...for details about the validation algorithm: see here
Interpretation of validation results
Best estimate vs. forecast
The forecast is the deterministic part of the TOPAZ simulation, which starts on the bulletin date. Thus, there is one 10 day forecast for each bulletin date. The best estimate is one long time series, built from the one-week ensemble runs which tie together the analysis and the state on the following bulletin date (the bulletin lags the corresponding analysis by one week).
The forecast is initialized with an analysis which is valid one week before the bulletin date. Results from the first simulation week of the forecast, which leads up to the bulletin date, are not validated, and consequently not displayed here.
RMS values
Root-mean Square (RMS) values are average values for the domain where the model results and ice chart data overlap. RMS values, like all validation quantities, are computed after the validation algorithm has been applied. While RMS is usually included in model validation, we note that here, there are large regions in which both model and data are ice free or belong to the densest ice concentration class.
The persistence line shows the RMS error if the ice chart data at the inital date is retained throughout the period. The bulletin date is written with green letters in the x-axis labels. Thin lines bridge periods with missing data in between.
Sea ice area
Sea ice area is computed as the no. of grid cells that belong to each sea ice class. Note that each cell corresponds to 100 km2. Of particular interest is the difference between the region in which the sea ice classes match, relative to the region covered with ice belonging to each class of sea ice. This is so, since this difference indicates geographical shifts and width of the marginal ice zone in the two products.
The line labelled overlap, best est. indicates the area over which the ice class overlap in the best estimate and the ice chart (with the most recent forecast appended to the best estimate time series). The line labelled overlap, persist. shows the area where the ice class is unaltered from the initial date. The bulletin date is written with green letters in the x-axis labels. Thin lines bridge periods with missing data in between.
Sea ice maps
Ice maps are included in order to provide a visual comparison of the products that are considered in the validation. Note that the region for which the sea ice concentration is displayed in these quick-look maps is somewhat smaller than the full region that is validated. A sample figure depicting the full region is displayed on the index page.