| Description: | A maintenence visit in January 1999 to work on the Raman lidar laser
resulted in a height offset being introduced into the raw data. This
offset was found and corrected, but approximately six weeks of data (of
which the lidar was only operational for about 14 days) have the ground
bin at #69 versus #65 (a 156 m offset).
A second, related but more serious, problem that resulted in height offsets was
due to different styles of multi-channel scalar (MCS) cards in the system. The first
(original) style was used in the system had the ground at bin #66. However,
these cards occasionally faulted and 5 of them were replaced simultaneously
at the end of the 1997 Water Vapor IOP. The new style of cards have slightly different
electronics, which resulted in the ground bin being at bin #65 rather
than #66. Since there were still 2 of the old style cards in the system
when it was restarted (they had not yet faulted), the result is that there are channel
dependent height offsets for a period of time, until finally new style
MCS cards were put in all channels.
Since most of the derived products from the Raman lidar are ratios of two channels, this
difference in the ground bin has a undesired and somewhat disguised effect on the data.
The mentor has decreed that ground bin #65 shall be the standard for all raman
lidar data. The data affected by the ground bin variability are in the queue for
reprocessing to remove the offset. In the interim, these data should be used with caution.
Ground bin number history:
==========================
prior to and up to 10/6/97
all channels bin #66
10/7/97 to 6/9/98
high & low water vapor channels bin #66
all other channels bin #65
6/10/98 to 7/27/98
low water vapor channel bin #66
all other channels bin #65
7/28/98 to 1/14/99
all channels bin #65
1/15/99 to 3/1/99
all channels bin #69
3/2/99 to current
all channels bin #65 |