SGP/MPL/C1 - Signal degrading

The MPL viewport window was blown off during a storm on 2002/09/25.  The MPL received a 
soaking of rain.  Following this event, although site operations cleaned and dried the 
optics, the lidar performance continued to degrade over the next few months.  Although 
initially suitable for cloud detection, by Dec 10th the lidar was providing useful results only 
during the day (oddly enough).  By Jan 16, the detector was dead.  

It is not recommended to depend on night-time cloud base heights after Dec. 10 2002. 

It is not recommended to use any of the data after 9/25 for aerosol retrievals.

• lon
• Pressure, associated geometric height, at altitude, NGM model output(height)
• range_offset
• laser_scalar_sync_offset
• Preliminary cloud base height above ground level(preliminary_cbh)
• filter_temp
• trigger_freq
• time
• energy_monitor
• transceiver_altitude_angle
• voltage_15
• voltage_10
• pulse_rep
• Backscatter(backscatter)
• laser_sync_offset
• range_bin_time
• laser_temp
• time_offset
• base_time
• scalar_sync_offset
• instrument_temp
• total_counts
• background_signal
• lat
• range
• shots_sum
• voltage_05
• max_altitude
• range_bins
• detector_temp
• shots_summed
• deadtime_correction
• alt
• property
• range_bin_width
• transceiver_azimuth_angle

• background_signal
• energy_monitor
• alt
• Cloud base height(cloud_base_height)
• cloud_top_attenuation_flag
• Backscatter(backscatter)
• lon
• baseline_update_time
• detector_temp
• cloud_mask_2
• random_error
• cloud_mask_1
• cloud top height(cloud_top_height)
• pulse_rep
• time_offset
• shots_summed
• lat
• instrument_temp
• base_time
• Pressure, associated geometric height, at altitude, NGM model output(height)
• laser_temp

SGP/MPL/C1 - Metadata errors

The latitude, longitude and altitude of the Micropulse Lidar
(MPL) were incorrectly entered into the ARM database.  The 
correct location of the SGP.C1 MPL is:
   Lat: 36.606N
   Lon: 97.485W
   Alt:    316m

• lat
• lon
• alt

• lon
• lat
• alt

operator error

DQR No:                               Platform: SGPSONDEC1

Subject: operator error

Date Submitted: 11/12/93
Submitted By: Barry Lesht             _X_  Instrument Mentor
                                      ___  EST Member
                                      ___  Science Team Member
                                      ___  Other _____________________________
 
For questions or problems, please contact the ARM Experiment Center at
509-375-6898 or via email at problems@arm.gov.

Platform/Measurement:  All
        What level data: (raw,a0,a1,b1,c1 etc): 

    What location was the data collected at: SGP/CF
         
    Period of time in question
        Begin Date  11/11/93   Time   19:27    (GMT)
        End Date      /  /     Time     :      (GMT)
   Sonde data files 11/11/93 19:27 and following may have bad data.

 Data should be labeled:
 _X_  questionable                      ___  All data fields affected
 ___  incorrect                         ___  Only some data fields affected
 ___  wrong calibration
 ___  others 
 
 Discussion of Problem:
 
 Mike Splitt of the site scientist team noted that the sounding done 11/11/93
 showed 0 RH at the ground.  I looked at the raw data file and also noted that
 the ground check humidity values were entered as 70 (reference) and 69 (sonde).
 The ground check humidity values should be zero.  This suggests an operator
 error of some sort.  Because 11/11 was a holiday, the usual sonde operator
 was not on site.  No entries of anything unusual were found in the daily
 ops log.  It may be coincidental that the SDS change-over moving Dorothy
 from the SPARC 2 to the SPARC 10 occurred at this time, but it may not be.

 The sounding done 11/12/93 also had problems.  Dave Glahn reported that the
 first sonde he tried showed 44% RH in the ground check set.  This typically
 results from using an incorrect calibration tape.  Dave opened a second
 sonde which passed ground check.  After launch, when Dave attempted to enter
 the surface observations, he says they were not written to the normal output
 file and that he was unable to graph the sounding on the sonde PC
 as it was occurring.  The operators played with the computer and ended up
 overwriting the standard output file - losing all data below about 5 km.

 It is difficult to determine the cause of the problem.  These data files
 should be flagged as questionable until we understand what happened.  My
 hypothesis is that the operators inadvertently modified the sonde software
 on 11/11 and that the output files are being written to the wrong directories.
 It is also possible that this problem resulted from the SDS change-over.
 SDS change-overs have, in the past, caused problems with the sonde data
 archiving.  I gave instructions to Dave Glahn to check the directory pointers
 before doing a sounding on Monday.  I will be on site Wednesday (for another
 purpose) and will check the system if we do not have resolution by then.
 
Other observations/measurements impacted by this problem:



Suggested Corrections of the Problem: (e.g. change calibration factor and
recompute, flag data with this comment, etc.)

Flag data.


