Occasional Problem with 2DVDA

Problem: During certain high shear events with weak trip echoes, the Two-Dimensional Velocity Dealiasing Algorithm (2DVDA) may produce a faulty background/internal wind map. When the background wind map becomes faulty, the velocity data may be incorrectly dealiased resulting in regions of errors in the velocity products (see example below).

Solution: There is a fix scheduled to be implemented in Build 18.2. A more comprehensive fix is being tested which may be included in Build 19 as well.

Work-Around: The problem seems to be reduced by using a higher PRF number. Until Build 18.2 is released, if areas of dealiasing errors are occurring, one option is to switch to manual PRF and choose a PRF higher than PRF4.

Reminders:

• The Manual PRF option is available for all VCPs except 31 & 121. However, for SZ-2 VCPs (212, 215, & 35) the PRF must be the same for all 3 sectors. VCPs 12 & 32 allow the sectors to have different PRFs.
• Higher PRF numbers have a shorter unambiguous range and can cause an increase in range folding, especially at further ranges.