Now visualise the data, again using the icon's context menu. You will see a map plot with the default contouring style in the Display Window (Figure 4). To plot the data with shaded colours, go to the Visual Definitions drawer (if this drawer is not visible, you may have to either expand your Metview desktop window to the right, or else click on the dots which appear to the right of the last visible drawer). Drop the Contouring icon onto your Metview desktop, rename it shade and edit it, providing these parameters: Legend | On | Contour Shade | On | Contour Shade Method | Area Fill | Contour Shade Max Level Colour | Red | Contour Shade Min Level Colour | Blue | Contour Shade Colour Direction | Clockwise |
Save the icon settings (Apply) and drop this into the Display Window (re-visualise the data if you have closed the plot window). The result should resemble Figure 5. Metview's Contouring icon provides much flexibility in choosing how to display gridded fields; this tutorial uses only simple colour schemes. The Display Window provides a number of facilities for further inspection of the data, not covered here. Retrieving the forecast dataCreate a copy of your temperature_analysis icon (right-click, duplicate) and rename the copy to temperature_forecast. Edit this icon and set the following parameters: Type | FC | Param | T | Date | -5 | Step | 48 | Grid | 1.0/1.0 |
The analysis data was valid for 3 days ago; this new icon retrieves a 48-hour forecast data generated 5 days ago, so it is also valid for 3 days ago. You don't need to separately execute and visualise the icon - if you visualise it, the data will automatically be retrieved first. The plot title will verify that this data is valid for the same date and time as the analysis data. It also contains the same set of vertical levels. Compute the forecast-analysis differenceCreate a new Simple Formula icon by taking a copy from the Macros icon drawer. Rename the copy to fc_an_diff. Edit the icon, ensure that the first tab is selected (F+G) and that the operator is minus ( - ). Drop your temperature_forecast icon into the Parameter 1 box, and drop temperature_analysis into the Parameter 2 box. Save the icon and visualise it. The difference will be computed and the result plotted. Note that all 6 fields in each data icon are used in the computation - the result is a set of 6 fields. The solutions folder contains two Contouring icons which can be used to show the differences: select both pos_shade and neg_shade with the mouse and drop them both into the Display Window (see Figure 6). It is also possible to drop them one at a time, but they do not accumulate - one will replace the other. |