SGP/RL/C1 - Ground bin channel variability introduced height offsets

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

• Count rate in the high depolarization channel(depolarization_counts_high)
• Count rate in the high elastic channel(elastic_counts_high)
• Count rate in the low nitrogen channel(nitrogen_counts_low)
• Count rate in the high water vapor channel(water_counts_high)
• Count rate in the high nitrogen channel(nitrogen_counts_high)
• Count rate in the low elastic channel(elastic_counts_low)
• Count rate in the low water vapor channel(water_counts_low)

SGP/RL/C1 - Terminated cable affected data quality

> From an email message from John Goldsmith (SNL)


The site personnel had some alignment problems restarting the Raman
lidar after they stopped it yesterday (4/17) morning to clean the window.  
They finally got it running late in the afternoon, but they left a
terminated cable hanging from a second output on the Aerosol High amplifier
(used with a scope to find the beam when the alignment is way off).
Electronics can be picky; that cable screwed up the Aerosol High data,
filling the column with large numbers (~60,000); the other six columns are
fine.  The cable was removed at my request this morning; the first dataset
with good Aerosol High values is 71080842.DAT, #992 in the sequence, start
time 14:36:17 Z.

• Count rate in the high depolarization channel(depolarization_counts_high)
• Count rate in the high elastic channel(elastic_counts_high)
• Count rate in the low nitrogen channel(nitrogen_counts_low)
• Count rate in the high water vapor channel(water_counts_high)
• Count rate in the high nitrogen channel(nitrogen_counts_high)
• Count rate in the low elastic channel(elastic_counts_low)
• Count rate in the low water vapor channel(water_counts_low)

SGP/RL/C1 - Metadata errors

The latitude, longitude and altitude of the Raman Lidar were
incorrectly entered into the ARM database.  The correct location
of the SGP.C1 Raman Lidar is:
      Lat: 36.609N
      Lon: 97.487W
      Alt:    311m

• lon(lon)
• lat(lat)
• Dummy altitude for Zeb(alt)

Noise in select Raman Lidar channels

Narrow field of view elastic channel data was corrupted 970415 to 970529 
with noise added by a malfunctioning multichannel scalar card; data could
recovered with considerable work.
Wide field of view elastic channel data was corrupted 970529 to 970815
with noise added by the above MCS card after it was changed 970529 to 
this channel.

• lon(lon)
• Count rate in the high depolarization channel(depolarization_counts_high)
• Count rate in the high elastic channel(elastic_counts_high)
• Dummy altitude for Zeb(alt)
• Count rate in the low elastic channel(elastic_counts_low)
• Time offset of tweaks from base_time(time_offset)
• base time(base_time)
• Count rate in the low nitrogen channel(nitrogen_counts_low)
• lat(lat)
• Count rate in the high water vapor channel(water_counts_high)
• Count rate in the high nitrogen channel(nitrogen_counts_high)
• Laser pulse energy(pulse_energy)
• Nominal number of seconds of data acquired(acquisition_time)
• Number of laser shots recorded(shots_summed)
• Count rate in the low water vapor channel(water_counts_low)
• Flag indicating the filters (or lack of) added to the instrument(filter)