1. Convection Group -- VCPs 11 and 12 are in this group
2. Shallow Precipitation Group -- VCP 21 is in this group
3. Clear Air Group -- VCPs 31 and 32 are in this group
4. Range Folding Mitigation Group -- VCPs 121, 211, 212, and 221 are in this group
|VCP||Scan Time (min)||Elevation scans||Elevation angles (°)||Usage||Special attributes|
|11||5||14||0.5, 1.5, 2.4, 3.4, 4.3, 5.3, 6.2, 7.5, 8.7, 10, 12, 14, 16.7, 19.5||Convection, especially when close to the radar||Has the best overall volume coverage.|
|211||Convection, especially when close to the radar||Improves range-obscured velocity data over VCP 11|
|12||4.5||14||0.5, 0.9, 1.3, 1.8, 2.4, 3.1, 4.0, 5.1, 6.4, 8.0, 10.0, 12.5, 15.6, 19.5||Convection, especially activity at longer ranges||Focuses on lower elevations to better sample the lower levels of storms.|
|212||Widespread severe convective events||Improves range-obscured velocity data over VCP 12|
|121||6||9||0.5, 1.5, 2.4, 3.4, 4.3, 6.0, 9.9, 14.6, 19.5||Large number of rotating storms, tropical systems, or when better velocity data is needed.||Scans lower cuts multiple times with varying pulse repetitions to greatly enhance velocity data.|
|21||5||Shallow precipitation||Rarely used for convection due to sparse elevation data and long completion time.|
|221||Widespread precipitation with embedded convection. (i.e., tropical systems)||Improves range-obscured velocity data over VCP 121|
|31||10||5||0.5, 1.5, 2.5, 3.5, 4.5||Detecting subtle boundaries or wintry precipitation||Long-pulse|
|32||Slow rotation speed allows for increased sensitivity. Default clear-air mode, reduces wear on antenna.||Short-pulse|
Sachinananda-Zrnic (SZ-2) Split Cut (SZCS/SZCD) (quoted from Warning Decision Training Branch training materials)
SZ-2 is a different range unfolding technique applied to the Split Cuts of VCPs 121, 211, 212, and 221. SZ-2 is able to reveal far more velocity data compared to the other range unfolding technique. Details on both of these techniques are presented in later sections of Topic 3.
NOTE: As with the standard Split Cut mode,
dual-polarization base data are processed from the SZ-2
Contiguous Surveillance rotation.
Multiple PRF Dealiasing Algorithm (MPDA)
(quoted from Warning Decision Training Branch training
The MPDA is implemented solely by invoking VCP 121. Though MPDA is not a waveform, it uses a unique combination of the SZCS, SZCD, CS, CD, and B waveforms. In the lower elevations of VCP 121, there are multiple Doppler rotations at each angle, each of which uses a different PRF.
Illustration of the elevations angles scanned and waveforms used during VCP 121.
Figure 21: Volume Coverage Pattern (VCP) 121 samples nine elevation angles in about 5.75 minutes. The lowest two angles apply the SZ-2 technique as part of MPDA, the lowest five angles apply the MPDA technique, while 6.0 deg uses Batch (B), and the higher angles use Contiguous Doppler without range unfolding (CD/WO) mode.