annual changes from large data sets.

8. The planned Hydrological Network could serve as a catalyst and support mechanism to facilitate the enhancement of GNIP in the future.

The Global Precipitation Climatology Centre (GPCC): Operational Analysis of Precipitation Based on Observations

Bruno Rudolf, Tobias Fuchs, and Udo Schneider

Deutscher Wetterdienst, Offenbach a.M., Germany

1 Introduction

The GPCC has been established in 1989 on invitation of the World Meteorological Organisation (WMO) as a German contribution to the World Climate Research Programme (WCRP). Later on, a long-term continuous operation of the centre has been accepted with regard to the Global Climate Observing System (GCOS). Data monitoring and quality control of the GCOS Surface Network Precipitation Data Set is performed at GPCC. The GPCC also operates a special arctic precipitation data archive for the Arctic Climate System Study (ACSYS, WCRP 1994) and it is active in the GEWEX Hydrometeorolgy Panel and contributes to regional projects, e.g. the Baltic Sea Experiment (BALTEX) and the Mesoscale Alpine Programme (MAP).

The GPCC is one of the major components of the Global Precipitation Climatology Project (GPCP). The common task of the GPCP is the compilation of global gridded precipitation data sets based all globally available observation systems, i.e. conventional surface networks and various satellite-observed radiances. Besides GPCC, contributors to the GPCP are the satellite operators (EUMETSAT, JMA, NOAA, and NASA) and several research institutes. The products are designed for the global climate research community and are especially required for the verification of global climate models, the investigation of climate variability and special phenomena such as the El Niño - Southern Oscillation, and the determination of the Earth's water balance and budgets (WCRP 1990).

The scientific and technical functions of the GPCC comprise:

Special functions within the Arctic Climate System Study (ACSYS) are:

2 The Observational Database

Conventionally measured data from raingauge networks are still the most reliable information to obtain area-averaged precipitation for the land surface. Satellite-based estimates are subject to larger biases and stochastic errors and need to be adjusted to in-situ observations (Barrett et al. 1994, Rudolf et al. 1996).

A first meteorological database for precipitation can be obtained from synoptically observed weather reports (at least with a daily resolution) and monthly climatic data, which are distributed world-wide as "SYNOP" and „CLIMAT" reports via the World Weather Watch Global Telecommunication System (GTS). GPCC regularly collects monthly precipitation totals from these sources for nearly 7,000 stations world-wide. These data being available near real-time are the basis for monthly monitoring of the global precipitation, resp. the "Monitoring Product" of the GPCC.

The data collection period as defined by the GPCP Implementation and Data Management Plan (WCRP 1990) starts with the year 1986. So far, national institutes from about 150 countries have supplied additional data on a voluntary basis, following the WMO requests and bilateral negotiation with GPCC. The entire GPCC database includes now monthly precipitation totals of about 48,000 stations (GPCC's full data set). The time series are largely complemented by climatological means for the normal period 1961-1990. The year with the best data coverage is 1987 with monthly precipitation data for about 38,000 stations.

A gradual decrease of the number of stations after 1987 down to 7,000 stations for 1999 (i.e. GPCC's GTS data) is caused by the delay of the delivery of additional data and by the time required by the national agencies and subsequently by GPCC for data processing and quality-control (Rudolf et al. 1998). Also the spatial distribution of the data shows large data poor areas. The GPCC's full data set still needs spatial and temporal complementation, as well as retrospective temporal extension (a precipitation re-analysis from 1961 onwards is required with regard to CLIVAR) and continuation of update deliveries to GPCC by the countries in future.

3 Problems of analyses of daily precipitation based on GTS data on a global scale

There is a strong demand from the international research community for analyses of daily precipitation. Just recently a satellite-based product of daily global precipitation on a 1° by 1° grid has become operational (http://rsd.gsfc.nasa.gov/912/gpcp/gpcp_daily_comb.html). Validation studies regarding this data set show, that it needs to be adjusted to raingauge data on a daily time scale. But until now it has not been possible to provide a global analysis of daily precipitation based on raingauge data, because of two major problems, the availability of raingauge data on a daily time resolution, and the definition of globally unique analysis days.

4 GPCC raingauge-based analyses of global land surface precipitation

The GPCC products, gridded data sets based on raingauge observations, are available in two resolutions, 2.5° by 2.5° and 1.0° by 1.0° geographical latitude and longitude, and with two different databases, i.e. near real-time with GTS data only ("GPCC Monitoring Product" based about 7,000 stations) and non real-time including complemented GTS data and additionally the data, which are delivered later from national institutions to the GPCC ("GPCC Full Data Product" based on 30,000 to 40,000 stations).

