## 4 Discussion  
The ability of ADDA for all the selected radar observations from the seven severe weather events was assessed statistically and also contrasted with the results obtained with the CIDA scheme, as described in HE2012 [17]. The judgment was built on the metrics of the false alarm ratio (FAR),  
Figure 5: Radar radial velocity from C-band radar stations in the CINRAD network: (**a**) raw velocity of the 3.3\({}^{\circ}\) elevation angle at 07:05 (UTC), 23 July 2009 from the Zhangbei radar; (**b**) dealiasing result of Figure a; (**c**) raw velocity of the 4.3\({}^{\circ}\) elevation angle at 08:06 (UTC), 27 June 2008 from the Datong radar; and (**d**) dealiasing result of Figure c. The spatial scales of the pairs of images at different elevations are different. probability of detection (POD), and critical success index (CSI). The following formulas were applied to compute the FAR, POD, and CSI:  
\[\text{FAR (false alarm rate)}=\text{C/A} \tag{4}\]  
\[\text{POD (probability of detection)}=\text{B/A} \tag{5}\]  
\[\text{CSI (critical success index)}=\text{B/(B+C+D)} \tag{6}\]  
where: A = total number of aliased gates; B = total number of correctly dealiased gates; C = total number of incorrectly dealiased gates; D = total number of missed dealiased gates. The FAR shows the percent of these velocity gates that should be aliased but are not; the POD gives the percent of all aliased velocity gates that are dealiased; and the CSI gives the number of properly dealiased velocities over all of the velocities that are correctly dealiased, missed, and erroneously dealiased. In other words, the denominator is all the velocities minus those that are not aliased. The period of continuously tested radar observations was more than 12 h for each of the seven cases. More than half of the velocity gates were aliased among the total 7463 tilts. Some of these gates were even aliased multiple times, especially in the hurricane or typhoon cases and the deep convection cases observed by the C-band radar systems with smaller Nyquist velocities. All of the tilts were dealiased, and the aliased tilts were hand-edited to produce \"truths\" for evaluation. The \"truths\" for the analysis were manually dealiased with SOLOII software developed by the National Center for Atmospheric Research. SOLOII software is a widget-driven piece of software that displays sweeps of radar data and enables the user to manually dealias the radial velocity data. Tables 1 and 2 show the statistical dealiasing results of the seven cases from ADDA and CIDA. First, it is shown that ADDA performs better CIDA for all the seven cases. The China Haikou and Taiwan Hualian radars for typhoons observation have the most obvious skill improvement, which was primarily attributable to the advanced selection of the first reference radial. The CINRAD Guangxi radar for the squall line case also resulted in significant skill improvement due to the ability of the algorithm in module 4 to distinguish the real shear caused by convection from the false shear caused by aliased velocities. For the two most inaccurate CINRAD C-band radars, the Datong radar showed a significant improvement while the Zhangbei radar had only minor improvements. In addition to the inherent difficulties in dealiasing the C-band radar data because of their small Nyquist velocities, the Zhangbei radar presented additional challenges due to the excessive data voids caused by topography. Comparing the statistical results of the seven cases, it was seen that the typhoon or hurricane cases resulted in higher skills than the continental convection cases. Moreover, the results for the S-band radar were noticeably better than those for the C-band radar, which is not surprising given the low Nyquist velocities of the C-band radar.