range resolution conversion NEXRAD to Rave

[adokter]

Certain older NEXRAD data has different range resolution for lowest three (250 m) and highest two (500 m) elevation scans, as well as different resolutions for different moments, e.g. https://noaa-nexrad-level2.s3.amazonaws.com/2010/09/11/KBGM/KBGM20100911_012056_V03.gz:

moment	range	azim	elev
R	1000	1	3.5, 4.5
R_HI	250	0.5	0.5, 0.5, 1.5, 1.5, 2.5, 2.5
V	250	1	3.5, 4.5
V_HI	250	0.5	0.5, 1.5, 2.5

• The file includes multiple reflectivity scans that do not have associated radial velocity
• When multiple scans at same elevation are available, WSRLIB uses largest PRF sweep for radial velocity and spectrum with, and lowest PRF for reflectivity. I think a better approach would be to keep the reflectivity scan acquired simultaneously with reflectivity, so largest PRF sweep in all cases.

rscale attribute of the higher two scans that sets the range resolution is kept at 250 m instead of 500 m.

See slack thread https://mlds-sheldon.slack.com/archives/DJJH17AHH/p1559065382000900?thread_ts=1559061983.000400&cid=DJJH17AHH

[adokter]

Fixed by commit https://github.com/adokter/vol2bird/commit/9bfe738775c3c188d0780664cfb407d0b2ae4888