Variables which are supplied with both products on the grid are:

The raingauge-based global land surface precipitation analyses of the GPCC are the in-situ data basis of the satellite-raingauge combined data sets of the GPCP (Huffman et al. 1997) as well as of CMAP (Xie and Arkin, 1997).

5 Error Assessment

Area-means of precipitation derived from point data are contaminated by errors of different origin. These errors types first have to be treated and quantified separately, and the results then need be merged to a total error of the area-mean precipitation. The GPCC approach is described in the following:

1. Stochastic quality-related errors resulting from erroneous input data are minimized by a full high-level quality-control of all data used in the raingauge analysis.

2. Systematic measuring errors are compensated using long-term mean correction factors, which were derived by Legates (1987).

3. The sampling error has been investigated by GPCC using data from dense networks of Australia, Canada, Finland, Germany and USA (Rudolf et al. 1994).

4. The methodical error is much smaller than the sampling errors, and is neglected for large-scale GPCC analyses.

The total stochastic error on the grid is calculated from the individual error components, after systematic errors have been eliminated.

6 Research Activities

GPCC is going to prepare products of higher resolution and to develop advanced methods for quality-control, error assessment and spatial analysis. Items are:

References:

Barrett, E.C., J. Doodge, M. Goodman, J. Janowiak, E. Smith & C. Kidd (1994): The First WetNet Precipitation Intercomparison Project (PIP-1). Remote Sensing Review, Vol. 11 (1-4), 49 - 60.

Fuchs, T., J. Rapp, F. Rubel and B. Rudolf (2000): Correction of synoptic precipitation observations due to systematic measuring errors with special regard to precipitation phases: submitted to Phys. Chem. Earth.

Huffman, G.J., R.F. Adler, P.A. Arkin, A. Chang, R. Ferraro, A. Gruber, J. Janowiak, A. McNab, B. Rudolf, U. Schneider (1997): The Global Precipitation Climatology Project (GPCP) Combined Precipitation Dataset. Bull. Americ. Meteor. Soc. 78(1), 5-20.

Legates, D.R. (1987): A climatology of global precipitation. Publ. in Climatology 40 (1), Newark, Delaware, 85 pp.

Rudolf, B., H. Hauschild, W. Rueth, U. Schneider (1994): Terrestrial Precipitation Analysis: Operational Method and Required Density of Point Measurements. NATO ASI I/26, Global Precipitations and Climate Change (Ed. M. Desbois and F. Desalmand), Springer Verlag Berlin, p. 173 - 186.

Rudolf, B., H. Hauschild, W. Rueth, U. Schneider (1996): Comparison of Raingauge Analyses, Satellite-Based Precipitation Estimates and Forecast Model Results. Advances in Space Research, 18(7), p. (7)53 - (7)62.

Rudolf, B., T. Fuchs, W. Rüth, U. Schneider (1998): Precipitation Data for Verification of NWP Model Re-Analyses: The Accuracy of Observational Results. Proceedings First WCRP International Conference on Reanalyses (Washington, DC, USA, 27-31 Oct 1997), WMO/TD-No. 876, 215-218.

Rudolf, B. and F. Rubel (2000): Regional Validation of Satellite-Based Global Precipitation Estimates. EUMETSAT Meteorological Satellite Data Users' Conference, Bologna, Italy, 29 May to 2 June 2000. Submitted to Conference Proceedings.

WCRP (1990): The Global Precipitation Climatology Project - Implementation and Data Management Plan. WMO/TD-No. 367.

WCRP (1994): Arctic Climate System Study (ACSYS) - Initial Implementation Plan. WCRP-85, WMO/TD-No. 627.

Xie, P. and P.A. Arkin, 1997: Global Precipitation: a 17-year monthly analysis based on gauge observations, satellite estimates, and numerical model outputs. Bull. Amer. Meteorol. Soc. 78, 2539-2558.

An extended version of this report including figures can be downloaded from the Meeting Website on Internet:

http://www.dwd.de/research/gpcc/ghyclim2000/

Dr Bruno Rudolf

Global Precipitation Climatology Centre

Tel.: + 49 - 69 - 8062 - 2765

Deutscher Wetterdienst

Fax: + 49 - 69 - 8062 - 3759

P.O. Box 10 04 65

email: [email protected]

63004 Offenbach/Main, Germany

ULR: http://www.dwd.de/research/gpc
[2] Water Systems Analysis Group, Complex Systems Research Center, Institute for the Study of Earth Oceans and Space, University of New Hampshire

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