TMP/XSACR/M1 - Reprocess: PPI scans at vertical incidence

During this time period, PPI scans in azimuth were done at zenith, i.e. elevation was 90 
degrees.  The data is intended for use in ZDR calibration.  While the data is similar to 
vertically pointing data, if there is any small unintended off-zenith radar misalignment, 
scanning in azimuth could impact the measured mean Doppler velocity due to variations in 
the horizontal velocity component sampled as part of the radial velocity measurement.

Use this data with caution. It will be reprocessed and stored as a different scan 

type, 'ZPPI' (zenith-pointing PPI), to avoid confusion with conventional low-elevation PPI 
scans.

• mean_doppler_velocity