Data Processing Notes                Date

• Dry Bulb Temperature(tdry)
• asc
• Eastward Wind Component(u_wind)
• base_time
• alt
• Pressure, atmospheric, constant value of model level, RUC model output(pres)
• lat
• Mean Wind Speed(wspd)
• lon
• time_offset
• Dewpoint Temperature(dp)
• wstat
• Northward Wind Component(v_wind)
• Humidity, relative(rh)
• Wind Direction(deg)

• Pressure, atmospheric, constant value of model level, RUC model output(pres)
• base_time
• lat
• wstat
• Dewpoint Temperature(dp)
• Humidity, relative(rh)
• Mean Wind Speed(wspd)
• asc
• alt
• time_offset
• lon
• Dry Bulb Temperature(tdry)
• Wind Direction(deg)

SGP/SONDE/C1 - Reprocess: Bad surface pressure

An incorrect value was entered by the operator for surface pressure. The value as entered 
as 873.9 (hPa) should be 973.9.  This error results in incorrect altitude values 
throughout the sounding and incorrect ascent rate values during the first few minutes.

• Dry Bulb Temperature(tdry)
• asc
• Eastward Wind Component(u_wind)
• base_time
• alt
• Pressure, atmospheric, constant value of model level, RUC model output(pres)
• lat
• Mean Wind Speed(wspd)
• lon
• time_offset
• Dewpoint Temperature(dp)
• wstat
• Northward Wind Component(v_wind)
• Humidity, relative(rh)
• Wind Direction(deg)

• Pressure, atmospheric, constant value of model level, RUC model output(pres)
• base_time
• lat
• wstat
• Dewpoint Temperature(dp)
• Humidity, relative(rh)
• Mean Wind Speed(wspd)
• asc
• alt
• time_offset
• lon
• Dry Bulb Temperature(tdry)
• Wind Direction(deg)

Instrument misalignment report

A low-resolution (300 m) MPL system (unit number 04) was installed at the
SGP site in April '97 upon the laser diode failure of the 02 unit in
March.  Calibration of this instrument in August found that the optics
were misaligned causing a near range focusing error in the data.  
Calibration files produced for this data, while acceptable, do not 
completely correct for the problem.  As a result, aerosol property 
retrievals using this data are not suggested.  Cloud boundary heights, 
though appear satisfactory.  This system was removed from SGP in early 
September

• Backscatter(backscatter)

Laser Output Energy Monitor at Zero

Energy monitor reading for laser output is at zero for intermittant
one-minute averaged shots during this flagged data period.  From the
lidar equation progressing to normalized relative backscatter the
laser energy is required and is a denominator.  Therefore a value of
zero will render the product as infinite.  Shots where this has taken
place are left as zeros.  It is suggested that the time period
19970425 2123 - 19970428 1459
be avoided for any quantitative analysis.

• Backscatter(backscatter)

Laser Output Energy Monitor at Zero

Energy monitor reading for laser output is at zero for intermittant
one-minute averaged shots during this flagged data period.  From the
lidar equation progressing to normalized relative backscatter the
laser energy is required and is a denominator.  Therefore a value of
zero will render the product as infinite.  Shots where this has taken
place are left as zeros.  It is suggested that the time periods 
19970902 2211 - 19970903 1359,
19970907 1445 - 19970908 1544,
and
19970910 2142 - 19970910 2355
be avoided for any quantitative analysis.

• Backscatter(backscatter)

SGP/MPL - Missing data due to blown detector

Sometime early 11/11 the detector on the
MPL-004 blew out.  The Detector was replaced by Albert Mendoza.
The instrument was operational on Jan. 23, 1999.

Link this to P981119.2 that reported the blown detector and the
corrective action taken

• Preliminary cloud base height above ground level(cbh)
• lon
• alt
• base_time
• time_offset
• lat

• lon
• Pressure, associated geometric height, at altitude, NGM model output(height)
• range_offset
• laser_scalar_sync_offset
• Preliminary cloud base height above ground level(preliminary_cbh)
• filter_temp
• trigger_freq
• time
• energy_monitor
• transceiver_altitude_angle
• voltage_15
• voltage_10
• pulse_rep
• Backscatter(backscatter)
• laser_sync_offset
• range_bin_time
• laser_temp
• time_offset
• base_time
• scalar_sync_offset
• instrument_temp
• total_counts
• background_signal
• lat
• range
• shots_sum
• voltage_05
• max_altitude
• range_bins
• detector_temp
• shots_summed
• deadtime_correction
• alt
• property
• range_bin_width
• transceiver_azimuth_angle

• background_signal
• energy_monitor
• alt
• Cloud base height(cloud_base_height)
• cloud_top_attenuation_flag
• Backscatter(backscatter)
• lon
• baseline_update_time
• detector_temp
• random_error
• cloud_mask_2
• cloud_mask_1
• cloud top height(cloud_top_height)
• pulse_rep
• time_offset
• shots_summed
• lat
• instrument_temp
• base_time
• Pressure, associated geometric height, at altitude, NGM model output(height)
• laser_temp

• Development raw data stream - documentation not supported