Sky Scanning Displays

By selecting the ‘2D IWV Map’ command from the Files -> Open Files list, the Display Normalized IWV Map menu pops up.
This menu displays normalized IWV data that has been measured using the 2D scanning feature described in the operating manual, section 5.9.4. The central cell corresponds to the zenith observation angle and the data cells located at the edge of the diagram are related to horizontal observations. The numbers around the circle label the azimuth angle during the scan which is referenced to the instrument azimuth 0-index. 
IWV is a level 2 data product which requires a retrieval file that contains the required coefficients. In a full sky scan the radiometer changes the observation elevation angle, thus a multi-angle IWV retrieval is required for a correct evaluation of the scan data. In the retrieval file name IWV_QR_MA_CC_V1.RET. The ‘MA’ term indicates that the IWV retrieval is a multi-angle retrieval. If the user selects a retrieval for constant observation angles, a warning message will be issued.
In order to display IWV data in this menu one has to load a *.WVL or *.BRT data file by clicking the Load TB File button. After loading a data file, the specified retrieval is automatically applied to convert the brightness temperature data to IWV data.
Close to the horizon the radiometer beam is often blocked by obstacles and at 0° elevation angle the beam is influenced by ground radiation. Therefore it is desirable to define an ‘obstacle’ pattern to mark those cells that are not relevant due to beam blocking. To do so, the Enable Obstacle Mode check box has to be checked and blocking cells can be defined by toggling the enter mode with Add Cells or Delete Cells and clicking on the relevant cell in the diagram. The result might look like:
Once a cell is marked as blocked (white colour), the cell’s data content is no longer be taken into account for calculations like the displayed ‘IWV Variation’. When the cursor is located on a blocked cell, the data content displayed on the right of the diagram is showing ‘NAN’ which means Not A Number. The obstacle pattern definition can be stored and loaded using the Store and Load commands.
The colour range for the IWV display can be adjusted in the ‘Color Scaling’ box. Typical IWV variations over the full sky are in the order of 3-20%.
The full sky scanning feature is typically used every 10 or 15 minutes to monitor changes of the water vapour distribution. Each scan is automatically stored in a separate data file. A ‘movie’ of the IWV evolution can be displayed by defining the list of *.BRT full sky scanning brightness temperature files with Define TB File List. A separate menu opens where the user may select multiple files for auto display. The Start button starts the sequence and Stop halts it. With Reverse the file sequence is processed in reversed chronological order and Reset jumps to the first data file of the list. When the auto display is halted by pressing Start, a manual file display progression can be performed by successively clicking Single. In auto display mode, the pausing interval between successive data file displays can be adjusted by selecting a different time from the combo box. 

A similar full sky display diagram is available for LWP data. 
If the auto IWV display is also activated, the LWP display can be synchronized to the IWV display by checking the Sync. with IWV checkbox. Then the file list defined in the IWV full sky display menu is used for both diagrams and the auto display is controlled by the IWV ‘Auto Display’ commands.