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River network map
The river network summary map layer shows the combined expected forecast anomaly and uncertainty signal in a simplified way for each forecast lead time (Figure 1). The lead time is weekly (always Monday to Sunday with the weekly average river discharge) in the sub-seasonal and monthly in the seasonal (always calendar month with the monthly average river discharge).
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Figure 2 shows an example, which highlights some river sections with the explanation of the assigned colours and the corresponding anomaly and uncertainty levels. Both Figure 2a and 2b include the colour legend with the 15 categories and the corresponding colours (same as in Figure 1), for easier interpretation.
The river network summary map also contains the reporting points, which are labelled in Figure 2b. These are river locations, where detailed information is provided about the evolution of the forecast signal over the forecast horizon. These reporting points are either either fixed points, which are also used in the medium-range flood products and the basin-representative points, which are selected locations on a one point per basin basis. Further details about the basins and the representative points are available here: Placeholder CEMS-flood sub-seasonal and seasonal basins and representative stations.
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Figure 6 shows an example snapshot in the same area as Figure 1a above. One can compare, how the variable signal on the river network averages into the basin signal. The averaging is done from the river pixel information. A Rank-mean and a Rank-std value will be calculated for each basin and with those the exact same method is used (as for the river pixels on the river network summary mapnetwork map) to define the forecast anomaly category and the uncertainty category and thus the colour of the basin (see the inset figure with the colour legend in Figure 4). The colours used are the same as for the river network summary mapnetwork map, except there is a slight shift in transparency, in order to allow visibility for all river pixels, even for those with the same colour as the basin colour.
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