This analytic tool provides access to the Northwest Africa Rivers Discharge stations from the Global River Discharge Database (v1.1) and to the Global Historical Climatology Network-Monthly (GHCN-M), providing historical precipitation data for the region. The Royal Netherlands Meteorological Institute (KNMI) Climate Explorer web application provides access to all of this information. The CCLME ECO-GIS Viewer makes use of the information gathered from this web application. Several graphs are displayed using all of the information stored in the stations that the user has selected.
• Global River Discharge Database (v1.1): The Global River Discharge Database development efforts are the first step in a continuous compilation of river discharge information. One of the primary sources of information for database development was the UNESCO river archives and the series of publications titled "The Discharge of Selected Rivers of the World," which were available in book form from 1969 to 1984. The series was a valuable source of information on approximately 1000 stations. RivDis v1.0 provides discharge data from the original UNESCO publication series in a digital format that researchers and planners in the water sciences community can easily access and analyse. The contents of RivDis v1.0 were recently published in book form (Vorosmarty et al. 1996a) and are available from UNESCO's International Hydrological Programme Headquarters (Offices: 1, Rue Miollis /75732 Paris CEDEX 15). This has resulted in the creation of a database known as RivDIS v1.0 and a full publication summarizing the database.
References:
Vörösmarty, C.J., B. Fekete, and B.A. Tucker. 1998. River Discharge Database, Version 1.1 (RivDIS v1.0 supplement). Available through the Institute for the Study of Earth, Oceans, and Space / University of New Hampshire, Durham NH (USA).
Vörösmarty, C.J., B. Fekete, and B.A. Tucker. 1996. River Discharge Database, Version 1.0 (RivDIS v1.0), Volumes 0 through 6. A contribution to IHP-V Theme 1. Technical Documents in Hydrology Series. UNESCO, Paris.
• Global Historical Climatology Network-Monthly (GHCN-M): The GHCN monthly climate dataset is provided by the National Oceanic and Atmospheric Administration/National Climatic Data Center. In late 2008, it had 20,586 precipitation stations, 7,279 mean temperature stations, 4,965 minimum/maximum temperature stations, and 2667 pressure stations, ranging in length from hundreds of years to only a few.
The data is presented in two forms: adjusted and unadjusted. The first set has been corrected for urban effects, while the second is biased by comparing urban stations to nearby rural stations. The adjusted data is only available for a few countries.
The KNMI Climate Explorer post-processed NCDC data by combining all-time series for each station. Currently, this is done very crudely. For each year, the first series of valid data is chosen. It is intended to merge these series more intelligently, taking into account all data and the possibility of bias.
The quality of the data varies. Most problematic are very old data, before observations were sufficiently standardized (1855, 1905, and 1950 are common discontinuities), and very new data from the Global Telecommunication System (GTS). The NCDC quality control system has removed the majority of errors, but some will inevitably remain. It's always a good idea to check the time series. It's also worth checking that the coordinates match those expected, such as in Google Earth, where some stations are mislocated. Please report any errors to NCDC.
The database is updated from NCDC into the Climate Explorer once every month.
References:
Peterson, Thomas C. and Russell S. Vose, 1997: An Overview of the Global Historical Climatology Network Temperature Data Base, Bulletin of the American Meteorological Society, 78, 2837–2849.
• KNMI Climate Explorer web application: The KNMI Climate Explorer is a web application used to analyse climate data statistically, developed by Geert Jan van Oldenborgh. It began in late 1999 as a simple web page for analysing ENSO teleconnections and has since grown to include over one terabyte (TB) of climate data and dozens of analysis tools. It is now part of the World Meteorological Organization (WMO) Regional Climate Centre at KNMI, together with the European Climate Assessment and Dataset (ECA&D).
This tool provides access to Northwest African River Discharge stations from the Global River Discharge Database (v1.1) and the Global Historical Climatology Network-Monthly, containing historical precipitation data for the region. This information is accessible through the KNMI Climate Explorer web application. The CCLME ECO-GIS Viewer makes use of the information gathered from this web application. Several graphs are displayed using all of the information stored in the stations that the user has selected.
When the user accesses this tool, the map region displays the position of the stations on the left side and a table with information about these stations, including name, code, river, country, and years, on the right side.
The tabs at the top of the table can show the River Discharges stations (orange icons) or the Precipitation stations (green icons).
When a user clicks on a row in the table, the station is selected. The user can also select a station on the map by clicking on it. That station is also immediately selected from the table.
Simultaneously, a popup with station information appears.
Once a station is selected (green row), the user can display graph information by clicking the
button.
• River Discharge: The first graph displays data on all-time series available for this station. It is possible to specify the start and end dates for the time window.
Clicking the "Trend & Linear Regression" button displays statistical information.
The second graph depicts anomalies with respect to the annual cycle.
To view the linear regression calculation, click the "Linear Regression" button.
The last graph depicts information about annual cycles computed using all data available.
After displaying the graphs, the 
button displays a table with raw data.
• Precipitation: The "Precipitation" tab provides information about precipitation.
The first graph shows information about all the time series available for this station. It is possible to select the start date and end date for the time window.
Clicking on the "Trend & Linear Regression" button displays statistical information.
The second graph shows anomalies with respect to the annual cycle.
Linear regression calculation is shown by clicking on the "Linear Regression" button.
The last graph shows information about annual cycles, computed with all data available.
Once the user has displayed the graphs, the "Show/Hide Data" button is available
, and when clicked, a table with the raw data is shown.
